Fitness costs associated with evolved herbicide resistance alleles in plants

Predictions based on evolutionary theory suggest that the adaptive value of evolved herbicide resistance alleles may be compromised by the existence of fitness costs. There have been many studies quantifying the fitness costs associated with novel herbicide resistance alleles, reflecting the importance of fitness costs in determining the evolutionary dynamics of resistance. However, many of these studies have incorrectly defined resistance or used inappropriate plant material and methods to measure fitness. This review has two major objectives. First, to propose a methodological framework that establishes experimental criteria to unequivocally evaluate fitness costs. Second, to present a comprehensive analysis of the literature on fitness costs associated with herbicide resistance alleles. This analysis reveals unquestionable evidence that some herbicide resistance alleles are associated with pleiotropic effects that result in plant fitness costs. Observed costs are evident from herbicide resistance-endowing amino acid substitutions in proteins involved in amino acid, fatty acid, auxin and cellulose biosynthesis, as well as enzymes involved in herbicide metabolism. However, these resistance fitness costs are not universal and their expression depends on particular plant alleles and mutations. The findings of this review are discussed within the context of the plant defence trade-off theory and herbicide resistance evolution

Evolved polygenic herbicide resistance in Lolium rigidum by low-dose herbicide selection within standing genetic variation

The interaction between environment and genetic traits under selection is the basis of evolution. In this study, we have investigated the genetic basis of herbicide resistance in a highly characterized initially herbicide-susceptible Lolium rigidum population recurrently selected with low (below recommended label) doses of the herbicide diclofop-methyl. We report the variability in herbicide resistance levels observed in F1 families and the segregation of resistance observed in F2 and back-cross (BC) families. The selected herbicide resistance phenotypic trait(s) appear to be under complex polygenic control. The estimation of the effective minimum number of genes (NE), depending on the herbicide dose used, reveals at least three resistance genes had been enriched. A joint scaling test indicates that an additive-dominance model best explains gene interactions in parental, F1, F2 and BC families. The Mendelian study of six F2 and two BC segregating families confirmed involvement of more than one resistance gene. Cross-pollinated L. rigidum under selection at low herbicide dose can rapidly evolve polygenic broad-spectrum herbicide resistance by quantitative accumulation of additive genes of small effect. This can be minimized by using herbicides at the recommended dose which causes high mortality acting outside the normal range of phenotypic variation for herbicide susceptibility

Economic impacts of high labour cost and herbicide resistance for the management of annual barnyardgrass (Echinochloa crus-galli) in rice production in the Philippines

Implications of increasing labour cost and development of herbicide resistance for profitable weed management in Philippine rice farming systems are investigated. The study employs RIMPhil (Resistance and Integrated Management in the Philippines), a bioeconomic simulation model developed to provide a comprehensive assessment of integrated weed management programmes for the control of annual barnyardgrass (Echinochloa crus-galli) in rice crops. Results indicate that herbicide application will become increasingly economically attractive, relative to manual weeding, as labour cost increases. This is important since urban migration in the Philippines continues to increase the scarcity of rural labour. Results also show that the onset of herbicide resistance results in substantial losses in farm profit. It may be worthwhile for farmers to take management actions to prevent or delay the onset of herbicide resistance, provided that these changes are effective and not too costly. The study highlights the complexity of decision making about integrated weed management on rice farms in the Philippines.Barnyardgrass, Bioeconomic model, Herbicide resistance, Integrated weed management, Rice production, Crop Production/Industries, Farm Management, Research and Development/Tech Change/Emerging Technologies,

Herbicide Resistance in Crops and Weeds

Herbicide resistance, whether as a potential problem in weeds, or as a potentially important agronomic tool, has become an extremely volatile issue in agriculture. Documents such as Biotechnology\u27s Bitter Harvest suggest that herbicide resistance in crops will be a major environmental and economic disaster. Industry representatives suggest that herbicide resistant crops will be excellent tools for growers and actually improve the environmental safety of herbicide use. Agronomists voice concerns about the appearance of weed biotypes that demonstrate herbicide resistance. This paper will provide an objective review of herbicide resistance in crops and weeds and suggest possible results of herbicide resistance specifically for Iowa agriculture

Herbicide Resistance

Herbicide resistance is defined as the inherited ability of a plant to survive a dosage of a herbicide to which the wild population is sensitive . Weeds that are resistant to specific herbicides have become dominant members of field populations in many locations throughout the world. These resistant populations have caused growers considerable economic loss and long term management considerations. Plant geneticists have recently introduced crops that have been developed specifically for enhanced tolerance or resistance to herbicides that typically cause serious injury to the hybrids or varieties. These events, the development of herbicide resistant weed populations and the release of herbicide resistant crops, likely will cause considerable change in how growers manage weeds. The issues surrounding herbicide resistance will have considerable impact on agriculture in the 1990\u27s. This paper will provide background information concerning these issues and suggest strategies that will lessen the likelihood of serious environmental and economic impact resulting from herbicide resistance

Herbicide resistance in turfgrass: a chance to change the future?

Herbicide resistance has for decades been an increasing problem of agronomic crops such as corn and soybean. Several weed species have evolved herbicide resistance in turfgrass systems such as golf courses, sports fields, and sod production—particularly biotypes of annual bluegrass and goosegrass. Consequences of herbicide resistance in agronomic cropping systems indicate what could happen in turfgrass if herbicide resistance becomes broader in terms of species, distribution, and mechanisms of action. The turfgrass industry must take action to develop effective resistance management programs while this problem is still relatively small in scope. We propose that lessons learned from a series of national listening sessions conducted by the Herbicide Resistance Education Committee of the Weed Science Society of America to better understand the human dimensions affecting herbicide resistance in crop production provide tremendous insight into what themes to address when developing effective resistance management programs for the turfgrass industry

Herbicide-resistant weeds : from research and knowledge to future needs

Synthetic herbicides have been used globally to control weeds in major field crops. This has imposed a strong selection for any trait that enables plant populations to survive and reproduce in the presence of the herbicide. Herbicide resistance in weeds must be minimized because it is a major limiting factor to food security in global agriculture. This represents a huge challenge that will require great research efforts to develop control strategies as alternatives to the dominant and almost exclusive practice of weed control by herbicides. Weed scientists, plant ecologists and evolutionary biologists should join forces and work towards an improved and more integrated understanding of resistance across all scales. This approach will likely facilitate the design of innovative solutions to the global herbicide resistance challenge

Pigweed Herbicide Resistance

One of the most amazing features of nature has been its ability to adapt and evolve. Through genetic drifts, mutations, and many more factorials, species change to be best suited to survive anything that may threaten the population. As society has advanced, we have become the threat to many things we consider pests. One of which is weeds. Since herbicides took off, and even more so with the creation of crops genetically modified against herbicides that allow mass spraying, the genetic pool of weeds have been becoming selected to largely consist of organisms that are resistant to herbicide. A common weed throughout much of North America, Pigweed is one known for its growing herbicide resistance. Different varieties are separately developing resistances to different herbicides. This study was conducted to test the herbicide resistance of different species with different herbicide types. Red root, prostrate, and powell pigweed varieties were grown for 18 days after which groups of plants from each variety will be treated with either 0.0 (control), 0.03125x, 0.0625x, 0.125x, 0.25x, 0.5x, or 1x dose rates of Spartan, Pursuit, 2 4-D, and Roundup. Then they will be checked on for updates 1, 3, 5, 7, 14, and 21 days after to gather data on how well they are doing, looking at the damage present on them. That data will then be used to see the plants resistance to the different herbicides

Fitness of herbicide-resistant weeds: Current knowledge and implications for management

Herbicide resistance is the ultimate evidence of the extraordinary capacity of weeds to evolve under stressful conditions. Despite the extraordinary plant fitness advantage endowed by herbicide resistance mutations in agroecosystems under herbicide selection, resistance mutations are predicted to exhibit an adaptation cost (i.e., fitness cost), relative to the susceptible wild-type, in herbicide untreated conditions. Fitness costs associated with herbicide resistance mutations are not universal and their expression depends on the particular mutation, genetic background, dominance of the fitness cost, and environmental conditions. The detrimental effects of herbicide resistance mutations on plant fitness may arise as a direct impact on fitness-related traits and/or coevolution with changes in other life history traits that ultimately may lead to fitness costs under particular ecological conditions. This brings the idea that a “lower adaptive value” of herbicide resistance mutations represents an opportunity for the design of resistance management practices that could minimize the evolution of herbicide resistance. It is evident that the challenge for weed management practices aiming to control, minimize, or even reverse the frequency of resistance mutations in the agricultural landscape is to “create” those agroecological conditions that could expose, exploit, and exacerbate those life history and/or fitness traits affecting the evolution of herbicide resistance mutations. Ideally, resistance management should implement a wide range of cultural practices leading to environmentally mediated fitness costs associated with herbicide resistance mutations.Fil: Vila Aiub, Martin Miguel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura; Argentina. University of Western Australia; Australi