Article

Herbicide Resistant Weeds

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Abstract

The International Survey of Herbicide-Resistant Weeds (www.weedscience.org) reports 388 unique cases (species x site of action) of herbicide-resistant weeds globally, with 210 species. Weeds have evolved resistance to 21 of the 25 known herbicide sites of action and to 152 different herbicides. The ALS inhibitors (126 resistant species) are most prone to resistance, followed by the triazines (69 species), and the ACCase inhibitors (42 species). Herbicide-resistant weeds first became problematic in the USA and Europe in the 1970s and early 1980s due to the repeated applications of atrazine and simazine in maize crops. Growers turned to the ALS and ACCase inhibitor herbicides in the 1980s and 1990s to control triazine-resistant weeds and then to glyphosate-resistant crops in the mid 1990s in part to control ALS inhibitor, ACCase inhibitor, and triazine-resistant weeds. The massive area treated with glyphosate alone in glyphosate-resistant crops has led to a rapid increase in the evolution of glyphosate-resistant weeds. Glyphosate-resistant weeds are found in 23 species and 18 countries and they now dominate herbicide-resistance research, but have not yet surpassed the economic damage caused by ALS inhibitor and ACCase inhibitor resistant weeds. Lolium rigidum remains the world's worst herbicide-resistant weed (12 countries, 11 sites of action, 9 cropping regimes, over 2 million hectares) followed by Amaranthus palmeri, Conyza canadensis, Avena fatua, Amaranthus tuberculatus, and Echinochloa crus-galli. In the years ahead multiple-resistance in weeds combined with the decline in the discovery of novel herbicide modes of action present the greatest threat to sustained weed control in agronomic crops. The discovery of new herbicide sites of action and new herbicide-resistant crop traits will play a major role in weed control in the future however growers must make the transition to integrated weed management that utilizes all economically available weed control techniques. © Springer Science+Business Media Dordrecht 2014. All rights are reserved.

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... These reports put a lower limit on 45 the estimated number of unique resistance cases-over 500 across the globe-based on just the 46 occurrence of resistance to different herbicide modes-of-action across different species (Heap,47 2014) and barring the probably minor role of interspecific hybridization. For acetolactate 48 synthase (ALS) inhibiting herbicides alone, over 160 species have evolved resistance since the 49 first report in 1986, which was only five years after their initial introduction (Comai and Stalker,50 1986; Heap, 2014;Whitcomb, 1999). These numbers are likely a vast underestimate of the 51 repeatability of herbicide resistance evolution. ...
... These numbers are likely a vast underestimate of the 51 repeatability of herbicide resistance evolution. For ALS herbicides, for example, non-52 synonymous substitutions at eight distinct codons confer resistance, with most of them found in 53 multiple species (Tranel and Wright, 2002), and with multiple independent causal mutations 54 often occurring in the same population (Heap, 2014;Kreiner et al., 2018). In addition to repeated 55 resistance evolution through distinct causal resistance loci, it is likely that for a single locus, 56 resistance mutations have arisen repeatedly within a species (Kreiner et al., 2019). ...
... Similarly, KIN10, a key positive regulator of autophagy in A. thaliana, 493 is activated in response to photosystem II herbicides (Baena-González et al., 2007; Chen et al., 494 2017; Fujiki et al., 2001). 495 Discussion 496 497The application of herbicides to manage agronomically important weeds has led to one of the 498 best-studied examples of parallel evolution outside the laboratory, with target-site-resistance 499 mutations to ALS-inhibiting herbicides identified in more than 150 species(Heap, 2014). We 500 have studied the evolution of resistance mutations at two genes, ALS and PPO, from a genome-501 wide perspective across a large fraction of the range of one of the most problematic weeds in the 502 US and Canada, A. tuberculatus. ...
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Causal mutations and their frequency in agricultural fields are well-characterized for herbicide resistance. However, we still lack understanding of their evolutionary history: the extent of parallelism in the origins of target-site resistance (TSR), how long these mutations persist, how quickly they spread, and allelic interactions that mediate their selective advantage. We addressed these questions with genomic data from 18 agricultural populations of common waterhemp ( Amaranthus tuberculatus ), which we show to have undergone a massive expansion over the past century, with a contemporary effective population size (N e ) estimate of 8x10 ⁷ . We found variation at seven characterized TSR loci, two of which had multiple amino acid substitutions, and three of which were common. These three common resistance variants show parallelism in their mutational origins, with gene flow having shaped their distribution across the landscape. Allele age estimates supported a strong role of adaptation from de novo mutations, with a median allele age of 30 suggesting that most resistance alleles arose soon after the onset of herbicide use. However, resistant lineages varied in both their age and evidence for selection over two different timescales, implying considerable heterogeneity in the forces that govern their persistence. The evolutionary history of TSR has also been shaped by both intra- and inter-locus allelic interactions. We report a signal of extended haplotype competition between two common TSR alleles, and extreme linkage with genome-wide alleles with known functions in resistance adaptation. Together, this work reveals a remarkable example of spatial parallel evolution in a metapopulation, with important implications for the management of herbicide resistance.
... Well-adapted weed species in a changing climate scenario (elevated [CO 2 ] and drought conditions) will become a bigger challenge in crop production [3]. Hence, proper weed management is indispensable for maximizing crop productivity by involving all control strategies, including "biological, cultural, mechanical and chemical" [14][15][16]. ...
... Among the herbicides, glyphosate has become one of the most successful herbicides due to its effectiveness against most types of dicotyledonous and monocotyledonous weeds, including S. cannabina. Glyphosate inhibits the action of 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS), an enzyme involved in the production of aromatic amino acids by the shikimate pathway [14][15][16][17]. Glyphosate enters the plants through the foliage and is translocated via the phloem to the sink tissues [5]. ...
Article
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An elevated atmospheric carbon dioxide (CO2) concentration and frequent droughts are two anticipated climate change scenarios in which certain invasive weeds may develop competitive advantages over crops and adversely impact productivity and herbicide efficacy. Hence, a study was conducted to explore the effect of different climatic scenarios on the growth and management of Sesbania cannabina (Retz.) Pers with glyphosate. The variables investigated were two CO2 concentrations (400 and 700 ppm), two soil moisture levels (100% and 50% of field capacity (FC)), and three glyphosate rates (0 (control), 517 (50% of recommended rate), and 1034 g ae ha-1 (recommended rate)). CO2 concentrations and soil moisture levels had different effects on the growth and management of S. cannabina. Overall, 100% FC and elevated [CO2] of 700 ppm recorded the maximum plant height (38 cm), leaves per plant (20), growth index (60), chlorophyll content (SPAD value 37), and dry biomass (3 g) in comparison with ambient [CO2] of 400 ppm and 50% FC treatment. The recommended glyphosate application gave 100% weed biomass reduction; however, efficacy was reduced (63%) when applied at 50% of the recommended rate under elevated [CO2] of 700 ppm and 50% FC conditions.
... The release of herbicide-tolerant glyphosate-tolerant Roundup Ready ® from Monsanto and glufosinate-tolerant Liberty Link ® from Bayer is known as the first commercialized transgenic crop in the USA in the 1990s [78]. Even though it was accepted and cultivated in several areas in the world, the adoption of glyphosate-tolerant traits has resulted in weed species developing resistance to the herbicide [79]. ...
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Global warming causes a range of negative impacts on plants especially due to rapid changes in temperatures, alterations of rainfall patterns, floods or drought conditions, and outbreaks of pests and diseases. These, in turn, affect crop production reducing the quality and quantity of agricultural produce. Climatic extremes and high population growth significantly increase the world’s food demand. Therefore, fulfilling the goal of attaining food security for the present and future generations is of prime importance. Biotechnology enables creating dramatic alterations on crops to withstand stress which is difficult to attain using conventional breeding approaches. It is a viable tool used to improve agricultural production. The development of biotechnological approaches such as genetic engineering, genome editing, RNA-mediated gene silencing armored with next-generation sequencing, and genome mapping have paved the way for precise and faster genetic modifications of plants. Such intensive efforts are currently underway creating desirable crop cultivars to meet the food demand and to support sustainable agricultural productivity for climate change adaptation.
... The overuse of herbicides has resulted in environmental pollution and human health issues therefore the situation demands the judicial use of herbicides for sustainable agriculture (Jabran and Chauhan, 2018;Aktar et al., 2009). The presence of Herbicide-resistant weeds in vegetable farms also requires alternative weed control methods (Heap, 2014). The growing demand for organic vegetables and fruits on a global scale urges for the development of better nonchemical weed control measures. ...
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A significant level of yield losses in the vegetable and fruit farms are attributed to the weed populations of the area. This study was conducted for eighteen months during 2019-2020 to assess the presence of various weed families, related species, and their densities in the vegetable (CROP A) and fruit (CROP B) farms of Taif, Saudi Arabia. During the study, fourteen and ten weed families were noted in the vegetable and fruit farms of the studied area, respectively. Poaceae family weeds (729) were significantly higher in numbers followed by the families Asteraceae (414), Chenopodiaceae (338), and Gisekiaceae (153). In the vegetable farms, two weed species of the family Poaceae including Setaria viridis (437) and Eleusine indica ssp (277) were present in the higher numbers followed by Chenopodium murale (166) of the Chenopodiaceae family. In the fruit farms, the weed species Cynodon dactylon of the family Poaceae represented the highest weed density (172) followed by Gisekia pharnaceoides L. species (153) of family Gisekiaceae and Portulaca oleracea (59) belonging to the family Portulacaceae. The vegetable and fruit farms of the Taif region face severe weed pressure that affects the cultivated crops. This study depicts a comprehensive picture of weed diversity and density in the vegetable and fruit farms of the area. The results of this study will be beneficial in developing effective weed management practices for better crop production.
... Already before cinmethylin had been registered for weed control in European winter wheat production, two out of 17 A. myosuroides populations with reduced sensitivity to preemergence herbicide flufenacet(Messelhäuser et al., 2021b) were also tolerant to recommended field rates of cinmethylin, even though flufenacet inhibits a different pathway in the fatty acid synthesis than cinmethylin.Repeated application of herbicides has rapidly selected for many resistant populations of A. myosuroides in Western Europe against almost all herbicide modes of action registered for A. myosuroides control. More populations were resistant to post-emergence herbicides inhibiting the photosystem II-(PS2), acetyl CoA carboxylase (ACCase)-and acetolactate synthase (ALS) than to pre-emergence herbicides(Drobny et al., 2006;Délye et al., 2007;Neve, 2007;Menne & Hogrefe, 2012;Menne et al., 2012;Bailly et al., 2012;Heap, 2014). However, it appears possible that A. myosuroides plants resistant to cinmethylin may also be selected during several seasons of cinmethylin use in winter annual crops and could then dominate the respective population. ...
Thesis
Alopecurus myosuroides Huds. is one of the most problematic grass weeds in cereal production in Western Europe. This grass weed spread rapidly due to the repeated and intensive use of herbicides with the same mode of action and changes in arable cropping and tillage systems. Herbicide applications are the common agricultural practice for successful control of A. myosuroides due to its high flexibility and low cost. However, due to European and national restrictions and the growth of herbicide-resistant populations, farmers are forced to reduce herbicide use to minimize chemical impacts on the environment and food chain. As a holistic approach for reducing herbicide use, integrated weed management (IWM) is a diversification of the control strategy of A. myosuroides. In this thesis, several aspects of IWM were examined and combined to test for a successful A. myosuroides control strategy in winter cereals. Special attention was paid to cinmethylin, a pre-emergence herbicide with a new mode of action in winter cereals to control A. myosuroides. The first article comprised the development of an agar bioassay sensitivity test to determine sensitivity differences in A. myosuroides populations to pre-emergence herbicides containing flufenacet and the re-discovered substance cinmethylin. All of the tested populations did not show reduced sensitivity to cinmethylin, but differences in resistance factors were observed between the agar bioassay sensitivity test and the standard whole plant pot bioassay in the greenhouse. Nevertheless, it was possible for the most part to confirm the results for cinmethylin and flufenacet of the standardized greenhouse whole plant pot bioassay in the agar bioassay sensitivity tests and hence create a reliable, faster test system. The second article focused on cultural measures like cover crop mixtures, various stubble tillage methods and glyphosate treatments and their effect on total weed infestation in particular on A. mysouroides and volunteer wheat. Within two field experiments, the cover crop mixtures and the dual glyphosate application achieved a control efficacy of A. myosuroides of up to 100%, whereas stubble tillage and the single glyphosate treatment did not reduce A. myosuroides population significantly. The results demonstrated, that besides a double glyphosate application, well developed cover crop mixtures have a great ability for weed control, even for A. myosuroides. The third article also dealed with the combination of cultural measures (delayed seeding) and herbicide application and their influence on A. myosuroides control efficacy and yield response of winter wheat and triticale. Results indicate that cultural methods such as delayed seeding can reduce A. myosuroides populations up to 75%, although to achieve control efficacy of > 95%, supplementary herbicides should be used. In the fourth article, a two-year experiment on two experimental sites was set up with a special focus on stubble tillage methods, glyphosate application and the application of the pre-emergence herbicide cinmethylin in two rates. Control efficiencies of 99-100% were achieved by ploughing, double glyphosate application or via false seedbed preparation, each in combination with a cinmethylin application. In the last article, over a period of three years the new pre-emergence herbicide cinmethylin was tested in combination with stubble treatments and delayed drilling of winter annual cereals in winter wheat and winter triticale in Southwestern Germany. Cinmethylin controlled 58-99% of A. myosuroides plants until 120 days after sowing. Additive and synergistic effects of cinmethylin and delayed drilling were found for all studies. In this study, the focus was set on monitoring, cultural and direct weed control methods. Considering especially A. myosuroides, a diverse control strategy needs to be implemented to ensure a sustainable and reduced herbicide use, high control levels, minimized crop damage, safeguarded grain yields and reduced risk of resistance development. However, IWM measures imply increased system complexity, which may make their adoption by farmers difficult. Nevertheless, the results show that cinmethylin can be successfully used for weed control systems in combination with different stubble tillage methods, glyphosate application, delayed seeding, or herbicide sequences and mixtures, making it a valuable tool in integrated weed and resistance management strategies with its novel and unique mode of action.
... Sorghum halepense is considered among the worst agricultural weeds worldwide (Holm et al. 1977). Especially in arable land, its success is favored by herbicide resistance and the spread of rhizomes through tillage (Vila-Aiub et al. 2007;Heap 2014;Kashif et al. 2015). Glyphosate-resistant ruderal populations are also known in Spain (Vazquez-Garcia et al. 2020). ...
Article
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Sorghum halepense is a synanthropic tall grass distributed worldwide from tropical to temperate zones, and it is often considered an invasive alien. It is a perennial, rhizomatous plant that tends to form dense stands derived from vegetative and sexual propagation. Despite roadside plant communities dominated by Sorghum halepense are very common in southern Europe, their phytosociological aspects are scarcely studied. In this work, we present the results of a vegetation survey in peninsular Italy, carried out by means of the phytosociological method. In total, we carried out 73 relevés in Liguria, Tuscany, Latium, Campania, Basilicata, and Apulia. We statistically compared our relevés to those from the Balkans classified in the Cynodonto-Sorghetum halepensis, an association of agricultural annual weed vegetation of the class Stellarietea mediae s.l. used in the past as a reference for Italian S. halepense-dominated communities. Our results show that the Italian communities are different from the Cynodonto-Sorghetum halepensis communities, since the latter are rich in annual species, while the former are rich in perennial species. From the syntaxonomic point of view, the Italian communities are better classified in the class Artemisietea vulgaris. We describe the new (sub-)ruderal association Potentillo reptantis-Sorghetum halepensis, including a meso-hygrophilous variant with Urtica dioica and an agricultural variant with Elymus repens. We have evidence that the Potentillo-Sorghetum occurs in Italy, Kosovo and Slovenia, but its distribution is possibly wider due to conspicuous presence of cosmopolitan species characterizing the association. Our work provides a baseline for the knowledge of an alien-dominated plant community that can invade habitats with high conservation value.
... The genus Amaranthus L. (Amaranthaceae Juss. in the strict sense) contains 70-75 species, the majority of which are native to the Americas (Hernández-Ledesma et al., 2015;Bayón, 2015). Several species are used as a food, medicines, or ornamentals and are able to escape from cultivation causing a negative impact on agricultural systems, mainly due to their high seed production and resistance to herbicides, observed at least in some species (see e.g., Tranel & Trucco, 2009;Iamonico, 2010a;Heap, 2014;Das, 2016). ...
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The occurrence and invasion status of Amaranthus hypochondriacus in Belarus, Estonia, Italy, the Netherlands, and the North Caucasus were discussed. For Italy, we change the status from casual to naturalized based on living populations which are able to sustain themselves for 5 and over 20 years. Concerning the other countries, we clarified the invasion status of the species (inconsistently reported in literature) indicating it as a casual alien in Belarus, Estonia, and the North Caucasus and naturalized in the Netherlands. Climatic data of the European stations in which Amaranthus hypochondriacus was found were compared with those referring to the native distribution area (Mexico and southeastern regions of the US). The occurrence of the species in Europe appears to be facilitated by the temperate climate (Dutch and Italian localities), which also characterizes the native distribution area (N-America). The occurrence of the species in Estonia, the Netherlands, and the North Caucasus is interesting. In fact, although the types of climates (“Cold, Dfb” and “Temperate, Cfb”) occur in America (northeastern US and central Mexico), there are some differences in precipitation and temperature values, i.e. lower mean precipitation [644.1 mm (Estonia) vs . 1119 mm (N-America); climate Dfb] and lower mean temperature [9.7–11.1 °C (Netherlands and North Caucasus) vs . 15.3 °C (Mexico); climate Cfb].
... As a result, weeds that emerge in the later stage of the crop (i.e. after the end of the CPWC) may cause damage to the system as a whole. The normal and predictable outcome of natural selection expressed as herbicide resistance (Heap, 2013) and the herbicide-resistant weeds (Sosnoskie and Culpepper, 2014) would add to the weed seed bank. ...
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Weeds are a major biotic constraint to the production of crops. Studies on the critical period of weed control (CPWC) consider the yield loss due to the presence of all weeds present in the crop cycle. The CPWC is the time interval between the critical timing of weed removal (CTWR) and the critical weed-free period (CWFP), and the weed presence before and after the extremes of CTWR and CWFP may not significantly reduce crop yield. The crop yield is taken into consideration and weed density or biomass of individual weeds (annual or perennial) is not so important while calculating the CPWC. Only weed density or biomass is considered for calculating weed control efficiency of a particular management practice for which the weed seed bank is also a criterion. However, weed biomass is the outcome after competition experienced by each weed species with the fellow crop and the weeds. Consequently, the weed pressure in the subsequent season will be the cumulative effect of the preceding season too, which is unaccounted for in CPWC. It is argued that in organic farming or low-input farming systems, where herbicides are not used, the concept of CPWC can be misleading and should be avoided. It is concluded that CTWR is more meaningful than the CPWC.
... Hedef dışı organizmalara etkileri denildiğinde ilk akla gelen etki şekli rüzgar gibi etmenlerle uygulanan kimyasalın sürüklenmesi nedeniyle polikültür yapılan alanlarda büyük sorun oluşabilmektedir. Ayrıca kalıcılığı toprakta yüksek olan kimyasallar bir sonraki üretim sezonunda münavebe bitkisinin üretimini dahi engelleyebilmektedir. Bununla birlikte herbisitlerin etkinliğinin azalmasının en büyük nedeni olan yabancı otlarda dayanıklılığın dünya genelinde artıyor olmasıdır (Heap, 2014). Günümüzde halen yabancı otlara karşı kullanılan herbisitler, ekonomik olması ve biyolojik olarak hedef organizmaya etkili oluşu nedeniyle tercih edilse dahi tüketicilerin organik ürünlere eğilimi ve insanların çevreye olan duyarlılığının artıyor olması nedeniyle yabancı otlara karşı herbisit uygulaması sürdürülebilir bir mücadele yöntemi olmaktan uzaklaşmaktadır (Slaughter ve ark., 2008). ...
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Dünya üzerinde tarımsal üretim, insanlığın var oluşundan itibaren, üretim metodları değişebilse de temelde insanların yaşamlarını sürdürme mücadelesidir. Tarımsal üretimde yetiştirilen üründen optimal verimi elde etmek asıl hedef olmaktadır. Yetiştirilen ürünlerde bir takım sorunlarla karşılaşılmakta ve sorunun boyutuna göre de elde edilen verim değişebilmektedir. Bitkisel üretimde olduğu gibi hayvansal üretimde de yabancı otlar verimin önündeki büyük bir engeli teşkil etmektedir. Yabancı otlar üstün rekabet güçleri ile verim kayıplarına sebebiyet verirler. Kültür bitkisinin yetişme aşamasında arazideki mevcut yabancı otlar var olan büyüme kaynaklarından daha etkin yararlanabilme özelliğine sahip olduklarından dolayı kültür bitkilerinden daha önce gelişimini tamamlayıp kültür bitkilerinin gelişimi için gerekli kaynaklara ulaşabilme imkanını kısıtlamaktadır. Tarımsal üreticiler tarafından çok eski tarihlerden bu yana herhangi bir verim kaybı olmaması için veya kayıpların minimize edilebilmesi için yabancı otlarla mücadele süregelmektedir. Yabancı otlarla elle mücadele şeklinde başlayan mücadele yöntemleri, sonraları teknolojide oluşan çeşitli gelişmelerle birlikte mekanik mücadele, fiziksel mücadele, kimyasal mücadele, biyolojik mücadele gibi çeşitli mücadele yöntemleri şeklinde uygulanmıştır. Bu yöntemler içerisinde en yaygını olanı işçilik ve ekonomik açıdan üreticiyi yormayan yöntem olan kimyasal mücadeledir. Ancak son yıllarda kimyasalların kullanımı sonucu yabancı otlarda direnç oluşması ve tüketicilerde halk sağlığı ve çevre konularında farkındalık oluşumu sebebiyle kimyasal kullanımından gelecekte uzaklaşılacağı düşünülmektedir. Bilim insanları günümüzde teknolojinin gelişimi ve kimyasallara alternatif yöntem arayışıyla robotik mücadeleye yönelmiştir. Robotikler ya hiç kimyasal kullanmayıp mekanik donanımlarıyla yabancı otların zararını önleyebilen ya da hedefe yönelik kimyasal püskürtme mekanizmasına sahip yabancı otlarla mücadele araçlarıdır. Robotikler kimyasallara alternatif olarak yabancı otlarla mücadelede kullanılmasının yanı sıra tarımsal üretimin bütün aşamalarında da kullanılabilmektedir. Bu derlemede yabancı otlarla mücadelede robotiklerin kullanılması ve robotik mücadele hakkında dünya üzerindeki gelişmeler incelenmiştir.
... That said, Roundup-resistant weeds are, indeed, a growing problem that needs to be addressed. However, to put it into perspective, by 2014, weeds have become resistant to 152 different herbicides, emphasizing the importance of managing weeds in a more integrated and sustainable manner [19]. Indeed, in the case of Roundup-resistant weeds, farmers are their own worst enemies-the more they continue to use this herbicide without rotation, the greater chance there will be for the development of resistant weeds. ...
Chapter
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This chapter will explore the reasons why some countries, broadly described as “developed,” do not allow their farmers to plant GM crops. It will then go on to discuss the effects that these attitudes held by “the West” have influenced the uptake of GM crops by Africa and “the Rest.” I will then investigate some of the myths that have been used to turn politicians, decision-makers, and inhabitants of such countries against GM crops, and to consider the importance of communication. As it is necessary to understand why and how certain countries “got it right” and are currently growing GM crops successfully, the last section deals with these issues. The conclusion points to the necessity for countries to learn from mistakes made in the past as we enter the era of new technologies such as genome editing.
... Reference [4] reported that sorghum crops grown in succession showed high sensibility to the residual activity of sulfentrazone, diclosulam, and imazethapyr. As reported by [11], weeds have evolved resistance to 21 out of the 25 known herbicide sites of action and to 152 different herbicides. The ALS inhibitors (126 resistant species) are most prone to resistance, followed by the triazines (69 species) and the ACCase inhibitors (42 species). ...
Article
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Abstract Weed is a serious problem in crop production as it competes with the crop for essential growth factors and results in remarkable yield losses. Conventionally, many agronomic practices have been adopted for weed management, but they are less efficient, expensive, and laborious. Chemical herbicides are effective, but their longterm repeated use may cause weed resistance and serious environmental pollution. Considering all the secondary effects and environmental impact of herbicides, the future of weed management is to rely on alternative approaches such as the biological method of weed control. One such upcoming biological approach to control weed is the use of deleterious rhizobacteria (DRB). DRB is reported to suppress the weed dynamics providing scope for the crop to compete with the suppressed weeds for the essential growth requirements. This review focuses on the potentiality of DRB to be used as a bioherbicide. Keywords: bioherbicide, deleterious rhizobacteria, phytotoxin, Pseudomonas, weed
... On the other side, multiple resistance refers to situations where a weed population is resistant to two or more herbicides possessing two or more distinct resistance mechanisms. Quick evolution of resistance occurs due to the selection pressure imposed by exposure to single herbicide or different herbicides with similar mode of action [7]. Poor herbicide efficacy has been reported in P. minor due to evolution of cross-resistance and/or multiple resistance. ...
Article
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Multiple resistance to different herbicides used for management of Phalaris minor Retz. in Northern India was quantified for its two populations—one susceptible and the other resistant to acetyl-CoA carboxylase (ACCase) inhibitor herbicide clodinafop-propargyl. Clodinafop-propargyl and pinoxaden at their recommended dose recorded complete control of clodinafop-propargyl susceptible P. minor population, whereas sulfosulfuron and mesosulfuron plus iodosulfuron at their recommended dose exhibited 48.5 and 51.5% control of this population. In clodinafop-propargyl-resistant P. minor population, sulfosulfuron and mesosulfuron plus iodosulfuron even at 4X dose did not cause any mortality; however, pinoxaden at 4X dose caused complete mortality at 30 DAS. Metribuzin plus clodinafop-propargyl applied at all the doses (0.25X, 0.5X, X, 2X and 4X) recorded complete mortality of both the populations. Application of different herbicides caused reduction in chlorophyll fluorescence and chlorophyll content index in leaves of both the populations in a dose-dependent manner. But the magnitude of reduction was higher in susceptible population as compared to the resistant population.
... Weeds are recognized as major biological constraints that hinder the attainment of optimal rice productivity (Smith, 1968). Currently, chemical herbicides have been used extensively throughout the world to control weeds, prevent crop decline, and enhance productivity (Heap, 2014). As a pre-emergent herbicide [2-chloro-2,6-diethyl-N-(2-propoxyethyl) acetanilide], pretilachlor has effective herbicidal activities against weeds in rice fields by preventing plant cells and algae from generating long-chain fatty acids (Diyanat et al., 2019). ...
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In this study, pretilachlor was encapsulated into polyurea microcapsules prepared by water-initiated polymerization of polyaryl polymethylene isocyanate and eventually made into pretilachlor microcapsules suspension (PMS). We used response surface methodology (RSM) combined with the Box–Behnken design (BBD) model to optimize the formulation of PMS. The encapsulation efficiency (EE) of PMS was investigated with respect to three independent variables including wall material dosage (X1), emulsifier dosage (X2), and polymerization stirring speed (X3). The results showed that the regression equation model had a satisfactory accuracy in predicting the EE of PMS. To achieve an optimal condition for PMS preparation, the dose of wall material was set to 5%, the dose of emulsifier was set to 3.5% and the polymerization stirring speed was set to 200 rpm. The EE of PMS was up to 95.68% under the optimized condition, and the spherical shape with smooth surface morphology was observed. PMS was also proven to have delayed release capability and in vivo herbicidal activity against barnyard grass [Echinochloa crusgalli (L.) Beauv.] with an LC50 value of 274 mg/L. Furthermore, PMS had efficient weed management compared to commercially available 30% pretilachlor emulsifier (PE), showing a promising potential application for weeding paddy fields.
... With the rapid growth of the world's population and the acceleration of industrialization, herbicides are widely used for weed control in farmlands, orchards and urban green spaces (Jiang et al., 2018;Masiol et al., 2018). At present, there are more than 300 herbicide active ingredients and 1500 products in the market (Heap, 2014). As much as 30 billion dollars of herbicides are applied in agricultural cultivation globally each year, which will continue to rise with the popularization of genetically modified crops (Bruinsma, 2017). ...
... Many farmers use herbicide-based weed control for conservation agriculture [4,5]. Such overreliance on herbicides is problematic because of the development of herbicide-resistant weeds, non-target impacts on biodiversity, and human health concerns associated with exposure to herbicides [6]. Ecological weed management will facilitate the sustainable intensification of conservation agriculture by reducing farmer reliance on herbicides. ...
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... In addition, when nonselective post-emergence herbicides could be used (e.g., glyphosate, glufosinate), single herbicides could be directly injected into the spray lines to control all species (Qui et al. 1994a, b;Ollila et al. 1990;Goudy et al. 2001). However, weed resistance to both pre-and post-emergence herbicides has become more commonplace (Owen and Zelaya 2005;Heap 2014Heap , 2020Zimdahl 2010), such that reliance on a single or limited mode-of-action spectrum of herbicides is highly undesirable and solutions other than synthetic herbicides are needed (Bridges 2000;Busi et al. 2013;Green 2014). In the short term, however, with a major reliance on herbicides, the current trend has been to return to multiple selective herbicides with weed species needing to be recognized. ...
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Nitrogen (N) is crucial for plant nutrition and is often a limiting factor for biomass production that feeds humans and animals and contributes to energy and material use. N fertilization aims at a high N use efficiency, with a maximum of N input taken up by the crop. Otherwise, N losses to water and air will harm the environment and the climate. Farmers should adopt a well-balanced crop N management, and variable-rate fertilization enables adjusting N fertilization according to plant status and needs. For more than 20 years, sensor technologies have involved handheld devices supplemented with satellite technology. Today, the launch of the two twin satellites Copernicus Sentinel-2A/B has yielded a higher spectral and spatial resolution. These data can help improve N fertilization. In this chapter, we describe our steps to evaluate sensor and satellite technologies using field data collected under optimal conditions and including different stages of N fertilization. The close cooperation between remote sensing experts, soil scientists, agronomists, and practitioners was crucial for the success of the field experiments. Our findings yielded productivity maps that serve as a basis for N fertilization maps for use by commonly applied farm machinery.
... In addition, when nonselective post-emergence herbicides could be used (e.g., glyphosate, glufosinate), single herbicides could be directly injected into the spray lines to control all species (Qui et al. 1994a, b;Ollila et al. 1990;Goudy et al. 2001). However, weed resistance to both pre-and post-emergence herbicides has become more commonplace (Owen and Zelaya 2005;Heap 2014Heap , 2020Zimdahl 2010), such that reliance on a single or limited mode-of-action spectrum of herbicides is highly undesirable and solutions other than synthetic herbicides are needed (Bridges 2000;Busi et al. 2013;Green 2014). In the short term, however, with a major reliance on herbicides, the current trend has been to return to multiple selective herbicides with weed species needing to be recognized. ...
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Agricultural crops require nutrients to support their growth and to produce abundant, nutritious food for humans and animals. Soil fertility researchers evaluate the nutrient status of soils before selecting the right source and amount of fertilizer to apply to crops. They also consider the best time and place to add fertilizers so the nutrients will be used efficiently by the crop. Technological advances make it possible to apply nutrient-rich fertilizers to crops in smaller doses and with greater precision at the field scale, which avoids nutrient losses from agroecosystems to surrounding environments. Low-cost sensors should improve our understanding of nutrient availability in slow-release fertilizers such as animal manure, which will lead to better storage and handling and precise application. Increasing the precision of soil fertility management will sustain the agricultural production of farms while protecting the health of ecosystems and populations in the surrounding environment.
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Competition from weeds often reduces wheat yields, especially in organic management systems or when herbicide-resistant weeds are present. Breeding wheat for increased competitive ability is an important aspect of integrated weed control. Selecting directly for weed-competitive ability (WCA), however, is challenged by difficult field measurements, genotype by environment interactions, and low heritability. To improve selection efficiency, breeding programs can utilize secondary selection traits that are easier to measure, have higher heritability and are highly correlated with WCA. To identify potential secondary selection traits for WCA, we conducted a meta-analysis of the published literature, and contributed new data from the northeastern United States. Among studies worldwide, early vigor was easy to measure and consistently correlated with WCA. Early plant height also showed promise as a correlated secondary selection trait for WCA, and had high heritability. Tillering, maturity timing, and growth habit were inconsistently correlated with WCA among environments and weed species studied. WCA and the correlated trait of early vigor were influenced by genotype by environment interactions. As a result, decentralized breeding would maximize gain from selection for WCA.
Chapter
Weeds affect crops by directly competing for water, nutrients, light, and space, and can cause a severe reduction in yield if left uncontrolled in the field. Weed management is one of the main aspects for successful crop production. Alopecurus myosuroides is a major annual weed, especially in Western Europe and Western Asia, and is well adapted to arable cropping situations. This weed causes substantial yield losses in a range of different crops, especially cereals. Due to its rapid emergence and adaption to arable cropping rotations, it can remain in the field for long periods of time and effectively compete with cultivated crops. A. myosuroides has a high reproductive rate, as a consequence of its high seed output, and populations can build up rapidly. It is one of the most important herbicide-resistant weeds in Europe and some West Asian countries, including Turkey and Israel, and its resistance evolution is much faster when compared with many other herbicide-resistant weeds. This weed species has become a serious threat to current cropping systems due to its wide genetic diversity, invasiveness, and ecological adaptations. This chapter reviews all aspects of A. myosuroides systematics and morphology, habitat and distribution, germination, reproduction, seed dispersal mechanism, seed biology, and its invasive properties. Management scenarios, including future prospects, are also discussed. The importance of the role that cultural practices play in weed control is emphasized (including crop rotation, plowing, delayed autumn sowing, use of competitive crop cultivars, spring cropping, fallowing, and use of high seed rates). Integrated management approaches, which include a greater emphasis on non-chemical methods, as well as more rational herbicide use, are vital in avoiding ever-increasing problems with herbicide resistance.
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The allelopathic effect of various concentrations (0, 6.25, 12.5, 50 and 100 g L−1) of Parthenium hysterophorus methanol extract on Cyperus iria was investigated under laboratory and glasshouse conditions. No seed germination was recorded in the laboratory when P. hysterophorus extract was applied at 50 g L−1. In the glasshouse, C. iria was mostly injured by P. hysterophorus extract at 100 g L−1. The phytochemical constituents of the methanol extract of P. hysterophorus were analyzed by LC-ESI-QTOF-MS=MS. The results indicated the presence of phenolic compounds, terpenoids, alkaloids, amino acids, fatty acids, piperazines, benzofuran, indole, amines, azoles, sulfonic acid and other unknown compounds in P. hysterophorus methanol extract. A comparative study was also conducted between P. hysterophorus extract (20, 40 and 80 g L−1) with a synthetic herbicide (glyphosate and glufosinate ammonium at 2 L ha−1) as a positive control and no treatment (negative control) on Ageratumconyzoides, Oryzasativa and C. iria. The growth and biomass of test weeds were remarkably inhibited by P. hysterophorus extract. Nevertheless, no significant difference was obtained when P. hysterophorus extract (80 g L−1) and synthetic herbicides (glyphosate and glufosinate ammonium) were applied on A.conyzoides.
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Isophorone (3,5,5‐trimethylcyclohex‐2‐en‐1‐one) is a plant‐derived volatile compound with strong phytotoxic activity. Here, we aimed to elucidate the mechanism of action of isophorone, and to this end, the effects of isophorone on shoot fresh weight, chlorophyll content, electrolyte leakage, and lipid peroxidation of Lactuca sativa L. and photosynthetic electron transport activity in chloroplast isolated from Spinacia oleracea L. were investigated. Isophorone induced light‐independent decreases in shoot fresh weight and light‐dependent chlorosis. In addition, increased electrolyte leakage and lipid peroxidation occurred under light conditions. However, the inhibitory activity on photosynthetic electron transport was unexpectedly low, and electrolyte leakage and lipid peroxidation were induced even under dark conditions. These results suggest that the inhibition of photosynthetic electron transport is not the main mechanism of action of isophorone and that the phytotoxic effects are mainly due to light‐independent oxidative damage and subsequent loss of cell membrane integrity.
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Genetic engineering is a molecular technique of altering the existing genome by inserting a novel gene from external. Genetically Modified Organisms (GMOs) are at the center stage of international debate because it causes many social, economic, and ecological problems. The commercialization of GMOs created more and more ethical dilemmas related to horizontal gene transfer and biodiversity. A critical analysis of genetic engineering (GE) and transgenic crops is indispensable in this situation. The science of biotechnology is essential for the advancement of human life. But the fundamental questions concerning biosafety and environment are still lingering unanswered. For example, the relationship between different genes and its traits is not so collinear as it was considered earlier. The more we know about genes the more the complexities of the gene expression. The role of regulatory genes in the expression, the combined outcome of many genetic factors, the pleiotropic effect of genes, the stable inheritance of DNA segment, the chances of escaping of genes from GMOs are questions still not responded. The influence of other epigenetic factors is also not appropriately investigated in recombinant DNA technology. The present article attempts to analyze these essential questions. The future of biotechnology lies in the development of GMOs with less environmental hazards. This is crucial as this is having a direct influence on human beings. A treatise of the debate taken place in the past 20 years concerning socio-economic, environmental, and ethical issues of genetic engineering is scrutinized in this review. The consequences of transgenics on biodiversity such as the evolution of pest and herbicide resistance and outcrossing of genes, impacts of GM crops on soil, controversies associated with the seed industry and IPR are the important arenas of discourse. The latest techniques like genome editing by altering the nucleotides and the benefits and threats of GM crops has also conversed. More advanced transgenic technologies would be required to develop successful GM plants on large scale to meet, food demands in the future. Public education about biotechnology is most important in this milieu. A new relationship between public and academics is necessary to develop research plans in plant biotechnology.
Article
Weed resistance to herbicides represents the acquired resistance of individuals to complete the life cycle and leave offspring in the conditions of extended exposure to the same herbicide, i.e. herbicides of the same mechanism of action to which they were sensitive at the beginning of the application. Based on the herbicide resistance mechanisms, all processes can be grouped as follows: target-site resistance, non-target-site resistance, cross-resistance and multiple-resistance. Currently, herbicide resistance has been reported in 514 cases (species x site of action) worldwide, in 262 weed species (152 dicotyledons, 110 monocotyledons). Many of those biotypes are resistant to als inhibitors, PS II inhibitors, EPSPS inhibitors and ACC-ase inhibitors. The higher degree of resistance to als inhibitors has been confirmed in the following weed species: Amaranthus retroflexus, Sorghum halepense, Ambrosia artemisiifolia and Helianthus annuus.
Chapter
Natural products obtained from microbes, plants and animals find their potential use as biofertilizers and biopesticides sustaining and enhancing crop production and protection. Among them microbes and their metabolites with excellent plant growth-promoting and biocontrol properties have been identified, mass produced successfully, appropriately formulated and are commercially available for use. Compounds of microbial origin which make them efficient biofertilizers and biopesticides enhancing plant growth and providing protection from various biotic and abiotic stress include production of plant growth-promoting hormones like auxins, giberrelins, cytokinins and 1-aminocyclopropane-1-carboxylate deaminase (ACCD); production of antagonistic compounds such as antibiotics, crystal proteins, hydrolytic enzymes, siderophores, hydrogen cyanide, etc. Additionally, these beneficial microbes also compete for food and habitat with phytopathogens or parasitize the pests and eliminate them. Majority of the microbes and their bioactive molecules are target specific, eco-friendly and biodegradable and play an important role in preserving the ecosystem. These eco-friendly natural products could either supplement or replace the hazardous agrochemicals thereby minimize or nullify their use. Screening and selection of the microbial strains based on its geographical origin will make the bioformulation more suitable for a particular agroclimatic condition, and this needs intensive studies on microbial ecology and interaction with other components of the ecosystem. Research focus on ways to improve the efficacy of these biomolecules, and mass production of these natural products for its utilization and commercial availability will build a path towards environment-friendly agriculture. Alternatively, research that focusses to elucidate the chemistry of natural compounds and to synthesize compounds that mimic them is also being done to ensure the demand-supply balance. This chapter will shed light on potentials and prospectives of the use of natural bioactive compounds of microbial origin in enhancing crop protection and yield.
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Climate change has greatly impacted agronomy. Climate forecasts for the coming years predict increases in global temperature, carbon dioxide concentration, and extreme weather events. These changes will continue to influence agricultural production by altering abiotic stress on plants, including crops and weeds. Kochia, one of the most common weeds in North America, is a C4 plant exceptional for its drought tolerance. Kochia has also demonstrated rapid adaption and evolution to the abiotic stress of herbicide application, particularly glyphosate. Abiotic stresses from both climate change and herbicides impact the distribution and expansion of kochia. Being aware of the features and properties of kochia, especially those resulting from herbicide resistance, will help anticipate how kochia responds or migrates under future climate change, and help create proper strategies for kochia weed management.
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There is growing consideration among farmers and researchers regarding the development of natural herbicides providing sufficient levels of weed control. The aim of the present study was to compare the efficacy of four different pelargonic acid products, three essential oils and two natural products' mixtures against L. rigidum Gaud., A. sterilis L. and G. aparine L. Regarding grass weeds, it was noticed at 7 days after treatment that PA3 treatment (pelargonic acid 3.102% w/v + maleic hydrazide 0.459% w/v) was the least efficient treatment against L. rigidum and A. sterilis. The mixture of lemongrass oil and pelargonic acid resulted in 77% lower dry weight for L. rigidum in comparison to the control. Biomass reduction reached the level of 90% as compared to the control in the case of manuka oil and the efficacy of manuka oil and pelargonic acid mixture was similar. For sterile oat, weed biomass was recorded between 31% and 33% of the control for lemongrass oil, pine oil, PA1 (pelargonic acid 18.67% + maleic hydrazide 3%) and PA4 (pelargonic acid 18.67%) treatments. In addition, the mixture of manuka oil and pelargonic acid reduced weed biomass by 96% as compared to the control. Regarding the broadleaf species G. aparine, PA4 and PA1 treatments provided a 96-97% dry weight reduction compared to the corresponding value recorded for the untreated plants. PA2 (pelargonic acid 50% w/v) treatment and the mixture of manuka oil and pelargonic acid completely eliminated cleaver plants. The observations made for weed dry weight on the species level were similar to those made regarding plant height values recorded for each species. Further research is needed to study more natural substances and optimize the use of natural herbicides as well as natural herbicides' mixtures in weed management strategies under different soil and climatic conditions.
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A prototype of a relatively cheap laser-based weeding device was developed and tested on couch grass (Elytrigia repens (L.) Desv. ex Nevski) mixed with tomatoes. Three types of laser were used (0.3 W, 1 W, and 5 W). A neural network was trained to identify the weed plants, and a laser guidance system estimated the coordinates of the weed. An algorithm was developed to estimate the energy necessary to harm the weed plants. We also developed a decision model for the weed control device. The energy required to damage a plant depended on the diameter of the plant which was related to plant length. The 1 W laser was not sufficient to eliminate all weed plants and required too long exposure time. The 5 W laser was more efficient but also harmed the crop if the laser beam became split into two during the weeding process. There were several challenges with the device, which needs to be improved upon. In particular, the time of exposure needs to be reduced significantly. Still, the research showed that it is possible to develop a concept for laser weeding using relatively cheap equipment, which can work in complicated situations where weeds and crop are mixed.
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Di-n-butyl phthalate (DBP) is an extensively used plasticizer. Most investigations on DBP have been concentrated on its environmental distribution and toxicity to humans. However, information on the effects of plasticizers on algal species is scarce. This study verified the impacts of endocrine disruptor di-n-butyl phthalate ester on microalga Chlorella vulgaris by approaches of proteomics and gene ontology. The algal acute biotoxicity results showed that the 24h-EC50 of DBP for C. vulgaris was 4.95 mg L-1, which caused a decrease in the chlorophyll a content and an increase in the DBP concentration of C. vulgaris. Proteomic analysis led to the identification of 1257 C. vulgaris proteins. Sixty-one more proteins showed increased expression, compared to proteins with decreased expression. This result illustrates that exposure to DBP generally enhances protein expression in C. vulgaris. GO annotation showed that both acetolactate synthase (ALS) and GDP-L-fucose synthase 2 (GER2) decreased more than 1.5-fold after exposure to DBP. These effects could inhibit both the valine biosynthetic process and the nucleotide-sugar metabolic process in C. vulgaris. The results of this study demonstrate that DBP could inhibit growth and cause significant changes to the biosynthesis-relevant proteins in C. vulgaris.
Article
Eucalyptus spp. and Acacia spp. have been reported as major invaders in several regions and Mediterranean climates. It has been documented that E. globulus and E. camaldulensis can serve as resources of allelochemicals, which can be used as tools of control strategy of noxious weed species infesting the agricultural areas of the Mediterranean region. Additionally, the remarkable allelopathy potential of A. dealbata Link against various weed species has been highlighted in many recent studies. There is also evidence that other species belonging to Acacia spp. can suppress the native vegetation, including weeds, due to their allelopathic potential. However, allelochemical extracts from different plant tissues seem variable in terms of their effects on various species germination and growth parameters. Furthermore, the effectiveness of the allelochemicals in weed management is also a matter of choosing the most appropriate application rate at any case. In the present review, aspects of the potential role of Eucalyptus spp. and Acacia spp. allelochemicals in weed management were discussed. Further research is needed in order to optimize the use of such allelochemicals produced by invasive plants in the Mediterranean region in both organic and sustainable agriculture systems.
Chapter
Weeds occur in patches across landscapes and vary in species, density, time of emergence, and growth rate depending on location. Precision weed management accounts for natural and management-induced variation to optimize inputs (control methodology) to reduce weed presence and improve crop yields across an area. When Anita and I started research on precision weed management, there were few options on data collection and fewer methods to change techniques on-the-go. Today, there are multiple methods to collect and process information and use these data to determine appropriate actions. In some cases, maps are made and utilized to direct herbicide type and appropriate rate. If autonomous weeders are used, data imagery collected by on-board sensors immediately signal an actuator for control placement. No matter the method, understanding which weeds are present, location, density, and the appropriate control and timing are critical for success. In the future, agronomists will be expected to have knowledge, skills, and abilities that range from traditional weed science (weed species identification, herbicide and other control information, potential crop loss) to today’s less common competencies, such as understanding robotics and manipulating and managing big data sets.
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Although the auxinic herbicides were the first selective organic herbicides developed and continue to be a very important class of herbicides, their precise mode of action is still unknown. These herbicides are generally phytotoxic to broadleaf plants, causing little or no damage to monocots, which makes these herbicides very important agrochemicals for selective weed control in grass and cereal crops. Auxins and auxinic herbicides appear to induce a large number of physiological and morphological responses in plants including cell elongation, epinasty, hypertrophy, root initiation and ethylene biosynthesis. On a biochemical level, these auxin effects have been associated with a rapid influx of calcium, activation of plasma membrane ATPase and an increase in nucleic acid and protein biosynthesis. These biochemical responses are thought to be initiated by a specific receptor that, when binding with auxins or auxinic herbicides, initiates a biochemical cascade. The precise nature of the putative auxin receptor and the nature of the signal that initiates the observed cascade of biochemical events remains unknown. Identification of plants that are resistant to auxins and/or auxinic herbicides may help us elucidate the exact mechanism of action, thereby shedding light on a fundamental plant hormonal response.
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In grasses, residues homologous to residues Ile-1,781 and Ile-2,041 in the carboxyl-transferase (CT) domain of the chloroplastic acetyl-coenzyme A (CoA) carboxylase (ACCase) from the grass weed black-grass (Alopecurus myosuroides [Huds.]) are critical determinants for sensitivity to two classes of ACCase inhibitors, aryloxyphenoxypropionates (APPs) and cyclohexanediones. Using natural mutants of black-grass, we demonstrated through a molecular, biological, and biochemical approach that residues Trp-2,027, Asp-2,078, and Gly-2,096 are also involved in sensitivity to ACCase inhibitors. In addition, residues Trp-2,027 and Asp-2,078 are very likely involved in CT activity. Using three-dimensional modeling, we found that the side chains of the five residues are adjacent, located at the surface of the inside of the cavity of the CT active site, in the vicinity of the binding site for APPs. Residues 1,781 and 2,078 are involved in sensitivity to both APPs and cyclohexanediones, whereas residues 2,027, 2,041, and 2,096 are involved in sensitivity to APPs only. This suggests that the binding sites for these two classes of compounds are overlapping, although distinct. Comparison of three-dimensional models for black-grass wild-type and mutant CTs and for CTs from organisms with contrasted sensitivity to ACCase inhibitors suggested that inhibitors fitting into the cavity of the CT active site of the chloroplastic ACCase from grasses to reach their active sites may be tight. The three-dimensional shape of this cavity is thus likely of high importance for the efficacy of ACCase inhibitors.
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Grass weed populations resistant to aryloxyphenoxypropionate (APP) and cyclohexanedione herbicides that inhibit acetyl-CoA carboxylase (ACCase; EC 6.4.1.2) represent a major problem for sustainable agriculture. We investigated the molecular basis of resistance to ACCase-inhibiting herbicides for nine wild oat (Avena sterilis ssp. ludoviciana Durieu) populations from the northern grain-growing region of Australia. Five amino acid substitutions in plastid ACCase were correlated with herbicide resistance: Ile-1,781-Leu, Trp-1,999-Cys, Trp-2,027-Cys, Ile-2,041-Asn, and Asp-2,078-Gly (numbered according to the Alopecurus myosuroides plastid ACCase). An allele-specific PCR test was designed to determine the prevalence of these five mutations in wild oat populations suspected of harboring ACCase-related resistance with the result that, in most but not all cases, plant resistance was correlated with one (and only one) of the five mutations. We then showed, using a yeast gene-replacement system, that these single-site mutations also confer herbicide resistance to wheat plastid ACCase: Ile-1,781-Leu and Asp-2,078-Gly confer resistance to APPs and cyclohexanediones, Trp-2,027-Cys and Ile-2,041-Asn confer resistance to APPs, and Trp-1,999-Cys confers resistance only to fenoxaprop. These mutations are very likely to confer resistance to any grass weed species under selection imposed by the extensive agricultural use of the herbicides.
Chapter
Humans have struggled against the negative impact of weeds since the cultivation of crops commenced around 10,000 B.C.¹ Weed control technologies have evolved from hand-weeding to include primitive hoes (6000 B. C.), animal-powered implements (1000 B. C.), mechanically powered implements (1920 A. D.), biological control (1930 A. D.), and chemical (herbicide) control (1947 A. D.). ¹ Since the introduction of the first selective herbicides, 2,4-D and MCPA, in 1947, herbicides have had a major positive impact on world agricultural production, initially in developed nations and more recently in developing nations. ² Herbicides are often the most reliable and least expensive method of weed control available, and the success of herbicides is largely responsible for the abundant and sustained food production necessary to support an increasing world population. ³ The availability of herbicides has allowed plant breeders to move from taller, more competitive crop varieties to shorter, higheryielding crop varieties. ⁴ The efficacy and cost-effectiveness of herbicides has led to heavy reliance on them in the developed world. Nevertheless, there are some real and perceived problems with herbicides. In recent years there has been increased concern about residues and associated food safety issues, their adverse impact on the environment, ⁵ and the widespread occurrence of herbicide-resistant weeds. ⁶ The focus of this book is on the last of these concerns.
Article
A naturally occurring prickly lettuce biotype resistant to a 5:1 formulated mixture of chlorsulfuron:metsulfuron (DPX-G8311) was identified in a no-till winter wheat field near Lewiston, ID, in April, 1987. Field and greenhouse studies were established to evaluate its resistance to other sulfonylureas, imidazolinones, and herbicides with alternate sites of action. The resistant biotype resisted eight sulfonylurea herbicides; resisted the imidazolinone herbicides, imazapyr and imazethypyr, but not imazaquin; and resisted no other herbicides included in the studies. The resistant biotype was identified in seven of nine fields on the farm where it was discovered.
Article
Failure to control common groundsel (Senecio vulgaris L.) was observed in 1968 in a nursery where 2-chloro-4,6-bis(ethylamino)- s -triazine (simazine) or 2-chloro-4-(ethylamino)-6-(isopropylamino)- s -triazine (atrazine) had been used once or twice annually since 1958. Seedlings from seed collected at that location were not controlled by pre-emergence applications of simazine or atrazine at rates up to 17.92 kg/ha. Seedlings from a seed source where triazine herbicides had not been in continuous use were completely controlled by 1.12 or 2.24 kg/ha of either chemical, and partially controlled by 0.28 to 0.56 kg/ha. Postemergence applications of atrazine at 1.12, 2.24, or 4.48 kg/ha did not affect common groundsel from the nursery source, but killed small seedlings from the other source. Preemergence applications of four other herbicides were equally effective against seedlings from both sources.
Chapter
In 1970, Ryan (Ryan, 1970) reported that a population of Senecio vulgaris (L.) was not controlled by recommended rates of simazine in a conifer nursery in Washington state (USA). Since this first report, resistance to photosystem II (PS II) inhibitor herbicides has become widespread. In terms of numbers of species, triazine resistance is the most prevalent type of herbicide resistance found in weeds (Holt and LeBaron, 1990; LeBaron, 1991; LeBaron and MacFarland, 1990). The most recent worldwide survey of herbicide resistance, which was conducted in 1989, indicated that there were 57 weed species with biotypes resistant to triazine herbicides (LeBaron, 1991). In the majority of cases, resistance to PS II-inhibiting herbicides is due to a modification at the target site, the DI protein of the PS II reaction center (Trebst, 1991). Since the mid-1980’s, there have been increasing reports of resistance to PS II inhibitors due to enhanced herbicide detoxification (Burnet et al., 1993a,b; Gronwald et al., 1989; Hoagland et al., this volume; Kemp et al., 1990; Leah et al., 1994).
Article
Reports the occurrence of a population of Wimmera ryegrass Lolium rigidum tolerant to a herbicide (known commercially as Hoegrass) used for emergence control of this weed, together with wild oats Avena fatua, in cereal and legume crops.-P.J.Jarvis
Article
A population of L. rigidum, which is known to have developed resistance to one of the diphenyl-ethertype of herbicides, diclofop-methyl, was tested for cross-resistance to three other herbicides of the same type, namely fluazifop-butyl, oxyfluorfen and the experimental herbicide CGA 82725. The population was also tested for cross-resistance to two sulfonylurea-type herbicides - chlorsulfuron and the experimental herbicide DPX-T6376. A population susceptible to diclofop-methyl was used as the controls in the tests. The two populations were treated with various rates of the herbicides during germination and at the two-leaf stage. The results show that the diclofop-methyl-resistant biotype was cross-resistant to fluazifop-butyl, CGA 82725, chlorsulfuron and DPX-T6376 but not to oxyfluorfen.
Article
Herbicide rotations and mixtures are widely recommended to manage herbicide resistance. However, little research has quantified how these practices actually affect the selection of herbicide resistance in weeds. A 4-yr experiment was conducted in western Canada From 2004 to 2007 to examine the impact of herbicide rotation and mixture in selecting for acetolactate synthase (ALS) inhibitor resistance in the annual broadleaf weed, field pennycress, co-occurring in wheat. Treatments consisted of the ALS-inhibitor herbicide, ethametsulfuron, applied in a Mixture with bromoxynil/MCPA formulated herbicide (photosystem-II inhibitor/synthetic auxin), or in rotation with the non-ALS inhibitor at an ALS-inhibitor application frequency of 0, 25, 50, 75, and 100% (i.e., zero to four applications, respectively) over the 4-yr period. The field pennycress seed batik at the start of the experiment contained 5% ethametsulfuron-resistant seed. Although weed control was only marginally reduced, resistance frequency of progeny of survivors increased markedly after one ALS-inhibitor application. At the end of the experiment, the level of resistance in the seed bank was buffered by susceptible seed, increasing from 29% of recruited seedlings after one application to 85% after four applications of the ALS inhibitor. The level of resistance in the seed bank for the mixture treatment after 4 yr remained similar to that of the nontreated (weedy) control or 0% ALS-inhibitor rotation frequency treatment. The results of this study demonstrate how rapidly ALS-inhibitor resistance can evolve as a consequence of repeated application of herbicides with this site of action, and supports epidemiological information from farmer questionnaire surveys and modeling Simulations that mixtures are more effective than rotations in mitigating resistance evolution through herbicide selection.
Article
The mechanism of glyphosate resistance in horseweed was investigated. Eleven biotypes of putative sensitive (S) and resistant (R) horseweed were obtained from regions across the United States and examined for foliar retention, absorption, translocation, and metabolism of glyphosate. Initial studies used spray application of 14C-glyphosate to simulate field application. When S and R biotypes were compared in the absence of toxicity at a sublethal dose, we observed comparable retention and absorption but reduced root translocation in the R biotypes. S and R biotypes from Delaware were further examined at field use rates and results confirmed similar retention and absorption but reduced root translocation in the R biotypes. Application of 14C-glyphosate to a single leaf demonstrated reduced export out of the treated leaf and lower glyphosate import into other leaves, the roots, and the crown in R relative to S biotypes. Examination of the treated leaf by autoradiography showed that glyphosate loading into the apoplast and phloem was delayed and reduced in the R biotype. Our results consistently showed a strong correlation between impaired glyphosate translocation and resistance. Tissues from both S and R biotypes showed elevated levels of shikimate suggesting that 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) remained sensitive to glyphosate. Analysis of tissue shikimate levels demonstrated reduced efficiency in EPSPS inhibition in the R biotypes. Our results suggest that resistance is likely due to altered cellular distribution that impaired phloem loading and plastidic import of glyphosate resulting in reduced overall translocation as well as inhibition of EPSPS. Nomenclature: Glyphosate; horseweed, Conyza canadensis (L.) Cronq. ERICA.
Article
Few studies on herbicide resistance report data to establish unambiguously the correlation between genotype and phenotype. Here we report on the importance of the EPSPS prolyl106 point mutation to serine (P106S) in conferring resistance to glyphosate in a goosegrass population from Davao, Mindanao Island, the Philippines (Davao). Initial rate-response studies showed clear survivors within the Davao population at glyphosate rates that completely controlled the standard sensitive goosegrass population (STD1). Assessment of potential resistance mechanisms identified the presence of P106S mutant individuals in the Davao population. Polymerase chain reaction (PCR) amplification of specific alleles (PASA) analysis established that the mixed-resistant Davao population was comprised of 39.1% homozygous proline wild-type (PP106), 3.3% heterozygous serine mutant (PS106), and 57.6% homozygous serine mutant (SS106) genotypes. Further rate-response studies on plants with a predetermined genotype estimated the Davao SS106 individuals to be approximately 2-fold more resistant to glyphosate compared to Davao PP106 individuals. Extensive analysis at different goosegrass growth stages and glyphosate rates established strong correlation (P < 0.001) between presence of P106S in EPSPS and the resistant phenotype. Importantly, no differences in the pattern of absorbed or translocated 14C–glyphosate were observed between PP106 and SS106 Davao genotypes or Davao and STD1 individuals, suggesting that glyphosate resistance in the Davao population was attributable to an altered target site mechanism. This study demonstrates that whilst P106S in EPSPS confers a moderate resistance level to glyphosate, the mechanism is sufficient to endow glyphosate failure at the recommended field rates. Nomenclature: Glyphosate; goosegrass, Eleusine indica (L.) Gaertn. ELEIN.
Article
After 25 years of sales, glyphosate (N-(phosphonomethyl)glycine) is the world's biggest selling and fastest growing agrochemical. Glyphosate has many strengths, particularly its systemicity and ability to control perennial weeds, which have facilitated its role as an essential tool in modern agriculture. Surveys of recent scientific and patent literature point to several key areas of current and future interest in glyphosate and its use. Biotechnology topics have been the most popular, but there is still much interest in the molecule per se, particularly in manufacturing processes. The mode of action and physiology of glyphosate are common subjects. More applied aspects concern the development of formulations with new adjuvants, or mixtures with other herbicides, to enhance performance. An increasing number of papers are reporting on its environmental fate and on agronomic techniques designed to improve the efficiency of application and minimise its environmental impact. Lack of weed resistance is a key feature of glyphosate despite its widespread use. However, differential levels of tolerance between species have led to changes in weed succession. There is a need to develop integrated weed management systems in which glyphosate still plays a key role. Glyphosate is an exceedingly effective herbicide and presents a considerable challenge to the development of new herbicides for sustainable cropping systems and situations in which cost-effective and environmentally considerate weed control is required.© 2000 Society of Chemical Industry
Article
Glyphosate herbicide is the largest-selling single crop-protection chemical product in the market today. This non-selective weedkiller was initially targeted at the non-crop areas in agriculture and for industrial applications but, with the continuing development of minimum- and no-tillage agricultural practices, glyphosate also found usage in a number of crop outlets. Most recently, glyphosate has found direct crop usage on plant varieties that have been genetically modified to be tolerant of glyphosate applications. Such has been the continuing success of the product that its annual volume consumption growth has averaged in excess of 20% in recent years in agricultural use.© 2000 Society of Chemical Industry
Article
Phalaris paradoxa (awned canary-grass) is an aggressive annual winter weed in wheat and other arable crops that is controlled mainly by ACCase-inhibiting herbicides: cyclohexanediones (DIMs), aryloxyphenoxypropionates (FOPs) and phenylpyrazolines (DENs, e.g. pinoxaden). The selection pressure imposed on the weed populations by repeated use of these herbicides has resulted in the evolution of increased numbers of ACCase-resistant populations of P. paradoxa in Israel and other countries. Two populations, Revadim (RV) and Mishmar Ha’emek (MH) that were exposed to differing weed and crop management tactics were investigated. Both populations were highly resistant to all FOPs, pinoxaden and cycloxydim, but responded differently to some DIMs. RV plants exhibited much higher resistance to tralkoxydim than MH plants, while showing similar low levels of resistance to tepraloxydim and clethodim. Both populations were equally susceptible to graminicides with other modes of action. The mutations responsible for the observed resistance were identified using PCR-RFLP and by sequencing the carboxyl transferase domain of the chloroplastic ACCase gene. RV plants possess a substitution of Asp2078 to Gly, whereas in MH population a mixture of Ile2041 to Asn or Asp2078 to Gly was found. Our study demonstrates that lack of herbicide and crop rotation may result in the evolution of diverse target site mutations and differential response of the whole plant to ACCase inhibitors.
Article
The development of herbicide resistance in weeds poses a severe threat to weed control and crop production. For the aryloxyphenoxypropionates and cyclohexanediones which act on the plastidic ACCase of grass weeds, resistance usually occurs by alteration of the target site protein. In three species, Setaria viridis, Lolium rigidum, and Avena fatua, this has been shown to be associated with a mutation in the ACCase gene, resulting in an isoleucine to leucine substitution in the enzyme. Here we report the same amino acid substitution in the ACCase of sethoxydim-resistant Alopecurus myosuroides. The presence of the leucine correlates with a resistant phenotype and the presence of an insensitive ACCase. In one population, plants heterozygous for the mutation showed different levels of sensitivity and in some cases it was demonstrated that both alleles were expressed in the same plant. The fact that the leucine present in the insensitive plastidic ACCases of several graminaceous species with evolved resistance is also present in the naturally occurring insensitive plastidic ACCase of dicotyledons suggests that the selectivity of these herbicides also results from the same amino acid differences.
Article
Pest management has changed dramatically during the past 15 years by the introduction of transgenes into crops for the purpose of pest management. Transgenes for herbicide resistance or for production of one or more Bt toxins are the predominant pest management traits currently available. These two traits have been rapidly adopted where available because of their superior efficacy and simplification of pest management for the farmer. Furthermore, they have substantially reduced the use of environmentally and toxicologically suspect pesticides while reducing the carbon footprint of pest management as reduced tillage became more common, along with fewer trips across the field to spray pesticides. The most successful of these products have been glyphosate-resistant crops, which cover approximately 85% of all land occupied by transgenic crops. Over-reliance on glyphosate with continual use of these crops has resulted in the evolution of highly problematic glyphosate-resistant weeds. This situation has resulted in some farmers using weed management methods similar to those used with conventional crops. Evolution of resistance has not been a significant problem with Bt crops, perhaps because of a mandated resistance management strategy. Transgenic crops with multiple genes for resistance to different herbicides and resistance to additional insects will be available in the next few years. These products will offer opportunities for the kind of pest management diversity that is more sustainable than that provided by the first generation of transgenic crops.
Article
The commercial launch of glyphosate-resistant soybeans in 1996 signaled the beginning of a new era in weed management in row crops. Today, over 80% of the soybeans grown in the USA are glyphosate resistant. Since that time, many crops have been transformed that have allowed crop applications of many classes of herbicide chemistries. Crops currently under production include maize, soybean, cotton and canola. Transformation technology and selection methods have improved and the rate of development as well as the breadth of crops being considered as commercial targets has increased. On the basis of recent adoption rates by growers around the world, it appears that glyphosate-resistant crops will continue to grow in number and in hectares planted. However, global public acceptance of biotechnology-derived products will continue to impact the rate of adoption of this and other new innovations derived from transformation technology.
Article
The sulfonylurea herbicide chlorsulfuron blocks the biosynthesis of the amino acids valine and isoleucine in plants. Addition of these two amino acids to excised pea root (Pisum sativum L. var Alaska) cultures incubated in the presence of chlorsulfuron completely alleviates herbicide-induced growth inhibition. The site of action of chlorsulfuron is the enzyme acetolactate synthase which catalyzes the first step in the biosynthesis of valine and isoleucine. This enzyme is extremely sensitive to inhibition by chlorsulfuron having I(50) values ranging from 18 to 36 nanomolar. In addition, acetolactate synthase from a wide variety of tolerant and sensitive plants species is highly sensitive to inhibition by chlorsulfuron.
Article
Glyphosate-resistant crops (GRCs) were first introduced in the United States in soybeans in 1996. Adoption has been very rapid in soybeans and cotton since introduction and has grown significantly in maize in recent years. GRCs have grown to over 74 million hectares in five crop species in 13 countries. The intent of this paper is to update the hectares planted and the use patterns of GRC globally, and to discuss briefly future applications and uses of the technology. The largest land areas of GRCs are occupied by soybean (54.2 million ha), maize (13.2 million ha), cotton (5.1 million ha), canola (2.3 million ha) and alfalfa (0.1 million ha). Currently, the USA, Argentina, Brazil and Canada have the largest plantings of GRCs. Herbicide use patterns would indicate that over 50% of glyphosate-resistant (GR) maize hectares and 70% of GR cotton hectares receive alternative mode-of-action treatments, while approximately 25% of GR soybeans receive such a treatment in the USA. Alternative herbicide use is likely driven by both agronomic need and herbicide resistance limitations in certain GR crops such as current GR cotton. Tillage practices in the USA indicate that > 65% of GR maize hectares, 70% of GR cotton hectares and 50% of GR soybean hectares received some tillage in the production system. Tillage was likely used for multiple purposes ranging from seed-bed preparation to weed management. GRCs represent one of the more rapidly adopted weed management technologies in recent history. Current use patterns would indicate that GRCs will likely continue to be a popular weed management choice that may also include the use of other herbicides to complement glyphosate. Stacking with other biotechnology traits will also give farmers the benefits and convenience of multiple pest control and quality trait technologies within a single seed.
Gene amplification is a mechanism for glyphosate resistance evolution
  • T A Gaines
  • C Preston
  • J E Leach
  • S T Chisholm
  • D L Shaner
  • T. A. Gaines
The International Survey of Herbicide Resistant Weeds
  • I Heap
Site of action of chlorsulfuron
  • T B Ray
Crop losses due to pests in major crops
  • E C Oerke
Introduction and overview of resistance
  • I M Heap
  • H Lebarron
  • I. M. Heap
The World’s Worst Weeds: Natural Histories and Distribution
  • L Holm
  • J Doll
  • E Holm
  • J Pancho
  • J Herberger
  • L. Holm
Investigations into glyphosate-resistant horseweed (Conyza Canadensis): Retention, uptake, translocation, and metabolism
  • P C C Feng
  • M Tran
  • R D Sammons
  • G R Heck
  • C A Cajacop
  • P. C. C. Feng
Importance of the P106S target-site mutation in conferring resistance to glyphosate in a goosegrass (Eleusine indica) population from the Philippines
  • S S Kaundun
  • I A Zelaya
  • R P Dale
  • A J Lycett
  • P Carter
  • S. S. Kaundun