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Uses and challenges of novel compounds for plant disease control

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Abstract

Fungicide research has produced a diverse range of products with novel modes of action during the last few years. These new classes of fungicides which include anilinopyrimidines, phenoxyquinolines, oxazolidinediones, spiroketalamines, scytalone dehydratase inhibitors, phenylpyrroles, strobilurins, and activators of systemic acquired resistance are expected to have a significant impact on disease control in the next decade. The most recent results in fungicide discovery originated from different approaches: traditional empirical screening of synthetic chemicals; traditional screening of natural products; biochemically directed screening of chemicals to discover; non-conventional agents stimulating plant defense. This review considers the different classes of recently developed fungicides, particularly focusing on their mode of action, resistance risk and impact on disease control.

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... In tropical and sub tropical Asia the disease was reported with the average loss of 5-10% (Willocquet et al., 2011) [93] . Sheath blight annual losses was (24)(25)(26)(27)(28)(29)(30)(31)(32)(33)(34)(35)(36)(37)(38) thousand tons in japan (Premalatha Dath., 1990) [84] . Philippines reported 24% of yield losses. ...
... Basically chemical control of any fungal plant disease consist of application of both systemic and contact fungicides. The application of systemic fungicides is prevalent since 1960 and found better management than non-systemic one (Gullino et al. 2000) [34] . The fungicides which belongs to strobulin group are most widely used for the control of this disease. ...
... Basically chemical control of any fungal plant disease consist of application of both systemic and contact fungicides. The application of systemic fungicides is prevalent since 1960 and found better management than non-systemic one (Gullino et al. 2000) [34] . The fungicides which belongs to strobulin group are most widely used for the control of this disease. ...
Article
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Sheath blight of rice caused by Rhizoctonia solani (Khun) is a potential threat to rice cultivation causing yield losses ranging from 32-70%. There are no host resistant varieties available so far. Fungicidal management for its control are damaging to environment. Eco-friendly approaches had attained major role in the suppression of the pathogen. Research studies are undertaken in order to reduce the incidence of the sheath blight all over the world. Seed and foliar spraying with Microbial agents such as Bacteria and Fungi provide the biological control of sheath blight. It infects all the stage of the crop. As the primary infection initiates with soil borne sclerotia. So the reducing the soil borne inoculum by the addition of organic amendments viz. rice chaff, neem cake, mustard cake, saw dust and farmyard manure helps in reducing the seedling infection. The application of Bioagents such as Trichoderma harzianum + Pseudomonas Floroscens + farmyard manure prior to transplanting in soil gives maximum reduction in the severity of the Disease. The application of bioagents along with organic amendments will manage the disease effectively and shows positive correlation in the yield. This review gives the overall innovative eco-friendly approaches using today worldwide for environment friendly and economical management of the most destructive disease in rice ecosystem (Sheath Blight).
... The most widely applied method for control of ShB is through the application of fungicides (Kandhari et al. 2003). Fungicides are toxic substances, often chemical compounds (natural or synthetic) with unique modes of action, used to kill or inhibit fungi (reviewed in Gullino et al. 2000). Selection of fungicide depends upon the intensity of the disease and also the tolerance level of the rice cultivar (Biswas 2004). ...
... However, this is not without important considerations over the choice of fungicide and application practices: The prolonged use of a single fungicide increases the risk of fungicide resistance (Uppala and Zhou 2018). Fungal genomes may mutate resulting in altered target sites of fungicide binding, increased production of the target protein, or reduced uptake or increased metabolic breakdown of the fungicide (reviewed in Gullino et al. 2000). The above processes result in varying levels of resistance described as quantitative fungicide resistance (Deising et al. 2008). ...
... The above processes result in varying levels of resistance described as quantitative fungicide resistance (Deising et al. 2008). Therefore, the composition of fungicides is frequently modified to enhance the specificity to recognise and attack target fungus (reviewed in Gullino et al. 2000). However, the process of screening and selection for more specific and durable fungicides creates a cost burden to developers that may end up being passed on to the farmers in terms of higher prices who may then continue to use less effective but lower-cost earlier generation fungicides. ...
Article
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Main conclusion Rice sheath blight research should prioritise optimising biological control approaches, identification of resistance gene mechanisms and application in genetic improvement and smart farming for early disease detection. Abstract Rice sheath blight, caused by Rhizoctonia solani AG1-1A, is one of the most devasting diseases of the crop. To move forward with effective crop protection against sheath blight, it is important to review the published information related to pathogenicity and disease management and to determine areas of research that require deeper study. While progress has been made in the identification of pathogenesis-related genes both in rice and in the pathogen, the mechanisms remain unclear. Research related to disease management practices has addressed the use of agronomic practices, chemical control, biological control and genetic improvement: Optimising nitrogen fertiliser use in conjunction with plant spacing can reduce spread of infection while smart agriculture technologies such as crop monitoring with Unmanned Aerial Systems assist in early detection and management of sheath blight disease. Replacing older fungicides with natural fungicides and use of biological agents can provide effective sheath blight control, also minimising environmental impact. Genetic approaches that show promise for the control of sheath blight include treatment with exogenous dsRNA to silence pathogen gene expression, genome editing to develop rice lines with lower susceptibility to sheath blight and development of transgenic rice lines overexpressing or silencing pathogenesis related genes. The main challenges that were identified for effective crop protection against sheath blight are the adaptive flexibility of the pathogen, lack of resistant rice varieties, abscence of single resistance genes for use in breeding and low access of farmers to awareness programmes for optimal management practices.
... Worldwide, 20% yield reductions occur in major food and cash crops due to the plant diseases (Gullino et al., 2000). Fungicides are a vital solution to control plant disease caused by pest and pathogen. ...
... Fungicides are the chemical compounds that may be fungicidal or fungistatic which kill or inhibit respectively the growth of fungi or fungal spores (Gullino et al., 2000). Fungicide use play crucial role in controlling the plant disease in the agriculture system. ...
Article
In order to feed increasing population there is need of solution which can provide quick result which is possible with fungicides. Fungicides are necessary evils to kill unwanted pest and disease causing organisms in the agro-ecosystem. These are indispensible tool for protecting the crops and increasing food production. Soil applications of fungicides have been frequently used to control soil borne fungal diseases. Fungicides are used for killing or inhibiting the growth of fungus. They are extensively used in pharmaceutical industry, agriculture, in protection of seed during storage and in preventing the growth of fungi that produce toxins. Hence, fungicides production is constantly increasing as a result of their great importance to agriculture. On the other hand some fungicides affect humans and beneficial microorganisms including insects, birds and fish thus public concern about their effects is increasing day by day. Moreover, certain fungicides, usually systemic fungicides, are said to be 'at risk' to the development of resistance if they are used repeatedly. In order to enrich the knowledge on beneficial and adverse effects of fungicides this article summarized impact of fungicide on photosynthesis, lipid steroid & membrane, nucleic acid, amino acid & protein synthesis, respiration, mitosis and cell division, and Multisite activity, as well as on their side effects on non target organisms
... El fungicida Captan (CAPTAN  50 WP, polvo humectable, 500 g i. a. kg −1 , ZENECA) es ejemplo de un plaguicida inespecífico, debido a su efecto inhibitorio en el crecimiento de HMVA inoculados en la raíz de fresa (Ferrera et al., 1998). El efecto nulo de la concentración efectiva del EC y A/DB en la colonización de HMVA y la nodulación de las raíces del frijol en campo es importante, ya que su efecto específico en agentes patógenos causales de enfermedades es una característica que deben poseer los compuestos bioactivos para ser incluidos dentro de programas de manejo integrado de plagas y enfermedades (Gullino et al., 2000). ...
... kg −1 , Zeneca) is an example of an unspecific pesticide, due to its inhibiting effect on HMVA growth, inoculated on strawberry root (Ferrera et al., 1998). The null effect of EC and A/DB effective concentration on HMVA colonization and bean root nodulation under field conditions is important, since its specific effect on disease-causing pathogenic agents is a characteristic that bioactive compounds must possess to be included in the integrated pest and disease management programs (Gullino et al., 2000). ...
Article
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For bean (Phaseolus vulgaris L.) anthracnose control under greenhouse and field conditions, the effect of crude extract and the mixture of bioactive afinina (A) compounds and bornyl decatrién (DB) obtained from Heliopsis longipes 'A. Gray' Blake root was assessed. Besides, the effect on bean root colonization by shrub vesicle mycorrhizal fungi (HMVA) and nodulation of nitrogen-fixing bacteria was evaluated. Two of the EC concentrations (700/70 and 70/7/µg mL-1) and A/DB (700/70 and 70/7 µg mL-1), under greenhouse conditions, reduced anthracnose incidence by 90%, without significant reduction (p > 0.05) of dry weight of the treated plants. Under field conditions, the evaluated EC concentrations (70/7 µg mL-1) and A/DB (70/7 µg mL-1) reduced anthracnose incidence reduction by 88%, without significant effect on dry weight of the treated plants (p>0.05), which confirmed the capacity of these compounds to reduce the disease. Application of EC and A/DB mixture under field conditions did not affect establishment of HMVA and nitrogen-fixing bacteria in bean roots.
... Plants have evolved effective resistance mechanisms that enable them to defend against pathogen attacks. Nevertheless, all crops are susceptible to a number of major fungal pathogens that cause up to 20% of yield losses (Gullino et al., 2000). In cereals, rusts, mildews and Septoria are the most damaging fungal diseases. ...
... Strobilurus tenacellus (Bartlett et al., 2002). The synthesis of derivatives of this molecule has led to several active compounds, including azoxystrobin (Gullino et al., 2000). Azoxystrobin and the other strobilurins are inhibitors of fungal mitochondrial respiration by blocking the electron transfer at the Q 0 site of cytochrome bc 1 (Affourtit et al., 2000). ...
... coli O157: H7 monoclonal antibodies. Although the modified electrode was competent to monitor E. coli efficiently, it suffered from a serious drawback of lack of regeneration of antibodies to use in real sample analysis [137]. ...
... These pesticides enter living beings through the food chain and agricultural activities. Fungicides are chemical compounds that are used to kill fungi [137]. The consumption of fungicides gradually increases due to inexpensive, user-friendliness, and competence. ...
Chapter
Determination of oxidation demand has been of interest to scientists for around 150 years. Various methods have been developed to determine chemical (COD) as well as biochemical oxygen demand (BOD). Numerous challenges, particularly interference with respect to COD and time of determination in the case of BOD, has always inspired scientists to develop analytical methods that can provide accurate results in a time-bound manner. Furthermore, real-time analysis of these parameters has also caught the attention of the research fraternity. In the last two decades, we have witnessed an increased use of instrumentation to overcome many issues related to the determination COD and BOD, which made it possible to carry out analysis in environmental and industrial set-ups as well as online monitoring.
... Una forma muy empleada para controlar los hongos del maíz es el control químico. Las aplicaciones frecuentes de fungicidas sintéticos provocan una presión de selección que resulta en el predominio de razas resistentes de los patógenos y en el consecuente incremento de las dosis utilizadas para su control ( Gullino et al., 2000). En general, estos productos presentan una lenta tasa de degradación, alta persistencia en suelo, acumulación en napas de agua y existen evidencias de que su uso provoca reducciones en las tasas de multiplicación de los hongos benéficos (Sosa- Gomez et al., 2003). ...
... Este compuesto químico posee como modo de acción la inhibición de la fosforilación de la glucosa, lo que resulta en una inhibición del crecimiento miceliar (PPDB, 2017). Mecanismos de acción específicos como este favorecen el desarrollo de resistencia, lo que también genera una necesidad de buscar opciones que suplementen su bioactividad (Sosa-Gomez et al., 2003;Gullino et al., 2000;. ...
... Fungicides are a class of pesticides used to inhibit fungal growth that can seriously damage crops [1,2]. In Galicia, Northwest Spain, viticulture represents a main support of its economy, and due to the extreme weather conditions in this region, the use of fungicides is necessary for the conservation of the vineyards. ...
... Due to this permeable fabric substrate and sponge-like porous architecture of sol-gel sorbent coating, the FPSE membrane has 400 times higher sorbent loading onto the substrate compared to SPME fiber and high surface area to facilitate the highly efficient analyte adsorption via sorbent-analyte interaction [19][20][21]. The strong, chemically bonded coating provides high chemical and solvent stability, being suitable for direct exposure to sample solution in a broad pH range (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12), and for the direct desorption with any organic solvent or mixtures to maximize the quantitative recovery of the extracted analytes. Moreover, the different FPSE sol-gel coating formulations can be easily adjusted to the type of substrate (i.e., cellulose/polyester/fiber glass) in order to maximize the selectivity of the FPSE membrane based on the physicochemical properties of the target analytes. ...
Article
A rapid environmental pollution screening and monitoring workflow based on fabric phase sorptive extraction‐gas chromatography‐tandem mass spectrometry (FPSE‐GC‐MS/MS) is proposed for the first time for the analysis of 17 widespread used fungicides (metalaxyl, cyprodinil, tolylfluanid, procymidone, folpet, fludioxonil, myclobutanil, kresoxim methyl, iprovalicarb, benalaxyl, trifloxystrobin, fenhexamid, tebuconazole, iprodione, pyraclostrobin, azoxystrobin and dimethomorph) in environmental waters. The most critical parameters affecting FPSE, such as sample volume, matrix pH, desorption solvent and time, and ionic strength were optimized by statistical design of experiment (DOE) to obtain the highest extraction efficiency. Under the optimized conditions, the proposed FPSE‐GC‐MS/MS method was validated in terms of linearity, repeatability, reproducibility, accuracy and precision. To assess matrix effects, recovery studies were performed employing different water matrices including ultrapure, fountain, river, spring, and tap water at 4 different concentration levels (0.1, 0.5, 1 and 5 μg L−1). Recoveries were quantitative with values ranging between 70–115%, and relative standard deviation (RSD) values lower than 14%. Limits of quantification (LOQs) were at the low ng L−1 for all the target fungicides. Finally, the validated FPSE‐GC‐MS/MS method was applied to real water samples, revealing the presence of 11 out of the 17 target fungicides. This article is protected by copyright. All rights reserved
... A shift in interest to naturally occurring compounds as antimicrobial agents or as components for chemical synthesis of new active ingredients, together with the understanding of their structures and properties, has motivated the synthesis of new broad spectrum "natural mimetic" fungicides that have different mechanisms of action from previously registered ones [15,16]. To cope with problems associated with resistance development to 'older fungicides' by current and emerging fungal pathogens, a number of novel fungicides have been developed for horticultural crops [15]. ...
... A shift in interest to naturally occurring compounds as antimicrobial agents or as components for chemical synthesis of new active ingredients, together with the understanding of their structures and properties, has motivated the synthesis of new broad spectrum "natural mimetic" fungicides that have different mechanisms of action from previously registered ones [15,16]. To cope with problems associated with resistance development to 'older fungicides' by current and emerging fungal pathogens, a number of novel fungicides have been developed for horticultural crops [15]. Among these is fludioxonil, a broad-spectrum fungicide with a different mode of action compared to older registered chemicals [13]. ...
Article
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The study investigated the effects of fludioxonil (FLU) on the postharvest quality of pomegranate fruit (cv. Wonderful). Fruits were dipped in FLU concentrations (control, 150, 300 and 600 mg/L) and stored for 4 months at 5 °C and 90–95% relative humidity (RH) plus an additional 4 days at 20 °C and 65% RH. Effects of FLU were evaluated on physiological responses, quality and sensory attributes. Results showed that fruit weight loss and decay incidence were reduced by FLU treatment, with fruit treated with 600 mg/L concentration showing the best results. Fruit respiration rate was more influenced by storage duration than FLU concentration. The severity and occurrence of physiological disorders increased with storage duration but were more pronounced in fruits treated with FLU. Storage duration influenced fruit colour whereas aril colour was affected by FLU concentration. Untreated fruit showed better aril redness and chroma although treated fruit also had acceptable red colour. Chemical quality attributes of fruit juice were not significantly affected by FLU concentrations. Fruit treated with FLU had significantly (p < 0.05) higher total phenolic content during storage although lower ascorbic acid content was observed compared to untreated fruit. Treating fruit with FLU resulted in better sensory attributes with regards to crispness, juiciness and sweetness. Overall, this study showed that fruit treated with FLU at 600 mg/L had the best quality with respect to decay incidence, weight loss, total phenolics and sensory attributes.
... Most oomyceticides (oomycete fungicides) were introduced and reported in the late 20 th century (Cohen and Coffey 1986;Gullino et al. 2000;Hirooka and Ishii 2013;Schwinn and Staub 1987). There are 4 major (widely-used) groups of oomyceticides within 16 different chemical groups that are effective in oomycete control: the phenylamides (PAs), quinone outside inhibitors (QoIs), carboxylic acid amides (CAAs), and multisite inhibitors (Fungicide Resistance Action Committee 2016; Gisi and Sierotzki 2015;Hirooka and Ishii 2013). ...
... They act through interrupting electron transport in cytochrome b (complex III) by binding to the Qo site, which is the ubiquinol oxidizing pocket at the outer side of mitochondrial membranes (Gisi 2002). Some of them can inhibit the zoospore liberation and motility of oomycetes (Gullino et al. 2000). ...
Thesis
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Pink rot of potato (Solanum tuberosum) is a widespread soilborne disease that causes significant losses in the field and storage. It is caused by Phytophthora erythroseptica (Pethybr.), an oomycete pathogen that produces sexual spores that can survive in soil for years. The management of pink rot mainly relies on chemical control. However, the most effective chemical in pink rot control, mefenoxam, is losing its efficacy owing to the development of mefenoxam resistance in P. erythroseptica. To evaluate alternative fungicides (including chemical and biological fungicides) to mefenoxam in pink rot control, two greenhouse experiments and three field trials were conducted. Crop rotation experiments were performed in the field to investigate the rotation effects of alfalfa, barley-ryegrass, canola, red clover, onion, pumpkin, sweet corn and oats on pink rot of potato. Thirty-four wild-type isolates of P. erythroseptica were collected for fungicide sensitivity assay and fungicide-resistant P. erythroseptica selection, to predict the resistance risk of fluopicolide, an alternative chemical to mefenoxam. Field trials showed that biologicals including Bacillus subtilis (Serenade Soil, Taegro), Bacillus amyloliquifaciens (Double Nickel, MBI-110), and extract of Reynoutria sachalinensis (Regalia) did not significantly reduce pink rot severity in the harvested potato tubers. The sole application of fluopicolide, some combinations of chemical fungicides (mefenoxam and oxathiapiprolin) and some combinations of chemical and biological fungicides (oxathiapiprolin/fluopicolide and Bacillus sp.) significantly reduced pink rot severity in the presence of mefenoxam-resistant P. erythroseptica population. In crop rotation trials, alfalfa, canola and pumpkin significantly increased potato tuber yield. However, the rotation crops had no significant effect on pink rot of potato. The results of the fungicide resistance study suggested a medium risk of P. erythroseptica developing intermediate resistance to fluopicolide, and that there was a trade-off between fluopicolide resistance and biological fitness in P. erythroseptica.
... Resistance to fungicides might be due to various procedures [19][20][21][22], including (a) reduced fungicide binding due to alteration of the target site, (b) overexpression of the target protein, (c) reduced fungicide absorption due to efflux pump removing toxic compounds, and (d) metabolic degradation of the fungicide through detoxification (Figure 3). The mechanisms involved in the appearance of resistance to fungicides in populations of field pathogens entail the study of the processes that intervene in the reduction of sensitivity to the compound and the genetic basis of the resistance trait. ...
... As with other external quinone inhibitor (QoI) fungicides, azoxystrobin is highly effective in preventing a wide variety of plant diseases [20,66], including citrus green mold [1]. Azoxystrobin (strobilurin) was registered as a new fungicide in the USA for the control of postharvest diseases of citrus [67,68]. ...
Article
Full-text available
The necrotrophic fungus Penicillium digitatum (Pd) is responsible for the green mold disease that occurs during postharvest of citrus and causes enormous economic losses around the world. Fungicides remain the main method used to control postharvest green mold in citrus fruit storage despite numerous occurrences of resistance to them. Hence, it is necessary to find new and more effective strategies to control this type of disease. This involves delving into the molecular mechanisms underlying the appearance of resistance to fungicides during the plant–pathogen interaction. Although mechanisms involved in resistance to fungicides have been studied for many years, there have now been great advances in the molecular aspects that drive fungicide resistance, which facilitates the design of new means to control green mold. A wide review allows the mechanisms underlying fungicide resistance in Pd to be unveiled, taking into account not only the chemical nature of the compounds and their target of action but also the general mechanism that could contribute to resistance to others compounds to generate what we call multidrug resistance (MDR) phenotypes. In this context, fungal transporters seem to play a relevant role, and their mode of action may be controlled along with other processes of interest, such as oxidative stress and fungal pathogenicity. Thus, the mechanisms for acquisition of resistance to fungicides seem to be part of a complex framework involving aspects of response to stress and processes of fungal virulence.
... It has led to new advances and innovation in fungicide invention which includes high action against plant diseases at very low use. There is a need for new fungicides because; around 70% of the global fungicide market by value is represented by high to medium resistance risk fungicides (Gullino 2000). On the other hand it can clearly be assured that a greater diversity of modes of action is needed to help the growers to manage the threat of resistance. ...
Article
Full-text available
In the modern, intensified agriculture, the efficient management of plant diseases is essential. At present the most reliable means of doing this is by the use of fungicides. Fungicides are the toxic substances which either kill or check the growth of the fungi. During the last two decades, fungicide research has produced a diverse range of fungicidal products with novel modes of action which had a significant impact on plant disease control. The need for new and innovative fungicides is driven, among other factors, by resistance management, regulatory hurdles, and increasing customer expectations. Compounds having a novel mode of action are of course of special interest, since they play a key role in resistance management strategies, but equally important are new fungicides with enhanced characteristics such as systemicity, curativity, and longevity of disease control. The technical feature of new generation fungicides are target specific action and safer to non target sites. Over the past few years, however, several truly novel compounds have been launched commercially and have reached an advanced stage of development, which include phenylpyrroles, anilinopyrimidines, strobilurin analogues etc with effects on respiration, cell membrane components, protein synthesis, signal transduction and cell mitosis. Many of the important plant diseases, which were not controlled satisfactorily by the previous traditional fungicides, can now be well managed by the new compounds which are mostly systemic in nature. In view the risk of resistance development with most of the systemic, site specific compounds, there is a need to develop more classes of fungicide with novel target sites.
... Basically, chemical control of any fungal plant disease consists of application of systemic or contact fungicide. The application of systemic fungicide is prevalent since 1960s and it is found that they provide better disease management than the non-systemic ones (Gullino et al., 2000). A vast range of fungicides differing in modes and formulations are available in the market for the management of sheath blight disease. ...
Article
Full-text available
Asia is the largest producer of rice, accounting for 20% of the total global rice production. Rice is the staple and pre-eminent food crop of Asia and its cultivation occupies 80% of the total cropped area. The production of rice should be enhanced to feed the increasing population of Asian countries and countries around the globe. Various biotic and abiotic stresses act as constraints on the rice production. Among them, Rice sheath Blight (ShB) disease is one of the major biotic stress cum constraint. The disease is prominent in the places where rice is intensively cultivated. R. solani is the major causal organism of this disease and the perfect stage is represented by Thanetophorus cucumeris. R. solani has a good survival and inoculums potential which also related to the incidence and severity of the disease. The commercially cultivated varieties of rice have very sufficient level resistant to ShB. Though there were many cultural and biological approaches, application of chemical fungicides is the only effective control measures for management of this disease. Still various research is going on to find genes which are responsible for sheath blight resistance in Rice. The role of plant growth-promoting rhizobacteria (PGPR) and various genera of PGPR in ShB suppression are discussed. The present mini review focused on various aspects relating to ShB suppression by cultural, chemical methods and PGPR such as antagonism and induction of systemic resistance and integrated management of ShB involving all the compatible combinations were mentioned in this review.
... Azoxystrobin (AZO) was one of the first QoI fungicides available in the market to control a wide range of fungi diseases in several crops (Gullino et al., 2000) and is classified as a reduced-risk fungicide by the US Environmental Protection Agency. In the USA, first, and subsequently in other countries, it was approved for postharvest treatments in several crops, including stone fruit and citrus fruit, to minimize the potential selection of resistant pathogen populations and for its low mammalian toxicity (Adaskaveg and Förster, 2010). ...
... Fungicides are a class of pesticides that are chemical compounds or biological organisms that destroy or inhibit the growth of fungi or fungal spores. The use of fungicides for an effective control of plant diseases has become crucial in the last decades in the agriculture system since it is estimated that fungal infections cause yield reductions of almost 20% of crops worldwide (Gullino et al., 2000). Due to their relatively low cost, ease of use, and effectiveness, fungicides became the primary means of fungi control (Xia et al., 2006). ...
Article
Abstract Background and aims Fungicides, though beneficial for agricultural productivity, are known to interfere with the basic metabolism and induce the formation of various biomolecules and also alter the physiological parameters of plant growth. The present study is an attempt to understand the effect of different conc. of benzimidazole (Carbendazim) and dithocarbamate (Mancozeb) fungicides on photosynthetic components such as chlorophyll content, total sugar and phenolic content and various antioxidative enzymes in developing seedlings of chickpea. Material and Methods: Chickpea seeds of two cultivars (PDG-4 and GPF-2) were incubated with different conc. (0.1, 0.25 and 0.5%) of the fungicide for 24 and 48 h and then allowed to germinate for 10 days in an incubated chamber. Seedlings were analyzed for various physiological parameters such as variation in root/shoot length, photosynthetic activity (chlorophyll content), total sugar and phenolic content and activity of antioxidative enzymes such as GPX, CAT and SOD etc. Results and conclusions Compared to the unstressed samples, fungicide stress resulted in an overall decrease in root/shoot length, relative water content etc. thus indicating that the applied fungicides adversely affects the rate of germination of seedlings. A differential behaviour of various chlorophyll (Chla, Chlb, total chlorophyll) contents suggests that fungicides stress affects the photosynthetic machinery. Estimations of sugar and total phenolic content indicated that higher conc. of the fungicide lowered the total sugar content at the 10-day-old seedling stage; thereby giving an indication that the fungicide may interferes with carbohydrate metabolism. We observed that the level of peroxidase increased at higher conc. of the both types of fungicide as compared to control samples whereas the catalase activity increased in PDG 4 but a lower activity was observed in GPF-2 under increasing conc. of both the fungicides. The levels of superoxide dismutase decreased in PDG-4 but increased in GPF-2 under higher conc. of both the fungicides thus indicating that different varieties of chickpea behaved differently and triggers various antioxidant enzymes as defence mechanism to counter the fungicides stress.
... Fungicides are biological organisms or chemical compounds that inhibit or destroy the growth of fungi or fungal spores. Recently, the use of fungicides for an effective control of plant diseases has become crucial in the agriculture system since it is estimated that fungal infections cause yield reductions of almost 20% of crops worldwide [4]. Due to their relatively low cost, ease of use, and effectiveness, fungicides became the primary means of fungi control [5]. ...
Article
Full-text available
Fungicides using for an effective control of plant diseases have become crucial in the last decades in the agricultural system. The efficiency of seed dressing fungicides in controlling damping off caused by Rhizoctonia solani under greenhouse conditions and its effect on plant growth and metabolism of cotton plant seeds was studied by treatment with systemic and contact fungicides. The results showed that Monceren showed the highest efficiency (72%) while each of Montoro and Sumi-8 showed the lowest efficiency (48% and 36 % respectively) in controlling damping off. Significant decrease in plant height, dry weight of plant, phytohormones, photo-synthetic pigments, soluble sugars, soluble proteins, total free amino acids, polyphenol oxidase caused by Bastin fungicide, but caused significant increases in total phenols, flavonoids, antioxidant enzymes, reduced glutathione, lipid peroxidation and hydrogen peroxide as compared with untreated plants. On the other hand, Topsim and Monceren fungicides increased all the above recorded parameters except phenols, MDA and H2O2 as compared with untreated plants. Our results indicated that Topsim Monceren and Premis fungicides can be used as growth regulators and decreased plant diseases.
... Fungicides are defined as the biological agents or the chemical compounds whose presence is having negative influence on the growth and development of fungi or their spores [2]. Population is increasing at an alarming rate. ...
Article
A study was carried out to investigate the effect of an fungicide difenoconazole (split and survival rate of Azolla cristata and Salvinia natans at concentrations of 0.005, 0.01, 0.025, 0.05, 0.1, 0.25, and 0.5ml per 4 litre of water. The inhibition was found to be dose dependent. The insecticide chloropyrifos was found to be detrimental to the developmental of Azolla cristata and Salvinia natans. However, the deleterious effects of difenoconazole on Azolla cristata and Salvinia natans were low. The experimental trials showed the significant reduction in growth and survival rate of Azolla cristata due to chloropyrifos treatment. Further, chloropyrifos exposure was considerably affecting the photosynthetic pigments of plant. The strong inhibitory effect on the growth and photosynthetic pigments could be related with chloropyrifos induced inhibition. In contrast to this, Salvinia natans, showed resistence and can withstand toxic effects of different pesticides. The results of our study showed that Azolla cristata have low tolerance to all concentrations of chloropyrifos and high tolerance to difenoconazole at the different concentrations, as compared to the Salvinia natans which showed more tolerance to the lower concentrations of chloropyrifos and different concentrations of difenoconazole.
... There are many diseases can attack tomato plants in the root system (fusarium wilt, verticiliun wilt, bacterial wilt, rhizoctonia), shoot system (early blight, leaf spot, bacterial canker, late blight), and fruits (bacterial spot, bacterial speck, anthracnose). Fungal diseases of tomato are resulted from several pathogenic fungi (Wani, 2011) and can cause marked decreases (20-35%) in its yield (Gullino et al., 2000;McGrath, 2004). Consequently, fungicides become crucial to control of fungal diseases. ...
Article
Vegetative growth of Tomato was negatively influenced by Tolclofos-methyl addition, and its phytotoxic effect was more pronounced on plant height and leaf area than other growth parameters. Application of Tolclofos-methyl fungicide at high rate caused marked decline in leaf chloroplast pigments, and carotenoids were more influenced. Total water content and leaf water deficit increased but the relative water content decreased as a result of Tolclofos-methyl application. Transpiration rate tended to increase at the lower dose of Tolclofos-methyl but decrease at its higher rate. Membrane integrity was increased with increasing the fungicide rate. Mineral elements (N, P, K, Ca, Mg, Fe, Zn, Mn), plant growth promoter substances (IAA, GA3, Cytokinins), and total free amino acids were reduced, whereas ABA, proline content, total phenol whereas the activity of phenoloxidase and peroxidase were increased in the fungicide exposed plants. Using Tolclofos-methyl fungicide at the high rate significantly reduced the number of flowers and fruit, vitamin C content of the fruits, yield, and water use efficiency of tomato plants. Total soluble solids and acidity in tomato fruits were increased, whereas lycopene content was decreased. Tolclofos-methyl fungicide residue in tomato fruits was dramatically enhanced above the maximum level of residue of Tolclofos-methyl fungicide (100 µg kg-1 in tomato fruits) and reached 176.8 and 423.2 µg kg-1 fresh weight at the rates of 2 and 4 g m-2 soil, respectively. Application of Bacillus, Trichoderma, GA3 and BP caused marked enhancements in the growth, yield, plant water relations, biochemical constituents, photosynthetic pigments and chemical properties of tomato fruits under both of the normal and fungicide pollution conditions. In addition, using these agents reduced the fungicide residue in fruits by about 42, 73, 35 and 5 % at the fungicide rate of 2 g m-2 soil and by about 80, 38, 68 and 47% at the rate of 4 g m-2 soil, respectively. It could be concluded that Trichoderma followed by Bacillus at the recommended dose of fungicide or Bacillus followed by GA3 at the exceeded dose of fungicide are useful tools to alleviate the phytotoxic effects and reduce the residue level of Tolclofos-methyl in tomato fruits below its maximum level.
... However, there is a growing concern about toxicity of synthetic pesticides due to retention of their residues in the food products [14]. Synthetic fungicide has negative effects on the environment because of its poor biodegradability leading to pollution, health hazards to the farmers, toxicity to non-target natural enemies, and loss of biodiversity among others [12]. ...
... Fungicides destroy or inhibit growth of fungi or fungal spores (Davidse, 1986;Yang et al.2011). About 20% of crops are affected by fungi (Gullino 2000) and fungicides are widely used due to low cost, ease of use, and effectiveness (Xia et al, 2006). Carbendazim (CBZ, methyl 2benzimidazole carbamate) is a broad spectrum fungicide widely used to control fungal diseases but is also used as a preservative (Veerappan et al. 2012). ...
Article
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Benzimidazoles are fungicides widely used in Agriculture. Gene mining and structure were used to dock carbendazim with glutathione reductase (GR) by BLAST, CLUSTALW, MEGA, GSDS, Swiss modeling, Autodock Vina and Discovery Studio visualizer. GR, a plant enzyme is a cellular antioxidant in the ascorbate-glutathione (ASH-GSH) cycle potentially conferring resistance to stress in crops. We found that the test plant chickpea genome had two subunits of GR – chloroplastic and cytoplasmic, based on domain architecture and gene introns and exons. By molecular docking, we found that carbendazim had binding pockets with amino acid residues in the N-terminal of signature domains Pyridine nucleotide-disulphite oxidoreducatase for GR protein. Further 2nd and 3rd iterations suggest that other amino acid residues change the GR cavity and structure thus potentially modifying its enzymatic activity. Our findings provide a plausible mechanism of inactivation of GR by benzimidazoles by binding to different amino acid residues.
... Fungicides destroy or inhibit growth of fungi or fungal spores (Davidse, 1986;Yang et al.2011). About 20% of crops are affected by fungi (Gullino 2000) and fungicides are widely used due to low cost, ease of use, and effectiveness (Xia et al, 2006). Carbendazim (CBZ, methyl 2benzimidazole carbamate) is a broad spectrum fungicide widely used to control fungal diseases but is also used as a preservative (Veerappan et al. 2012). ...
Article
Full-text available
Singh G, Kaur M., A molecular docking mechanism model for benzimidazole to inactivate glutathione reductase in chickpea., Onl J Bioinform., 20(2):, 2019. Benzimidazoles are fungicides widely used in Agriculture. Gene mining and structure were used to dock carbendazim with glutathione reductase (GR) by BLAST, CLUSTALW, MEGA, GSDS, Swiss modeling, Autodock Vina and Discovery Studio visualizer. GR, a plant enzyme is a cellular antioxidant in the ascorbate-glutathione (ASH-GSH) cycle potentially conferring resistance to stress in crops. We found that the test plant chickpea genome had two subunits of GR-chloroplastic and cytoplasmic, based on domain architecture and gene introns and exons. By molecular docking, we found that carbendazim had binding pockets with amino acid residues in the N-terminal of signature domains Pyridine nucleotide-disulphite oxidoreducatase for GR protein. Further 2 nd and 3 rd iterations suggest that other amino acid residues change the GR cavity and structure thus potentially modifying its enzymatic activity. Our findings provide a plausible mechanism of inactivation of GR by benzimidazoles by binding to different amino acid residues.
... Their activity, however, depends on the presence of (E)-β-methoxyacrylate moiety [58]. Strobilurin fungicides have become valuable tools for managing plant diseases [59]. These strobilurins are site specific (inhibition of mitochondrial respiration) and translaminar (systemic) compounds that provide control of Oomycota, Ascomycota, Basidiomycota, and Deuteromycota fungi. ...
Article
In agriculture, there is an urgent need for alternate ecofriendly products to control plant diseases. These alternate products must possess preferable characteristics such as new modes of action, cost effectiveness, biodegradability, and target specificity. In the current scenario, studies on macrofungi have been an area of importance for scientists. Macrofungi grow prolifically and are found in many parts of the world. Basidiomycetes (mushrooms) flourish ubiquitously under warm and humid climates. Basidiomycetes are rich sources of natural antibiotics. The secondary metabolites produced by them possess antimicrobial, antitumor, and antioxidant properties. The present review discusses the potential role of Basidiomycetes as anti-phytofungal, anti-phytobacterial, anti-phytoviral, mosquito larvicidal, and nematicidal agents.
... A wide variety of synthetically produced pesticides including fungicide, herbicide and insecticides are used to protect plants and plant products all over the world. Especially fungicides are most commonly used to improve crop yields against diseases of crops in many countries [1] [2] [3]. Fungicides are chemical compounds used to inhibit or kill fungal spores or fungi which can cause severe damage in agriculture resulting in serious losses of yield, profit and quality [4]. ...
Article
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This research was to evaluate the effects of dodine on the physiology of Vicia faba L. through total protein content and peroxidase (POX) activity. According to this, four weeks old seedlings were treated with 0.04 mL/L, 0.08 mL/L and 0.16 mL/L concentrations of dodine. Then, the leaves of plant samples were harvested with 24, 48 and 72 hours intervals. Our results have showed that while the total protein content were decreased significantly, POX activity was increased with the increased concentration of dodine and exposure time when compared with control seedlings. This research have shown that dodine can stimulate the plant defense system.
... Such diseases are usually managed with the application of proper fungicides. However, persistent and excessive use of agrichemicals could have adverse effects on environment (Gullino et al., 2000). To combat this limitation, scientists have relied on selected gene transfer into wheat with valuable agronomic characteristics (Anthony et al., 2001;Goyal and Prasad, 2010). ...
Article
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The enormous development in gene transfer technology made it possible to evolve new cultivars with valuable agronomic traits but escape of transgenes from genetically modified crops is one of the major concerns for biosafety. This study was aimed to investigate the potential flow of rice chitinase gene (RCG3) from transgenic wheat. Soil nutritional analysis was done through AB-DTPA method, while soil bacteria were isolated and identified based on 16S rRNA gene sequencing. The transgenic plant showed the presence of RCG3 gene after PCR analysis while it was absent in control plants. The same gene was absent in both soil samples collected from transgenic and non-transgenic plants. Soil nutritional analysis showed KNO3 (1.53 mg/kg) and phosphorous contents (1.35 mg/kg) in transgenic wheat soil as compared to their counterparts that gave 3.01 and 2.51 mg/kg KNO3 and phosphorous contents, respectively. Bacterial colonies count showed the maximum number in transgenic wheat rhizosphere (2x10⁴ CFU/g of a total replication in dilution factor 10⁻²). Results showed that both strains of transgenic and control rhizospheric wheat were from the same group (97% sequence similarity) showing the same common ancestor. These results clearly demonstrated that neither vertical nor horizontal gene flow occurred from transgenic wheat.
... In addition, several reports have indicated that GSB has developed resistance to carbendazim, azoxystrobin, pyraclostrobin, pristine, and difenoconazole fungicides [8,9]. Fungicide resistance is mediated by various mechanisms [10][11][12]. Previous studies have shown that changes at codons 6th, 50th, 198th, and 240th in the β-tubulin gene could result in the development of carbendazim-resistant isolates in the field [13], and mutations in different codons may lead to different levels of resistance. ...
Article
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Gummy stem blight (GSB) caused by Didymella bryoniae (D. bryoniae) is a worldwide fungal soil-borne disease that can cause severe yield reduction of watermelon. To shorten the monitoring time of carbendazim-resistant strains of D. bryoniae in the field, in this study, we developed a loop-mediated isothermal amplification (LAMP) assay for rapid detection of carbendazim-resistant strains of D. bryoniae. The β-tubulin gene of carbendazim-resistant strains was selected as the target for primer design. Based on the color change of hydroxy naphthol blue (HNB) and gel electrophoresis, the optimal reaction conditions for LAMP were determined at 65 °C for 50 min. In specificity tests, the LAMP assay was able to distinguish between carbendazim-resistant and sensitive strains of D. bryoniae. Moreover, in sensitivity tests, the detection limit was 1 ng/μL D. bryoniae DNA of the carbendazim-resistant strain. In addition, the LAMP method was successfully applied to detect carbendazim-resistant strains in D. bryoniae-infested samples. Therefore, the developed LAMP assay provides a new method for the rapid detection of carbendazim-resistant strains of D. bryoniae.
... A sustainable and effective control is achieved by the use of plant activators which reduce speed of multiplication of pathogen and produce resistance. On the other hand, some activators are also reported to boost up plant vigour and yield (Gullino et al., 2000). It is a powerful tool to stimulate the plant defense responses against insect-pest and diseases. ...
... The development of sustainable agriculture requires us take into account pathogen adaptation to agricultural practices (Bousset and Chèvre 2013;Denison 2012;Gilligan 2007;McDonald and Linde 2002;Zhan et al. 2014Zhan et al. , 2015. Processes that have received much attention to date relate to pathogen evolution in response to the use of pesticides (Brent and Hollomon 2007;Deising et al. 2008;Fisher et al. 2018;Gullino et al. 2000;Hahn 2014;Hayes et al. 2016;Hewitt 1998;Ma and Michailides 2005;REX Consortium 2015;Sierotzki and Scalliet 2013;Urech et al. 1997;Walker et al. 2017) as well as resistant cultivars (Biffen 1905;Fabre et al. 2015;Kilpatrick 1975;McDonald and Linde 2002;McIntosh and Brown 1997;Rimbaud et al. 2018). These studies show that such pathogen control methods are usually not sustainable because of pathogen adaptation. ...
Article
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One of the conclusions of evolutionary ecology applied to agroecosystem management is that sustainable disease management strategies must be adaptive to overcome the immense adaptive potential of crop pathogens. In this context, knowledge of how pathogens adapt to changes in cultural practices is necessary. In this paper, we address the issue of the evolutionary response of biotrophic crop pathogens to changes in fertilisation practices. For this purpose, we compare predictions of latent period evolution based on three empirical fitness measures (seasonal spore production, within-season exponential growth rate, and area under disease progress curves [AUDPC]) with predictions based on the concept of invasion fitness from adaptive dynamics. We use pairwise invisibility plots to identify the evolutionarily stable strategies (ESSs) of the pathogen latent period. We find that the ESS latent period is in between the latent periods that maximise the seasonal spore production and the within-season exponential growth rate of the pathogen. The latent periods that maximise the AUDPC are rather similar to those of the ESS latent periods. The AUDPC may therefore be a critical variable to determine the issue of between-strain competition and shape pathogen evolution.
... Introduction: 25 Fungicides are considered one of the most effective control measures for mitigating fungal diseases 26 (Gullino et al. 2000). Several studies demonstrated that fungicides boost plant defences through 27 phytoalexin synthesis and cell wall lignification or stimulate enzymes involved in the synthesis of 28 phenolic compounds (Saladin et al. 2003). ...
Preprint
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Fungicide-coated seed protects sugar beet plants from soilborne diseases, but seedlings coming from coated seeds often encounter phytotoxicity under field conditions. To understand the phytotoxic impact, fungicide-coated seed and the uncoated seed of two cultivars were sown with holes or no holes in plastic trays in greenhouse conditions. Our study demonstrated without fungicide coat on sugar beet seed and holes in plastic trays resulted in just above 90% germination. While fungicide-coated seed and no hole's underneath trays- showed the lowest germination (>20%). Fungicide-coated seed, having holes in plastic trays showed 90% germination. No fungicide coat on seed, having no hole's underneath trays showed 70% germination. We further estimated the percentage of stunted seedlings in both cultivars. Fungicide-coated seed with holes underneath plastic trays showed above 5% stunted seedlings while fungicide-coated seed, having no hole's underneath trays- showed the highest percentage of stunted seedlings (>10%) in both cultivars. In summary, our data demonstrated that the phytotoxicity of fungicide-coated sugar beet seed depends on growth conditions.
... Both biotic and abiotic stresses, especially biotic stresses (e.g., pests, diseases, and weeds) [1], are important factors restricting plant growth and agricultural production. Among them, fungal diseases have caused a loss in global crop yields of nearly 20% [2]. The application of chemical fungicides has been considered the primary method to protect crops from numerous diseases due to their convenience and low cost [3]. ...
Article
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Difenoconazole is one of the most commonly used fungicides to prevent and treat plant diseases caused by certain fungi. Due to increasing usage, more difenoconazole has been released into the environment and caused environment pollution. However, the potential impact of difenoconazole on plant growth and development and its involved mechanism are unclear. In this study, we discovered that difenoconazole exposure significantly inhibited plant growth, evidenced by the decrease in root dry weight, total root length, and surface area by 20–70%, 43–73%, and 26–66%, respectively, under different regimes of treatment concentrations and periods. Difenoconazole exposure also significantly inhibited shoot growth and development by decreasing 33–61% of the shoot dry weight and 50–65% of the leaf area. Difenoconazole exposure induced plant leaf cells to generate more ROS (O2•− and H2O2) and MDA, which resulted in a decreased chlorophyll content and then inhibited leaf photosynthesis. Difenoconazole exposure also induced the activities of superoxide dismutase (SOD), catalase (CAT), guaiacol peroxidase (G-POD), and ascorbate peroxidase (APX) in the roots and leaves of the wheat seedlings. SOD and APX activities were higher and more stable in the roots than those in the leaves. Based on our study, plant roots exhibited a more pronounced superoxide radical scavenging ability than plant leaves. In summary, difenoconazole exposure caused oxidative stress, reduced chlorophyll biosynthesis and functions, and then inhibited wheat plant growth and development.
... They are therefore very environmentally friendly molecules. Moreover, with their indirect mode of action, it seems difficult for biocontrols to induce resistance like pesticides (Gullino et al., 2000). Furthermore, the use of biocontrols alternating with "classic" phytosanitary products would allow to reduce the number of fungicide treatments thanks to the gain in efficiency, to avoid or delay the appearance of resistance to these products and therefore increase their resistance. ...
Article
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The heavy use of pesticides in banana cultivation is associated to environmental and human health degradation. Environmentally friendly alternatives for sustainable agriculture are needed to mitigate the negative impacts of chemicals. This study aims to evaluate the efficiency of biocontrols in the synthesis of bioactive secondary metabolites, mainly polyphenols. Thus, three biocontrols (Vacciplant ® , Callel ® , and Calliete ®) were applied on three cultivars of banana (Orishele, Corne, and French) for 24 h, 48 h, and 72 h and the polyphenol contents were measured. Results showed that the polyphenol contents varied in function of the incubation time and the variety of banana. The highest polyphenol contents were 170.8 and 169.47 µg/g FM and were obtained with Corne-Calliete (Co-Ca) and Corne-Vacciplant (Co-V) respectively. Biocontrols Vacciplant ® and Calliette ® showed had the best action in stimulating polyphenol production in the three cultivars of banana.
... 273. 5 Matthews (2018) (Matthews, 1998 [1]). excellent fungal performance on fruits and vegetables (Liu et al., 2018 [4]). ...
Article
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Henry's law constants (HLC) play a key role in the environmental fate of pesticides and their distribution between the different phases, i.e., between air, water and soil. For certain compounds such as fenpropidin and pyrimethanil, HLC values are poorly documented in the literature and in particular their temperature dependence. This work reports the experimental HLC values of two pesticides, namely fenpropidin and pyrimethanil, determined by means of a dynamic equilibrium system coupled to an off-line analysis performed by Gas Chromatography–Photoionisation Detection (GC–PID). The measurements were conducted over the range 278–293 K. In pure water, the experimental average values of HLC at 293 K were: HLC293K(fenpropidin) = (10.0 ± 3.1) × 104 M atm–1, HLC293K(pyrimethanil) = (8.2 ± 0.7) × 104 M atm–1. The obtained data were used to derive the following Arrhenius expressions where the quoted errors represent 2σ: ln HLC (fenpropidin) = (6060 ± 2420)/T – (9.1 ± 8.3); ln HLC (pyrimethanil) = (14570 ± 1800)/T – (38.4 ± 6.2). The environmental implications are then discussed in terms of lifetime or partitionning between the different atmospheric compartments.
... Con base a su origen sintético, los metabolitos secundarios de las plantas pueden ser divididos en tres grandes grupos: terpenoides, compuestos fenólicos y alcaloides (Sepúlveda et al. 2003). Estas sustancias pueden ser una fuente importante de agentes antifúngicos y al ser desarrollados como productos per se pueden tornarse como punto de partida para la síntesis de nuevos compuestos amigable con el ambiente (Gullino et al. 2000). ...
Article
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RESUMEN Con el objetivo de evaluar el efecto de extractos vegetales sobre el crecimiento in vitro del hongo fitopatógeno Sclerotium rolfsii Sacc., se realizó un ensayo con hojas de yerba mora (Solanum nigrum); orégano (Origanum vulgare); mastranto (Mentha suaveolens); algodón de seda (Calotropis procera); cundeamor (Momordica charantia), tarantán (Senna reticulata); mata ratón (Gliricidia sepium); semillas trituradas de neem (Azadirachta indica) y pulpa de tapara (Crescentia cujete). Para la elaboración de los extractos, se empleó la decocción de cada material vegetal molido en agua destilada mezclados con dextrosa y agar; el testigo correspondió al medio papa dextrosa agar (PDA) solo. Se colocó un disco de 1 cm 2 del aislamiento del hongo, en el centro de la placa de Petri y se incubaron en condiciones de laboratorio. Se empleó el diseño experimental de bloques al azar, con tres repeticiones. Las mediciones del crecimiento micelial y producción de esclerocios se realizaron a los 4 y 16 días después de la siembra, respectivamente, y sus comparaciones analizadas por la prueba de Scott & Knott con una significación de 5%. Todos los extractos evaluados inhibieron el crecimiento fúngico, tanto en área como en diámetro, y sus valores promedio difirieron significativamente del testigo. En los medios elaborados con tapara, mata ratón, algodón de seda y cundeamor, no se observó producción de esclerocios, mientras que para la yerba mora hubo producción profusa de esclerocios que superó al testigo. Los extractos acuosos de tapara, mata ratón y cundeamor in vitro se presentan como alternativas válidas para el manejo integrado de S. rolfsii. PALABRAS CLAVE: Añublo sureño, extractos, inhibición in vitro, manejo integrado. ABSTRACT With the purpose to evaluate the effect of plant extracts on the in vitro growth of the phytopathogenic fungus Sclerotium rolfsii Sacc. an essay was made with leaves of nightshade (Solanum nigrum); oregano (Origanum vulgare); apple mint (Mentha suaveolens); cotton silk (Calotropis procera); bitter gourd (Momordica charantia), mangerioba grande (Senna reticulata); mother of cocoa (Gliricidia sepium), neem (Azadirachta indica) and fruit pulp of calabash tree (Crescentia cujete). For extract elaboration, the decoction of each ground vegetable material in distilled water was used mixed with dextrose and agar; the control corresponded to the medium potato dextrose agar (PDA). Once the media were solidified, a 1 cm 2 disc of the fungus isolation was placed in the center of each Petri dish and incubated under laboratory conditions. The experimental design of random blocks was used, with three repetitions. Measurements of mycelial growth and sclerotia production were made at 4 and 16 days after inoculation, respectively, and their comparisons analyzed by the Scott & Knott test at 5% probability. Unlike the PDA, all the extracts evaluated inhibited the growth of the fungi both in area and in diameter of the colony, and their average values differ significantly from the control. In the media elaborated with calabash tree, mother of cocoa, silk cotton and bitter gourd, sclerotia production was not observed, while with nightshade there was profuse production of sclerotia that surpassed the control. The aqueous extracts of calabash tree, mother of cocoa and bitter gourd, in vitro, are presented as valid alternatives for the integrated management of S. rolfsii. KEY WORDS: Añublo sureño, extracts, inhibition, in vitro control, integrated management.
... Generally, fungicide resistance can be conferred by five major mechanism: (i) alterations in the target site that decrease binding to the fungicide; (ii) overproduction of the target protein; (iii) presence of an alternative metabolic pathway capable of bypassing the process inhibited by the fungicide; (iv) metabolic breakdown of the fungicide; and (v) active export or exclusion of the fungicide [31][32][33]. The resistance mechanisms known for P. viticola can be found in the references listed in Table 1. ...
Article
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The use of single-site fungicides to control plant pathogens in the agroecosystem can be associated with an increased selection of resistance. The evolution of resistance represents one of the biggest challenges in disease control. In vineyards, frequent applications of fungicides are carried out every season for multiple years. The agronomic risk of developing fungicide resistance is, therefore, high. Plasmopara viticola, the causal agent of grapevine downy mildew, is a high risk pathogen associated with the development of fungicide resistance. P. viticola has developed resistance to most of the fungicide classes used and constitutes one of the most important threats for grapevine production. The goals of this review are to describe fungicide resistance evolution in P. viticola populations and how to conduct proper monitoring activities. Different methods have been developed for phenotyping and genotyping P. viticola for fungicide resistance and the different phases of resistance evolution and life cycles of the pathogen are discussed, to provide a full monitoring toolkit to limit the spread of resistance. A detailed revision of the available tools will help in shaping and harmonizing the monitoring activities between countries and organizations.
... Modern agriculture and industry base on a wide variety of synthetically produced pesticides including fungicides, insecticide and herbicides. Especially fungicides are most commonly used to improve crop yields against diseases of crops in many countries [1][2][3]. But these chemicals or their derivatives can accumulate in the organisms and cause risk of mutagenicity, carcinogenicity or teratogenicity [4][5][6]. ...
... The fruit plants are observed to be infected by several plant pathogens simultaneously making it difficult to manage or control by using chemicals. The use of excess chemicals and fertilizers not only disturb and pollute the environment but also build resistance of pathogen towards chemicals (Gullino et al ., 2000). Therefore, we can follow Integrated Disease Management approach to get rid of the problems described above. ...
Chapter
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India is one of the major countries in producing more fruits and ranked in second. But several biotic and abiotic stress are causing the main barrier decreasing the yield and export causing heavy economical losses. One of the most effective method is the chemical method, but it is highly hazardous to environment and a limiting factor in terms of export to foreign countries. Hence, Integrated disease management is the best alternative for chemical control where all chemicals are used up to a safer extent. In Integrated disease management approach, wide range of diseases and pests can be controlled through cultural practices and careful handling, by knowing favourable environmental conditions and epidemiological studies. Physical, cultural, biological and chemical control measures when combined, various major and minor disease of cucumber, watermelon, sapota and jamun can be controlled simultaneously. In India. many farmers are not educated and not aware of this approach. Govt should take some action to make this practice reach out to a greater number of farmers. Keeping view of the recent context, the diseases, its symptoms and IDM approach for cucumber, watermelon, sapota and jamun are described in this chapter.
... Nativo Ò has active ingredient Trifloxystrobin + Tebuconazole belongs to inhibitors of cytochrome bc 1 (strobilurins) and inhibitor of sterol biosynthesis (triazoles) whereas Axiom has active ingredient Mancozeb + Matalaxyl belongs to Dithiocarbamate and Anilides group of fungicides respectively (Morton & Staub, 2008;Yang et al., 2011). Trifloxystrobin is a popular fungicide because of its versatility at controlling disease from different taxonomic classes, however, strobilurin enhances plant greening and improves yield (Gullino et al., 2000;Bartlett et al., 2002;Balba, 2007). Triazole fungicides are systemic and curative fungicides that cause leaves to be greener and improve yield depending on the crop (Buchenauer, 1995;Pernak et al., 2015). ...
Article
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Root-knot nematodes Meloidogyne incognita (Kofoid and White) Chitwood and Rhizoctonia bataticola (Taub.) Butler are very dangerous root damaging pathogens. Present study was planned to establish a chemical control of these root deteriorating pathogens under lab conditions as well as in field. Maximum death rate of nematode juveniles and minimum numbers of nematode eggs hatched were recorded in plates treated with Cadusafos (Rugby ® 100G) @12g/100ml and Cartap ® (4% G) @9g/100ml. Chemical treatment of Rhizoctonia bataticola with Trifloxystrobin + Tebuconazole (Nativo®) @0.2g/100 ml and Mancozeb + Matalaxyl (Axiom) @0.25g/100ml significantly controlled the mycelial growth in plates. The best treatments tested in laboratory were applied in field as protective and curative treatments. Results proved that chemical control of root-knot nematode and root rot fungi by tested chemicals at recommended time and dose is a significant management technique under field conditions.
... Newly developed products with their wide or narrower specificity may or may not be effective depends on modifying complex adoptability and fungicidal resistance of a particular pathogen (Gullino et al., 2000). Past experiences clearly indicating application of fungicidal level will be more effective under the umbrella of IDM (De warrd et al., 1993). ...
Article
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Sustainable agricultural intensification through integrated disease management (IDM) approaches is considered to be the most powerful tool for any developing country. The principles and components of integrated disease management approaches are crudely followed sustainable agriculture for our future generation and better soil health. These approaches must be incorporate into our farming system for better food security, armouring biodiversity and improving climate resilience. Grapes are the major tropical fruit crop in India and by huge production it generates substantial revenue in Indian agro-economic context. Every year each socio economic classes of farmers starting from small to marginal to big has facing some difficulties on gape production, diverse diseases attack, post-harvest management and marketing strategies and policies. Application of IDM skills in grape production is not only a challenging task but also wide adoptability of the same in farmer’s level facing diverse barriers in global scenario. The fact revealed that inadequate and inappropriate knowledge and skills of IDM strategies are the major core component of this problem. IDM is found to be the most effective management strategy as because it’s includes all the possible suggestive measure of disease management with an eco-friendly approach. For the successful implementation of IDM framework into our farming system Government activity and newly developed policies play an important role in all over the time. The present investigation is a review of studies and analysis of IDM centric barrier of grape production, forecasting and challenges.
... Mixing of curative and preventive fungicides is the best tactic to get rid of fungicidal resistance (Briggs et al., 2007). Repeated use of chemicals build up resistance in pathogens against fungicides (Gullino et al., 2000). Despite the fungicide usage is an effective strategy to control plant diseases (Matheron and Porchas 2013) but continuous use may deteriorate the environment. ...
... Its main principle as a fungicide is that it can easily adsorb on the surface of negatively charged microorganisms, penetrate their membranes, and destroy their cell structure. It thus has a sterilizing effect and eliminates algae [1][2][3]. In addition, it is used as a disinfectant in industrial water treatment agents, detergents, and seed treatment agents, and to disinfect women's and children's products as well as food packaging [4,5]. ...
Article
We report herein a new fluorescent probe for the selective recognition and determination of dodine among 20 different pesticides. This fluorescent probe was assembled through host-guest complexation between cucurbit[10]uril (Q[10]) and aminopropyl-1-pyrenebutanamide (PBA) and is designated as [email protected][10]. Addition of dodine to [email protected][10] results in a dramatic enhancement of fluorescence intensity at 390 nm, accompanied by fluorescence quenching at 488 nm. On this basis, the detection limit is 6.78 × 10⁻⁷ mol/L. The response mechanism is a competitive interaction: dodine occupies the cavity of Q[10] and forces PBA to leave.
... A binding site has been identified for this elicitor molecule in rice and soybean [236][237][238]. These molecules, similar to pathogenic and non-pathogenic organisms, are able to mimic plant-pathogen response and activate SAR [239,240]. These non-microbial molecules successfully activate SA, JA, and systemin, leading to the activation and induction of systemic protection [241]. ...
Article
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Pathogen-associated molecular patterns (PAMPs), microbe-associated molecular patterns (MAMPs), herbivore-associated molecular patterns (HAMPs), and damage-associated molecular patterns (DAMPs) are molecules produced by microorganisms and insects in the event of infection, microbial priming, and insect predation. These molecules are then recognized by receptor molecules on or within the plant, which activates the defense signaling pathways, resulting in plant’s ability to overcome pathogenic invasion, induce systemic resistance, and protect against insect predation and damage. These small molecular motifs are conserved in all organisms. Fungi, bacteria, and insects have their own specific molecular patterns that induce defenses in plants. Most of the molecular patterns are either present as part of the pathogen’s structure or exudates (in bacteria and fungi), or insect saliva and honeydew. Since biotic stresses such as pathogens and insects can impair crop yield and production, understanding the interaction between these organisms and the host via the elicitor–receptor interaction is essential to equip us with the knowledge necessary to design durable resistance in plants. In addition, it is also important to look into the role played by beneficial microbes and synthetic elicitors in activating plants’ defense and protection against disease and predation. This review addresses receptors, elicitors, and the receptor–elicitor interactions where these components in fungi, bacteria, and insects will be elaborated, giving special emphasis to the molecules, responses, and mechanisms at play, variations between organisms where applicable, and applications and prospects.
... Strobilurin fungicides are one of the most widely applied fungicide classes worldwide (Balba 2007). However, because of their site-specific activity, they have a high risk of selecting for resistant individuals within a fungal population (Gullino et al. 2000). There are two types of fungicide resistance: polygenic, which results in a gradual shift towards insensitivity due to an interaction of many mutant genes, and major gene resistance, which leads to complete insensitivity as a result of a mutation in one gene (Georgopoulos and Skylakakis 1986). ...
Article
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Strobilurin fungicides can be used to manage blackleg (Leptosphaeria maculans) of canola (Brassica napus); however, they have a high risk of selecting for resistance in fungal populations. In 2011, single-spore isolates of L. maculans were obtained from infected canola stubble representing six fields in Alberta, Canada. The isolates were grown on fungicide-amended agar plates and percent growth inhibition was calculated based on colony diameter relative to non-amended controls. Using probit regression analysis, the effective concentration of pyraclostrobin needed to inhibit mycelial growth by 50% (EC50) was determined to be 0.09 mg L⁻¹ based on 13 isolates. To identify highly insensitive isolates, 117 isolates were grown on agar plates amended with a discriminatory dose of 6.25 mg L⁻¹. Isolates in which growth was inhibited <50% were considered insensitive. Growth inhibition values ranged from 66.6% to 100.0% with a mean of 84.3%, indicating that all of the isolates were sensitive to pyraclostrobin. Forty-one of the 117 isolates were also tested via a microtiter plate assay. Based on conidial germination and subsequent growth, the EC50 values obtained for each isolate ranged from 1.0 × 10⁻⁴ to 7.4 × 10⁻³ mg L⁻¹, which were not significantly different from those of the sensitive controls (4.1 × 10⁻³ and 5.7 × 10⁻³ mg L⁻¹). While pyraclostrobin insensitivity was not detected in L. maculans populations from Alberta, continued monitoring will be necessary to track future changes.
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Rice sheath blight, caused by Rhizoctonia solani, is one of the increasing concerns in rice causing severe economic losses worldwide. Chemical control measures are already in practice for the management of this disease but approach for discovery of new chemicals with improved disease control potential is essential. The present investigation involves the development of nanoformulations of halogen substituted azomethines as new potent fungicide for the management of sheath blight disease in rice. The halogen substituted azomethines were synthesized and screened for in-vitro bioefficacy. Then the azomethines were nanoformulated for their in-vivo pot culture evaluation against Rhizoctonia solani. Transmission electron microscopy confirmed the particle size of the developed nanoformulations in the range of 1–100 nm. In-vitro inhibition results of test compounds revealed their ED50 values in the range of 11.9 to 22.4 μg/ml with best performer 2,4,5-trichloro-N-(2,4-dichlorobenzylidene)aniline. 3-Chloro-N-(2,6-dichlorobenzylidene)-4-fluoroaniline displayed maximum in-vivo efficacy against R. Solani which was comparable with that of hexaconazole, a standard recommended fungicide.
Article
Phytophthora capsici Leonian is a destructive oomycete plant pathogen that causes diseases in a wide range of crops worldwide. Benzothiostrobin is a broad-spectrum strobilurin fungicide that may control pepper Phytophthora blight. In the current study, the sensitivities of 90 P. capsici isolates collected from different regions in southern China to benzothiostrobin were measured. The curative and protective effects of benzothiostrobin against pepper Phytophthora blight were also determined. The formation of sporangia was inhibited by lower concentrations of benzothiostrobin, approximately 1 μg mL⁻¹ on V8 media, than was necessary to inhibit zoospore discharge. The frequency distribution curve for the benzothiostrobin sensitivity was unimodal with mean EC50 values of 1.84 ± 0.24, 0.60 ± 0.10 and 4.44 ± 0.27 for inhibiting mycelial growth, sporangia formation and zoospore discharge, respectively. The P. capsici isolates used in this study exhibited decreased sensitivity to several commonly used effective fungicides, including mefenoxam, cyazofamid, fluazinam and propamocarb. Furthermore, benzothiostrobin had no cross-resistance with azoxystrobin, pyraclostrobin or famoxadone. The disease severity of pepper Phytophthora blight on pepper leaves and plants was dramatically reduced by benzothiostrobin application of 150 μg mL⁻¹. Benzothiostrobin provided both curative and protective properties against pepper Phytophthora blight on detached pepper leaves and potted pepper plants, with greater protective activity than curative activity. These results suggested that benzothiostrobin may be used for the management of P. capsici.
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Thifluzamide fungicide has novel modes and sites of action against the wide range of fungi. Its unique single-site inhibition of the succinate ubiquinone reductase or succinate dehydrigenase (Sdh) complex in the respiratory chain was found so much effective. Effectiveness of Thifluzamide 24% SC against sheath blight of paddy was checked and for this evaluation B. H. U. Agricultural FarmVaranasi (U.P.) selected during the kharif 2016 and kharif 2017. Results of field experiment revealed that the treatment Thifluzamide 24% SC @ 90 g. a.i./ha recorded lowest disease index of sheath blight (29.58 % and 32.58%) after prophylactic spray and curative spray i.e. first spray and second spray during kharif 2016. In Kharif 2017 the same fungicide (Thifluzamide 24% SC @ 90 g. a.i./ha) again showed the decreased disease index (30.12% and 32.96%) after first and second spray. Other combination of fungicide i.e. Thifluzamide 24% SC @ 90 g a.i./ha recorded sheath blight percent disease incidence of 37.02 % which was statistically on par with Propiconazole 13.9% + Difenoconazole 13.9% @ 0.02% g a.i./ha (% disease index 38.20) and Tebuconazole 50% EC + Trifloxystrobin 25% WG @ 100+50 g a.i./ha (% disease index 39.28) but Carbendazim 25% + Flusilazole 12.5% SE @ 300 g a.i./ha showed highest % disease index compare to all treatments. Effects of Thifluzamide on % yield increase over check in both the season were highest with Thifluzamide 24% SC (24.56 % and 27.13 %). Under second spray i.e. curative spray the disease severity and PDI of sheath blight was minimum with Thifluzamide 24% SC @ 90 g. a.i./ha.
Chapter
Fungicides are essential components of crop protection and have played a significant role in managing several devastating crop diseases and realizing optimum crop yields. Their use has assumed importance in the control of more damaging plant pathogens against which host resistance is not easily available or is unstable, such as polycyclic oomycete pathogens. In some cases, the benefit gained through fungicide use is more critical to the extent that certain crops, such as potato, melons, and grapes, to name a few which cannot be cultivated in the absence of disease control that remains heavily dependent on the use of fungicides. About 150 different chemicals belonging to diverse classes are used as fungicides the world over. The need to produce more food per unit area necessitates the rationale behind producing novel fungicides to be developed to protect precious cultivars, which lack genetic disease resistance. This equilibrium between genetic resistance and disease control metabolites of chemical, biochemical, or biological nature will persist and is not likely to alter dramatically in the nearest future.
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We present a quantum dots (QDs)‐based lateral flow immunoassay for the determination of pyrimethanil in fruit and vegetable samples. This QDs‐based strip immunoassay had a cut‐off value of 25 ng/ml, under optimal conditions; linear calibration for pyrimethanil was obtained in the range of 1.9–13.3 ng/ml. The entire sample detection operation could be completed in 30 min. With the strip assay, vegetable and fruit samples spiked with pyrimethanil were extracted and tested, the average recoveries were ranging from 85.6 to 104.3%, with the coefficient of variation below 15%. The results tested from the strip assay were consistent with that obtained from liquid chromatography coupled with tandem mass spectrometry (R² = .98), indicating the developed QDs‐based strip assay is a convincing and useful tool.
Article
The use of fungicides for an effective control of plant diseases has become crucial in the last decades in the agriculture system. Seeds of cotton plants were treated with systemic and contact fungicides to study the efficiency of seed dressing fungicides in controlling damping off caused by Rhizoctonia solani under greenhouse conditions and its effect on plant growth and metabolism. The results showed that Mon-cut showed the highest efficiency (67.99%) while each of Tondro and Hemixet showed the lowest efficiency (31.99%) in controlling damping off. Rhizolex T, Mon-cut and Tondro fungicides caused significant decrease in plant height, dry weight of plant, phytohormones, photosynthetic pigments, soluble sugars, soluble proteins, total free amino acids but caused significant increases in total phenols, flavonoids, antioxidant enzymes, ascorbic acid, reduced glutathione, MDA and hydrogen peroxide as compared with untreated plants. On the other hand, the other fungicides (Maxim, Hemixet and Flosan) increased all the above recorded parameters as compared with untreated plants. Our results indicated that the fungicides application could be a potential tool to increase plant growth, the antioxidative defense mechanisms and decreased infection with plant diseases.
Thesis
Les agro-écosystèmes occupent un tiers de la surface globale terrestre (FAOSTAT 1999), constituant la surface la plus importante en terres exploitées par l’homme. Cette expansion considérable, associée à une intensification de la production agricole au cours la révolution verte a permis de subvenir aux besoins alimentaires de la population mondiale à la sortie de la deuxième guerre mondiale mais à un coût environnemental et sanitaire élevé. Ainsi, en l’espace de 50 ans l’utilisation de fertilisants a augmenté de 500% (Matson et al. 1997; Tilman et al. 2001), perturbant les cycles naturels des nutriments et entraînant une pollution généralisée des écosystèmes et des ressources en eau douce. Tandis que l’utilisation immodérée de pesticides pour la protection des cultures a causé de nombreux effets néfastes sur la santé humaine (FAO 2000; Pimentel 2005) et l’environnement (Green et al. 2005; Foley et al. 2005). Malgré ces effets négatifs, la consommation en pesticides à l’échelle mondiale a été estimée à 2,6 millions de tonnes dans les années 1990 (Aspelin 1997) et continue à augmenter (EPA USA 2011), avec dans certains cas une augmentation de la fréquence d’usage et des concentrations appliquées afin de contourner le développement de résistances chez les bioagresseurs ciblés (Chandrasekara et al. 1985; WRI 1998).Une perte de biodiversité, soit directement par la conversion des espaces naturels en terres arables, soit indirectement sous l’influence de pratiques intensives, a été également le prix à payer pour nourrir le monde. Ainsi, en moins de 20 ans un déclin des abondances a été avéré pour 83% des espèces d’oiseaux des champs et une restriction de leur distribution pour 86% rien qu’en Grande Bretagne (Fuller et al. 1995) mais les mêmes observations sont notées dans tous les paysages agricoles européens (Donald et al. 2001a). Des tendances similaires ont été aussi observées pour les mammifères (Flowerdew et al. 1997), pour les plantes et les arthropodes (Donald 1998 ; Sotherton & Self 2000 ; Geiger et al. 2010 ; Prieto-Benítez & Méndez 2010).
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Research for the development of biological control agents as an alternative to agrochemicals for controlling plant pathogens has gained considerable attention for the acquirement of agricultural sustainability. The present study reports a qualitative assessment of the potential of one promising antagonistic bacteria isolated from soil collected from Ultapani reserve forest, Assam, India, identified as Bacillus subtilis isolate AKP based on the morphological, biochemical, and molecular characteristic (NCBI GenBank Accession no. MW052029). The bacteria exhibited antagonistic activity against Chilli anthracnose fungus Colletotrichum capsici (61.5% growth inhibition in dual culture plate assay) which established the basis of further investigation. The strain AKP was found to exhibit biosurfactant producing ability with high emulsification index (83.1%) and surface tension reduction activity (83.8 to 21.9±0.21). The crude extract from AKP strain also caused a significant reduction in disease incidence (anthracnose symptoms) by 16.66 ±0.23% thus, providing good biocontrol efficiency against C. capsici based on in-vitro detached fruit assay. B. subtilis AKP showed the presence of surfactin (srfAA), iturin (ituC), and fengycin (fenD) antimicrobial biosynthetic genes in PCR assay. LC-MS analysis identified different homologues of surfactin, iturin, and fengycin lipopeptide biosurfactant from the methanolic fraction. Furthermore, the application of cell suspension-based B. subtilis also showed potentials for plant growth promotion both under in-vitro assays as well as in-vivo conditions in pot experiments. Our study revealed the potential of B. subtilis AKP in suppression of C. capsici as well as plant growth promotion which can be used on a commercial scale for the management of Anthracnose disease.
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The inhibitory effect of ethanolic extracts against Alternaria sp. in greenhouse cabbage cultivation (Oleracea brassica) and in-situ potato growing (Solanum tuberosum) was tested. Ethanolic extracts were prepared from Eucalyptus leaves (Eucalyptus globulus) with a Soxhlet extractor. Phytochemical analysis revealed the presence of considerable amounts of quinones, lactones and coumaranes, and small amounts of triterpenes and steroids. The experimental layout in the greenhouse cabbage cultivation consisted of three ethanol levels, one classical chemical treatment (Trizimand) and one control, ten cabbages per treatment, three repetitions, arranged in a randomized complete block design. The effect of three concentration levels of ethanol, one time sprayed on the leaves of the potato crop, was tested. The treatment plots, including a control plot, were randomized, each block 4 times repeated. In the greenhouse trial, the treatments with the effective dose increased by 50 and 25% displayed a comparable activity with the chemical treatment. Those treatments showed an increased effectiveness, compared with the effective dose at lab conditions. In the potato field essay, based on the incidence of pustules measured in the period of 65 to 85 days after planting, all treatments had an equal effect. It is believed that the observed overall minor and equal impact of the ethanol treatments on the potato crop is due to the high plot-to-plot variability and the more than normal wet conditions during the growing season. Keywords: Eucalyptus globulus, biologic control, genus Alternaria, greenhouse experiment, field experiment.
Article
Plant pathogenic fungi cause devastating damage to crop production worldwide. The growing global population necessitates reduced crop losses to improve food security, and the control of fungal plant pathogens is vital to help maintain food production. Providing a concise and balanced review of fungicides used in crop protection, this book describes the science of fungicide use, selection and resistance within the context of farming situations. Major updates and additions reflecting the emergence of two new classes of fungicides (strobilurins and SDHI) and the increased incidence of fungicide resistance are included in this new edition, which also discusses legislative requirements to reduce fungicide applications, and current trends in fungicide use.
Article
Uncinula necator subcultures from 19 vineyards in four regions in California were analyzed for sensitivity to triadimefon, myclobutanil, and fenarimol. The means of EC 50 values to triadimefon, myclobutanil, and fenarimol of U. necator subcultures from a vineyard without previous exposure to demethylation inhibition (DMI) fungicides were 1.40, 0.15, and 0.13 mg/liter, respectively. The highest means of EC 50 values were found in the Central Coast region, and frequency distributions were skewed most toward higher resistance to all three fungicides. Subcultures with high resistance levels also were present in the other regions examined. A time course study performed in one vineyard, where resistant strains were reported, demonstrated a steady and significant increase in EC 50 values for all three fungicides during the growing season after multiple applications of triadimefon. Increased resistance to triadimefon, but not to myclobutanil and fenarimol, was maintained in early-formed ascospores released after the growing season.
Article
The phenylpyrrole fungicide fenpiclonil inhibited the metabolism of glucose in mycelium of Fusarium sulphureum Schlecht at a concentration which only slightly inhibited mycelial growth (EC15). At the same concentration, fenpiclonil also inhibited accumulation and, to a greater extent, phosphorylation of 2-deoxy[U-14C]glucose in starved mycelium loaded with unlabelled 2-deoxyglucose. Fenpiclonil did not affect cell-free phosphorylation of 2-deoxyglucose or the ATP content of mycelium. Therefore, the primary mode of action of the fungicide may be based on inhibition of transport-associated phosphorylation of glucose. This may cause a cascade of metabolic events which eventually lead to fungal growth inhibition and death. One major event affected by inhibition of transport-associated phosphorylation is the accumulation of polyols, such as glycerol and mannitol, in mycelium. This was not observed in an osmotically sensitive, fenpiclonil-resistant laboratory isolate of the fungus.
Article
The control of Botrytis cinerea and Plasmopara viticola, two of the most important parasites on grapevines, is achieved by using fungicides. Recently several highly active compounds have been introduced but with some of them, failures of disease control have been observed in French vineyards. These phenomena are due to the build-up of resistance to benzimidazoles (benomyl, carbendazim, thiophanate-methyl) or to di-carboximides (iprodione, procymidone, vinclozolin) in Botrytis cinerea and to phenylamides (metalaxyl, ofurace) in Plasmopara viticola. The characteristics of the various resistant strains (levels of resistance, patterns of cross-resistance, fitness) are described. In 1982 and 1983 there has been monitoring for resistance in most French vineyards: the tests used and the results with regard to the frequencies of resistant strains are discussed.
Article
Between 1995 and 1997, 278 grape downy mildew (Plasmopara viticola) populations originating from European vineyards were characterised for their sensitivity to cymoxanil in a leaf-disc assay. The sensitivity profile revealed a wide distribution, with minimum inhibitory concentrations (MIC) ranging from 10 to more than 800 mg litre−1. EC50 values ranged from 1 to more than 800 mg litre−1 with an average of 125 mg litre−1. The sensitivity distribution was stable between 1995 and 1997. Surprisingly, populations from Portugal appeared significantly more sensitive than those from France or Italy, which could not be linked to differential cymoxanil usage in these countries. P viticola populations collected outside Europe and never exposed to cymoxanil appeared significantly more sensitive than exposed European populations, with an average EC50 value of 10 mg litre−1. The level of sensitivity of European P viticola populations was relatively unaffected by the number of cymoxanil applications made during a season or by the number of years of cymoxanil use. No link was found between the level of sensitivity in the leaf-disc assay and the level of performance of the cymoxanil mixtures used in the fields where the populations originated. Specific field trials conducted in Italy and Portugal have shown that the performance of cymoxanil-based mixtures remained good even on populations of the grape downy mildew fungus characterised as less sensitive in the leaf-disc assay. While there are no baseline sensitivity data for pre-commercialisation P viticola populations, the results of our study suggest that a shift in sensitivity (12.5-fold) may have occurred in some areas since introduction of cymoxanil on grapes nearly 20 years ago. Because cymoxanil is never used alone, it is difficult to determine whether or not practical resistance is occurring in European vineyards.
Article
Apart from its fungicidal effect, the strobilurin kresoxim-methyl (BAS 490 F) was found to induce physiological and developmental alterations in wheat (Triticum aestivum L.) which are seen in connection with improved yield. In a series of biotests including heterotrophic maize and photoautotrophic algal cell suspensions, duckweed, isolated mustard shoots and germinating cress seeds, kresoxim-methyl showed a similar response pattern to standard auxins (e.g. indol-3-ylacetic acid, IAA; 2-(1-naphthyl)acetic acid, α-NAA). Auxin-like activity of kresoxim-methyl was also found when stem explants of tobacco were cultured on a hormone-free medium. Kresoxim-methyl stimulated shoot formation, particularly at 10-7M. The same effect was induced by 10-8M IAA. The determination of phytohormone-like substances in shoots of wheat plants foliar-treated with 7×10-4M kresoxim-methyl revealed only slightly changed levels of endogenous IAA, gibberellins and abscisic acid. In contrast, the contents of dihydrozeatin riboside-type cytokinins increased to 160% of the control, while trans-zeatin riboside- and isopentenyladenosine-type cytokinins remained nearly unchanged. The most remarkable alterations were the reductions in 1-aminocyclopropane-1-carboxylic acid (ACC) levels and ethylene formation which were demonstrated in intact plants, leaf discs and the shoots of wheat subjected to drought stress. Kresoxim-methyl affected the induction of ACC synthase activity which converts S-adenosyl-methionine to ACC in ethylene biosynthesis. In shoots from foliar-treated wheat plants, 10-4M kresoxim-methyl inhibited stress-induced increases in endogenous ACC synthase activity, ACC levels and ethylene formation by approximately 50%. Reductions in ACC synthase activity and ACC levels of 30% were also obtained at low concentrations of α-NAA (10-6M). In contrast, ACC synthase activity in vitro was not influenced by adding the compounds. In wheat leaf discs, the inhibiting effect of kresoxim-methyl, α-NAA and IAA on ethylene formation was accompanied by delayed leaf senescence, characterized by reduced chlorophyll loss. However, in contrast to kresoxim-methyl which showed only inhibitory activity on ethylene synthesis over a wide range of concentrations applied, the auxins stimulated ethylene production at high concentrations of about 10-4M. The inhibition of ethylene biosynthesis by kresoxim-methyl, together with an increase in endogenous cytokinins could explain the retardation of senescence and the intensified green leaf pigmentation in wheat exposed to this strobilurin. © 1997 SCI.
Article
(E)-2-Methoxyimino-N-methyl-2(2-phenoxyphenyl) acetamide (SSF-126) inhibited respiration of Pyricularia oryzae mycelia by blockade of the electron flux through the cytochrome bc 1 segment of the mitochondrial respiratory chain. However, the mycelia again began to respire at 20 min after treatment. The recovered respiration was sensitive to salicylhydroxamic acid, a potent inhibitor of cyanide-resistant respiration, but not to potassium cyanide, indicating that SSF-126 had the ability to induce cyanideresistant respiration in P. oryzae. The recovered respiration was partially linked to energy transduction because SSF-126 could not completely suppress the mycelial growth. SSF-126 caused a rapid depletion of ATP content, but the ATP levels showed recovery, resulting in improvement of energy charge values. However, the total adenylate pool gradually decreased, resulting in only 60% remaining 48 h after treatment. SSF-126 markedly suppressed the mycelial growth, the duration for mass doubling in cultures incubated with SSF-126 being 2.4 times that in the control ones. Thus, SSF-126 works deleteriously on the supply of metabolic energy in P. oryzae
Article
SA has been shown to play an important signaling role in the activation of various plant defense responses following pathogen attack. These responses include the induction of local and systemic disease resistance, the potentiation of host cell death, and the containment of pathogen spread. The mechanisms through which SA mediates these effects are varied and can involve alterations in the activity or synthesis of certain enzymes, increased defense gene expression, potentiation of several defense responses, and/or the generation of free radicals. Through the analysis of mutant plants exhibiting aberrant responses to pathogen infection, many genes encoding products involved in the SA-mediated defense pathway(s) have been isolated. In addition, mounting evidence suggests that certain defense responses can be activated via a SA-independent pathway(s). This review focuses primarily on recent discoveries pertaining to the SA signaling pathway(s) leading to disease resistance; however, a very brief discussion of the SA-independent pathway (s) and its ability to cross-talk with the SA pathway is also presented.
Article
Pesticide resistance management needs an indication of the risk of resistance developing in pests against pesticide applications. This paper describes an evaluation system for the ranking of these risks. The term pests includes all organisms which are causing economic damage in agriculture, including weeds and plant pathogens. The system distinguishes six broad risk categories. It is based on expert judgement of answers to a maximum of ten questions on crop husbandry, pest biology and pest control. The system has been developed for registration purposes in The Netherlands, and is currently being discussed within the European and Mediterranean Plant Protection Organisation (EPPO). ©1997 SCI
Article
Induced resistance to the apple scab fungus Venturia inaequalis was demonstrated in greenhouse tests with 12-day-old seedlings of the apple cultivar Golden Delicious treated with methyl 2,6-dichloro-isonicotinate or 3,5-dichlorosalicylic acid prior to inoculation with the causal fungus. Studies of the dose-response of flusilazole on induced resistant plants revealed synergistic effects between both crop protection principles. Therefore, the use of such resistance-inducing compounds in the field might allow a reduction in the number of fungicide applications, and possibly a reduction in dose, thus resulting in improved efficacy of fungicides. There was also evidence that induced resistance could prove to be a valid strategy for the treatment of pathogen populations with reduced sensitivity to a given fungicide. © 1998 SCI
Article
The effect of phenylpyrroles on glycerol synthesis in Neurospora crassa has been investigated and compared with the mode of action of vinclozolin (a dicarboximide). The results indicated that fenpiclonil, fludioxonil and vinclozolin at concentrations which inhibit growth by 50% induce accumulation of glycerol in the mycelium of N. crassa. Furthermore a protein kinase (PK-III) possibly involved in the regulation of the glycerol synthesis is inhibited by phenylpyrroles, whereas vinclozolin is without effect. This implies that the target sites of phenylpyrroles and dicarboximides in the osmosensing signal transmission pathway are different. Comparative experiments with enzymes from human and animal sources revealed that PK-III could be a protein kinase Cδ. It is suggested that inhibition of PK-III activity may result in an increased concentration of a non-phosphorylated regulatory protein which may activate a MAP-kinase cascade of reactions resulting in increased glycerol synthesis. © 1997 SCI.
Article
This paper reviews the impact of resistance to fungicides and insecticides/acaricides on the way crop protection is practised. It is now clear that resistance can develop to virtually any crop-protection product, in any pest, fungal pathogen or even weed. As a limiting factor in crop protection, it is a fact of life. A positive side-effect is the precision with which products are used today, with increasing implementation of Integrated Pest Management (IPM) programmes. This is a vital step towards sustainability. This paper describes: past experiences; current status of resistance; how resistance management influences current crop protection practices; regulatory aspects; and the outlook for the future. It concludes that EU regulations on resistance management must be simple and workable. Chemicals will continue to have a central role in optimising yields from the world's crops, as new tools, including biotechnology, become available for crop protection and resistance management. The crop-protection industry's innovations and product stewardship programmes will contribute to sustainable agriculture. This will provide continued benefits to users, the environment and society. ©1997 SCI
Article
When mycelium of Botrytis cinerea was treated with low concentrations of the anilinopyrimidine fungicide pyrimethanil the total amount of free amino acids increased. Qualitative variations were also induced: alanine, glutamine, lysine, glycine, histidine, asparagine, arginine, threonine and moreover, α-aminobutyrate and β-alanine were accumulated; cyst(e)ine, valine, leucine and citrulline were reduced. When mycelium of B. cinerea was incubated with Na2[35S]O4, pyrimethanil at 1·5 μM induced a decrease of [35S]methionine and simultaneously an increase of [35S]cystathionine. These data indicate that the anilinopyrimidine fungicide pyrimethanil inhibits the biosynthesis of methionine and suggest that the primary target could be the cystathionine β-lyase. © 1997 SCI.
Article
Fenpiclonil [4-(2,3-dichlorophenyl)pyrrole-3-carbonitrile], a new agricultural fungicide, is a structural analogue of the antibiotic pyrrolnitrin used as an antimycotic in animals. Its spectrum of antifungal activity is similar to that of iprodione and tolclofos-methyl, which are representatives of dicarboximide and aromatic hydrocarbon fungicides. Laboratory mutants of Botrytis cinerea and Fusarium nivale were simultaneously resistant to fenpiclonil, iprodione and tolclofos-methyl and they showed an increased susceptibility to high osmotic pressure (sodium chloride, glucose). Strains of B. cinerea, collected in Champagne vineyards, which were resistant to dicarboximides were not resistant to fenpiclonil and tolclofos-methyl. The antioxidant α-tocopheryl acetate, and the cytochrome P-450 inhibitors piperonyl butoxide and tebuconazole antagonized the fungitoxicity of fenpiclonil and iprodione in a wild-type strain of B. cinerea. The uncoupling activity of fenpiclonil, iprodione and tolclofos-methyl was detected in mitochondria from both a wild-type strain and a laboratory mutant of B. cinerea. The concentrations effective towards this process were greater than those inhibiting the mycelial growth of wild-type strains. These results suggest that fenpiclonil, iprodione, tolclofos-methyl and related fungicides have the same biochemical mode of action. However, a primary effect on respiration, previously considered for pyrrolnitrin, seems to be improbable.
Article
The effect of pyrimethanil on the levels of cell wall degrading enzymes secreted by Botrytis cinerea Pers. was investigated in diseased plant tissues and in liquid B. cinerea cultures. Total proteinase activity isolated from infected carrot slices which were treated with 5.0 μM pyrimethanil was decreased by 76%, 3 d after inoculation. Polygalacturonase, cellulase, proteinase and laccase activities were all decreased in the medium of three day-old cultures grown in the presence of pyrimethanil. The pyrimethanil concentrations resulting in 50% reduction in total enzyme activities (IC50) were approximately 0.25 μM for polygalacturonase, cellulase and proteinase, and approximately 1.0 μM for laccase. No significant growth inhibition was observed at these pyrimethanil concentrations. Pyrimethanil did not inhibit the enzymes directly, nor did it inhibit the synthesis of cytosolic proteins. Therefore, it was proposed that the fungicide inhibits protein secretion at a post-translational stage in the secretory pathway.Large differences were found in the effects of pyrimethanil on the growth of B. cinerea in liquid cultures and on agar plates, depending on the composition of the medium. In liquid media containing cellulose and protein as carbon and nitrogen sources, growth inhibition occurred at 5.0 μM pyrimethanil, whilst no growth inhibition was observed with 50 μM pyrimethanil in malt extract. Similarly, growth occurred on potato/dextrose agar (PDA) at 0.5 μM pyrimethanil, but no growth was seen at this concentration on agars containing cellulose and protein. Thus it appears that pyrimethanil is most active in media where the fungus has to utilise extracellular enzymes to mobilise the nutrients it requires for growth.
Article
The broad-spectrum fungicide CGA 219417 inhibits mycelial growth of Botrytis cinerea Pers ex Fr. Pseudocercosporella herpotrichoides (Fron.) Deighton and Helminthosporium oryzae B. de Haan on defined media lacking amino acids. The growth inhibition of B. cinerea is reversed by the addition of a mixture of 19 amino acids at a concentration of 100 μM each or by the addition of methionine or homocysteine in concentrations of 100 μM or 1 mM, respectively. In the case of B. cinerea, the reversal of growth inhibition by methionine could also be shown for pyrimethanil and mepanipyrim. These findings suggest that the pyrimidinamine fungicides inhibit the biosynthesis of methionine in phytopathogenic fungi.
Article
The mechanism of resistance to ICIA 5504 (azoxystrobin) in a Septoria tritici mutant raised in the laboratory has been investigated. This mutant was approximately 10 times less sensitive than the wild-type strain in in-vitro tests towards spore germination or fungal growth. Glucose oxidation in whole cells was inhibited in the wild type (80% inhibition at 0·1 μg ml-1), whereas in the resistant mutant, oxygen uptake was stimulated (50% stimulation at 1·0 μg ml-1). Respiration of the wild-type strain was inhibited by antimycin A and cyanide but not that of the mutant. These results indicate the existence of an efficient alternative respiratory pathway in the mutant, which was inhibited by the addition of 2 mM salicylhydroxamate (SHAM). Using mitochondria, antimycin A and ICIA 5504 did not completely inhibit NADH oxidation in either strain. Addition of SHAM inhibited part of the antimycin- and ICIA 5504-insensitive oxygen uptake only in mutant mitochondria. For complete inhibition of oxygen reduction, SHAM and cyanide need to be present. Thus, three systems of electron transfer from exogenous NADH to oxygen are present in S. tritici mitochondria: the cytochrome pathway which is sensitive to ICIA 5504 and antimycin A inhibition in both strains, the system of NADH-cytochrome c reductase which bypasses the methoxyacrylate inhibition at the cytochrome bc1 complex, and the alternative oxidase which is inhibited by SHAM, and which is partially functioning only in mitochondria isolated from the ICIA 5504-resistant mutant.When the S. tritici isolates were tested for their in-vivo sensitivity to ICIA 5504 on wheat, the resistant strain was controlled better than the wild type. This indicates that the decreased ATP formation by the alternative pathway of respiration was inadequate for efficient parasitic growth on the host. © 1997 SCI.
Article
Famoxadone is a preventative and curative fungicide recently developed for plant disease control. The molecule and its oxazolidinone analogs (OADs) are potent inhibitors of mitochondrial electron transport, specifically inhibiting the function of the enzyme ubiquinol:cytochrome c oxidoreductase (cytochrome bc1). Visible absorbance spectral studies on the purified enzyme suggested that famoxadone bound close to the low potential heme of cytochrome b. This binding mode was confirmed in competitive binding experiments by studying the displacement of a radiolabelled OAD from submitochondria. EPR studies on the binding of famoxadone to submitochondria and purified bc1 suggested its binding mode was more like that of myxothiazol than that of stigmatellin (ligands known to bind near the low potential heme). Zoospores of Phytophthora infestans, when given low concentrations of famoxadone and other OADs, were observed to cease oxygen consumption and motility within seconds and later the cells disintegrated, releasing the cellular contents. Famoxadone was a potent inhibitor of the growth of Saccharomyces cerevisiae when grown on non-fermentable carbon sources and it was an approximately 50-fold less potent inhibitor of growth when the yeast was grown on a fermentable carbon source, glucose. Such physiological observations are consistent with the loss of mitochondrial function imposed by famoxadone and OADs. Single amino acid changes in the apocytochrome b of baker's yeast cytochrome b located near the low potential heme altered the inhibition constants for the inhibitors famoxadone, myxothiazol, azoxystrobin and kresoxim-methyl differentially, thus strongly suggesting different binding interactions of the protein with the inhibitors.© 1999 Society of Chemical Industry
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This review considers the effect of various fungicides, especially synthetic strobilurins, on fungal respiration, discusses recent contributions of biochemistry to the anilinopyrimidines and the phenylpyrroles and also discusses the future development of chemical inducers of systemic acquired resistance in host plants.