scholarly journals Detecting herbicide-resistant Apera spica-venti with a chlorophyll fluorescence agar test

2018 ◽  
Vol 64 (No. 8) ◽  
pp. 386-392 ◽  
Author(s):  
Linn Alexander Ingo ◽  
Košnarová Pavlína ◽  
Soukup Josef ◽  
Gerhards Roland
Keyword(s):  
Chlorophyll Fluorescence ◽  
Herbicide Resistance ◽  
Resistance Management ◽  
Screening Methods ◽  
Response Curves ◽  
Herbicide Resistant ◽  
Alopecurus Myosuroides ◽  
Assessment Time ◽  
Herbicide Concentration ◽  
Maximum Quantum Efficiency

Reliable tests on herbicide resistance are important for resistance management. Despite well-established greenhouse bioassays, faster and in-season screening methods would aid in more efficient resistance detection. The feasibility of a chlorophyll fluorescence agar-based test on herbicide resistance in Apera spica-venti L. was investigated. Herbicide resistant and sensitive A. spica-venti seedlings were transplanted into agar containing pinoxaden and pyroxsulam herbicides. Chlorophyll fluorescence was measured and the maximum quantum efficiency of photosystem II (F<sub>v</sub>/F<sub>m</sub>) was determined 48 h and 72 h after the transplantation to agar, respectively. The F<sub>v</sub>/F<sub>m</sub> values decreased with increasing herbicide concentration. Dose-response curves and respective ED<sub>50</sub> values (herbicide concentration leading to 50% decrease of the F<sub>v</sub>/F<sub>m</sub> value) were calculated. However, each experiment repetition exhibited different sensitivities of the populations for both herbicides. In certain cases, resistant populations demonstrated similar F<sub>v</sub>/F<sub>m</sub> values as sensitive populations. Contrary to the findings in Alopecurus myosuroides Huds., discrimination of sensitive and resistant A. spica-venti populations was not feasible. An increased importance of the assessment time due to the herbicide concentrations calibrated for fast responses was assumed in this study.

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.

scholarly journals Herbicide Resistance Management in Florida Tomato Production

EDIS ◽  
2020 ◽  
Vol 2020 (6) ◽  
Author(s):  
Shaun Sharpe ◽  
N S Boyd ◽  
Ramdas G Kanissery ◽  
Peter Dittmar
Keyword(s):  
Herbicide Resistance ◽  
Resistance Management ◽  
Extension Agents ◽  
Tomato Production ◽  
Herbicide Resistant ◽  
Horticultural Crops ◽  
Agronomic Crops ◽  
Small Fruit ◽  
Definition Of ◽  
Management Recommendations

Herbicide resistance was historically not a significant issue in most horticultural crops because few herbicides were applied. Close proximity of agronomic crops and the loss of methyl bromide has led to a gradual increase in herbicide inputs and the increased occurrence of herbicide-resistant weeds in tomato fields. Very few herbicides are registered for tomato, and resistance is a major concern. This new 11-page publication of the UF/IFAS Horticultural Sciences Department provides a definition of herbicide resistance, explains how it develops, and provides management recommendations for tomato growers. It was written for growers and Extension agents, but the information may be of interest to anyone concerned about herbicide resistance in vegetable and small fruit crops. Written by Shaun M. Sharpe, Nathan S. Boyd, Ramdas G. Kanissery, and Peter J. Dittmar.https://edis.ifas.ufl.edu/hs1398

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.

Germinability and seed biochemical properties of susceptible and non–target site herbicide-resistant blackgrass (Alopecurus myosuroides) subpopulations exposed to abiotic stresses

Weed Science ◽  
2020 ◽  
Vol 68 (2) ◽  
pp. 157-167
Author(s):  
Zahra Ghazali ◽  
Eshagh Keshtkar ◽  
Majid AghaAlikhani ◽  
Per Kudsk
Keyword(s):  
Antioxidant Enzymes ◽  
Drought Stress ◽  
Herbicide Resistance ◽  
Accelerated Aging ◽  
Biochemical Properties ◽  
Target Site ◽  
Evolutionary Development ◽  
Herbicide Resistant ◽  
Alopecurus Myosuroides ◽  
Aged Seeds

AbstractQuantifying the level of ecophysiological, biochemical, and agronomical fitness of herbicide-resistant (R) and herbicide-susceptible (S) weeds is useful for understanding the evolutionary development of herbicide resistance, but also for implementing herbicide-resistance management strategies. Although germination is a key fitness component in the life cycle of weeds, germinability of S and R weeds has rarely been evaluated under stressful conditions. Germinability traits of S and non–target site resistant subpopulations of blackgrass (Alopecurus myosuroides Huds.) sharing closely related genetic background were tested under salinity, drought stress, and accelerated seed-aging (i.e., exposed to 100% relative humidity at 45 C from 0 to 134 h) conditions. In addition, the activity of three antioxidant enzymes and protein concentration of accelerated aged seeds of the subpopulations were studied. There were no differences in maximum seed germination (Gmax) and time to 50% germination between the two subpopulations under optimum conditions. However, under salinity, drought stress, and accelerated aging conditions, there were differences between the subpopulations. The salinity, drought, and accelerated aging treatments reducing Gmax of the S subpopulation by 50% were 18 dS m−1, 0.75 MPa, and 90 h, respectively, while for the R subpopulation the corresponding values were 15 dS m−1, 0.66 MPa, and 67 h. No differences were found in the activity of the antioxidant enzymes and the content of protein between non-aged seeds of the subpopulations. The aging treatments reducing the activity of catalase and superoxide dismutase enzymes by 50% were 118 and 82 h for the S subpopulation, respectively, while they were 54 and 58 h for the R subpopulation. In contrast, there were no differences in the effect of the aging treatments on the peroxidase activity and protein content between subpopulations. The results provided clear evidence that the non–target site resistant loci of blackgrass is associated with fitness costs under environmental stress.

scholarly journals Herbicide Resistance, Tillage, and Community Management in the Pacific Northwest

2021 ◽  
Vol 13 (4) ◽  
pp. 1937
Author(s):  
Katherine Dentzman ◽  
Ian Cristofer Burke
Keyword(s):  
Pacific Northwest ◽  
Herbicide Resistance ◽  
Large Scale ◽  
Conservation Tillage ◽  
Resistance Management ◽  
The United States ◽  
Community Management ◽  
Herbicide Resistant ◽  
The Pacific ◽  
Fail Safe

The use of glyphosate as a replacement for tillage has been credited with spurring the adoption of conservation tillage in the United States. With herbicide-resistant weeds becoming a significant agronomic problem, however, it is unclear whether conservation tillage gains are in danger of being reversed as farmers turn to tillage to manage weeds that herbicides can no longer kill. Using 2015 focus groups, a 2016 national survey, and an ongoing Community Herbicide Resistance Management Initiative in four communities of the Pacific Northwest we assess the following questions: (1) How do U.S. farmers view tillage as an option for controlling herbicide-resistant weeds, (2) Do attitudes towards and experience with herbicide-resistant increase farmers’ usage of tillage, and (3) Can community management provide an avenue for maintaining conservation tillage while also increasing effective management of herbicide-resistant weeds? We find that many farmers consider tillage to be an emergency fail-safe in managing weeds, that there is a complex relationship between herbicide resistance awareness, concern, and tillage use that can be partly explained by experience and dedication to conservation tillage, and finally that community management has the potential to provide the support and resources necessary to prevent a large-scale increase in tillage related to herbicide resistance management.

Assessing Fitness Costs from a Herbicide-Resistance Management Perspective: A Review and Insight

Weed Science ◽  
2018 ◽  
Vol 67 (2) ◽  
pp. 137-148 ◽  
Author(s):  
Eshagh Keshtkar ◽  
Roohollah Abdolshahi ◽  
Hamidreza Sasanfar ◽  
Eskandar Zand ◽  
Roland Beffa ◽  
...  
Keyword(s):  
Herbicide Resistance ◽  
Weed Management ◽  
Genetic Background ◽  
Management Practices ◽  
Evolutionary Ecology ◽  
Resistance Management ◽  
Single Population ◽  
Herbicide Resistant ◽  
Scientific Disciplines ◽  
Cost Studies

AbstractIn recent years, herbicide resistance has attracted much attention as an increasingly urgent problem worldwide. Unfortunately, most of that effort was focused on confirmation of resistance and characterization of the mechanisms of resistance. For management purposes, knowledge about biology and ecology of the resistant weed phenotypes is critical. This includes fitness of the resistant biotypes compared with the corresponding wild biotypes. Accordingly, fitness has been the subject of many studies; however, lack of consensus on the concept of fitness resulted in poor experimental designs and misinterpretation of the ensuing data. In recent years, methodological protocols for conducting proper fitness studies have been proposed; however, we think these methods should be reconsidered from a herbicide-resistance management viewpoint. In addition, a discussion of the inherent challenges associated with fitness cost studies is pertinent. We believe that the methodological requirements for fitness studies of herbicide-resistant weed biotypes might differ from those applied in other scientific disciplines such as evolutionary ecology and genetics. Moreover, another important question is to what extent controlling genetic background is necessary when the aim of a fitness study is developing management practices for resistant biotypes. Among the methods available to control genetic background, we suggest two approaches (single population and pedigreed lines) as the most appropriate methods to detect differences between resistant (R) and susceptible (S) populations and to derive herbicide-resistant weed management programs. Based on these two methods, we suggest two new approaches that we named the “recurrent single population” and “recurrent pedigreed lines” methods. Importantly, whenever the aim of a fitness study is to develop optimal resistance management, we suggest selecting R and S plants within a single population and evaluating all fitness components from seed to seed instead of measuring changes in the frequency of R and S alleles through multigenerational fitness studies.

scholarly journals Rethinking Outreach: Collaboration Is Key for Herbicide-Resistance Management

Weed Science ◽  
2016 ◽  
Vol 64 (SP1) ◽  
pp. 655-660 ◽  
Author(s):  
Amy Asmus ◽  
Jill Schroeder
Keyword(s):  
Herbicide Resistance ◽  
Management Practices ◽  
Interdisciplinary Collaboration ◽  
Resistance Management ◽  
Information Delivery ◽  
Effective Resistance ◽  
Herbicide Resistant

Effective outreach is critical to achieving success in managing herbicide-resistant weeds. Interdisciplinary collaboration is needed to adapt information delivery and to engage communities to address the herbicide-resistance problem. Weed scientists must partner with the production community to adapt herbicide-resistance practices for local needs, to work collaboratively with state and regional stakeholders to create effective resistance-management practices, and to provide an overarching national message as to the causes of, and solutions to, resistance.

scholarly journals Herbicide Resistance in Brazil: Status, Impacts, and Future Challenges

2020 ◽  
Author(s):  
Ricardo Alcántara-de la Cruz ◽  
Guilherme Moraes de Oliveira ◽  
Leonardo Bianco de Carvalho ◽  
Maria Fátima das Graças Fernandes da Silva
Keyword(s):  
Herbicide Resistance ◽  
Resistance Management ◽  
Acetolactate Synthase ◽  
Agricultural Activity ◽  
Weed Species ◽  
Herbicide Resistant ◽  
Crop Fields ◽  
Future Challenges ◽  
High Selection ◽  
Continuous Use

Brazil is a large producer and exporter of crops in global terms. Weeds may be responsible for ~14% of crop losses, depending on the crop system. Herbicides occupy 58% of the Brazilian pesticide market; however, the continuous use of these products and the high selection pressure have led to the emergence of weeds resistant to herbicides. Today, there are 51 weed species reported as being resistant to herbicides in Brazil, of which 17 involves cross and multiple-resistance. Acetolactate synthase (ALS), acetyl coenzyme A carboxylase (ACCase) and 5-enolpiruvylshikimate-3-phosphate synthase (EPSPs) inhibitors are the herbicidal groups with the most resistance cases. Soybean, corn, rice, wheat and cotton present 30, 12, 10, 9 and 8 cases, respectively, occurring mainly in herbicide-resistant crop fields from the Southern and Central West regions of the country. To better understand the dimensions of herbicide resistance, in this chapter, we will explore the size of agricultural activity in Brazil, the pesticide market and the use of herbicides in the main crops. In addition, the agronomic, scientific-technical and economic aspects that have contributed, directly or indirectly, to the selection of resistant weeds will be discussed in order to have an overview of the economic impact of herbicide resistance management.

Herbicide Resistance in Rigid Ryegrass (Lolium rigidum)Has Not Led to Higher Weed Densities in Western Australian Cropping Fields

Weed Science ◽  
2009 ◽  
Vol 57 (1) ◽  
pp. 61-65 ◽  
Author(s):  
Rick S. Llewellyn ◽  
Francis H. D'Emden ◽  
Mechelle J. Owen ◽  
Stephen B. Powles
Keyword(s):  
Herbicide Resistance ◽  
Resistance Management ◽  
Multiple Resistance ◽  
Harvest Time ◽  
Lolium Rigidum ◽  
Herbicide Resistant ◽  
Rigid Ryegrass ◽  
Susceptible Populations ◽  
Western Australian ◽  
Very High

The aim of this study was to test whether herbicide resistance in rigid ryegrass has led to increased densities of this weed in Western Australian (WA) cropping fields. A total of 503 wheat fields with previously unknown management history and weed status were visited prior to harvest across 15 agronomic areas of the central WA cropping belt in 1998 and 2003. Rigid ryegrass density was visually assessed and, where possible, seed was collected from the population. Ryegrass was found in 91% of the wheat crops sampled. Ryegrass populations were tested in the following year for resistance to chlorsulfuron, sulfometuron, diclofop, and clethodim. With the use of nonparametric and regression statistical methods, resistance status, including multiple-resistance status, was not found to be associated with higher weed density. The results show that growers are generally maintaining low densities in fields with herbicide-resistant rigid ryegrass. The most common rigid ryegrass density at harvest time was less than 1 plant m−2in both resistant and susceptible populations. Field and model-based studies of weed and herbicide resistance management that allow populations to continue at very high densities are unlikely to reflect common grower practice.

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