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Tackling the threat to food security caused by crop pests in the new millennium
Abstract
Crop yields are reduced and destabilized by pests which also affect the quality of harvested produce. To keep pace with growing
demand, global food production needs to increase by an estimated 70% by 2050. Thus, the losses caused by pests need to be
tackled. Synthetic pesticides have provided cost-effective control of pests over the last few decades but have several disadvantages.
They may adversely affect natural enemies of insect pests, which would otherwise provide a degree of control and pests may
evolve resistance to the pesticide. The discovery rate of novel bioactive compounds is low and their exploitation increasingly
inhibited by stringent regulatory requirements. Use of resistant crop cultivars is another solution but when based on single
genes it also suffers from the evolution of biotypes of pests that can overcome the resistance conferred by the gene. Biocontrol
with natural enemies can contribute to pest management but biocontrol agents are often hard to maintain at sufficiently high
levels in open field environments. New solutions could include novel resistant cultivars with multiple resistance genes, suitable
epigenetic imprints and improved defence responses that are induced by attack. Plant activator agrochemicals could be used
to switch on natural plant defence. Habitat manipulations such as push-pull can improve pest management and yields in less
intensive systems. Genomic and transcriptomic information will facilitate development of new resistant crop cultivars once
annotation and availability of data on multiple cultivars is improved. Knowledge of the chemical ecology of pest-plant interactions
will be better exploited once the genes for biosynthesis of key plant metabolites are discovered. Genetic modification of
crops has the potential for speeding the development of crops with novel resistance.
KeywordsCrop pest–Food security–Induced defence–IPM–Resistant cultivar
... Also, the cost of synthetic pesticides has proved to be unaffordable to the resource poor farmers. Moreover, relying on chemical control may result to undesirable effects such as effects on non-target organisms, resistance development, up-surge of secondary pests, environmental pollution and poisoning of the farmers (Chadwick and Marsh, 1993;van den Berg et al., 1998;Bruce, 2010;Karuku, 2012). This has called for alternative methods to manage the stemborer. ...
... This makes the grass to qualify as an ideal trap plant candidate for use in the push-pull strategy for stemborer management by smallholder farmers in western Kenya and indeed in similar agro-ecologies where the stemborer pests are a menace. This approach should be introduced or activated in maize plants (Bruce, 2010 ;Tamiru et al., 2012). Nyamula. ...
The Lepidopteran stemborer Chilo partellus is a key constraint to cereal production in most resource-poor farming systems as it causes damage to the crop, accruing up to 80%. When plants are damaged by herbivorous insects, they produce herbivore-induced plant volatiles (HIPVs) which can act as repellants for these insect pests and as attractants for organisms antagonistic to these pests (parasitic wasps and predators). Plants can also produce signals that warn other plants of impending attack. Thus, HIPVs potentially have a practical role in crop protection by directly deterring further colonization in already infested and neighbouring plants and indirectly by attracting natural enemies of the pests, particularly parasitoids. The study sought to evaluate the effect of herbivore-induced plant volatiles on maize plants exposed to neighbouring Brachiaria brizantha (A.Rich) Stapf (Poaceae) grass oviposited by the spotted stemborer Chilo partellus (Swinhoe) (Lepidoptera: Crambidae). This was done using six maize varieties; four local varieties and two hybrids. Treatments comprised of maize seedlings exposed to B. brizantha with C. partellus eggs versus non-exposed ones and or maize seedlings exposed to B. brizantha without C. partellus eggs. Responses of stemborers and larval parasitoids to HIPVs collected from maize plants exposed to B. brizantha with and without stemborer eggs was determined by olfactometer and oviposition bioassays respectively. Qualitative and quantitative analyses of these HIPVs was determined through gas chromatography (GC) and GC-Mass spectrometry (GC-MS) to identify electrophysiologically active compounds. The results of this study demonstrated that exposing farmers‟ local maize varieties to Brachiaria brizantha with Chilo partellus eggs induced the plants to emit volatile blends that are attractive to the parasitoid Cotessia sesamiae Cameron (Hymenoptera: Braconidae) parasitoid. Also the same volatile blends were repellent to Chilo partellus. On the other hand the hybrids exposed to Brachiaria brizantha with Chilo partellus eggs were not induced. The biologically active chemical compounds responsible for the behaviour of Cotessia sesamiae and Chilo partellus obtained from local maize exposed to B. brizantha with eggs were (E)-4, 8-Dimethyl-1, 3, 7-nonatriene, Decanal, (E)-Caryophyllene, Linalool, linalool (plus Nananal), E-β-fernesene, Methyl salicylate and (3E, 7E)-4, 8, 12-trimethyl-1, 3, 7, 11-tri-decatetraene. Hybrids did not produce any biologically active chemical compounds. Attraction of larval parasitoids implies that natural enemies can be recruited to attack the newly hatched stemborer larvae before they cause damage to the crop. In addition, this grass can be used as a trap crop to ward off Chilo partellus from the maize crop in the field. The results reported in this study are of great significance for the management of Chilo partellus stemborers as they provide insights into possible exploitation of the signalling of defence responses in the smart maize varieties using an equally smart plant. In addition, it also would open up opportunities for a more efficient exploitation of natural enemies as they would be recruited earliest before larvae of the pest hatch from eggs to cause damage to maize plants. It is recommended that resource poor farmers adopt the findings of this research to increase food on the table and cash in the pocket.
... The current status of fruit fly pest population control Fueled by globalization, climate change and poor farming practices, agricultural pest populations are predicted to expand into new areas, putting more people at risk of food insecurity (Bruce, 2010;Langille et al., 2017;Phophi & Mafongoya, 2017;Gutierrez et al., 2021;Tonnang et al., 2022). Fruit flies from the Drosophilidae and Tephritidae families are some of the key attackers of a vast array of fruit and vegetable species (Papadopoulos et al., 2024). ...
Sterile insect technique (SIT) has become a key component of efficient pest control. Fruit fly pests from the Drosophilidae and Tephritidae families pose a substantial and overwhelmingly increasing threat to the agricultural industry, aggravated by climate change and globalization among other contributors. In this review, we discuss the advances in genetic engineering aimed to improve the SIT‐mediated fruit fly pest control. This includes SIT enhancement strategies such as novel genetic sexing strain and female lethality approaches. Self‐pervasive X‐shredding and X‐poisoning sex distorters, alongside gene drive varieties are also reviewed. The self‐limiting precision‐guided SIT, which aims to tackle female removal and male fertility via CRISPR/Cas9, is additionally introduced. By using examples of existing genetic tools in the fruit fly pests of interest, as well as model species, we illustrate that the population control intensity may be modulated depending on strategy selection.
... Finally, international collaboration and knowledge sharing should be strengthened to accelerate the global adoption of green pest control. This can involve the establishment of international research networks, the harmonization of regulations and standards, and the sharing of data and best practices across countries and regions [52]. ...
Agriculture faces the critical challenge of meeting growing food demands while minimizing environmental impacts. Conventional pest control methods heavily reliant on synthetic pesticides have led to numerous ecological problems, including pesticide resistance, biodiversity loss, and ecosystem disruption. This chapter explores pioneering approaches in green pest control that offer sustainable alternatives for managing agricultural pests. We discuss the principles and strategies underpinning ecological pest management, including promoting beneficial insects, using biopesticides and semiochemicals, and employing cultural practices like intercropping and crop rotation. Cutting-edge technologies such as CRISPR-based gene drives and RNAi-mediated insect control are also examined for their potential to provide targeted, environmentally friendly solutions. The chapter further delves into successful case studies demonstrating the efficacy of green pest control methods in various agroecosystems worldwide. These examples showcase how integrating ecological knowledge with innovative tools can significantly reduce pest populations while fostering biodiversity and ecosystem resilience. However, we also acknowledge the challenges in broadly adopting these approaches, including the need for further research, education, and policy support. The chapter concludes by outlining future research directions and recommendations for transitioning to green pest management on a global scale. Pioneering Green Pest Control 216 Ultimately, pioneering green pest control holds immense potential for revolutionizing agriculture and building a sustainable future.
... Another application field where GO measures could prove useful is for the study of invasive populations. Indeed, global trade and climate change amplify the need to develop strategies allowing to predict future biological invasions (Gallien et al., 2010) and to mitigate their negative impacts (Hulme, 2017(Hulme, , 2021, especially for species of agricultural interest, for example, crop pests which represent a significant threat to global food security (Bradshaw et al., 2016;Bruce, 2010). In this context, GO measures could help predict the optimal regions for population establishment, taking into account intraspecific local adaptation. ...
Predicting the risk of establishment and spread of populations outside their native range represents a major challenge in evolutionary biology. Various methods have recently been developed to estimate population (mal)adaptation to a new environment with genomic data via so‐called Genomic Offset (GO) statistics. These approaches are particularly promising for studying invasive species but have still rarely been used in this context. Here, we evaluated the relationship between GO and the establishment probability of a population in a new environment using both in silico and empirical data. First, we designed invasion simulations to evaluate the ability to predict establishment probability of two GO computation methods (Geometric GO and Gradient Forest) under several conditions. Additionally, we aimed to evaluate the interpretability of absolute Geometric GO values, which theoretically represent the adaptive genetic distance between populations from distinct environments. Second, utilizing public empirical data from the crop pest species Bactrocera tryoni, a fruit fly native from Northern Australia, we computed GO between “source” populations and a diverse range of locations within invaded areas. This practical application of GO within the context of a biological invasion underscores its potential in providing insights and guiding recommendations for future invasion risk assessment. Overall, our results suggest that GO statistics represent good predictors of the establishment probability and may thus inform invasion risk, although the influence of several factors on prediction performance (e.g., propagule pressure or admixture) will need further investigation.
... Crops produce only about half of their potential yield under field conditions due to abiotic stresses such as drought, salinity, temperature extremes, pollution, poor soil quality, and flooding (Hatfield & Walthall, 2015). Abiotic stress also contributes significantly to the yield gap, with field losses to insect pests estimated at more than 10% (Kerchev et al., 2011) and rising to 50-80% in the absence of control measures (Bruce, 2010). Insects, fungi, bacteria, viruses, and other pathogens can attack crops, causing damage to leaves, stems, roots, and fruits. ...
... Systemic pesticides, which are absorbed by the plant and spread throughout its tissues, may be more effective in controlling concealed larvae. However, repeated use of chemical pesticides is not only expensive to smallholder farmers but can have increased risks for pollinators, human health, and the environment, including non-target beneficial species and the overall ecosystem (Bruce, 2010). Hence, integrated pest management (IPM) programs incorporating a range of complementary and ecologically friendly tactics are needed for sustainable FAW control. ...
... Asian corn borer, Ostrinia furnacalis (Guenée), is one of the most destructive pests to the maize crop in Asia, Australia and the Solomon Islands, 1 causing 10-30% of maize yield loss every year in China. 2 At present, pesticides are still the main method for pest control, but their use results in environmental pollution, human health threats and pest resistance. 3,4 Thus, development of novel technologies is necessary for efficient and environmentally friendly pest control. ...
BACKGROUND
Omnivores, including humans, have an inborn tendency to avoid risky or non‐nutritious foods. However, relatively little is known about how animals perceive and discriminate nutritious foods from risky substances. In this study, we explored the mechanism of feeding selection in Ostrinia furnacalis larvae, one of the most destructive pests to the maize crop.
RESULTS
We identified a gustatory receptor, Gr43a, for feeding regulation in larvae of Ostrinia furnacalis, which highly expresses in the mouthparts of the first‐ (the period of just hatching out from eggs) and fifth‐instar larvae (the period of gluttony). The Gr43a regulates foraging plasticity by discriminating sorbitol, a nonsweet nutritious substance, and sucralose, a sweet non‐nutritious substance through the labra of mouthparts, while it differentiates fructose/sucrose and sucralose via the sensilla styloconica of mouthparts. Specially, Gr43a responds to fructose and sucrose via the medial and lateral sensilla styloconica in O. furnacalis, respectively. Furthermore, Gr43a is negatively regulated by the neuropeptide F system, a homologous mammalian neuropeptide Y system.
CONCLUSION
This study reveals a smart feeding strategy for animals to meet both nutritional needs and sweet gratification, and offers an insight into complex feeding selections dependent on food resources in the surrounding environment. © 2023 Society of Chemical Industry.
... Reaction's ability as well alterations through education manner, like if a certain single or group of singles is connected through a remuneration [14]. There is a lot attention in plant-eating insects because of their functions as insects in agrarian environmental system and the passive impact this has on diet protection for mankind [15]. Anyway, another kind of insects-vegetation reactions occur. ...
Co-evolved is the mostly passable opinion for the development of insect-harbor-cultivate connections, whilst, it enable be offered that its essential prelude are unsuitable: (1) generality Plant-eating insects have highly minimum inhabitance intensities comparison to the bio conglomerate of their harbor cultivates , subsequently, they ability seldom be significant chosen agents for the vegetative; (2) insect- harbor-cultivate reactions are not indispensable hostile: monoeater- and oligoeater insects, whether their count is obviously elevated, may perfect organize the multitude of their harbor cultivates (reciprocal usefulness); Therefore, (3) durability to insects is not a comprehensive needful in vegetation and it Not possible clarify the existence of subaltern vegetation materials; (4) equivalent development pathways of vegetations and insects which must outcome from co development reactions are scarce, whereas numerous intimately concerning insects nourish on Vegetarian highly Away vegetation Varieties - a connection which not possible be concerning to co- development. So, the opinion of successive development is suggested: the development of blossom vegetations encouraged via chosen agents (e.g., environment, ground, vegetation- vegetation, reactions etc.), which are numerous extra powerful than insect offensives originate the biochemically varied dietary rule for the development of Plant-eating insects, whereas the last do not Significantly impact the development of vegetations.
... Irrigation is one of the most widely discussed topics in today's world due to its high importance in the ever-increasing population. Food production is at higher risk due to many reasons including water shortages (Mancosu et al., 2015;Rockström et al., 2009), agricultural land conversion (Appiah et al., 2019;Rondhi et al., 2018), pest attacks (Bruce, 2010;Demay et al., 2023;Elakya and Manoranjitham, 2018;Neuenschwander et al., 2023), soil fertility issues (Çakmakçı and Çakmakçı, 2023;Zhong et al., 2014), and natural disasters (De Haen and Hemrich, 2007;Gimpel et al., 2021;Klomp and Hoogezand, 2018). Water-related issues are significant in food production; therefore, planning an irrigation system is highly important (Sojka et al., 2002). ...
Ancient Minipe Anicut, Sri Lanka is world-famous for its engineering excellence. Due to its importance, conserving the ancient anicut, another anicut was constructed downstream in the 20th century. Nevertheless, the water diverted from the ancient anicut to the Minipe Left Bank (LB) canal was kept as it was due to inherited agricultural importance. This research focuses on studying the contributions made by the adjacent catchment along the Minipe LB Canal. There are several level crossings along the Minipe Left Bank Canal from which the runoff of the local catchment flow into the Minipe LB Canal. Hydrologic Modeling System (HEC-HMS) is used to obtain the yield from each catchment into the Canal, which was compared with the annual diversions from Minipe anicut. The total yield from each stream has been compared with the annual diversion of the Minipe LB Canal from 2014 to 2020. The results obtained from this study reveal that there is sufficient water available for water augmentation in the basin, with an estimated annual average cumulative yield from the catchment of 453.6 MCM. This cumulative yield is 1.7 times the annual average diversion from the Mahaweli River, which is 271.9 MCM. With the findings, it is concluded that there is a potential to augment water from the catchment to address pertaining water shortages conveyance in the command area.
... Since Norman Borlaug, we have had three generations dedicated to the continued increase in yield through crop breeding and supportive pesticides. 18 Recognizing the potential of biological solutions, we have seen advances in biofungicides and bioinsecticides. There have been bioherbicide efforts related to phytotoxic allelochemicals (e.g., strigolactones, plant extracts) and plant pathogens (e.g., Fusarium oxysporum). ...
The high‐level view of global food systems identifies three all‐encompassing barriers to the adoption of food systems solutions: knowledge, policy, and finance. These barriers, and the siloed characteristics of each of these, have hindered the development and adoption of microbial herbicides. How knowledge, policy, and finance are related to the Toothpick Project's path of commercializing a new bioherbicide, early in the scope of the industry, is discussed here. The Toothpick Project's innovation, developed over four decades and commercialized in 2021, uses strains of Fusarium oxysporum f.sp. strigae selected for overproduction and excretion of specific amino acids, killing the parasitic weed Striga hermonthica (Striga or witchweed), Africa's worst pest threat to food security. Historically, bioherbicides have not been a sufficient alternative to the dominant use of synthetic chemical herbicides. To be used safely as bioherbicides, plant pathogens need to be host specific, non‐toxic, and yet sufficiently virulent to control a specific weed. For commercialization, bioherbicides must be affordable and require a sufficient shelf life for distribution. Given the current triple storm encountered by the chemical herbicide industry (herbicide‐resistant weeds, lawsuits, and consumer pushback), there exists an opportunity to use certain plant pathogens as bioherbicides by enhancing their virulence. By discussing barriers in the scope of knowledge, policy, and finance in the development of the Toothpick Project's new microbial bioherbicide, we hope to help others to anticipate the challenges and provide change‐leaders, particularly in policy and finance, a ground level perspective of bioherbicide development. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.
... While maize yields are poor due to declining soil fertility coupled with reduced rainfall and pests, cowpea is highly vulnerable to numerous pests, diseases and weeds resulting in low production levels. The food shortage trends have to be reversed by all means through use of appropriate improved agricultural technologies [3]. Use of cultural methods such as timely planting, mulching and use of cover crops has been reported to be effective in suppressing and reducing weeding costs, conservation of soil moisture and addition of organic matter upon decomposition. ...
Maize and cowpeas are important staple foods in Kilifi county and their productivity is highly constrained by increased incidences of pests, weeds and prolonged drought. These adversely affect maize yields and availability of cowpea leafy vegetables during the dry seasons. Sonchus oleraceaous, a common weed in most maize-cowpea cropping systems is widely used and most preferred in most households of the Kenyan coast as a leafy vegetable. However, its role as a vegetable and cover crop have not been exploited and or documented. This study was conceived to investigate the effects of Sonchus on maize-cowpea cropping systems, specifically as a cover crop. A randomized complete block design experiment replicated thrice was set at Pwani University Crop Science farm for two (2) cropping seasons in 2014 to 2016. Treatments included three (3) intercropping systems composed of maize, Sonchus and cowpeas, and the sole crops as a control with maize spacing of 90 by 60 and cowpea and Sonchus at 15cm by 60cm. Plant height, % ground cover, and biomass yields were determined for each treatment. High groundcover was observed in all the intercrops, and was highest where cowpea was part of the treatment. Biomass of Sonchus was highest in the sole crop, followed by the maize-Sonchus intercrop (>7.5tons/ha) and was lowest (2.5-2.78) in the Sonchus-cowpea intercrop (82-84% lower compared to the other treatments). The results showed that intercropping maize with Sonchus was feasible where in between space was sufficient. The implication is that Sonchus can be integrated in maize farming systems for crop diversification as a vegetable to maximize on land productivity and contribute to nutrition. Further research on spacing and density for maize and Sonchus intercrop should be carried out to develop an agronomic package that would ensure maximum returns for promotion to farmers.
... Systemic pesticides, which are absorbed by the plant and spread throughout its tissues, may be more effective in controlling concealed larvae. However, repeated use of chemical pesticides is not only expensive to smallholder farmers but can have increased risks for pollinators, human health, and the environment, including non-target beneficial species and the overall ecosystem (Bruce, 2010). Hence, integrated pest management (IPM) programs incorporating a range of complementary and ecologically friendly tactics are needed for sustainable FAW control. ...
... If farming is to support human population, however, additional feasible strategies for crop protection and improved integrated pest management systems ought to be developed. Alternative solutions to the use of pesticides comprise the development of new resistant cultivars, the development and use of biological control agents, the employment of agrochemicals to turn natural plant defenses on (Bruce, 2010), and the use of the recently developed genome engineering tools, or gene editing, such as CRISPR/Cas technology (Clustered Regularly Interspaced Short Palindromic Repeats/ CRISPR associated genes; Jansen et al., 2002). ...
With the continuous deterioration of arable land due to an ever-growing population, improvement of crops and crop protection have a fundamental role in maintaining and increasing crop productivity. Alternatives to the use of pesticides encompass the use of biological control agents, generation of new resistant crop cultivars, the application of plant activator agrochemicals to enhance plant defenses, and the use of gene editing techniques, like the CRISPR-Cas system. Here, we test the hypothesis that epigenome editing, via CRISPR activation (CRISPRa), activate tomato plant defense genes to confer resistance against pathogen attack. We provide evidence that edited tomato plants for the PATHOGENESIS-RELATED GENE 1 gene (SlPR-1) show enhanced disease resistance to Clavibacter michiganensis subsp. michiganensis infection. Resistance was assessed by evaluating disease progression and symptom appearance, pathogen accumulation, and changes in SlPR-1 gene expression at different time points. We determined that CRISPRa-edited plants develop enhanced disease-resistant to the pathogen without altering their agronomic characteristics and, above all, preventing the advancement of disease symptoms, stem canker, and plant death.
... To date, ensuring a satisfactory yield and quality of the harvest requires an extensive use of systemic and protectant fungicides for their management. But the continued application of fungicides has several negative consequences including the development of fungicide-resistant races of the pathogen, increase of residue levels, and serious risks for human health (Kashyap et al. 2019;Kashyap et al., 2018b;Bruce et al., 2010). Moreover, wheat breeders have been unable to locate complete resistance against fungal diseases in any of the wheat cultivars, although, some of them shown varying degree of resistance against the diseases. ...
The concept of induced resistance (IR) in crop protection has bloomed in the past few decades as it offers improved plant protection in an environmentally safe and economically sound manner. A large number of resistance-inducing compounds of different origins have been reported and tested in different plant-pathogen systems. Several reports indicated that the mechanism of action of these compounds differs from fungicides because they restrict plant pathogen development indirectly via triggering plant defense. Additionally, resistance inducers can be combined with biological control agents and even fungicides, which could result in reduced agrochemical usage in agriculture sector. A number of biological control agents are available for field applications, but further development and effective implementation will require a better understanding of the complex interactions among plants, people, and the environment. To that end, the chapter presents an advanced survey of the nature and practice of biological control based on IR as it is applied to the suppression of wheat diseases.
... Insecticide applications are used to control O. furnacalis in maize, but it is very difficult to control larvae once they tunnel into the stalk (Gibson et al., 2009). Insecticides are often viewed unfavorably because of possible impacts to human health and the environment, and the potential for development of pest resistance and outbreaks of secondary pests (Bruce, 2010;Mitchell et al., 2016). ...
Asian corn borer, Ostrinia furnacalis (Guenée), is an important insect pest of maize throughout most of Asia. The rind of a maize stalk is a key barrier against corn borer larvae boring into the plant. There is a need to better understand the relationship between stalk strength and O. furnacalis larval injury, particularly for elite maize genotypes. To determine whether stalk strength is involved in maize resistance to O. furnacalis larval injury, 39 maize lines were evaluated in 2012 and 2013. Rind penetration strength (RPS) was measured at tassel (VT) and milk (R3) stages as a possible stalk resistance trait for O. furnacalis. RPS of primary ear internode at VT and R3 accounted for 37 and 38% of the variance in O. furnacalis injury (measured as number of holes) for simulated (artificially infested) first and second generation O. furnacalis, respectively. Relationships between stalk RPS values and tunnel length were weak. Results suggest that harder stalks have enhanced resistance to stalk boring but not to pith feeding or tunneling of O. furnacalis larvae. The RPS measures could provide classical maize breeders an important tool for evaluating stalk strength and corn borer resistance in maize. The assessments should focus on the internodes primary ear or above/below primary ear during both VT stage for first generation and R3 stage for second generation O. furnacalis resistance.
... Kovalikova et al. [47] emphasized the importance of phenols in plant protection against insect pests. The use of elicitors of plant defenses, or 'plant activators' as they have been termed, has been proposed as an alternative approach to crop protection [48][49][50]. However, commercial success in this area is currently limited. ...
The aim of this study was to analyze the effects of different variants of insecticidal treatment against Agrotis spp. caterpillars on the technological yield from sugar beet using the AMMI (Additive Main Effect and Multiplicative Interaction) model. Data for the analysis of sugar beet yield and different insecticidal treatments were obtained from a trial in Winna Góra between 2011 and 2018. White sugar yield was estimated for each variant of treatment, and it was found to be directly proportional to the root weight and polarization. The content of potassium in molasses had an inversely proportional effect on the sugar yield in the variant of treatment based on phenological observations with calculated heat sums, as well as in controls. The content of α-amino-N had an inversely proportional effect on the technological yield of sugar for each variant of tested chemical treatments. The content of α-amino-N had a statistically significant effect on the sugar beet yield for all tested experimental combinations. AMMI analysis used to estimate the interaction of treatments based on environmental conditions showed the additive effect of the applied treatments on the quality parameters of white sugar yield from sugar beet. These effects were demonstrated for polarization and the content of sodium in molassigenic substances. Regarding the AMMI model, the results of the analysis of variance showed a significant interaction between treatment and year for all considered characteristics in the experiment.
... Biocontrol predators are used to control herbivorous pest populations on crops by increasing pest mortality and reducing their abundance (Memmott et al. 2000;Stiling and Cornelissen 2005;Singh 2014;Anwer 2017;Kumar and Omkar 2018). Managing these pests is crucial to providing food for a growing human population, as food security is a critical concern in the twenty-first century, and animal pests cause an estimated loss of 10-16% in pre-harvest crop production (Oerke 2006;Bruce 2010;Bebber et al. 2013). Biocontrol is an economically important tool to reduce pest populations to tolerable levels, becoming increasingly popular as a more environmentally friendly alternative to chemical pesticides and as a component of integrated pest management (IPM) (Clausen 1978;Costanza et al. 1997;Neuenschwander et al. 2003;van Lenteren 2012;Naranjo et al. 2015Naranjo et al. , 2019van Lenteren et al. 2018). ...
Biocontrol with predators is a key tool for controlling agricultural pests and preserving the productive efficiency of crops. Determining which predators to use for biocontrol often involves measuring their functional response—the relationship between foraging rate and prey abundance, yet comparisons of functional responses across predators are complicated by differences in experimental procedures. Here we use a compilation of functional responses standardized for time and space units to illustrate key sources of variation in functional responses for predators being tested for control of aphids and mites. Our results show that arena size (as a proxy for habitat structure) is a crucial predictor of predator performance, indicating that assessments of functional responses on the crops of interest may be necessary for accurate comparisons. Our results also suggest that larger predators may generally be more efficient, and that warming linked to climate change could make biocontrol using predators more effective when pests are abundant.
... Tarımda kullanılan kimyasallar aynı zamanda çevre üzerine de olumsuz bir etkiye sahip olmakta, toprak ve su kaynaklarını kirletmekte, hedef olmayan organizmaları etkilemekte ve kısa sürede tüm popülasyonlarda problemlere yol açmaktadır (Bruce, 2010;van Wijngaarden ve ark., 2003). Sonuç olarak bu problemler, bitkilerle beslenen böceklerin ürün kaybını minimize etmeyi hedefleyen yeni kontrol stratejilerinin ele alınmasına ve düşünülmesine neden olmuştur (Ceasar ve Ignacimuthu, 2012). ...
Patojen infeksiyonları ve böcek saldırılarının elimine edilmesinde bitkinin kendi fizyolojisinin bir parçası olarak bazı böcek kovucuproteinler (lektin, kitinaz, proteaz ve defensin proteinleri) üretilebilmektedir. Bu kapsamda birçok bitki türü tarafından protein
sentezini durdurma yeteneğinde olan proteinler de üretilebilmektedir (Agrios, 2005). Ribozom inaktive eden proteinlerin (RIP) adı verilen bu grup proteinler, kapsamlı bir şekilde araştırılmış ve fungal, antiviral, bakteriyel patojenler ile tümör ve böcekler üzerindeki inhibisyon etkileri doğrulanmıştır.
Güncel olan bu araştırma derlemesi ile Ribozom inaktive eden proteinlerin agro-ekonomik anlamda önemli olan farklı böceklerin hayat döngüleri ve yumurtlama üzerine olan engelleyici etkileri ele alınacaktır. Sunulan bu derlemenin, tarımsal ekosistemde güvenilir
insektisitler olarak bu proteinlerin kullanılması yönüyle bu kapsamda araştırma yapan öğretim elemanları ve Ziraai İlaç üretim firmalarına ilaç temelli stratejiler geliştirmesi açısından ışık tutacağı kanaatindeyiz.
... striga. Weeds also reduces harvests quality and makes farmers to utilize more resources in terms of time and money to control weeds which reduces returns [24]. ...
Kenya experiences huge production-consumption deficit in relation to rice. This is due to changing eating habits that has adopted more rice in the menu and rapidly rising population. Rice production has remained low being unable to meet consumption. Rice ecosystems in Kenya include irrigated, rainfed lowland and rainfed upland. Irrigated ecosystem has over the years been given more emphasis despite rainfed rice farming having double the potential over irrigation system. Ecologically rice grows well in abundant water supply, warm to high temperatures and in Clay sandy to loamy soils with slightly acidic to neutral pH. Rice varieties grown in Kenya are mainly traditional, introduced improved, hybrids and landraces. Rainfed rice farming faces constraint’s key among them being; drought and erratic rainfall, weeds, pest and diseases, cheap imports, land ownership and poor infrastructure. Mitigating against drought and erratic rainfall, improving farm inputs and equipment, increasing germplasm production and distribution, credit support and marketing to farmers, improving farmers skills through technological transfers and infrastructural development are prospects that if adopted could increase rainfed rice productivity. More attention towards improvement of rainfed rice farming could greatly contribute to bridging the production-consumption deficit that is bridged through imports. It is with this, that this review updates our understanding of rain fed rice farming in Kenya in terms of ecological conditions, ecological systems, varieties, constraints and prospects.
... Insects have a highly sensitive olfactory system that can detect and discriminate relevant volatile organic compounds with high degree of selectivity and specificity (Chung et al., 2002;Tamiru et al., 2015). Unlike chemical insecticides, volatiles are difficult for insect to develop resistance against and work by a non-toxic mode of action through modifying the behavior of the pest (Bruce, 2010). Particularly important ones are the effects of host plants volatiles on pheromone behavior, which appears to be part of male strategies (to maximize encounters with females) as well as female strategies (to gain access to new feeding and oviposition sites) (Reddy and Angel, 2004). ...
Brinjal Fruit and Shoot Borer- Leucinodes orbonalis Guenee is a major insect pest on brinjal- Solanum melongena worldwide. An effective strategy used in developing pest controlling agents is the synergism between insect pheromones and host plant volatiles, which can increase the attraction of insect pest. The present study was aimed at investigating the chemical constituents and attractant effects of the volatiles extracted from different parts of the host plant brinjal on the behavior of adult L. orbonalis. Bioassay using Y-shaped olfactometer revealed that the one-day old virgin female, gravid female and male insects respond positively to the host plant volatiles extracted from fruits, leaves and shoots but not to that of flowers. It was shown that the gravid females were significantly attracted to all three volatiles (p < 0.05). Bioassay using X-shaped olfactometer identified that all three types of insects highly preferred the volatiles from fruits (p < 0.05). Gas chromatography-mass spectrometry analysis of volatiles indicated that brinjal plant produces volatile secondary metabolites, which include 2,2'-(Ethane-1,2-diylbis(oxy))bis(ethane-2,1-diyl) dibenzoate (12.11%), 3,7-dimethylocta-1,6-dien-3-ol (22.38 %), Benzyl alcohol (22.9 %) and Benzyl alcohol (27.06 %) as major constituents from fruits, shoots, leaves and flowers respectively. Responses of insects to the volatiles from host plant in the absence of visual cues direct us to focus on the importance of host plant volatiles to locate the plant. Results of this study emphasize the major role that host plant volatiles play in the attraction of insect pests towards the plant.
... Studies has been showing that oviposition by herbivorous insects can induce indirect plant defense responses by volatiles emitted that attract egg parasitoids (Fatouros et al., 2005;Hilker and Meiners, 2006). The OIPVs provide early warning and chemical cues to the parasitoids toward colonized plants by their host and thus enhance their foraging efficacy (Bruce, 2010). Plants that produce OIPVs after to oviposition of pest insects, have the advantage for defending themselves early and before larval hatching reducing plant damage. ...
Plants not only respond to herbivorous damage but adjust their defense system after egg deposition by pest insects. Thereby, parasitoids use oviposition-induced plant volatiles to locate their hosts. We investigated the olfactory behavioral responses of Trichogramma pretiosum Riley, 1879 (Hymenoptera: Trichogrammatidae) to volatile blends emitted by maize ( Zea mays L.) with singular and stacked events after oviposition by Spodoptera frugiperda Smith, 1797 (Hymenoptera: Trichogrammatidae) moths. Additionally, we examined possible variations in gene expression and on oviposition-induced volatiles. We used a Y-tube olfactometer to test for the wasp responses to volatiles released by maize plants oviposited by S. frugiperda and not-oviposited plants. Using the real-time PCR technique (qRT-PCR), we analyzed the expression of lipoxygenase and three terpene synthases genes, which are enzymes involved in the synthesis of volatile compounds that attract parasitoids of S. frugiperda. Olfactometer tests showed that T. pretiosum is strongly attracted by volatiles from transgenic maize emitted by S. frugiperda oviposition (VTPRO 3, more than 75% individuals were attracted). The relative expression of genes TPS10, LOX e STC was higher in transgenic hybrids than in the conventional (isogenic line) hybrids. The GC-MS analysis revealed that some volatile compounds are released exclusively by transgenic maize. This study provides evidence that transgenic hybrids enhanced chemical cues under oviposition-induction and helped to increase T. pretiosum efficiency in S. frugiperda control. This finding shows that among the evaluated hybrids, genetically modified hybrids can improve the biological control programs, since they potentialize the egg parasitoid foraging, integrating pest management.
... Despite some methods have been proposed to control the disease, the most commonly used approach is chemical control with pesticides. Against the relative success achieved by the pesticide, intensive use of chemicals has led to negative effects on environmental health, it also causes pathogens to develop resistance to these chemicals (Vidaver, 2002;Bruce, 2010;Griffin et al., 2017). On the other hand, organic inputs promoting contribute to plant health and development are gaining increasing interest. ...
In this study, the effect of solid and liquid forms of vermicompost on plant growth and bacterial common blight disease in different growth media were investigated. Vermicompost was applied at the rate of 1/100, 1/150, 1/200 in liquid form and vermicompost in solid form at the rate of 10%, 20%, 40% to peat and soil growing medium. The pathogen, Xanthomonas axonopodis pv. phaseoli (Xap), was applied to the leaves by spraying at a concentration of 107 CFU mL-1. The effects of applications on plant growth parameters, total chlorophyll content, and disease severity were evaluated. It was determined that the effects of the applications varied according to vermicompost form and growth medium. Liquid vermicompost applications displayed more positive effects on root growth in the soil growing medium. However, the application of liquid vermicompost did not affect disease severity. It was observed that the 40% dose of vermicompost in solid form inhibited plant growth and caused chlorosis in both growth media. However, 10 and 20% of doses had no adverse effects on plant growth. Also, the application of 10% solid vermicompost to peat growing medium reduced the disease development by 48%. In soil growth medium, application doses of 10% and 20% prevented disease development by 62% and 54%.
... In addition, the adverse effects of the pesticide use on the environment and human health are well understood recently (McManus et al., 2002). The importance of biological control of plant diseases, especially the use of Endophytic bacteria (EB), one of the most promising biological control agents, is increasing day by day (Bruce, 2010). ...
Endophytic bacteria (EB) are ubiquitous in most plant species and they colonize plant tissues actively and systemically. Their colonization and persistence in the plant may be crucial to plant growth, yield and suppressing diseases. In this study, the long-term population dynamics of the two EB, namely Ochrobactrum spp. strain CB36/1 and Pantoea agglomerans strain CC37/2 in cucumber plants (Cucumis sativus L. cv. Gordion F1), were monitored. Also, the potential effects of these EB on plant growth, fruit quality, and yield, as well as the influences on Angular leaf spot disease of cucumber (ALS) and the yield under the disease pressure, were investigated. Plants were grown using the soilless cultivation technique in the greenhouse. Inoculation of the EB took place twice, and their population in plant tissues were monitored periodically for 62 days. Both EB isolates survived in plant organs until the end of the growing season, but over time, population densities dropped from 10⁵ to 10³ CFU g. plant⁻¹ with the age of the plant. The EB applications had significant effects on fruit length, color and firmness. Total yield increased by 22% with CB36/1 and 21% with CC37/2 without disease pressure. Only CC37 / 2 significantly reduced the severity of ALS disease by 41% and increased yield by 22% compared to pathogen treatment alone. In this study, it was observed that the EB strain CC37/2 might contribute to reducing the chemical input and prevent the yield losses in soilless growing systems within the integrated agricultural concept.
... Synthetic pesticides are one of the alternatives to reduce the incidences of pests in plants. Compared with other alternatives (i.e., resistant crop cultivars and biocontrol with natural enemies), synthetic pesticides provided a low control-cost with easy availability of products to farmers (BRUCE, 2010). The use of synthetic pesticides, seeds, and fertilizers are considered the main production costs in Brazilian agriculture (CENTRO DE PESQUISAS ECONÔMICAS, 2020; INSTITUTO MATO-GROSSENSE DE ECONOMIA AGROPECUÁRIA, 2020). ...
PERFORMANCE AND EFFICIENCY OF GLASS AND CARBON FIBER BARS FOR SELF-PROPELLED SPRAYERS DANILO FERNANDES ALBERNAZ1, RISELY FERRAZ-ALMEIDA1 1Luiz de Queiros College of Agriculture, Departament of Soil Sciente, University of São Paulo, Avenida Pauda Dias, 11, 13418-900, Piracicaba, São Paulo, Brazil, albernazdanilof@hotmail.com; rizely@gmail.com ABSTRACT: Agribusiness has a fundamental role in the Brazilian economy, responsible for stimulating the Gross Domestic Product, creating investment and development opportunities. High yields have been faced in pest-free areas in different crop regions. However, pest control with high efficiency is a challenge for many farmers. In this context, self-propelled sprayers with a high efficiency are necessary to increase the quality and speed of application with a direct decreasing equipment's operational cost. This work aims: (i) present the advantages of using carbon fiber booms in the performance of self-propelled sprayers; (ii) compare weight and fuel consumption of self-propelled sprayers with carbon fiber booms and conventional carbon steel booms. The results showed that the self-propelled sprayers with glass/carbon fiber boom presented better application performances, considered 6% more productive, 1.8% lighter, and 44% more economical in fuel consumption than the conventional carbon steel boom. Based on the results, the self-propelled glass/carbon fiber boom is a better alternative to increase agricultural spraying productivity. Keywords: efficiency of the application, carbon fiber, composite, fuel consumption. DESEMPENHO E EFICIÊNCIA DE BARRAS DE VIDRO E FIBRA DE CARBONO PARA PULVERIZADORES AUTO-PROPELIDO RESUMO: O agronegócio tem papel fundamental na economia brasileira com significante participação no Produto Interno Bruto, criando oportunidades de investimento e desenvolvimento no Brasil. Em todas as culturas, altas produtividades estão associadas a áreas livres de pragas, no entanto, o controle de pragas é um desafio para muitos agricultores. Nesse contexto, a escolha de pulverizadores eficientes para aplicação de pesticidas torna-se uma necessidade para aumentar a qualidade e velocidade da aplicação, e diminuir o custo operacional deste equipamento. Este trabalho tem como objetivos: (i) apresentar as vantagens do uso de barras de fibra de carbono no desempenho de pulverizadores; (ii) comparar o peso e o consumo de combustível de pulverizadores com barras de fibra de carbono, e pulverizadores com barras convencionais de aço carbono. Os resultados mostraram que os pulverizadores com barra de fibra de vidro/carbono apresentaram melhores desempenhos de aplicação, considerado 6% mais produtivo, 1,8% mais leve, e 44% mais econômico em consumo de combustível em comparação com a barra de aço carbono convencional. Portanto, pode-se concluir que para otimizar a pulverização de culturas agrícolas, a barra de fibra de vidro/carbono é uma alternativa mais eficiente para aumentar a produtividade na pulverização agrícola. Palavras-chaves: eficiência de aplicação, fibra de carbono, composto, consumo de combustível.
... The use of elicitors of plant defenses, or so-called plant activators, has been proposed as an alternative approach to chemical crop protection (Bruce 2010;Sobhy et al. 2014;Thaler et al. 2001;Vallad and Goodman 2004;Worrall et al. ...
Miridae is the largest Heteroptera family, with a tremendous worldwide economic impact, both as pests and natural enemies. Unlike most Hemiptera, herbivorous and omnivorous mirid bugs are lacerate/macerate and flush feeders, not phloem feeders. Plant responses to damage by arthropods of this feeding guild therefore occur via jasmonic acid or ethylene signaling pathways rather than the salicylic acid pathway. Moreover, unlike most other Heteroptera that lay eggs on the plant surface, mirids insert their eggs in plant tissues, resulting in oviposition injury. Similarly, regarding phytopathogenic fungi and oomycetes, a distinction should be made between biotrophic fungi (triggering the salicylic acid pathway plant response), and necrotrophic and/or hemibiotrophic fungi or oomycetes (triggering jasmonic acid or ethylene pathway plant responses). In that respect, phytopathogenic fungi or oomycetes (PFO) differ from phytopathogenic viruses and bacteria, the former being all biotrophic while the latter are theoretically hemibiotrophic. Here, for the first time, we review tripartite interactions between mirids, PFO, and crop plants. The major deliverables are as follows: Five major interaction frameworks are identified: (i) crop plant infection by PFO mechanically facilitated by prior mirid infestation; (ii) crop plant infection by PFO hampered by prior mirid infestation via crop plant signaling; (iii) crop plant infestation by mirids facilitated by prior PFO infection via crop plant signaling; (iv) crop plant infestation by mirids hampered by prior PFO infection via crop plant signaling; (v) crop plant infestation by mirids and/or infection by PFO hampered by prior mirid infestation and/or PFO infection via crop plant resource quality alteration. PFO and mirids may also occur concomitantly, favored by the same conditions, i.e., climatic or linked to endogeneous factors (e.g., redox status) in crop plant. Instances from each framework are described, and highlighted interactions are examined in view of managing mirid–PFO complexes on crop plants.
... Plants being sessile face many abiotic and biotic stresses from the natural environment. Biotic stresses coming from herbivores and pathogens are signi cant constraints that adversely affect plant growth and yield (Bruce, 2010). Plants have developed an intricate morphological, physiochemical and molecular defense mechanism to cope with herbivore attack (LIU et al., 2020;Palial et al., 2018;Tian et al., 2018). ...
Background: The cotton armyworm (Spodoptera litura) is one of the most devastating pests of many economically important crops including cotton which cause substantial yield losses due to its feeding pattern on leaves and other plant parts. Plants respond to herbivore damage through an array of defense responses to ensure their survival. This study was aimed to appraise biochemical defense responses of cotton genotypes to S. litura infestation.
Methods: Two Bt cotton cultivars namely Bt-886 and CIM-622 and one non-Bt PB-896 cultivar were used in the study. The experiment was conducted in greenhouse conditions. Leaf samples for biochemical analysis were collected after 24 hrs of infestation by third instar larvae.
Results: Data revealed that infestation caused significant reduction in chlorophyll pigments of all cultivars. Infestation caused a marked increase in hydrogen peroxide and malondialdehyde concentrations as well as activities of various antioxidant enzymes such as superoxide dismutase, peroxidase and catalase. The levels of other secondary metabolites such as phenolics, proline and glycine betaine were also found to be higher after infestation.
Conclusion: Among the cotton cultivars, cv. PB-896 was found to be considerably resistant to pest attack due to an efficient antioxidant system, lower chlorophyll degradation, and lesser accumulation of hydrogen peroxide and malondialdehyde that manifested minimal oxidative injury.
... Insect pest attack causes huge crop losses 1 affecting the potential availability of food for over one billion people 2 , and threatening global food security 3 . Effective pest management is critical to meeting global food demands [4][5][6] and synthetic insecticides have been the principal tool in the past six decades 7,8 . Even with the introduction of newer and relatively safer insecticides 8 and increased application per unit area and time 9 , crop loss resulting from insect damage has doubled in the past four decades 1,10,11 . ...
Besides providing food and shelter to natural enemies of crop pests, plants used in conservation biological control interventions potentially provide additional ecosystem services including providing botanical insecticides. Here we concurrently tested the strength of these two services from six non-crop plants in managing cabbage pests in Ghana over three successive field seasons. Crop margin plantings of Ageratum conyzoides, Tridax procumbens, Crotalaria juncea, Cymbopogon citratus, Lantana camara and Talinum triangulare were compared with a bare earth control in a three-way split plot design such that the crop in each plot was sprayed with either a 10% (w/v) aqueous extract from the border plant species, a negative control (water) and a positive control (emamectin benzoate ‘Attack’ insecticide). Pests were significantly less numerous in all unsprayed treatments with non-crop plant margins and in corresponding sprayed treatments (with botanical or synthetic insecticide positive control) while treatments with bare earth margin or sprayed with water (negative controls) had the highest pest densities. Numbers of predators were significantly depressed by synthetic insecticide but higher in other treatments whether unsprayed or sprayed with botanical insecticide. We conclude that some plant species have utility in both conservation biological control and as source of botanical insecticides that are relatively benign to natural enemies. In this crop system, however, the additional cost associated with using botanical insecticides was not justified by greater levels of pest suppression than achieved from border plants alone.
... They characterize the chemical landscape of various ecosystems wherein they mediate intraspecific and interspecific interactions (44). In some plants, these volatile compounds are the main compounds that are responsible for the attraction of insects, while in other plants attraction and recognition involve a blend of compounds released in specific ratios (45)(46). In response to particular host plant cues insects either produce or release sex pheromones; and chemicals from host plants often synergistically enhance the response of an insect to sex pheromones (32). ...
Leucinodes orbonalis Guenee, Brinjal fruit and shoot borer (BFSB), is the major pest on brinjal world wide. Larvae of this pest cause the damage; which at initial stages adversely affect the shoot growth, and in later stages diminish fruit quality. Spraying of insecticides is the main pest control method. This has been absolutely ineffective due to concealed habit of the larvae. Such a phenomenon apprehends to the development of insecticides resistance which demands continuously increasing doses. Manipulating the insect behavior using semiochemicals could be an opportunity for better management of insect pest. Application of BFSB sex pheromone components (E)-11-hexadecenyl acetate (E11-16: Ac) alone or in combination with (E)-11-hexadecen-1-ol (E11-16: OH) in traps can be used to suppress the populating growth. Goal-oriented interdisciplinary research on semiochemicals for sound administration of BFSB will depend on a better understanding of the key chemical ecology stimuli of relevance to the pest.
... Furthermore, there is an increasing restriction in the registration of conventional pesticides, which globally limits the future availability of active ingredients that are currently used for controlling crop pests (Birch et al., 2011). Thus, more sustainable and ecologically safer alternatives are urgently sought (Bruce, 2010). ...
In response to herbivory, plants synthesize and release variable mixtures of herbivore-induced plant volatiles (HIPVs) as indirect defense traits. Such induction of indirect plant defense can also be “switched on” by certain chemicals known as priming agents. Preceding work showed that the plant HIPV cis-jasmone (CJ) induced the emission of aphid defense-related volatiles affecting their behavioral response. However, little is known about the extent to which CJ-induced volatiles impacts aphid performance. In the current study, we conducted growth assays of potato aphids, Macrosiphum euphorbiae, observing their reproduction, development, and survival on CJ-primed potato plants. Adult M. euphoribae produced fewer neonates on CJ-treated plants compared to untreated plants. The weight and survival of M. euphorbiae reproduced neonates were significantly lower on CJ-treated plants. Additionally, there was a significant reduction in mean relative growth rate (MRGR) of M. euphoribae nymphs that fed on CJ-treated plants. Furthermore, the intrinsic rate of population increase (rm) of M. euphoribae was significantly reduced on CJ-treated plants. Volatile analysis showed that CJ treatment significantly increased the emission of differently assigned volatile groups that have functional or biosynthetic characteristics, i.e., alcohols, benzenoids, homoterpenes, ketones, and sesquiterpenes at all sampling periods. Such enhanced volatile emissions were persistent over 7 days, suggesting a long-lasting effect of CJ defense priming. A negative correlation was found between volatile emission and MRGR of M. euphoribae. Principal component analysis (PCA) of data for the volatiles showed that (Z)-3-hexen-1-ol, α-pinene, (E)-ocimene, (E)-4,8-dimethyl-1,3,7-nonatriene (DMNT), cis-jasmone, indole, and (E,E)-4,8,12-trimethyl-1,3,7,11-tridecatetraene (TMTT) were the main volatiles contributing to the emitted blends, suggesting possible involvement in the reduced performance of M. euphorbiae. Overall, our findings demonstrate that priming potato with CJ significantly results in elevated emission of known biologically active volatiles, which may negatively impact aphid settling and other performance traits on primed plants.
... Therefore, reducing the use of synthetic chemical pesticides and fertilizers is one of the challenges in modern society. Some of the strategies involved in sustainable crop production and integrated pest management include development of novel cultivars exhibiting disease resistance, abiotic stress tolerance, and high nutritional value, application of genetic engineering tools to develop non-legume crops participating in N-fixing symbioses, and the use of biological control agents and plant growth promoting rhizobacteria (PGPR) (Bruce, 2010;Ubertino et al., 2016;Gouda et al., 2018). The use of PGPR is one of the most promising tools for disease management in contemporary agriculture and an alternative that could minimize reliance on agrochemicals (Timmermann et al., 2017). ...
Symbiotic Rhizobium-legume associations are mediated by exchange of chemical signals that eventually result in the development of a nitrogen-fixing nodule. Such signal interactions are thought to be at the center of the plants’ capacity either to activate a defense response or to suppress the defense response to allow colonization by symbiotic bacteria. In addition, the colonization of plant roots by rhizobacteria activates an induced condition of improved defensive capacity in plants known as induced systemic resistance, based on “defense priming,” which protects unexposed plant tissues from biotic stress.Here, we demonstrate that inoculation of common bean plants with Rhizobium etli resulted in a robust resistance against Pseudomonas syringae pv. phaseolicola. Indeed, inoculation with R. etli was associated with a reduction in the lesion size caused by the pathogen and lower colony forming units compared to mock-inoculated plants. Activation of the induced resistance was associated with an accumulation of the reactive oxygen species superoxide anion (O2 ⁻) and a faster and stronger callose deposition. Transcription of defense related genes in plants treated with R. etli exhibit a pattern that is typical of the priming response. In addition, R. etli–primed plants developed a transgenerational defense memory and could produce offspring that were more resistant to halo blight disease. R. etli is a rhizobacteria that could reduce the proliferation of the virulent strain P. syringae pv. phaseolicola in common bean plants and should be considered as a potentially beneficial and eco-friendly tool in plant disease management.
... On the other hand, the pathogen has potential of the development of resistance against some chemicals which are used for controlling the disease (Griffin et al., 2017). Also, adverse effects of pesticide on the environment and human health are well understood (Bruce, 2010). Within this framework, alternative disease control methods and induced resistance in particular, have been gaining significant attention for their potential. ...
Abstract
Direct activation of induced resistance is recommended for the prolonged and effective control of plant diseases. However, there are some potential risks to this method in field application. The priming form of resistance has less risk; nevertheless, it is necessary to increase adaptation and efficacy. Recently, it was shown that the priming as a form of resistance mechanism in plants was transferred epigenetically. In our study, the use of this parentally-inherited resistance for disease control and the possibility of increasing resistance capacity were investigated. For this aim, plant growth parameters, population dynamics of Xanthomonas axonopodis pv. phaseoli (Xap), and severity and development of the common bean bacterial blight disease were investigated in the primed generation obtained from acibenzolar-S-methyl (ASM) treated parent bean. It was revealed that the primed progeny suppressed the disease by 11%, according to the area under the disease progress curve (AUDPC). Moreover, when the primed progeny were treated with a low dose of ASM (20 μM), they showed nearly twice the resistance capacity and suppressed the disease by 60%. In primed progeny, ASM treatment significantly slowed the development of Xap populations until the 14th day, also did not adverse effects on plant development. All these results indicated that seed production with this method offers the possibility of increasing the resistance capacity of later generations, just as it ensured the protection of parents. Thus, using the appropriate dose of activator at primed progeny will ensure that the efficacy of control methods is increased, while pesticide inputs can be reduced.
... 53 Thus, alternative answers to the excessive use of pesticides include the development of new resistant crop cultivars, the use of biological control agents, and the exploitation of plant activator agrochemicals, in combination with PGPR, to activate natural plant defenses. 54 Consequently, it is useful to explore the potential of using Rhizobium spp., in combination with BABA, for the targeted induction of systemic immunity against pathogens. For example, we tested if and how the combination of R. tropici CIAT899-GUS and BABA induces resistance in the common bean against P. syringae pv. ...
The symbiotic rhizobium–legume relationship is mediated by an exchange of chemical signals that ultimately result in the formation of a nitrogen fixation root-derived nodule. During establishment of the symbiotic process, Rhizobium bacteria trigger the jasmonic acid and ethylene-dependent response pathways, leading to induced systemic resistance (ISR). Application of β-aminobutyric acid induces resistance in common bean plants to pathogen infection, via systemic acquired resistance (SAR). Both pathways (ISR and SAR) display a faster and/or stronger activation of plant defense responses against a second stimulus. This physiological condition, known as “priming”, is associated with enhanced resistance to a broad spectrum of biotic and/or abiotic types of stress. We discuss the role of BABA as a priming agent and within the rhizobium–legume relationship, as well as its effect on the development of nitrogen-fixing root nodules, and suggest the use of BABA, to help produce, through breeding, new common bean varieties.
... Second-generation synthetic pesticides are useful for controlling pests, but they have many disadvantages (e.g., effects on human health, environmental damage, effects on beneficial organisms, evolution of resistance to the pesticide, elevated production costs, and risks to the environment, farmers, and consumers; Bai and Lindhout 2007;Bruce et al. 2016). Alternative answers to the use of pesticides include the development of new resistant crop cultivars, the use of biological control agents, the exploitation of plant activator agrochemicals to turn on natural plant defenses (Bruce 2010), and the use of genome engineering tools or gene editing, such as clustered, regularly interspaced, short palindromic repeat-CRISPR-associated protein (CRISPR-Cas). ...
Crop protection plays a central role in maintaining and increasing crop productivity. Many pathogens continue to affect crop production, however, and losses generated by pests must be halted. Thus, if farming is to support the human population, additional viable strategies for crop production and improved integrated pest management systems must be developed. Genome editing is an alternative to conventional breeding that can facilitate the molecular breeding of crops with desired properties. We propose here the implementation of targeted modification of epigenetic marks (epigenome editing via CRISPR activation or CRISPRa) to activate plant defense genes to confer resistance against pathogen attack. Work on CRISPRa in plants is lacking, although its potential application to crops is one of the greatest challenges in the field. Future exploitation of this approach in crop improvement programs will reduce important economic losses and benefit society.
... Drought and pathogen infections are two major types of stresses that result in significant reduction in plant growth and yield (Wang et al., 2003;Bruce, 2010;Maxmen, 2013;Hatfield and Walthall, 2015). Agricultural production will increasingly suffer from abiotic stresses, including drought (Melillo et al., 2014) and biotic stresses (Oerke, 2005;Fischer et al., 2009). ...
Insight into how plants simultaneously cope with multiple stresses, for example, when challenged with biotic stress from pathogen infection and abiotic stress from drought, is important both for understanding evolutionary trade‐offs and optimizing crop responses to these stresses. Mechanisms by which initial plant immune signaling antagonizes abscisic acid (ABA) signal transduction requires further investigation. Using a chemical genetics approach, the small molecule [5‐(3,4‐dichlorophenyl)furan‐2‐yl]‐piperidine‐1‐ylmethanethione (DFPM) has previously been identified due to its ability to suppress ABA signaling via plant immune signaling components. Here, we have used forward chemical genetics screening to identify DFPM‐insensitive loci by monitoring the activity of ABA‐inducible pRAB18::GFP in the presence of DFPM and ABA. The ability of DFPM to attenuate ABA signaling was reduced in rda mutants (resistant to DFPM inhibition of ABA signaling). One of the mutants, rda2, was mapped and is defective in a gene encoding a lectin receptor kinase. RDA2 functions in DFPM‐mediated inhibition of ABA‐mediated reporter expression. RDA2 is required for DFPM‐mediated activation of immune signaling including phosphorylation of MAP kinase 3 (MPK3) and MPK6 and induction of immunity marker genes. Our study identifies a previously uncharacterized receptor kinase gene that is important for DFPM‐mediated immune signaling and inhibition of abscisic acid signaling. We demonstrate that the lectin receptor kinase RDA2 is essential for perceiving the DFPM signal and activating MAP kinases, and that MKK4 and MKK5 are required for DFPM interference with ABA signal transduction.
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... Conventional pesticides are widely used in crop production and very effective against target organisms [1]. So, they are known to make risks and impacts on human health and environment [2]. ...
The leaching of a large amount of pollutants derived from agricultural and domestic activities (fertilizers, pesticides, detergents) might contaminate especially the aquatic environments affecting several non-target aquatic organisms such as crustacean species. The current study aimed to evaluate under laboratory conditions the potential side-effects of novaluron (20% Wettable Powder), a potent benzoylurea derivative insecticide on mosquito larvae, against a non-target shrimp, Palaemon adspersus Rathke, 1837 (Decapoda, Palaemonidae). This species is abundant in the lagoon El-Mellah (Northeast Algeria) and a relatively important species for the local fishery industry. The compound was tested at two concentrations (0.91 mg/L and 4.30 mg/L) corresponding respectively to the LC50 and LC90 determined against fourth-instar larvae of Culiseta longiareolata (Diptera, Culicidae). The newly ecdysed adult shrimps were exposed for 15 days, i.e. stage A until D during a moult cycle. Under normal conditions, changes in hemolymphatic ecdysteroid concentrations during the molting cycle presented a peak at stage D, just before the ecdysis while in the treated series, we note an increase in hemolymphatic ecdysteroid concentrations at stages C and D and an absence of the peak as compared to the controls. Histological observations of integuments revealed that novaluron caused a significant reduction in thickness of the new cuticle at its LC50 and an inhibition of the new cuticle secretion at its LC50. The determination of chitin amounts, showed that exposure of shrimps to novaluron resulted in a significant decrease of values at all molting stages with a dose-response manner in comparison to controls. Thus, the overall data confirm the primary mode of action of novaluron on chitin. This insecticide can
present secondary effects on this non-target shrimp species commercially important for the local economy.
... It proposes to use a combination of inducers and alternative control methods, such as implementing resistant cultivars, to effectively control T. urticae on bean plants. To control plant pests, inducers could serve as an environmentally friendly replacement to existing chemical compounds, which is suggested by relevant literature as an alternative method to protecting plants (Vallad & Goodman 2004;Bruce 2010). Because a low dosage of inducing compounds are needed to activate the plants' defense mechanisms and because the compounds do not interfere with the well-being of predators, they are being used successfully for managing plant pests. ...
In this study the effects of soil application of potassium phosphite, amino acid complex, and biolog siderophoric on the life table parameters of Tetranychus urticae have been investigated on bean plants, under laboratory conditions. The results revealed significant differences in the total developmental times, oviposition periods, and fecundity of T. urticae among the treatments. The shortest total developmental time and longevity was observed in biolog siderophoric treatment. The intrinsic rate of increase, the net reproductive rate, the finite rate of increase and the mean generation times of T. urticae were remarkably different among the treatments and lower than in the control. The lowest values of these parameters were observed in the biolog siderophoric treatment, which suggests that this inducer could be employed toward a sustainable management of T. urticae.
Crop protection is essential for maintaining and improving agricultural productivity. While pesticides are commonly used to control pests, they pose several challenges, including environmental harm and health risks. Alternative strategies to pesticides include breeding resistant crop varieties, biological control, and utilizing genome-editing tools like CRISPR/Cas. However, the application of epigenome editing, particularly CRISPR activation (CRISPRa), in plants remains underexplored. Phenylalanine ammonia-lyase (PAL), a key enzyme in the phenylpropanoid pathway, plays a pivotal role in plant defense by producing lignin and other secondary metabolites essential for pathogen resistance. In this study, we engineered tomato plants by fusing the SET-domain of the SlATX1 coding gene, a histone H3 lysine 4 tri-methyltransferase, to dCas12a, targeting the SlPAL2 promoter with the aim to increase PAL2 gene expression. CRISPRa-edited plants demonstrated increased deposition of the H3K4me3 epigenetic mark and significantly upregulated SlPAL2 expression. This enhanced lignin accumulation and conferred increased resistance to Clavibacter michiganensis subsp. michiganensis (Cmm) without significant reduction in plant height or fruit yield. Disease resistance was also associated with reduced pathogen load and lesion size, and higher lignin levels persisted even after SlPAL2 expression declined post-infection. These findings highlight the potential of CRISPRa for reprogramming plant defense responses through targeted histone modifications, offering a sustainable approach for crop improvement. Furthermore, CRISPRa could also be applied to enhance crop resilience in other contexts, such as addressing food security challenges by enhancing productivity.
Spatiotemporal modelling has received increased attention from entomologists as it meets various demands, from understanding ecological patterns to predicting pest outbreaks. Recent challenges from modern agriculture require efficient analytical methods to analyze population dynamics and insect movement patterns. Also, the efficacy of control actions and outbreak predictions depends on well-trained professionals properly employing models to guarantee successful management programs. This chapter aims to provide the reader with an overview of the diversity of analytical tools available for application in various scenarios, accompanied by examples of applications in entomology taxonomically classified by orders of insects.
Considered as economically significant pests with worldwide distribution, aphids feed on hundreds of cultivated and ornamental plants and cause considerable economic loss on a global scale.
The peach-potato aphid, Myzus persicae, is one of the most severe model aphid pests and successfully colonizes hundreds of plant species from 40 different families. It is a complex aphid pest known for its high reproductive rate, biotype formation, suppression of plant defenses, and wide range of host plants. This book covers ecological aspects - including life cycle, damage, and host range - which make aphids an economically important pest. A wide range of topics are covered, including ecological aspects of M. persicae; challenges with management approaches; damage; suppression of plant defenses; evolution; the mechanism of resistance against major classes of insecticides; the potential of biological control and natural plant-derived compounds (plant defense elicitors) as an alternative to the use of synthetic chemical insecticides to control M. persicae; and integrated pest management for M. persicae. As the peach-potato aphid is a model aphid pest, studying it helps to develop control strategies against the entire group of aphids.
Written for professionals, as well as students, teachers, and researchers in the fields of entomology, ecology, and bioscience, this book is an enriching new addition to its field.
This book presents the current approaches for insect pest control as a "green" alternative to classical and more toxaic agrochemicals. An overview of the recent advances in insecticide chemistry is also included, which will be of interest to a vast group of researchers - agrochemists, biochemists, chemists and toxicologists. The combination of both chemical and toxicological aspects of insecticides is unique and the book includes contributions from synthetic chemists, entomologists, environmentalists and toxicologists giving it wide appeal. Throughout the book, the different approaches that involve "greener chemicals" are emphasized. The book is divided into 9 chapters, each considering the state of art of each family of insecticides, together with future expectations. Each chapter gives a description of useful biorational insecticides, highlighting environmentally-friendly processes and then the mode of action is fully-described, emphasizing selectivity towards targeted species. Finally, for every family of compounds, their environmental effects (toxicity, bioaccumulation and metabolism) is considered, comparing them to classical insecticides, including human and environmental risk assessments. In addition the formulation, dispersal and persistence in the environment are covered as key aspects in developing greener agrochemicals. The book also includes a general introduction to entomology, with special emphasis on those insects that act as vectors in the spread of diseases. Insects that may be potential pests against humans and livestock are included, focusing on their life cycles, and physiology, as a logical comprehension of mode of action of insecticides. In addition there is a chapter on classical insecticides (covering both, approaches prior to the chemical era, and classical chemical insecticides, organochlorinated, organophosphorus, and carbamates) for comparison with current trends in pest control. The negative environmental effects that such insecticides have caused in nature, such as poisonings, bioaccumulation or toxic effects are highlighted. It is hoped that the use of more specific agrochemicals and approaches may avoid, or at least considerably reduce such severe and irreversible effects in nature. The insecticides covered are considered from numerous points of views: chemistry, toxicological profile, risk assessment, legal status, environmental behaviour and selectivity. The most important families of currently used insecticides are covered and critical discussions about future perspectives are included with frequent comparisons to classical insecticides. The following topics are covered in the book, as greener alternatives to classical insecticides: " Pyrethrins and pyrethroids " Neonicotinoids " Spynosins " Insect growth regulators " Botanical insecticides " Microbial insecticides " Integrated Pest Management Programs (IPM)
Plant resistance inducers (PRI) are emerged as a novel and prospective option to manage fungal diseases in agriculture, as they offer improved plant protection in an environmentally safe and economically sound manner. A galaxy of resistance inducing compounds of different origins have been reported and tested in different plant-pathogen systems. Published literature illustrate that the mechanism of action of PRI molecules differs from agrochemicals as they protect plant from pathogen via stimulating plant defense machinery. Moreover, resistance inducers can be integrated with biological control agents and even fungicides, which could result in reduced use of agrochemicals in agriculture. A plenty of biological control agents are identified and validated for field usages, but further expansion in product development and their effective deployment in wheat and other disease management will inevitably require in depth knowledge and understanding of multifaceted interactions operating between plant and microbe. The current review offers an overview of PRI’s that have been tested in wheat in order to activate wheat’s own defense system for attaining durable protection against fungal invasions. Additional attempts have been made to highlight the nature and applications of biological control based on induced resistance and their mechanism of action along with contemporary status and future developments with other measures of disease tactics in spatiotemporal manner.
Insect pests still cause substantial quantitative and qualitative grain loss ranging from 20 to 100% in small holder farming systems in tropical countries. Synthetic pesticides are recommended as stop gap measures for the management of stored product insect pests. However, their application has not been fully exploited in small scale farming due to environmental, health, and economic concerns. As a result, new researches have shifted focus to exploiting pesticidal plants as alternatives to synthetic pesticides. Therefore, the current study evaluated mixtures of plant powders and reduced amount of Actellic superTM (pirimiphos-methyl + permethrin) as alternative insecticide formulation against Callosobruchus chinensis and Sitophilus zeamais. Green grams and wheat grains were mixed with a mixture of plant powders in the ratios of 1:1, 1:3 and 1:9 to obtain four rates (0.0, 2.0, 6.0 and 10%w/w). Grains and plant powders were also mixed with reduced amount (10, 25, and 50 %) of recommended rate of Actellic SuperTM to obtain dosages as above. Twenty unsexed adults, 1-5 day old S. zeamais and C. chinensis were introduced into treated grains. The mixture of C. lusitanica: T. vogelii powders in the ratios of 1:1, 1:3 and 1:9 caused mortality in C. chinensis of 55, 95 and 85%, respectively. At the same ratio, E. saligna: L. camara mixture produced mortality in S. zeamais of 77, 82, and 85% respectively. In mixture of C. lusitanica and T. vogelii and reduced amount of Actellic SuperTM by 50% the mortality of C. chinensis was 85 and 80 % respectively. Similarly, E. saligna and L. camara and reduced amount of Actellic SuperTM by 50% caused a mortality of S. zeamais of 48 and 97% respectively. The application of plant powders and reduced amounts of synthetic insecticide has the potential to be applied in stored product pest control
Plants are biosystems, they made-up with cells, which are responsible for all biological actions as well as responding to their micro- and macro-environment. Therefore, environment has direct and indirect influence on plant growth and development. The global climatic changes have created many harmful effects on crop production systems. However, global population will increase by nine billions in 2050. As a result of that food production has to be increased by 70% than today because human and animals largely depend upon the plants derived foods. These goals can only be achieved through sustainable technological innovations to develop higher yielding, nutritionally rich crop cultivars with resistance to biotic and abiotic stress factors. In order to develop such resistance crop cultivars, proper understanding of systems biological approaches to find out genomics, transcriptomics, proteomics, and metabolomics regulators, signal molecules, and their functional attributes within the cells is essential. Present findings of biological researches highlighted that introduction of novel omics technologies has contributed immensely to overcome the many bottle neck drawbacks in the field of crop improvement. This chapter will discuss the potential roles of genomics, transcriptomics, proteomics, metabolomics, lipidomics, proteogenomics, ionomics, bioinformatics, prime-omics, miRNA omics, and phenomics in plant stress management.
Scientific literature pertaining to the investigations on insect–plant interactions spans more than a century. This is a challenging frontier area today as it was for the pioneers, and it would continue to be so for researchers in their pursuit to help elucidate the complex relationship between the insects and plants. Despite the ready availability of exhaustive literature on this subject, the mechanisms of insect–plant interactions are still not completely understood. Insect–plant interaction is an extremely rich subject that transcends several disciplines of science and has far-reaching implications, especially in the management of ecosystem and crop protection. The interaction between pests and plants starts at the interface of plasma membrane and in response to perception of a pest and release of herbivore-associated molecular patterns (HAMPs); plants respond quickly by setting up the electrical signalling followed by depolarization of membrane, leading to increase in Ca²⁺ ion concentration and activation of calcium-sensing proteins. Further, this interaction is primarily governed by various signalling mechanisms, such as mitogen-activated kinase (MAP-kinase), jasmonic acid (JA), salicylic acid (SA) and ethylene (ET)-based pathways that regulate changes in gene and protein expression leading to synthesis of defensive compounds. Plants defend themselves not only by direct means but also by indirect means, wherein plants emit volatiles to attract natural enemies of the herbivores. Herein, we summarize the molecular and ecological aspects of complex insect–plant interactions to enable researchers to direct their course of action towards addressing them for making a meaningful contribution in this field, which will have far reaching implications in the success of insect pest management programs.
The study of insect-plant interaction is a complex and dynamic process that employs multidimensional and multidisciplinary approaches. A comprehensive understanding of plant defense mechanisms against insect plunderer is fundamental, to build up a profitable and effective pest management strategy. In the last few decades, the technological evolution of various high-throughput omics technologies (i.e., genomics, transcriptomics, proteomics, metabolomics) enabled a qualitative as well as the quantitative record of several biological molecules. Transcriptomics involves genome-wide analysis studies that delineate gene expression pattern of cells and tissues. The extensive use of transcriptomics in the field of agriculture offers an excellent route of genomic research beyond traditional “model” organisms. It easily provides accessible and affordable data for almost any organism, both model and non-model plants, which can be exploited in developing pest-resistant crops. This chapter aims to summarize contemporary research conducted using transcriptomics techniques to decipher the mystery of insect-plant interaction along with a brief analysis of its limitations, technological expansion, and prospects of omics in solving the enigma of plant-insect interaction.
The Importance of Soil Fertility for Sustainable Agriculture:
The relationship between soil and man is approximately equivalent to human history. Mankind has achieved a large part of soil’s development, production, industry and economy with the soil, by cultivating and using it, and still continues to do so. However, it can be said that this important resource of ours has been threatened more than ever due to factors such as increasing population, landfilling of pollutants to soil and water, erosion and flooding. In order for our soil under these conditions to feed us and our generations after us, we need to use it more carefully more than it is. The meaning of careful soil using is to knowing soil properties such as physical, chemical and biological. These knowledges include performing some cultural practices such as planting, planting, fertilizing, tillage and contain processing carefully, consciously and without harming to the soil. In this review, the characteristics of soils, their importance and protection were discussed.
Mapping the distribution of crop pests and pathogens is essential to safeguard food security and sustainable livelihoods. However, these data are unavailable for many neglected and underutilised crops, particularly in developing countries. In Ethiopia, the world's largest historic recipient of food aid, the indigenous banana relative enset (Ensete ventricosum) is threatened by multiple pests and pathogens whilst providing the staple starch source for 20 million people. Foremost among these is Xanthomonas Wilt of enset (EXW), caused by Xanthomonas vasicola pv. musacearum (Xvm), a globally important disease of bananas (Musa sp.) that likely originated in enset. Here we collate 1069 farm surveys to map the distribution and relative prevalence of enset pests and pathogens across the entire enset growing region. We find that EXW is the most frequently encountered pathogen, and that farmers consistently ranked EXW as the most significant constraint on enset agriculture. Our surveys also showed that corm rot, and the pests root mealybug, mole rat and porcupine are all virtually ubiquitous. Finally, we apply genotyping-by-sequencing to the detection of Xvm and demonstrate that it is present even in asymptomatic domesticated and wild enset samples, suggesting that management of plants displaying symptoms alone may not be sufficient to reduce disease transmission. Holistic understanding of pests and pathogen distributions in enset may have significant benefits for both food security in Ethiopia, and preventing proliferation in related crops such as banana across central and east Africa.
The quest for a sustainable agriculture requires a reduction in the use of synthetic inputs. In this perspective, agroecology seeks to use interactions between organisms in the agroecosystem to replace inputs by ecosystem services, such as the natural regulation of pests and diseases. In this context, this thesis studies the effect of crop fertilization on epidemics of crop fungal foliar pathogens. We also take into account the evolution of these pathogens in response to fertilization scenarios. This allows us to study the sustainability of agricultural practices that contribute to the regulation of epidemics. To answer these questions, we adopted a modelling approach that simulates the effect of different fertilization scenarios. The starting point and originality of our approach was to consider the pathosystem as a consumer-resource system and to use concepts of evolutionary ecology to answer the abovementioned agronomic questions. In the two models developed in this thesis, fertilization directly determines the quantity of resources available for the pathogen. We focus on one of the pathogen's life history traits, the latent period (time period between infection and the onset of sporulating lesions), which corresponds to the minimum duration of an infectious cycle and constrains the pathogen's resource allocation strategy. The latent period determines the amount of resource that will be allocated to either growth of mycelium (and therefore to pathogen size at maturity) or to sporulation (proportional to the pathogen’s size). The models we developed make it possible to study the epidemiological and evolutionary responses of fungal foliar pathogens to crop fertilization. We parameterized our models according to our biological knowledge of the wheat-rust pathosystem. Our modelling work encompasses different spatial and temporal scales: from the lesion where the pathogen feeds directly on its host, to the field and the landscape where the spores that flow between fields are the source of epidemics in the agroecosystem. The first model, at the intersection of the "SEIR" epidemiological models and structured population models, covers the scales of a lesion, the crop canopy and the field. The second model, at the intersection of SEIR and spatial landscape epidemiology models, covers the scales of the field and the agricultural landscape. We study epidemiological and evolutionary dynamics of pathogen populations by comparing empirical and invasion fitness concepts. We show that crop fertilization, by determining the dynamics of available resources for pathogens, has a strong impact on foliar fungal epidemics. Our models predict that pathogen latent period evolves in response to various ecological trade-offs; on the one hand to optimize resources allocation at the leaf scale, on the other hand to win the race against canopy growth. By changing the leaf metabolite content and the rate of canopy growth, fertilization therefore impacts both epidemics and evolutionary responses of pathogen latent period. At the landscape scale, the introduction of various fertilization practices in a previously homogeneous landscape could help to partially regulate epidemics. However, our model predicts that the beneficial effects of heterogeneity will vanish due to the evolution and diversification of pathogens in heterogeneous landscapes. This work sets the stage for further work on the effect and sustainability of agricultural practices on the regulation of crop epidemics in agroecosystems. Finally, by performing a meta-analysis, we bring out a strong relation between pathogen trophic type and latent period, suggesting that different trophic types of pathogens will respond differently to decreasing fertilization scenarios
Plants possess a range of defenses that can be actively expressed in response to pathogens and parasites of various scales, ranging from microscopic viruses to insect herbivores. The timing of these defense responses is critical and can be the difference between being able to cope or succumbing to the challenge of a pathogen or parasite. Systemic acquired resistance (SAR) and induced systemic resistance (ISR) are two forms of induced resistance; in both SAR and ISR, plant defenses are preconditioned by prior infection or treatment that results in resistance (or tolerance) against subsequent challenge by a pathogen or parasite. Great strides have been made over the past 20 yr in understanding the physiological and biochemical basis of SAR and ISR. Much of this knowledge is due to the identification of a number of chemical and biological elicitors, some of which are commercially available for use in conventional agriculture. However, the effectiveness of these elicitors to induce SAR and ISR as a practical means to control various plant diseases is just being realized. In this review, we first briefly summarize the fundamentals of ISR and SAR, for which a number of critical reviews already exist. We then examine the efficacy of SAR and ISR in published field-based studies. We place special emphasis on the benefits, drawbacks, and future considerations for the improved use of chemical and biological elicitors of induced resistance in conventional agriculture; this includes the potential to exploit genetic variability within populations of crop species to improve the utility of SAR and ISR in the field.
Learning from successes in agricultural development is now more urgent than ever. Progress in feeding the world’s billions has slowed, while the challenge of meeting future food needs remains enormous and is subject to new uncertainties in the global food and agricultural systems. In the late 1950s around a billion people were estimated to go hungry every day. Scientists, policymakers, farmers, and ordinary people initiated a concerted push to boost agricultural production and productivity in developing countries. Great strides were also made in improving the quality of food and the ability of vulnerable people to access food needed for survival. All these efforts have done more than just feed millions. They have also demonstrated that agriculture can be a key driver of growth and development for many of the world’s poorest countries.
Populations of grasses exposed to grazing by vertebrates often exhibit reduced stature, increased tillering, reduced flowering,
and other morphological differences which distinguish them from ungrazed populations. These differences frequently are interpreted
as an adaptive response that reduces grazing damage; however, there are few experimental tests of this hypothesis. This paper
describes a field experiment designed to determine whether morphological variation among genotypes of the grass Bouteloua gracilis is related to variation in their responses to grazing. Eleven genotypes differing in morphological and reproductive characters
were transplanted into a shortgrass steppe community near Fort Collins, Colorado. Replicates of each genotype were subjected
to clipping treatments intended to realistically simulate three grazing intensities. After two growing seasons, different
genotypes still maintained significant differences in a wide range of morphological and demographic characters. However, there
were few significant effects of grazing treatment, and no significant genotype×treatment interactions. These results suggest
that for B. gracilis clipped in simulation of natural grazing, defoliation has few short-term effects on fitness components, and intrapopulation
morphological variation has few consequences for defoliation resistance.
The possibility of communication between plants was proposed nearly 20 years ago, although previous demonstrations have suffered from methodological problems and have not been widely accepted. Here we report the first rigorous, experimental evidence demonstrating that undamaged plants respond to cues released by neighbors to induce higher levels of resistance against herbivores in nature. Sagebrush plants that were clipped in the field released a pulse of an epimer of methyl jasmonate that has been shown to be a volatile signal capable of inducing resistance in wild tobacco. Wild tobacco plants with clipped sagebrush neighbors had increased levels of the putative defensive oxidative enzyme, polyphenol oxidase, relative to control tobacco plants with unclipped sagebrush neighbors. Tobacco plants near clipped sagebrush experienced greatly reduced levels of leaf damage by grasshoppers and cutworms during three field seasons compared to unclipped controls. This result was not caused by an altered light regime experienced by tobacco near clipped neighbors. Barriers to soil contact between tobacco and sagebrush did not reduce the difference in leaf damage although barriers that blocked air contact negated the effect.
Elucidating the chemical ecology of natural enemies, herbivores and host plants is important in the development of effective and successful integrated pest management (IPM) strategies where abundance and distribution of natural enemies could be manipulated by semiochemicals for improved conservation biological control (CBC). In response to attack by herbivores, plants produce semiochemicals called Herbivore-Induced Plant Volatiles (HIPVs) which act to repel pests and attract their natural enemies. Damaged, and in some cases, intact plants may also produce volatile signals that warn other plants of impending attack. Some of these intact plants are used as intercrops in ‘push–pull’ strategies; cropping systems based on stimulo-deterrent principle, where the target crop is intercropped with herbivore repellent plants (push) while attractant plants (pull) are planted around this intercrop. The intercrop, in addition to repelling the herbivores, attracts and conserves natural enemies thereby ensuring continued suppression of the pests. This natural delivery of semiochemicals for CBC is currently being exploited by smallholder farmers in eastern Africa in the management of cereal stemborers in maize and sorghum. Synthetic HIPVs also have the potential to effectively recruit natural enemies, thereby improving CBC as has been demonstrated in a series of field experiments in vineyards and hop yards in the Pacific Northwest of the United States. Potentially, plants could be ‘turned on’ by synthetic HIPV signals, and therefore become sources of natural enemy-recruiting volatiles. With the rapid development of plant molecular biology, modification of secondary plant metabolism is also possible which could allow appropriate semiochemicals to be generated by plants at certain growth stages. By identifying the promoter sequences associated with external plant signals that induce biochemical pathways, plant defense genes could be ‘switched on’ prior to insect attack. We review recent research on ‘push–pull’ strategies and synthetic HIPVs in recruitment of beneficial arthropods and warding off pest attack.
Plants may “eavesdrop” on volatile organic compounds (VOCs) released by herbivore-attacked neighbors to activate defenses
before being attacked themselves. Transcriptome and signal cascade analyses of VOC-exposed plants suggest that plants eavesdrop
to prime direct and indirect defenses and to hone competitive abilities. Advances in research on VOC biosynthesis and perception
have facilitated the production of plants that are genetically “deaf” to particular VOCs or “mute” in elements of their volatile
vocabulary. Such plants, together with advances in VOC analytical instrumentation, will allow researchers to determine whether
fluency enhances the fitness of plants in natural communities.
Continuing population and consumption growth will mean that the global demand for food will increase for at least another 40 years. Growing competition for land, water, and energy, in addition to the overexploitation of fisheries, will affect our ability to produce food, as will the urgent requirement to reduce the impact of the food system on the environment. The effects of climate change are a further threat. But the world can produce more food and can ensure that it is used more efficiently and equitably. A multifaceted and linked global strategy is needed to ensure sustainable and equitable food security, different components of which are explored here.
Due to the inherent difficulties associated with gene delivery into regenerable explants and recovery of plantlets with the introduced transgene, wheat was the last among cereals to be genetically transformed. This review attempts to summarize different efforts in the direction of achieving genetic transformation of wheat by various methods. Particle bombardment is the most widely employed procedure for the introduction of marker genes and also for the generation of transformed wheat with introduction of agronomically important genes for quality improvement, engineering of nuclear male sterility, transposon tagging, resistance to drought stress, resistance against fungal pathogens and insect resistance. The other methods of choice of gene delivery into wheat tissues include electroporation and co-cultivation with Agrobacterium . Several alternative approaches including microinjection, direct imbibition, permeabilization, silicon carbide fiber-mediated and pollen tube pathway have also been attempted for introduction of foreign DNA with varied degrees of success. In future, use of marker assisted selection and genomics approaches will increase the effectiveness and efficiency of wheat breeding programs, and will also provide insights into genetic control of key traits to be used for genetic manipulation.
Feeding by herbivores induces plant defences, but we still do not know all the signals that mediate this response. Here, I argue that a general principle in this mediation is 'damaged-self recognition', that is, the perception of motifs by the plant that indicate disintegrated plant cells. Most defence-inducing molecules are (or contain) plant-derived motifs or disintegrate plant cells and thereby release defence elicitors. By perceiving the 'damaged self', plants can retain evolutionary control over their interactions with herbivores rather than allowing herbivores to dominate the interaction. The concept of 'damaged-self recognition' provides a paradigm for plant responses to herbivory and helps the search for the currently unknown elicitors of those defence responses, which have so far only been described at the phenotypic level.
Plant resistance to herbivores was induced in a field experiment to evaluate the consequences of induced responses for subsequent
herbivory and plant fitness. Induction early in the season resulted in halving of herbivory by chewing herbivores and a reduction
in the abundance of phloem-feeding aphids when compared with controls. A correlate of lifetime plant fitness, seed mass, was
enhanced by over 60 percent for individuals that were induced.
The plant-signaling molecules salicylic acid (SA) and jasmonic acid (JA) play an important role in induced disease resistance pathways. Cross-talk between SA- and JA-dependent pathways can result in inhibition of JA-mediated defense responses. We investigated possible antagonistic interactions between the SA-dependent systemic acquired resistance (SAR) pathway, which is induced upon pathogen infection, and the JA-dependent induced systemic resistance (ISR) pathway, which is triggered by nonpathogenic Pseudomonas rhizobacteria. In Arabidopsis thaliana, SAR and ISR are effective against a broad spectrum of pathogens, including the foliar pathogen Pseudomonas syringae pv. tomato (Pst). Simultaneous activation of SAR and ISR resulted in an additive effect on the level of induced protection against Pst. In Arabidopsis genotypes that are blocked in either SAR or ISR, this additive effect was not evident. Moreover, induction of ISR did not affect the expression of the SAR marker gene PR-1 in plants expressing SAR. Together, these observations demonstrate that the SAR and the ISR pathway are compatible and that there is no significant cross-talk between these pathways. SAR and ISR both require the key regulatory protein NPR1. Plants expressing both types of induced resistance did not show elevated Npr1 transcript levels, indicating that the constitutive level of NPR1 is sufficient to facilitate simultaneous expression of SAR and ISR. These results suggest that the enhanced level of protection is established through parallel activation of complementary, NPR1-dependent defense responses that are both active against Pst. Therefore, combining SAR and ISR provides an attractive tool for the improvement of disease control.
The interactions of two economically important gall midge species, the rice gall midge and the Hessian fly, with their host plants, rice and wheat, respectively, are characterized by plant defense via R genes and insect adaptation via avr genes. The interaction of a third gall midge species, the orange wheat blossom midge, with wheat defense R genes has not yet exhibited insect adaptation. Because of the simple genetics underlying important aspects of these gall midge-grass interactions, a unique opportunity exists for integrating plant and insect molecular genetics with coevolutionary ecology. We present an overview of some genetic, physiological, behavioral, and ecological studies that will contribute to this integration and point to areas in need of study.
When attacked by herbivorous insects or mites, some plant species call on other arthropods for help. They emit mixtures of volatile compounds, dominated by terpenes, to attract carnivorous arthropods that prey on or parasitise herbivores and so reduce further damage. This fascinating defence strategy offers a new, environmentally friendly approach to crop protection. Using recent advances in the biochemistry and molecular genetics of terpene biosynthesis, it should now be possible to engineer crop plants that release terpenes for attracting herbivore enemies. By introducing or selectively altering the existing rate of terpene emission and composition, plant breeders could enable attacked plants to attract enemies and reduce additional herbivory, without compromising the effectiveness of other modes of defence.
This paper examines induced resistance (SAR) in plants against various insect and pathogenic invaders. SAR confers quantitative protection against a broad spectrum of microorganisms in a manner comparable to immunization in mammals, although the underlying mechanisms differ. Discussed here are the molecular events underlying SAR: the mechanisms involved in SAR, including lignification and other structural barriers, pathogenesis-related proteins and their expression, and the signals for SAR including salicylic acid. Recent findings on the biological role of systemin, ethylene, jasmonates, and electrical signals are reviewed. Chemical activators of SAR comprise inorganic compounds, natural compounds, and synthetic compounds. Plants known to exhibit SAR and induced systemic resistance are listed.
Induced resistance protects plants against a wide spectrum of diseases; however, it can also entail costs due to the allocation of resources or toxicity of defensive products. The cellular defense responses involved in induced resistance are either activated directly or primed for augmented expression upon pathogen attack. Priming for defense may combine the advantages of enhanced disease protection and low costs. In this study, we have compared the costs and benefits of priming to those of induced direct defense in Arabidopsis. In the absence of pathogen infection, chemical priming by low doses of β-aminobutyric acid caused minor reductions in relative growth rate and had no effect on seed production, whereas induction of direct defense by high doses of β-aminobutyric acid or benzothiadiazole strongly affected both fitness parameters. These costs were defense-related, because the salicylic acid-insensitive defense mutant npr1-1 remained unaffected by these treatments. Furthermore, the constitutive priming mutant edr1-1 displayed only slightly lower levels of fitness than wild-type plants and performed considerably better than the constitutively activated defense mutant cpr1-1. Hence, priming involves less fitness costs than induced direct defense. Upon infection by Pseudomonas syringae or Hyaloperonospora parasitica, priming conferred levels of disease protection that almost equaled the protection in benzothiadiazole-treated wild-type plants and cpr1 plants. Under these conditions, primed plants displayed significantly higher levels of fitness than noninduced plants and plants expressing chemically or cpr1-induced direct defense. Collectively, our results indicate that the benefits of priming-mediated resistance outweigh the costs in environments in which disease occurs.
• induced resistance
• innate immunity
• plant defense
Food security and environmental conservation are two of the greatest challenges facing the world today. It is predicted that food production must increase by at least 70% before 2050 to support continued population growth, though the size of the world's agricultural area will remain essentially unchanged. This updated and thoroughly revised second edition provides in-depth coverage of the impact of environmental conditions and management on crops, resource requirements for productivity and effects on soil resources. The approach is explanatory and integrative, with a firm basis in environmental physics, soils, physiology and morphology. System concepts are explored in detail throughout the book, giving emphasis to quantitative approaches, management strategies and tactics employed by farmers, and associated environmental issues. Drawing on key examples and highlighting the role of science, technology and economic conditions in determining management strategies, this book is suitable for agriculturalists, ecologists and environmental scientists.
The links between food attributes, food consumption and utilization, and subsequent insect performance are a primary focus of insect nutritional ecology. Development of effective host plant resistance (HPR) tactics requires an understanding of these links to successfully manipulate insect pest performance. Thus, the principles of insect nutritional ecology provide a logical basis for research in HPR. Nutritional, allelochemical and morphological attributes of crop plants may be altered through selective breeding, biotechnology and cultural practices to affect target pest biochemistry, physiology and behavior, including food consumption, digestion and absorption, conversion to biomass, metabolism, detoxication, sequestration and excretion. These actions are designed to reduce crop damage by deleteriously affecting insect performance; lowered consumption, slowed growth and reduced weight gain increase mortality and decrease reproduction in survivors. Responses by the target pest (e.g., detoxication enzyme induction and increased food consumption) may act to counter certain HPR tactics, but additional tactics may derive from manipulating these responses. Use of a single plant attribute to cause heavy mortality associated with a genetically simple mechanism in the target insect (e.g., an allelochemical toxin in the plant acting analogous to a synthetic insecticide applied to the crop), is likely to lead to relatively rapid evolution of resistance in the pest population to the HPR tactic. A better strategy for maintaining long-term effectiveness of resistant crop varieties (i.e., slowing the development of resistance in the target pests to our HPR efforts) should probably involve multiple HPR tactics, especially if deployed within a genetically diverse crop variety (such that the plants in a crop field differ in the extent of expression of the various attributes serving as resistance factors) and/or by alternating in subsequent plantings crop varieties manifesting different resistance factors. Also, HPR tactics should be used which require genetically complex alterations in physiology and behavior for an insect to evolve resistance. /// El eslabón entre los atributos de alimentos, consumo de comida y utilización, y el subsequente comportamiento del insecto, son el foco principal de la ecología nutricional del insecto. El desarrollo de tácticas efectivas de un program de resistencia de plantas hospederas requiere un entendimiento de estos eslabones para manipular con éxito el comportamiento de la plaga de insecto. De aquí que los principios de la ecología nutricional de insectos provee una base lógica para hacer investigaciones sobre resistencia de plantas hospederas. Atributos nutricionales, aleloquímicos y morfológicos de plantas de cultivo pueden ser alterados por fitomejoramiento selectivo, la biotecnología o por prácticas culturales que afectan la bioquímica, la fisiología y el comportamiento, incluyendo el consumo de alimentos, la digestión, y la absorción, la conversión a masa biológica, el metabolismo, detoxificación, reclusión y excreción, de la plaga señalada. Estas accions están diseñadas para reducir los daños al cuitivo por la acción dañina al comportamiento del insecto; el consumo menor, el crecimiento retardado y el reducido aumento de peso, aumenta la mortandad y disminuye la reproducción en los sobrevivientes. La reacción de la plaga escogida (tal como la inducción de enzimas detoxicantes y el aumento del consumo de alimentos) pueden actuar para contrarrestar ciertas tácticas de resistencia de plantas hospederas, pero se pudieran derivar otras tácticas manipulando esas reacciones. El uso de un solo atributo de la planta que cause una gran mortandad asociada con un mecanismo genético simple en el insecto escogido (tal como una toxina aleloquímica en la planta que actue análoga a un insecticida sintético aplicado al cultivo), es probable que lleve a una evolución rápida el desarrollo de resistencia en la población de la plaga hacia la táctica de resistencia de planta hospedera. Una estrategia mejor para mantener una efectividad más duradera de las variedades resistentes (tal como demorando el desarrollo de resistencia de la plaga escogida como blanco de nuestros esfuerzos en la resistencia de plantas hospderas) probablemente deben de incluir varias tácticas de resistencia de plantas hospederas, especialmente si es desplegada dentro de una variedad geneticamente diversa (tal como que las. plantaa en el campo difieren en la expresión de los varios atributos que sirven como factores de resistencia) y/o alternando la siembra de variedades que manifiestan distintos factores de resistencia. También deben de usarse táticas de resistencia de plantas hospederas que requieran complejas alteraciones genéticas fisiológicas y de comportamiento para impedir que el insecto desarrolle resistencia.
During 1989 and 1990, field studies were conducted to determine effects of cypermethrin and sulprofos, which are used for control of Heliothis virescens and Helicoverpa zea in cotton, on outbreaks of cotton aphid, Aphis gossypii Glover. During 1989, cotton aphid outbreaks occurred in both insecticide-treated and untreated plots. However, aphid densities were greatest in the sulprofos-treated plots and lowest in the cypermethrin-treated plots, even though insecticide-induced aphid mortality could not be detected in either treatment. In 1990, sulprofos-treated plots contained the most aphids, but unlike 1989, the untreated plots had the fewest aphids. Rates of aphid parasitism by Lysiphlebus testaceipes (Cresson) were low in 1989 and 1990, and aphidopathogenic fungus infections were common only late in the season during 1990. Parasitism and fungal infections were most common in the sulprofos-treated plots, which contained the most aphids. Sulprofos-induced cotton aphid outbreaks could not be attributed entirely to the destruction of natural enemies. Late-season growth and fruiting patterns of the cotton plants indicated that sulprofos-treated plants continued active growth after the plants in the other treatments had begun to senesce. Furthermore, higher concentrations of the amino acid threonine and total essential amino acids were detected in the plant sap of sulprofos-treated cotton plants. Sulprofos may have contributed indirectly to aphid outbreaks by altering the biochemistry of the plant in a way that better suited the aphid's nutritional requirements, thus increasing aphid population growth.
Genetically engineering inherent crop resistance to insect pests offers the potential of a user-friendly, environment-friendly and consumer-friendly method of crop protection to meet the demands of sustainable agriculture in the 21st century. Work to date has concentrated on the introduction of genes for expression of modified Bacillus thuringiensis (Bt) toxins. Impressive results on the control of Bt-susceptible pests have been obtained in the laboratory and the field, and the first commercial Bt transgenic crops are now in use. A main alternative approach exploits plant-derived insect control genes. Enhanced resistance to a wide spectrum of pests has been demonstrated in laboratory trials of transgenics expressing various protease inhibitors, lectins, etc. and some promising field trials have been carried out, but the scale of effects produced by plant-derived insect control genes has not been deemed convincing enough to lead to serious attempts at commercialization. Both classes of compounds have limitations: there have been serious failures in resistance to targeted pests in Bt cotton; most plant-derived resistance factors produce chronic rather than acute effects; and many serious pests are simply not susceptible to known resistance factors. We have analysed the characteristics which would be desirable in an ideal transgenic technology: these include being environmentally benign, relatively inexpensive to develop, with a potentially wide spectrum of activity (although targetable at pests and not beneficials), generated by a flexible technology that allows any insect site to be targeted and readily adaptable so that alternatives can be produced as required. We are developing such a technology based on the expression of single-chain antibody genes in crop plants which would be compatible with the likely trends in pesticide discovery using biology-driven target-based methods. The importance of a changed, more socially responsible attitude in this sector is emphasised as is the need for much improved presentation of the benefits and need for responsible deployment of genetically engineered crops.
Plants can be treated with natural plant elicitors to induce resistance to herbivores. To use elicitors in agriculture we must know the net effects of induction on plant yield. For 4 yr, I induced plant resistance to insect herbivores in tomato plants using the natural plant hormone jasmonic acid. Foliar jasmonic acid application increased levels of polyphenol oxidase, an oxidative enzyme implicated in resistance against several insect herbivores. Induced plants received 60% less leaf damage than did control plants. I then looked at the effects of this induction on seedling survivorship, phenology, fruit production, and plant biomass in the presence and absence of herbivores. Induced plants produced fewer flowers than control plants, but this did not translate into differences in yield between treatments. In addition, there was no difference in yield between induced and control plants under natural and experimentally reduced herbivore levels. This lack of effect on yield may have been caused by low levels of herbivory in the unmanipulated controls. Thus, it appears that jasmonic acid induces resistance in tomato plants and that this resistance produces no measurable costs to tomato plants. Elicitors such as jasmonic acid may be valuable pest management tools, especially when there are high densities of herbivores that can reduce yield.
The idea that plants might be able to develop a form of acquired immunity to infection following exposure to a pathogen has been current ever since discovery of the animal immune system in the later years of the nineteenth century. Early attempts to demonstrate a comparable system in plants focused on the detection of precipitating antibodies and hence were doomed to failure. Nevertheless, largely anecdotal evidence for plant immunisation continued to accumulate, culminating in the discovery of phytoalexins in the 1940s. Convincing evidence for systemic changes in plant resistance following an inducer inoculation was not available until 20 years later, when pioneering work on tobacco infected with blue mould (Peronospora tabacina) or tobacco mosaic virus (TMV) showed that tissues remote from the inoculation site were altered in disease reaction type. Increased resistance was expressed as a reduction in lesion numbers and size, and a reduced rate of pathogen reproduction. Systemic acquired resistance (SAR) has now been demonstrated in at least 20 plant species in at least six plant families, although detailed genetic or molecular analysis has mainly been confined to a few models, such as tobacco, cucumber and Arabidopsis. SAR is associated with the coordinate induction of genes encoding defence proteins which can be used as molecular markers of the response. The availability of Arabidopsis mutants altered in the induction and expression of SAR is now providing new insights into the signal transduction pathway(s) involved, and will enable comparison with the molecular mechanisms operating in other plant taxa. Important unresolved questions concern the nature of the translocated signal, the mechanism of defence ‘priming’, efficacy of the response against different pathogens, and practical exploitation of SAR in crop protection. The first generation of chemical plant defence activators is now commercially available and optimal use of these SAR inducers in integrated disease control requires further evaluation. The prospects for engineering transgenic crops altered in the regulation or expression of SAR is also a subject for further investigation.© 1999 Society of Chemical Industry
The ‘push–pull’ technology (PPT), developed in Africa, offers effective control of cereal stemborers and Striga weed in maize-based cropping systems. It involves intercropping maize with desmodium, Desmodium uncinatum, with Napier grass, Pennisetum purpureum, planted as border around this intercrop. Desmodium repels the stemborer moths (push) that are subsequently attracted to the Napier grass (pull). Desmodium also suppresses and eliminates Striga. We assessed economic performance of this technology compared to the conventional maize mono- and maize–bean intercropping systems in six districts in western Kenya over 4–7 years. Ten farmers were randomly recruited in each district and each planted three plots representing the three cropping systems. The cost–benefit analyses were carried out, together with the systems’ net returns to land and labour and their discounted net present values (NPV). Maize grain yields and associated gross margins from the PPT system were significantly higher than those in the other two systems. Although the production costs were significantly higher in the PPT than in the two cropping systems in the first cropping year, these reduced to either the same level or significantly lower than in the maize–bean intercrop from the second year onwards in most of the districts. Similarly, the net returns to land and labour with the PPT were significantly higher than with the other two systems. The PPT consistently produced positive NPV when the incremental flows of its benefits compared to those of the two conventional systems were discounted at 10–30%, indicating that PPT is more profitable than the other two systems under realistic production assumptions. PPT is thus a viable option for enhancing productivity and diversification for smallholder farmers who largely depend on limited land resource. Hence, enhancing farmers’ access to less costly planting materials and promoting quality education and training in the use of this knowledge-intensive technology could stimulate its successful adoption.
The levels of resistance to shoot fly, Atherigona soccata in sorghum germplasm are low to moderate and therefore, we evaluated 17 wild relatives of sorghum under field and greenhouse conditions as an alternate source of genes for resistance to this pest. Thirty-two accessions belonging to Parasorghum, Stiposorghum and Heterosorghum did not suffer any shoot fly damage under multi-choice conditions in the field, while one accession each of Heterosorghum (Sorghum laxiflorum) and Chaetosorghum (S. macrospermum) suffered very low shoot fly damage. Accessions belonging to S. exstans (TRC 243601), S. stipoideum (TRC 243399) and S. matarankense (TRC 243576) showed absolute non-preference for oviposition under no-choice conditions. Accessions belonging to Heterosorghum, Parasorghum and Stiposorghum were preferred for oviposition, but suffered low deadheart formation. Manual infestation of seedlings with shoot fly eggs did not result in deadheart formation in some of the accessions belonging to S. exstans (TRC 243601), S. stipoideum (TRC 243399), S. matarankense (TRC 243576) and S. purpureosericeum (IS 18944). Larval mortality was recorded in main stems of the Parasorghums. Within section Sorghum, accessions belonging to S. bicolor ssp. verticilliflorum were highly susceptible to shoot fly, as were those of S. halepense. However, a few accessions such as IS 18226 (race arundinaceum) and IS 14212 (S. halepense) resulted in reduced survival and fecundity. Wild relatives of sorghum exhibited very high levels of antibiosis to A. soccata, while only low levels of antibiosis have been observed in the cultivated germplasm. Therefore, wild relatives with different mechanisms of resistance can be used as a source of alternate genes to increase the levels and diversify the basis of resistance to shoot fly, A. soccata.
Induction of plant defence against herbivores may include the attraction by volatile infochemicals of natural enemies of the
herbivore. The emitted volatiles that mediate this attraction may also affect the behaviour of the herbivore itself. In this
paper we investigate the response of the herbivorous spider miteTetranychus urticae and the predatory mitePhytoseiulus persimilis towards volatiles whose production is induced in detached Lima bean leaves. Detached uninfested Lima bean leaves were incubated
on wet cotton wool on which bean leaves infested with spider mites (T. urticae) were present simultaneously or had been present previously. These treatments induce the production of volatile infochemicals
in the uninfested bean leaf tissue: predatory mites are attracted and spider mites are deterred. These are the first data
on the response of predators and herbivores to plant volatiles whose production was induced in detached uninfested leaves.
Although common wheat and durum may be attacked by a large number of diseases and pests, less than 20 diseases and about five
insect or mite pests are of major significance. Some of these have a global distribution and occur in most wheat-growing areas,
whereas others are restricted to certain geographic regions or climatic zones. A small group of diseases and pests, such as
Karnal bunt and Russian wheat aphid, are a major threat to countries and regions in which they are absent. Although there
is genetic variation in response to most diseases and pests, resources available to national programs limit the number that
can be included as breeding objectives. Ideal sources of resistance are those present in closely related, commercial genotypes,
but care must be exercised to avoid genetic uniformity. Any effort to transfer resistance from related species and genera
should be considered long term. The chance of successful exploitation of resistance based on alien genetic material declines
with reducing genetic relatedness between recipient and donor species. Breeders must maintain an awareness of potential problems
associated with very high levels of resistance controlled by single genes. Lower levels of resistance with established durability
or resistance based on a number of genes may be preferred. In many situations, resistance with moderate to low effectiveness
will contribute significantly to crop protection. Unusually susceptible genotypes should be avoided irrespective of perceived
risk based on local surveys. Molecular and other markers for genes of interest are having an increasing role in the selection
process. Although genetic engineering in wheat is in its infancy, significant contributions to disease resistance, starting
with virus resistances, can be expected.
Actual and potential crop losses of eight major food and cash crops have been estimated by evaluating data from literature and field experiments. Total losses were calculated from yield reductions due to pathogens, animal pests and weeds on a regional, continental and global level. Since 1965, worldwide production of most crops has increased considerably. Simultaneously, crop losses in wheat, potatoes, barley and rice increased by 4 to 10 percent, in maize, soybean, cotton and coffee losses remained unchanged or slightly decreased. The efficacy of crop protection practices was calculated as the percentage of potential losses prevented by control. The efficacy is highest in cotton (55 percent), it reaches only 34 to 38 percent in the food crops rice, wheat and maize. The variability among cropping areas is high: In Western Europe, 61 percent of potential crop losses is prevented, in North America and Oceania 44, in all other regions 38 percent. Due to the small share of Western Europe in worldwide production of 8 percent, the efficacy of actual crop protection worldwide is only 40 percent.
In view of population growth and rising food demand crop production has to be increased substantially. As potential loss rates often increase with attainable yields high productivity largely depends on effective crop protection management. Scenarios for the production of food crops by the year 2025 in developed and in developing countries are given. Recent and future developments in crop protection can contribute to establish sustainability in agriculture and to preserve natural resources. However, although effective control methods have been developed for most biotic yield constraints, the use of crop protection products is regulated by economic considerations rather than by food demand.
Causes of spider mite (Acari: Tetranychidae) population resurgences consequent upon exposure to synthetic pyrethroid (SP) treatments are reviewed. Resurgences may be seen as soon as 1 week, or even as late as a whole season, post-treatment. Synthetic pyrethroids vary in their adverse effects on spider mites, and also differ in their ability to invoke resurgences of different spidermite species on diverse plants. These pesticides are lethal as well as repellent to phytoseiids and other predators that prey on spider mites, may inhibit fungi which attack the latter, and affect phytophagous competitors. Spider mites are likewise repelled by SPs, thus becoming more evenlydistributed and less web-restricted, with a resultant increase in fecundity. Spider-mite development is shortened due to SPs and the sex ratio becomes more female-biased; onset of winter diapause also seems to be delayed. Synthetic pyrethroids appear to sensitize to spider-mite infestation plants which have not hitherto been attacked. Some SP effects (whether on spider mites, natural enemies or competitors) appear to be direct, whereas others may be mediated through the host plants. The effect of SPs on the other Acari is variable within the Prostigmata and Astigmata. Most Mesostigmata and Metastigmata (ticks) are very sensitive, whilst the Cryptostigmata (Oribatei) appear to be insensitive. Synthetic pyrethroids-induced resurgences of Homoptera are comparatively reviewed, with the conclusion that some of the phenomena may be similar to those observed in spider mites. Various resurgence models are discussed, as well as the three main causes of variation (SPs, spider-mite species, host plants) in the observed phenomena. The need for more rigorous and carefully controlled experimentation is emphasized.
Conventional agriculture has caused economic problems associated with over production of crops, increased costs of energy-based inputs and decreased farm incomes. It has also produced ecological problems such as poor ecological diversity, soil and water pollution and soil erosion. The adoption of integrated systems of agricultural production involving lower inputs of fertilizer, pesticides and cultivations can alleviate these economic and ecological problems. Such systems are dependent upon a good understanding of the nature of interactions between the four main components of such systems, which are fertilizers, pesticides, cultivations and rotations, and how these interactions influence crop yields and farm income. Alternatives to energy-based inputs include: legume rotations; use of waste organic matter as well as that from animals and crops; integrated pest management; pest and disease forecasting; biological and cultural pest control; living mulches and mechanical weed control; conservation tillage; specialized innovative cultural techniques, including intercropping, strip cropping, undersowing, trap crops, and double-row cropping. It is essential to integrate the components of agricultural systems fully so that their impact of other inputs is taken into account. Our knowledge of the main inputs and how these practices interact must increase before we can design fully integrated farming systems that minimize energy-based chemical inputs, produce good yields, increase farm profits and decrease environmental problems. There is considerable scope for the development of computer-based, farmer-operated, integrated management systems.
The ‘push–pull’ technology is a novel pest management strategy developed for control of stemborers and striga weed, Striga hermonthica, in maize-based farming systems in eastern Africa, where maize is intercropped with desmodium, a forage legume, and Napier grass is planted as a border crop. Desmodium repels stemborer moths while Napier grass attracts them. Desmodium also suppresses the parasitic striga weed through a series of mechanisms ranging from shading to allelopathy through the root system. The technology is currently being disseminated among smallholder farmers in eastern Africa and adoption rates are rising. Our on-station studies have reported efficacy of this technology against the two pests resulting in increased grain yields. The current study was conducted between 2003 and 2006 in 14 districts in western Kenya to assess effectiveness of the technology under farmers’ own conditions. Twenty farmers from each district, who had adopted the technology, were randomly selected for the study. Each farmer had a set of two plots, a ‘push–pull’ and a maize monocrop. Seasonal data were collected on percentage of maize plants damaged by stemborers, the number of emerged striga, plant height and grain yields. Similarly, farmers’ perceptions on the benefits of the technology were assessed using a structured questionnaire. Stemborer damage and striga counts to maize plants were significantly lower in the ‘push–pull’ plots than in the maize monocrop plots. Similarly, maize plant height and grain yields were significantly higher in the former. Farmers rated the ‘push–pull’ technology significantly superior in having reduced stemborers and striga infestation rates and increased soil fertility and grain yields. These results demonstrate that the technology is equally effective in controlling both pests with concomitant yield increases under farmers’ conditions in the districts studied.
Transgenesis is a powerful research tool that can be adapted to investigate many aspects of gene function. It has been used widely in model plants such as Arabidopsis, tobacco and rice but until recently, bottlenecks in DNA-delivery and tissue culture meant that it could not be used routinely for wheat research. However, many aspects of grain development and composition are unique to wheat and cannot be easily investigated in model species. Over the last decade, progress in biolistic- and Agrobacterium-mediated DNA delivery, reduction in genotype-dependency in wheat tissue culture and in the development of a range of supplementary technologies has enabled its application in this traditionally recalcitrant crop. The use of genetic modification has already made a significant impact on our understanding of interactions between high molecular weight glutenin subunits and their individual contribution to dough strength. As candidate genes become available the application of genetic transformation is set to play a major part in the elucidation of their function in determining other important grain traits such as starch and lipid composition, dietary fibre composition and grain texture.
Wheat plants respond to attack by Hessian fly in a gene-for-gene manner resulting in either a compatible or an incompatible interaction depending on the genotype of the infesting larvae. We previously reported a Hessian fly-responsive wheat gene (Hfr-1), up-regulated during incompatible interactions, that showed high sequence identity to a wheat gene (Wci-1) known to be induced by benzothiadiazole (BTH). Here, we analyze the temporal expression of these genes under biotic (Hessian fly/aphid/virus) and abiotic (mechanical wounding/water-deficit) stresses, as well as during treatments with the global signaling molecules, salicylic acid (SA), BTH, methyl jasmonate (MeJa) and abscisic acid (ABA) using northern hybridization and quantitative real-time PCR. Virulent Hessian fly infestation increased the expression of both Hfr-1 and Wci-1 in the crown tissue, while low systemic induction was observed in the leaf blade tissue. Although both genes were up-regulated to higher levels during incompatible interactions in multiple wheat genotypes, Hfr-1 transcripts accumulated to a higher level than Wci-1 transcripts. In response to infestation by non-viruliferous and viruliferous bird cherry-oat aphids, Wci-1 was up-regulated, while Hfr-1 was not. SA and BTH treatments up-regulated both genes, whereas MeJa and ABA up-regulated only Wci-1. When leaves were mechanically wounded, Wci-1 mRNA was up-regulated but Hfr-1 was not, while water-deficit stress up-regulated Hfr-1, but not Wci-1. Our results show that despite high sequence identity, Hfr-1 and Wci-1 exhibit differential expression profiles in response to various stresses and are regulated through separate signaling pathways. Hfr-1 responds to defense mechanisms elicited by feeding of Hessian fly larvae and water stress, while Wci-1 shows characteristics of a general defense-response gene in most of the biotic and abiotic stresses we investigated.
A history of exposure to a range of different types of stress alters subsequent plant responses. The process of priming or hardening involves prior exposure to a biotic or an abiotic stress factor making a plant more resistant to future exposure. This feature, in higher plants, indicates some capacity for “memory”. However, the molecular mechanism(s) by which this plant memory works must be entirely different from the memory in animals which is dependent on the nervous system. We therefore use the term “stress imprint” in this review to describe this plant-based phenomenon. Sustained alterations in levels of key signalling metabolites or transcription factors could provide an explanation for how plant metabolism is altered by exposure to various stresses. Alternatively epigenetic changes could play a role by enabling long-term changes in gene expression. Exposure to a priming agent could activate a gene or set of genes but instead of reverting to the transcriptionally silent state once the stimulus is removed, an epigenetic mark could perhaps be left, keeping the region in a ‘permissive’ state, facilitating quicker and more potent responses to subsequent attacks. Future research is needed to establish the molecular mechanism by which plants store information on stress exposure because biotic and abiotic stresses limit agricultural production and stress responses often lead to down-regulation of yield determining processes such as photosynthesis.
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To feed the several billion people living on this planet, the production of high-quality food must increase with reduced inputs,
but this accomplishment will be particularly challenging in the face of global environmental change. Plant breeders need to
focus on traits with the greatest potential to increase yield. Hence, new technologies must be developed to accelerate breeding
through improving genotyping and phenotyping methods and by increasing the available genetic diversity in breeding germplasm.
The most gain will come from delivering these technologies in developing countries, but the technologies will have to be economically
accessible and readily disseminated. Crop improvement through breeding brings immense value relative to investment and offers
an effective approach to improving food security.
As part of a programme for controlling lepidopteran stem-borers in cereal crops in Africa, we have investigated the effectiveness of combined cropping regimes of cultivatedand wild plants for reducing stem-borer damage. Intercropping with the non-host molasses grass, Melinis minutiflora, significantly decreased levels of infestation by stem-borers in the main crop and also increased larval parasitism of stem-borers by Cotesia sesamiae. Volatile agents produced by M. minutiflora repelled female stem-borers and attracted foraging female C. sesamiae. One of the volatile components released by intact M. minutiflora which attract parasitoids is also produced by herbivore-damaged plants and is implicated more widely as a cue for stimulating predation and parasitism.
Plants attacked by hungry herbivores can release chemicals that attract their assailants' predators. Could these responses be exploited to develop environmentally friendly pest-control strategies? John Whitfield investigates.
Inducible defensive responses in plants are known to be activated locally and systemically by signaling molecules that are produced at sites of pathogen or insect attacks, but only one chemical signal, ethylene, is known to travel through the atmosphere to activate plant defensive genes. Methyl jasmonate, a common plant secondary compound, when applied to surfaces of tomato plants, induces the synthesis of defensive proteinase inhibitor proteins in the treated plants and in nearby plants as well. The presence of methyl jasmonate in the atmosphere of chambers containing plants from three species of two families, Solanaceae and Fabaceae, results in the accumulation of proteinase inhibitors in leaves of all three species. When sagebrush, Artemisia tridentata, a plant shown to possess methyl jasmonate in leaf surface structures, is incubated in chambers with tomato plants, proteinase inhibitor accumulation is induced in the tomato leaves, demonstrating that interplant communication can occur from leaves of one species of plant to leaves of another species to activate the expression of defensive genes.
Forty-one accessions of wild and cultivated wheats belonging to 19 Triticum species were tested in the field for resistance to three species of aphids, Rhopalosiphum padi Linnaeus, Sitobion avenae Fabricius and Schizaphis graminum Rondani. Antibiotic resistance was estimated by the increase in biomass of aphids over 21 days on adult plants. Overall resistance was estimated by the plant biomass lost due to aphid infestation. All three species of aphids survived and reproduced on all wheats, and reduced spike biomass compared to uninfested controls. The level of antibiosis varied among wheat species and among accessions, with accessions from three, five and one species showing antibiosis to R. padi, S. avenae and S. graminum, respectively. Overall resistance to the three aphid species was observed in five to seven accessions per aphid species. Resistance was usually specific to one aphid species. The frequency of accessions with antibiosis or overall resistance was associated with the ploidy level of the plant species. Except for overall resistance to R. padi, resistance was highest for diploid species and lowest for hexaploid species. No consistent relationship between resistance and level of domestication was detected. Accessions of the wild wheats, Triticum boeoticum Bois, Triticum tauschii (Coss.) Schmal. and Triticum araraticum Jakubz. exhibited high levels of resistance to aphids, as did Triticum monococcum L. which is derived from T. boeoticum. Nevertheless, individual susceptible or resistant accessions occurred at all levels within the evolutionary tree of wheat.
By 2050, the human population will probably be larger by 2 to 4 billion people, more slowly growing (declining in the more
developed regions), more urban, especially in less developed regions, and older than in the 20th century. Two major demographic
uncertainties in the next 50 years concern international migration and the structure of families. Economies, nonhuman environments,
and cultures (including values, religions, and politics) strongly influence demographic changes. Hence, human choices, individual
and collective, will have demographic effects, intentional or otherwise.
Induction of local defence, as well as systemic resistance, of plants is associated with transcriptional reprogramming. Here we report on defence gene induction by natural and synthetic stimulants of plant immunity. Gene expression changes in Arabidopsis thaliana were monitored in response to several plant immunity stimulants (plant activators) using Northern blotting and an application-based array representing c. 750 genes involved in several aspects of plant defence and/or plant stress. The commercial plant activators Bio-S, Neudo-Vital and PRORADIX have been shown to induce systemic resistance. Here, Neudo-Vital, PRORADIX and Bio-S treatment induced different patterns of salicylic acid (SA) and jasmonic acid (JA) accumulation. Gene induction by these plant activators proved to be very complex. Rather than simply mimicking one of the known defence pathways induced by SA or JA, the response to the plant activators showed aspects of both major defence systems. A general feature was the transient activation of JA biosynthesis genes, combined with a much more sustained SA-associated defence gene induction. Our results demonstrate that plant immunity stimulants activate systemic immunity at the transcriptional level, and they provide insight into the coordinated transcriptional regulation of several classes of plant defence genes.
Biotic elicitors produced by plant pathogens or herbivore pests rapidly activate a range of plant chemical defenses when translocated to plant tissue. The fatty acid conjugate volicitin has proven to be a robust elicitor model for studying herbivore-induced plant defense responses. Here we review the role of insect-derived volicitin (N-[17-hydroxylinolenoyl]-L-glutamine) as an authentic elicitor of defense responses, specifically as an activator of signal volatiles that attract natural enemies of herbivore pests. Comparisons are drawn between volicitin as an elicitor of plant defenses and two other classes of signaling molecules, C(6) green-leaf volatiles and C(4) bacterial volatiles that appear to prime plant defenses thereby enhancing the capacity to mobilize cellular defense responses when a plant is faced with herbivore or pathogen attack.
Terpenoids are important for plant survival and also possess biological properties that are beneficial to humans. Here, we describe the state of the art in terpenoid metabolic engineering, showing that significant progress has been made over the past few years. Subcellular targeting of enzymes has demonstrated that terpenoid precursors in subcellular compartments are not as strictly separated as previously thought and that multistep pathway engineering is feasible, even across cell compartments. These engineered plants show that insect behavior is influenced by terpenoids. In the future, we expect rapid progress in the engineering of terpenoid production in plants. In addition to commercial applications, such transgenic plants should increase our understanding of the biological relevance of these volatile secondary metabolites.
Plant-mediated interactions between pathogenic microorganisms and arthropod herbivores occur when arthropod infestation or pathogen infection changes the shared host plant in ways that affect a subsequent attacker of the opposite type. Interest in such "tripartite" interactions has increased as the ecological and plant physiological framework for understanding and contextualizing them has developed. The outcomes of plant-mediated interactions are variable, and only a few provisional patterns can be identified at present. However, these interactions can have important consequences not only for individual pathogens and herbivores, but also for the population dynamics of both types of organisms in managed and natural ecosystems. Research has focused on the role of two plant response pathways in mediating tripartite interactions, one involving jasmonic acid and the other salicylic acid. Further studies of plant-mediated interactions will facilitate an understanding of how plants coordinate and integrate their defenses against multiple biotic threats.