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1.
BACKGROUND: Environmental heterogeneity in space or time can drive the evolutionary trajectory of an adaptive trait. This concept could be of practical significance in pesticide resistance management that aims to delay the evolution of a resistance allele. Using a population genetics model, the dynamics of herbicide resistance in a weed species was simulated in a heterogeneous environment with alternation of two unrelated herbicides in time, in space or in both time and space. The level of the environmental heterogeneity (habitat grain) was simulated by a variation in the size of the herbicide-treated areas. RESULTS: The model confirms that several strategies based on habitat heterogeneity efficiently slow down and even prevent resistance evolution. For a recessive resistant trait in outcrossing species, a medium level of environmental heterogeneity (intermediate habitat grain) was found to be the best for delaying herbicide resistance, as previously observed for insecticide resistance management. In selfing species or for a dominant resistant trait in outcrossing species, a low level of environmental heterogeneity (coarse-grained habitat) was more efficient in delaying resistance evolution when heterogeneity in both space and time were considered. CONCLUSION: This model suggests that the choice of optimal tactics for delaying herbicide resistance by enhanced heterogeneity in space or time firstly depends on the interactions between the breeding system and the dominance of the resistance allele in the presence of herbicide, then on the value of the fitness cost and lastly on the dominance of this fitness cost.  相似文献   

2.
Cyperus difformis (smallflower umbrella sedge) is an economically important weed of rice in California where its control has recently been complicated by the evolution of herbicide resistance. Knowledge of the mating system of this weed is needed to elucidate the dynamics of resistance evolution and to design mitigation strategies that delay its occurrence. The aim of this study was to estimate the outcrossing rate of C. difformis using molecular and phenotypic markers. Outcrossing rates were estimated in natural field populations using sequence-related amplified polymorphism (SRAP) molecular markers and in glasshouse and field experiments using resistance to the acetolactate synthase-inhibiting herbicide bensulfuron-methyl as a phenotypic marker. Using SRAP markers, the multilocus ( t m) and average single-locus ( t s) outcrossing rates varied from 0.014 to 0.025 and from 0.008 to 0.012, respectively, among natural weed populations in rice fields. Using resistance to bensulfuron-methyl as a genetic marker, the average C. difformis outcrossing rate estimated was 0.009 in the glasshouse and 0.0084 in the field. These results indicate that C. difformis is a highly self-fertilising species. Therefore, the primary mechanism by which genes for herbicide resistance can be transferred among C. difformis populations in different rice fields is probably seed dispersal. Weed management should emphasise prevention of seed production and dispersal to preclude the further spread and evolution of resistance in C. difformis .  相似文献   

3.
Diclofop-methyl resistance was evaluated in populations of Italian ryegrass ( Lolium multiflorum Lam.) infected and uninfected with fungal endophyte ( Neotyphodium ). Survival was tested in susceptible populations using herbicide screening. The results served as inputs to a model for investigating the role of endophyte infection in the evolution of L. multiflorum resistance to herbicide. The tolerance of infected plants varied depending on the origin of the population and the herbicide dose. Only in some populations and at some diclofop-methyl doses did plants infected with these endophytes have higher survivorship than endophyte-free plants. The model demonstrated that endophytes might indeed play an important role in the evolution of herbicide-resistant weeds, delaying the appearance of herbicide resistance.  相似文献   

4.
It is suggested that selection for late germinating seed cohorts is significantly associated with herbicide resistance in some cropping systems. In turn, it is conceivable that rotating herbicide modes of action selects for populations with mutations for increased secondary dormancy, thus partially overcoming the delaying effect of rotation on resistance evolution. Modified seed dormancy could affect management strategies – like herbicide rotation – that are used to prevent or control herbicide resistance. Here, we review the literature for data on seed dormancy and germination dynamics of herbicide‐resistant versus susceptible plants. Few studies use plant material with similar genetic backgrounds, so there are few really comparative data. Increased dormancy and delayed germination may co‐occur with resistance to ACCase inhibitors, but there is no clear‐cut link with resistance to other herbicide classes. Population shifts are due in part to pleiotropic effects of the resistance genes, but interaction with the cropping system is also possible. We provide an example of a model simulation that accounts for genetic diversity in the dormancy trait, and subsequent consequences for various cropping systems. We strongly recommend adding more accurate and detailed mechanistic modelling to the current tools used today to predict the efficiency of prevention and management of herbicide resistance. These models should be validated through long‐term experimental designs including mono‐herbicide versus chemical rotation in the field. © 2017 Society of Chemical Industry  相似文献   

5.

Background

Annual sowthistle is a weed that is difficult to control in lentil crops in southern Australia due to a lack of herbicide options, widespread herbicide resistance and prolific production of highly mobile seed. This study investigates herbicide resistance in annual sowthistle in the Mid-North (MN) and Yorke Peninsula (YP) regions of South Australia, identifies and characterizes the mechanisms of acetolactate-synthase (ALS)-inhibitor resistance in this amphidiploid species, and combines this with analyses of population structure and gene flow.

Results

ALS-inhibitor-resistant annual sowthistle is widespread across the YP and MN of South Australia and is associated with a variety of Proline-197 mutations of the ALS gene, including leucine, alanine, arginine, serine, threonine and histidine. These mutations were found in different combinations on either of the two copies of the ALS gene. An additional 200 tissue samples were collected from across a single field on the YP and the ALS gene was sequenced for all these individuals. Different ALS-inhibitor resistance profiles were evident between mutation combinations and within mutation combinations, possibly mediated by differing subgenome assortment of the mutations, or altered gene experession of the two ALS homeologs. Population genetics analysis showed evidence of long-distance dispersal, resulting in highly mobile resistance genes, and multiple instances of resistance mutation evolution.

Conclusions

Continuing selection of Sonchus oleraceus populations with ALS-inhibiting herbicides has resulted in the accumulation of additional mutations within the ALS gene. New practices to control herbicide-resistant S. oleraceus should be examined, and control should focus on reducing seed set and dispersal to prevent the spread of emerging cases of resistance. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.  相似文献   

6.
The management of weeds in Malaysian rice fields is very much herbicide‐based. The heavy reliance on herbicide for weed control by many rice‐growers arguably eventually has led to the development and evolution of herbicide‐resistant biotypes in Malaysian rice fields over the years. The continuous use of synthetic auxin (phenoxy group) herbicides and acetohydroxyacid synthase‐inhibiting herbicides to control rice weeds was consequential in leading to the emergence and prevalence of resistant weed biotypes. This review discusses the history and confirmed cases and incidence of herbicide‐resistant weeds in Malaysian rice fields. It also reviews the Clearfield Production System and its impact on the evolution of herbicide resistance among rice weed species and biotypes. This review also emphasizes the strategies and management options for herbicide‐resistant rice field weeds within the framework of herbicide‐based integrated weed management. These include the use of optimum tillage practices, certified clean seeds, increased crop competition through high seeding rates, crop rotation, the application of multiple modes of action of herbicides in annual rotations, tank mixtures and sequential applications to enable a broad spectrum of weed control, increase the selective control of noxious weed species in a field and help to delay the resistance evolution by reducing the selection pressure that is forced on those weed populations by a specific herbicidal mode of action.  相似文献   

7.
Despite frequent use for the past 25 years, resistance to glyphosate has evolved in few weed biotypes. The propensity for evolution of resistance is not the same for all herbicides, and glyphosate has a relatively low resistance risk. The reasons for these differences are not entirely understood. A previously published two‐herbicide resistance model has been modified to explore biological and management factors that account for observed rates of evolution of glyphosate resistance. Resistance to a post‐emergence herbicide was predicted to evolve more rapidly than it did to glyphosate, even when both were applied every year and had the same control efficacy. Glyphosate is applied earlier in the growing season when fewer weeds have emerged and hence exerts less selection pressure on populations. The evolution of glyphosate resistance was predicted to arise more rapidly when glyphosate applications were later in the growing season. In simulations that assumed resistance to the post‐emergence herbicide did not evolve, the evolution of glyphosate resistance was less rapid, because post‐emergence herbicides were effectively controlling rare glyphosate‐resistant individuals. On their own, these management‐related factors could not entirely account for rates of evolution of resistance to glyphosate observed in the field. In subsequent analyses, population genetic parameter values (initial allele frequency, dominance and fitness) were selected on the basis of empirical data from a glyphosate‐resistant Lolium rigidum population. Predicted rates of evolution of resistance were similar to those observed in the field. Together, the timing of glyphosate applications, the rarity of glyphosate‐resistant mutants, the incomplete dominance of glyphosate‐resistant alleles and pleiotropic fitness costs associated with glyphosate resistance, all contribute to its relatively slow evolution in the field.  相似文献   

8.
Dominance of a resistance trait can be defined as a measure of the relative position of the phenotype of the heterozygote RS compared with the phenotype of the two corresponding homozygotes, SS and RR. This parameter has been shown to have primary importance in the dynamics of pesticide resistance evolution. Literature on insecticide resistance suggests that dominance levels in the presence of insecticide vary greatly from completely recessive to completely dominant. With insecticides, both the chemical applied and the dosages used have been demonstrated to affect the dominance. By contrast, almost all herbicide resistances have been found to be inherited as partially to totally dominant traits. This discrepancy between weeds and insects may partly result from the methodologies applied to measure the dominance, ie a single dose for herbicide versus several doses for insecticide. Using two well-known resistances (csr1-1 and csr1-2) to acetolactate synthase (ALS) inhibitors in Arabidopsis thaliana (L) Heynh (mouse-ear cress), we used several herbicide doses to determine the dominance level to six ALS-inhibiting herbicides. The dominance level in the presence of herbicide varied from completely dominant to completely recessive, depending on the resistance allele and the herbicide tested. The dominance of the csr1-1 and csr1-2 resistance alleles ranged from 0 (completely recessive) to 1.1 (dominant) and from 0 to 0.3 (partially dominant), respectively. The recessivity of some resistance alleles in the presence of herbicide could lead to the development of improved resistance management in order to delay or avoid herbicide resistance evolution, especially in the control of outcrossing weed species.  相似文献   

9.
A simple life-cycle-based demography model was adapted for two contrasting weed species ( Alopecurus myosuroides and Poa annua ). This model included a seed production function that accounted for population self-regulation through weed:weed interactions. The A. myosuroides version of the model was tested with field data. Long-term simulations of population demography were then performed to investigate the relationship between weed control strategies based on density thresholds and both the frequency of herbicide use and the long-term economic profitability. This study confirms that threshold-based weed management strategies are more cost-effective than spraying every year and may allow important reductions in herbicide use. However, after the first transient years of either systematically spraying or withholding herbicide, the long-term spraying frequency was insensitive to threshold values between 0.01 and 100 plants m−2. The highest long-term profitability was obtained for the lowest threshold tested, and the profitability decreased rapidly when the threshold was raised above 4–6 and 10–20 plants m−2 for A. myosuroides and P. annua respectively. The study thus indicates that the exact threshold value is of little importance for the long-term reliance of the system on herbicide, provided that it is reasonably low. For species with low competitive ability, high thresholds may be used in some cropping systems to reduce the spraying frequency for environmental considerations, but those options would also reduce the profitability if no compensatory measures were taken.  相似文献   

10.
An invasive plant species may restrict its spread to only one type of habitat,or,after some time,may continue to spread into a different,often stressful,secondary,habitat.The question of whether evolution is required for an invasive species to spread from one habitat to another is currently hotly debated.In order for local adaptation to occur,genetic variation must be present within invasive populations.In this paper,I focus on the effect of habitat on the maintenance of genetic variation during the lag phase,the phase of population stability prior to expansion.Genetic diversity in invasive plant populations accumulates through multiple introductions,gene flow,mutation,and hybridization,but diversity is maintained by population level processes influencing effective population size(Ne).I show that when the plastic response to the environment results in little variation in reproductive output among individuals,Ne is maximized and genetic variation is maintained.Established models of plant competition show that below-ground competition reduces the variation in reproductive output,whereas competition for light increases variation in reproductive output.The same environments that maintain high Ne also reduce the opportunity for selection and minimize the response to selection,and thus the effects of the environment are synchronized to prevent genetic purges.When the primary invasion habitat supports high Ne,conditions are ripe for local adaptation to a secondary habitat,particularly if the secondary habitat has high opportunity for selection.When the primary invasion habitat supports low Ne,genetic diversity is less likely to be sufficient for local adaptation to secondary habitat to occur.  相似文献   

11.
In recent years the potential for evolutionary change to drive ecological dynamics, and vice versa, has been widely recognized. However, the convincing examples of eco-evolutionary dynamics mainly stem from highly artificial experimental systems, with conspicuously few examples contributed by field systems. While rarely considered in the eco-evolutionary literature, the gene-for-gene hypothesis inherently recognizes the tight link between evolutionary and ecological dynamics. The boom-and-bust dynamics of some agricultural pathogens are an extreme demonstration of this. In this perspective, we place plant-pathogen systems in a spatial eco-evolutionary framework, which recognizes that ecology and evolution are tightly linked, take place at the same time scale and are strongly influenced by spatial structure. Specifically, we: i) exemplify how the ecological process of dispersal modifies rapid local coevolutionary dynamics and thereby shapes spatial variation in resistance, infectivity, and local adaptation; and ii) illustrate how the outcome of coevolution (spatial distribution in resistance, infectivity and local adaptation) drives ecological metapopulation processes. Overall, we conclude that both agricultural and wild pathosystems provide a unique illustration of the high relevance of spatial eco-evolutionary feedback in understanding species interactions.  相似文献   

12.
A simulation study was conducted to examine the effect of pattern of herbicide use on development of resistance to two herbicides with different modes of action in finite weed populations. The effects of the size of the treatment area (analogous to initial weed population), germination fraction and degree of self‐pollination in the weed were investigated. The results indicate that the probability of developing resistance to one or both herbicides decreases as the size of the area/initial population decreases. For treatment areas of 100 ha or less with an initial weed seedbank of 100 seeds m?2 and initial frequencies of the resistance genes of 10?6, development of resistance to both herbicides (double‐resistance) is uncommon within 50 years for all types of weeds if both herbicides are used in all years (used in combination). If herbicides are used in alternate years (rotated) double‐resistance almost always occurs in 100 ha areas but is uncommon in areas of 1 ha or less. The results suggest that adoption of practices that limit movement of weeds in conjunction with using herbicides in combination rather than in rotation can substantially delay development of herbicide resistance.  相似文献   

13.
牛筋草是一年生禾本科恶性杂草, 在我国黄淮海流域及长江以南地区的农田危害严重。草甘膦是一种优良的非选择性除草剂, 随着生物育种产业化的推进, 草甘膦会逐步在玉米、大豆等作物田登记应用。育种基地抗草甘膦杂草的产生是其快速传播的潜在因素。为明确三亚一育种基地牛筋草种群对草甘膦的敏感性, 本研究利用生物测定、分子生物学等方法检测了待测种群的抗性水平, 并分析了可能的分子机制。结果发现, 草甘膦对牛筋草种群的生长抑制中量为2 053.0 g/hm2(有效成分用量), 抗性指数(RI)为5.0; 靶标基因EPSPS的保守区域无突变, 但相对表达量是敏感种群的47.4倍; 抗性植株中EPSPS蛋白的浓度是敏感植株的17.1倍。以上结果表明, 该牛筋草种群对草甘膦产生了中等水平抗性, 靶标基因过量表达是其抗性机制之一。  相似文献   

14.
BACKGROUND: Herbicide mixtures are commonly proposed to delay the selection of herbicide resistance in susceptible populations (called the SM strategy). However, in practice, herbicide mixtures are often used when resistance to one of the two active ingredients has already been detected in the targeted population (called the RM strategy). It is doubtful whether such a practice can select against resistance, as the corresponding selection pressure is still exerted. As a consequence, the effect of mixtures on the evolution of an already detected resistance to one of the herbicides in the combination remains largely unexplored. In the present work, a simple model was developed to explore further the necessary and sufficient conditions under which a binary RM strategy might stabilise or even reduce resistance frequency. RESULTS: Covering the hypothetical largest range of parameters, 39% of 9000 random simulations attest that the RM strategy might theoretically reduce resistance frequency. When strong enough, high genetic cost of resistance, negative cross‐resistance between the herbicides associated in the mixture and reduced selection differential between resistant and susceptible plants can counterbalance the resistance advantage to one of the two applied herbicides. However, the required conditions for an RM strategy to ensure resistance containment in natural conditions seldom overlap with experimental parameter estimates given in the literature. CONCLUSION: It is concluded that the sufficient conditions for an RM strategy to be effective would rarely be encountered. As a consequence, the strategy of formulating mixtures with herbicides for which resistance has already been detected should be avoided. Copyright © 2008 Society of Chemical Industry  相似文献   

15.
The potential impact of herbicide-tolerant winter oilseed rape ( Brassica napus L.) on future herbicide use was investigated with a simulation model. The model uses a sigmoid function to simulate the growth of crops and weeds that compete for a maximum yield potential. Thresholds for weed control are based upon critical levels of weed biomass. The dynamics of the weed population are determined by the efficacy of representative herbicides on individual weed species and by seedbank parameters. Herbicide efficacy is determined by a log-logistic dose–response curve for each species. Simulation of a rotation with winter oilseed rape/wheat/wheat/barley showed contradictory predictions of herbicide use, because herbicide use in a rotation with either glyphosate- or glufosinate-tolerant oilseed rape was not reduced in the amount of kg a.i. ha–1 compared with a traditional treatment, whereas the treatment frequency (number of standard recommended doses per unit area) decreased.  相似文献   

16.
Populations of Lolium multiflorum (ryegrass) exposed to increasing levels of herbicide selection have variability in the rate of evolution of herbicide resistance. We tested the hypothesis that herbicide dose and gene flow with related species are important factors regulating the rate of evolution of herbicide resistance in L. multiflorum. Seeds of the latter were planted in pure stands and in mixture with Festuca rubra and subjected to four herbicide rates. The level of herbicide resistance attained by the offspring after two years of selection was evaluated. Evolution of resistance observed in the field was compared to that calculated by Gressel and Segel's rotational model. ©1997 SCI  相似文献   

17.
As herbicide‐resistant weeds have spread in the agricultural fields of grain‐exporting countries, their seeds could be introduced into other countries as contaminants in imported grain. The spread of resistance genes through seed and pollen can cause significant economic loss. In order to assess the extent of the problem, we investigated the contamination by herbicide‐resistant annual ryegrass (Lolium rigidum) of wheat imported from Western Australia into Japan. Annual ryegrass seeds were recovered from wheat shipments and seed bioassays were conducted to identify resistance to the herbicides that are commonly used in Australia: diclofop‐methyl, sethoxydim, chlorsulfuron, and glyphosate. Nearly 4500 ryegrass seeds were detected in 20 kg of wheat that was imported in both 2006 and 2007. About 35% and 15% of the seeds were resistant to diclofop‐methyl, 5% and 6% were resistant to sethoxydim, and 56% and 60% were resistant to chlorsulfuron in 2006 and 2007, respectively. None was resistant to glyphosate in either year. As the contamination of crops by herbicide‐resistant weeds is probably a common phenomenon, the monitoring of incoming grain shipments is necessary to stem the further spread of herbicide‐resistant weeds into importing countries.  相似文献   

18.
A molecular genetic assessment of herbicide-resistant Sinapis arvensis   总被引：1，自引：0，他引：1  
MEIKLE  FINCH  McROBERTS  & MARSHALL 《Weed Research》1999,39(2):149-158
The acquisition of resistance to both the auxinic herbicide dicamba and the sulfonylurea herbicide chlorsulfuron has been recorded in Canadian populations of the weed species Sinapis arvensis L. (charlock, wild mustard) To study the effect of this selection for herbicide resistance on levels of genetic variation, polymerase chain reaction-based DNA fingerprinting techniques were used to characterize two herbicide-resistant and one susceptible population of S. arvensis . Analysis of the resultant DNA marker profiles revealed extensive polymorphism between individuals. However, segregation of the three biotypes was detectable despite high levels of intrabiotype polymorphism. No reduction in the levels of heterozygosity within the resistant populations were found compared with the susceptible population.  相似文献   

19.
Two major weeds in rice in the Philippines, Sphenochlea zeylanica Gaertn. and Echinochloa crus‐galli (L.) Beauv., are controlled with chemical and cultural methods. In the 1980s, after >10 years of continuous use of 2,4‐D, S. zeylanica evolved resistance to the chemical in those rice fields that had been treated with 2,4‐D once or twice every cropping season. In the 1990s, E. crus‐galli evolved resistance to butachlor and propanil in rice monocrop areas where both herbicides were used continuously for 7–9 years. Rice farmers continue to use 2,4‐D, butachlor and propanil extensively and are often unaware of herbicide resistance or the potential for cross‐resistance, its causes or its implications. In order to control herbicide‐resistant E. crus‐galli, farmers are shifting to locally available herbicides with different modes of action, such as bispyribac, an acetolactate synthase inhibitor, and cyhalofop, an acetyl coenzyme A carboxylase inhibitor. Follow‐up manual weeding or rotary weeding after herbicide spraying, a common farmers’ practice, removes the susceptible and resistant biotypes and could help to delay or prevent the evolution of resistance. Although the resistance mechanisms of both weeds are not determined yet, they could be related to enhanced degradation that is similar to the mechanisms that are shown by the resistant biotypes in other countries.  相似文献   

20.
植物谷胱甘肽转硫酶及其与杂草抗药性的关系   总被引：2，自引：0，他引：2  
谷胱甘肽转硫酶(GSTs)是由一个超基因家族编码的广泛存在于好氧生物中的多功能蛋白。GST通常都是成簇地非随机地分布在染色体中。每种植物GSTs家族一般有25～60个成员。根据植物GST序列的相似性、基因结构、蛋白中的活性位点,分成6类(6个家族)。其中Phi类和Tau类是植物特有的常见类型,Zeta和Theta类通常存在于动物中。GST基因尽管在序列和功能上表现很高的多样性,但它们都有相似的空间结构。大部分GST都是胞质型的,通常以二聚体的形式发挥功能,具有亲电疏水性异物谷胱甘肽化酶、谷胱甘肽依赖的异构化酶、谷胱甘肽过氧化物酶和还原毒性有机过氧化物酶等酶学功能,还以非酶学结合的方式来保护植物细胞,例如作为内源性毒物的植物激素或类黄酮类物质的配体(分子伴侣或载体)与GST结合。酶学和非酶学这两种功能都与异物或有毒内源性物质的解毒和防止细胞氧化损伤有关。除草剂的谷胱甘肽化是杂草产生抗药性的机制之一。谷胱甘肽通过过氧化物酶功能消除除草剂造成的氧化逆境而间接参与杂草抗药性。  相似文献   

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