scholarly journals Herbicide-resistant crops : A weed scientist’s perspective

2005 ◽  
Vol 75 (4) ◽  
pp. 71-77 ◽  
Author(s):  
W.E. Dyer
Keyword(s):  
Herbicide Resistance ◽  
Resistance Genes ◽  
Weed Management ◽  
Alternative Strategy ◽  
Environmentally Benign ◽  
Valuable Alternative ◽  
Herbicide Resistant ◽  
Genetic Modifications ◽  
Selection Of

Herbicide-resistant crops offer a potentially valuable alternative strategy for weed management. If used appropriately, they may promote the use of agrichemicals more environmentally benign than the herbicides they replace, and provide producers with additional tools for controlling weeds. However, the controversy surrounding the development and use of these cultivars may limit and eventually prevent their widespread adoption. Concerns include: overuse of herbicides, escape of herbicide resistance genes from resistant cultivars into weedy relatives, genetic modifications for resistance conferring weediness to the cultivar (i.e. volunteer plants in subsequent crops), potential pleiotropic effects of genetic modifications for resistance, and selection of new herbicide-resistant weeds in the new herbicide regime. Of these concerns, the potential for selecting new resistant weeds may have the highest likelihood of affecting the long-term success of herbicide-resistant crops.

scholarly journals Economic Barriers to Herbicide-Resistance Management

Weed Science ◽  
2016 ◽  
Vol 64 (SP1) ◽  
pp. 585-594 ◽  
Author(s):  
Terrance M. Hurley ◽  
George Frisvold
Keyword(s):  
Herbicide Resistance ◽  
Weed Management ◽  
Resistance Management ◽  
Common Goal ◽  
Multifaceted Approach ◽  
Herbicide Resistant ◽  
Biological Perspective ◽  
Economic Barriers ◽  
Near Term

Herbicide-resistant weeds are the result of evolutionary processes that make it easy to think about the problem from a purely biological perspective. Yet, the act of weed management, guided by human production of food and fiber, drives this biological process. Thus, the problem is socioeconomic as well as biological. The purpose of this article is to explain how well-known socioeconomic phenomena create barriers to herbicide-resistance management and highlight important considerations for knocking down these barriers. The key message is that the multidimensional problem requires a multifaceted approach that recognizes differences among farmers; engages the regulatory, academic, extension, seed and chemical suppliers, and farmer communities; and aligns the diverse interests of the members of these communities with a common goal that benefits all—more sustainable weed management. It also requires an adaptive approach that transitions from moreuniform and costly standards and incentives, which can be effective in the near-term but are unsustainable, to more-targeted and less-costly approaches that are sustainable in the long term.

Lessons Learned From the History of Herbicide Resistance

Weed Science ◽  
2014 ◽  
Vol 62 (2) ◽  
pp. 427-431 ◽  
Author(s):  
Dale L. Shaner
Keyword(s):  
Herbicide Resistance ◽  
Weed Management ◽  
Management System ◽  
Rapid Evolution ◽  
Acetolactate Synthase ◽  
Management Program ◽  
Lessons Learned ◽  
Triazine Resistance ◽  
Herbicide Resistant ◽  
Selection Of

The selection of herbicide-resistant weed populations began with the introduction of synthetic herbicides in the late 1940s. For the first 20 years after introduction, there were limited reported cases of herbicide-resistant weeds. This changed in 1968 with the discovery of triazine-resistant common groundsel. Over the next 15 yr, the cases of herbicide-resistant weeds increased, primarily to triazine herbicides. Although triazine resistance was widespread, the resistant biotypes were highly unfit and were easily controlled with specific alternative herbicides. Weed scientists presumed that this would be the case for future herbicide-resistant cases and thus there was not much concern, although the companies affected by triazine resistance were somewhat active in trying to detect and manage resistance. It was not until the late 1980s with the discovery of resistance to Acetyl Co-A carboxylase (ACCase) and acetolactate synthase (ALS) inhibitors that herbicide resistance attracted much more attention, particularly from industry. The rapid evolution of resistance to these classes of herbicides affected many companies, who responded by first establishing working groups to address resistance to specific classes of herbicides, and then by formation of the Herbicide Resistance Action Committee (HRAC). The goal of these groups, in cooperation with academia and governmental agencies, was to act as a forum for the exchange of information on herbicide-resistance selection and to develop guidelines for managing resistance. Despite these efforts, herbicide resistance continued to increase. The introduction of glyphosate-resistant crops in the 1995 provided a brief respite from herbicide resistance, and farmers rapidly adopted this relatively simple and reliable weed management system based on glyphosate. There were many warnings from academia and some companies that the glyphosate-resistant crop system was not sustainable, but this advice was not heeded. The selection of glyphosate resistant weeds dramatically changed weed management and renewed emphasis on herbicide resistance management. To date, the lesson learned from our experience with herbicide resistance is that no herbicide is invulnerable to selecting for resistant biotypes, and that over-reliance on a weed management system based solely on herbicides is not sustainable. Hopefully we have learned that a diverse weed management program that combines multiple methods is the only system that will work for the long term.

No-tillage adoption decisions in southern Australian cropping and the role of weed management

2006 ◽  
Vol 46 (4) ◽  
pp. 563 ◽  
Author(s):  
F. H. D'Emden ◽  
R. S. Llewellyn
Keyword(s):  
Herbicide Resistance ◽  
Weed Management ◽  
Management Strategies ◽  
No Tillage ◽  
Long Term Effects ◽  
Herbicide Resistant ◽  
Increased Risk ◽  
System Use

Adoption of no-tillage sowing systems has increased rapidly in many Australian grain growing regions over the past decade. The extent of herbicide resistant weed populations in these regions has also increased over the same period. A survey of growers in the South and Western Australian cropping regions was conducted to identify opportunities for more effective tillage and weed-related extension. Trends in sowing system use are determined, as are growers’ perceptions of the long-term effects of no-tillage on herbicide costs, herbicide resistance, and soil erosion. The results suggest a major expansion in the adoption of no-tillage sowing in most South Australian cropping regions over the next 5 years, although growers expect increased herbicide costs in no-tillage systems and an increased risk of herbicide resistance. Herbicide resistance and weed control issues are the main reasons given for reducing no-tillage use. A key research and extension challenge is to develop and implement weed management strategies that are able to sustain long-term no-tillage use in a cropping environment where growers place a high value on the soil and production benefits of no-tillage, but over-reliance on herbicides can rapidly lead to resistance in major crop weeds.

scholarly journals Herbicide-resistant crops in resistant weed management : An industrial perspective

2005 ◽  
Vol 75 (4) ◽  
pp. 79-84 ◽  
Author(s):  
D. Shaner
Keyword(s):  
Weed Control ◽  
Weed Management ◽  
Wild Species ◽  
Integrated Weed Management ◽  
Herbicide Resistant ◽  
Resistant Varieties ◽  
Selection Of

Some of the first products of biotechnology to reach the marketplace have been herbicide-resistant crops. Industry sees the development of herbicide-resistant varieties as a way to increase the availability of proven herbicides for a broader range of crops. However, the development of herbicide- resistant crops requires special attention to potential environmental questions such as herbicide usage, selection of resistant weed biotypes and spread of resistance from the resistant crop to wild species. Industry is actively addressing these concerns during the process of development. Proper development and use of herbicide-resistant crops in integrated weed management programs will provide farmers with increased flexibility, efficiency, and decreased cost in their weed control practices without increasing the risk of herbicide-resistant weeds. Furthermore, herbicide-resistant crops should prove to be valuable tools in managing herbicide- resistant weeds.

scholarly journals A New Approach to Weed Management to Mitigate Herbicide Resistance in Argentina

Weed Science ◽  
2016 ◽  
Vol 64 (SP1) ◽  
pp. 641-648 ◽  
Author(s):  
Claudio Rubione ◽  
Sarah M. Ward
Keyword(s):  
Herbicide Resistance ◽  
Weed Management ◽  
Integrated Weed Management ◽  
National Committee ◽  
Weed Species ◽  
Corn Production ◽  
Public And Private ◽  
Herbicide Resistant ◽  
Crop Varieties ◽  
Export Taxes

The evolution of herbicide-resistant weeds is a major concern in the corn- and soybean-producing Pampas region of Argentina, where growers predominantly plant glyphosate-resistant crop varieties and depend heavily on glyphosate for weed control. Currently, 16 weed species in Argentina are resistant to one or more of three different herbicide mechanisms of action, and resistant weed populations continue to increase, posing a serious threat to agricultural production. Implementation of integrated weed management to address herbicide resistance faces significant barriers in Argentina, especially current land ownership and rental patterns in the Pampas. More than 60% of Pampas cropland is rented to tenants for periods that rarely exceed 1 yr, resulting in crop rotation being largely abandoned, and crop export taxes and quotas have further discouraged wheat and corn production in favor of continuous soybean production. In this paper we discuss ways to facilitate new approaches to weed management in Argentina, including legal and economic reforms and the formation of a national committee of stakeholders from public and private agricultural sectors.

Evaluation of Cereal and Brassicaceae Cover Crops in Conservation-Tillage, Enhanced, Glyphosate-Resistant Cotton

2011 ◽  
Vol 25 (1) ◽  
pp. 6-13 ◽  
Author(s):  
Jason K. Norsworthy ◽  
Marilyn McClelland ◽  
Griff Griffith ◽  
Sanjeev K. Bangarwa ◽  
Joshua Still
Keyword(s):  
Herbicide Resistance ◽  
Cover Crops ◽  
Weed Management ◽  
Conservation Tillage ◽  
White Mustard ◽  
Early Season ◽  
Pitted Morningglory ◽  
Second Year ◽  
Herbicide Programs ◽  
Selection Of

Research was conducted for 2 yr at Marianna, AR, to determine whether the fall-planted cover crops rye, wheat, turnip, and a blend of brown and white mustard (Caliente) would aid weed management programs in conservation-tilled, enhanced, glyphosate-resistant cotton. Wheat and rye easily were established both years and turnip and mustard blend stands were better in the second year. The cover crops alone were more suppressive of Palmer amaranth, pitted morningglory, and goosegrass in 2007 than in 2008. Rye was generally superior to wheat in suppressing the three evaluated weeds. Once herbicides were applied, there were seldom differences among cover crops for a particular herbicide program as a result of the highly efficacious herbicide programs. Cotton yields were not affected by wheat, rye, or the mustard blend, but yields were lowest in plots that followed turnip both years, possibly because of allelopathy. Integration of cover crops, especially cereals, into conservation-tilled, glyphosate-resistant cotton aided early-season weed management and could reduce the selection of glyphosate for herbicide resistance.

Genetic Aspects of Herbicide-Resistant Weed Management

1999 ◽  
Vol 13 (3) ◽  
pp. 647-652 ◽  
Author(s):  
Michael J. Christoffers
Keyword(s):  
Herbicide Resistance ◽  
Weed Management ◽  
Selection Pressure ◽  
Management Strategies ◽  
Resistance Management ◽  
Wild Type ◽  
Frequency Increase ◽  
Specific Nature ◽  
Herbicide Resistant ◽  
Case Basis

Weed populations develop herbicide resistance when they evolve due to selection pressure. Mutations and gene flow contribute to genetic variability and provide resistant alleles. The speed of resistance gene frequency increase is determined by the inheritance of resistance alleles relative to wild-type susceptibility and is influenced by the interaction between gene expression and selection. The goal of herbicide resistance management is to minimize selection pressure while maintaining adequate weed control. However, the specific nature of each herbicide, weed, and resistance combination determines the practices that optimize undesirable selection pressure. Therefore, generalized management strategies should be recommended with caution and must not be mandated without thorough evaluation on a case-by-case basis.

scholarly journals Modification of auxinic phenoxyalkanoic acid herbicides by the acyl acid amido synthetase GH3.15 from Arabidopsis

2018 ◽  
Vol 293 (46) ◽  
pp. 17731-17738 ◽  
Author(s):  
Ashley M. Sherp ◽  
Soon Goo Lee ◽  
Evelyn Schraft ◽  
Joseph M. Jez
Keyword(s):  
Butyric Acid ◽  
Herbicide Resistance ◽  
Side Chain ◽  
High Catalytic Activity ◽  
Herbicide Resistant ◽  
Biotechnology Products ◽  
Acid Herbicides ◽  
Indole 3 Acetic Acid ◽  
Selection Of ◽  
Resistance Traits

Herbicide-resistance traits are the most widely used agriculture biotechnology products. Yet, to maintain their effectiveness and to mitigate selection of herbicide-resistant weeds, the discovery of new resistance traits that use different chemical modes of action is essential. In plants, the Gretchen Hagen 3 (GH3) acyl acid amido synthetases catalyze the conjugation of amino acids to jasmonate and auxin phytohormones. This reaction chemistry has not been explored as a possible approach for herbicide modification and inactivation. Here, we examined a set of Arabidopsis GH3 proteins that use the auxins indole-3-acetic acid (IAA) and indole-3-butyric acid (IBA) as substrates along with the corresponding auxinic phenoxyalkanoic acid herbicides 2,4-dichlorophenoxylacetic acid (2,4-D) and 4-(2,4-dichlorophenoxy)butyric acid (2,4-DB). The IBA-specific AtGH3.15 protein displayed high catalytic activity with 2,4-DB, which was comparable to its activity with IBA. Screening of phenoxyalkanoic and phenylalkyl acids indicated that side-chain length of alkanoic and alkyl acids is a key feature of AtGH3.15's substrate preference. The X-ray crystal structure of the AtGH3.15·2,4-DB complex revealed how the herbicide binds in the active site. In root elongation assays, Arabidopsis AtGH3.15-knockout and -overexpression lines grown in the presence of 2,4-DB exhibited hypersensitivity and tolerance, respectively, indicating that the AtGH3.15-catalyzed modification inactivates 2,4-DB. These findings suggest a potential use for AtGH3.15, and perhaps other GH3 proteins, as herbicide-modifying enzymes that employ a mode of action different from those of currently available herbicide-resistance traits.

scholarly journals Reducing the Risks of Herbicide Resistance: Best Management Practices and Recommendations

Weed Science ◽  
2012 ◽  
Vol 60 (SP1) ◽  
pp. 31-62 ◽  
Author(s):  
Jason K. Norsworthy ◽  
Sarah M. Ward ◽  
David R. Shaw ◽  
Rick S. Llewellyn ◽  
Robert L. Nichols ◽  
...  
Keyword(s):  
Weed Control ◽  
Herbicide Resistance ◽  
Best Management Practices ◽  
Weed Management ◽  
Crop Production ◽  
Management Practices ◽  
Production Systems ◽  
Herbicide Resistant ◽  
Economic Thresholds ◽  
Soil Seedbank

Herbicides are the foundation of weed control in commercial crop-production systems. However, herbicide-resistant (HR) weed populations are evolving rapidly as a natural response to selection pressure imposed by modern agricultural management activities. Mitigating the evolution of herbicide resistance depends on reducing selection through diversification of weed control techniques, minimizing the spread of resistance genes and genotypes via pollen or propagule dispersal, and eliminating additions of weed seed to the soil seedbank. Effective deployment of such a multifaceted approach will require shifting from the current concept of basing weed management on single-year economic thresholds.

scholarly journals Virulence Dynamics and Regional Structuring of Puccinia striiformis f. sp. tritici in France Between 1984 and 2009

Plant Disease ◽  
2012 ◽  
Vol 96 (1) ◽  
pp. 131-140 ◽  
Author(s):  
Claude de Vallavieille-Pope ◽  
Sajid Ali ◽  
Marc Leconte ◽  
Jérôme Enjalbert ◽  
Marc Delos ◽  
...  
Keyword(s):  
Resistance Genes ◽  
Host Resistance ◽  
Evolutionary Biology ◽  
Puccinia Striiformis ◽  
Regional Level ◽  
The North ◽  
Pathogen Populations ◽  
Successive Acquisition ◽  
Selection Of

Understanding of long-term virulence dynamics of pathogen populations in response to host resistance gene deployment is of major importance for disease management and evolutionary biology. We monitored the virulence dynamics of Puccinia striiformis f. sp. tritici, the causal agent of wheat stripe rust, over 25 years in France. Virulence dynamics was explained by estimates of area associated with resistance genes carried by farmers' cultivars. The epidemics assessed through disease severity significantly correlated with the number of P. striiformis f. sp. tritici isolates collected each year, used to describe virulence dynamics. In the south, the dominance of the Mediterranean pathotype 6E16 and the cultivation of a susceptible cultivar were associated with an epidemic from 1997 to 1999. In the north, five epidemics occurred due to successive acquisition of virulence to the resistance genes Yr7, Yr6, Yr9, Yr17, and Yr32, either by acquisition of the virulence in the previous dominant pathotype or by incursion or selection of one or two new pathotypes. Frequency of pathotypes with Vr7 and Vr6 declined with the reduction in the cultivation of corresponding Yr gene cultivars, whereas the virulence Vr9 persisted longer than the cultivation of Yr9 cultivars. Although the first pathotypes carrying Vr9 decreased, this virulence persisted in other pathotypes even in the absence of Yr9 cultivars. At the regional level, Yr9 cultivars in the north caused a shift from high Vr6 frequency to high Vr9 frequency whereas, in the central region, where Yr9 cultivars were rare, Vr6 remained prevalent.

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