scholarly journals Identification and documentation of herbicide resistance

2005 ◽  
Vol 75 (4) ◽  
pp. 85-90 ◽  
Author(s):  
I.M. Heap
Keyword(s):  
Herbicide Resistance ◽  
Rapid Development ◽  
Resistance Management ◽  
Petri Dish ◽  
Response Curves ◽  
Susceptible Population ◽  
Development Of Resistance ◽  
Whole Plant ◽  
Biochemical Detection ◽  
Annual Weeds

Proactive herbicide resistance management programs rely upon early detection of resistant populations and knowledge of which combinations of weed and herbicide are prone to the development of resistance. Annual weeds that are prolific seed producers, genetically diverse, and repeatedly exposed to a single herbicide mode of action, are prone to rapid development of resistance. When resistance is suspected, seed samples are collected and evaluated using a whole plant bioassay. Whole plant bioassays are conducted underfield, growth room, or Petri dish conditions. Complete dose response curves for the suspected resistant and a reference susceptible population are used to verify resistance. Bioassay, conducted in growth rooms, is the most reliable method for identification of new cases of herbicide resistance. Bioassays, based on the biochemical detection of a single mechanism of resistance, are not reliable for screening for new occurrences of resistance.

Negative Cross Resistance; a Possible Key to Atrazine Resistance Management: A Call for Whole Plant Data

1990 ◽  
Vol 45 (5) ◽  
pp. 470-473 ◽  
Author(s):  
Jonathan Gressel ◽  
Lee A. Segel
Keyword(s):  
Resistance Management ◽  
Cross Resistance ◽  
Response Curves ◽  
Maize Crop ◽  
Ps Ii ◽  
Atrazine Resistance ◽  
Whole Plant ◽  
Herbicide Mixtures ◽  
Plant Data ◽  
Plant Level

Many photosystem II inhibiting herbicides still inhibit this process in triazine-resistant plants; i.e. they have no cross resistance with atrazine. Five- to twenty-fold lower concentrations of phenolic type herbicidcs and 5-fold less of the active ingredient of pyridate and half as much ioxynil are required to inhibit thylakoid PS II in atrazine-resistant biotypes than in sensitive biotypes; i.e., they even show “negative cross resistance”. Negative cross resistance may be the major reason that atrazine resistance did not evolve where herbicide mixtures were used, when the mixed herbicide (usually a non-PS II inhibiting acetanilide) also controlled triazine-sensitivc weeds. Mathematical modeling in principle allows quantification of the very low field levels of herbicides possessing negative cross resistance that could be mixed with atrazine that would stop or delay the evolution of resistant populations without affecting the maize crop. There are few available actual dose response curves of atrazine-resistant vs. susceptible weeds at the whole plant level for herbicidcs exerting negative cross resistance. Thus, “real situation” modeling cannot be done. Data acquisition is called for so that the model can be extrapolated from the thylakoid to the field.

Acaricide resistance in Panonychus citri and P. ulmi (Acari: Tetranychidae): Molecular mechanisms and management implications

2021 ◽  
Author(s):  
Jahangir Khajehali ◽  
Elaheh Shafiei Alavijeh ◽  
Mohammad Ghadamyari ◽  
Dejan Marčić
Keyword(s):  
Molecular Mechanisms ◽  
Rapid Development ◽  
Resistance Management ◽  
Panonychus Ulmi ◽  
Acaricide Resistance ◽  
Panonychus Citri ◽  
Citrus Red Mite ◽  
Development Of Resistance ◽  
Citrus Groves ◽  
Fruit Orchards

The European red mite, Panonychus ulmi (Koch), and the citrus red mite, P. citri (McGregor) (Acari: Tetranychidae), are destructive mite pests in pome/stone fruit orchards and citrus groves, respectively, the management of these two spider mites species has relied largely on the use of synthetic acaricides. However, frequent, long-term use of acaricides has caused rapid development of resistance in P. ulmi and P. citri populations worldwide. Levels of resistance in P. ulmi and P. citri are exceeded only by that in the two-spotted spider mite, Tetranychus urticae Koch. Recent research on T. urticae has provided new insights into the molecular mechanisms of acaricide resistance. The molecular basis of resistance in P. ulmi and P. citri populations has been less thoroughly studied. In this brief review, the current understanding of the molecular mechanisms of toxicokinetic and toxicodynamic resistance of P. ulmi and P. citri to acaricides, as well as implications of the findings for the resistance management, are discussed.  

Fungicide Resistance—Lessons for Herbicide Resistance Management?

1995 ◽  
Vol 9 (4) ◽  
pp. 840-849 ◽  
Author(s):  
Tobin L. Peever ◽  
Michael G. Milgroom
Keyword(s):  
Disease Control ◽  
Fungicide Resistance ◽  
Rapid Development ◽  
Management Strategies ◽  
Experimental Studies ◽  
Resistance Management ◽  
Pathogenic Fungi ◽  
Systemic Fungicides ◽  
Development Of Resistance ◽  
Pathogen Populations

Resistance to agricultural fungicides has increaséd dramatically in the past twenty years, following the introduction of systemic fungicides. Disease control failures associated with fungicide resistance have occurred with many classes of fungicides and in many genera of plant-pathogenic fungi. In some cases, resistance evolved extremely rapidly making the chemicals ineffective for disease control only a few years after they were introduced.The rapid development of resistance to systemic fungicides has led to efforts to develop strategies to avoid or delay the evolution of fungicide resistance in plant pathogen populations. Despite a widespread interest in managing fungicide resistance, very few experimental studies have been performed to elucidate the important factors controlling resistance development. Most fungicide resistance studies have consisted of anecdotal field observations which have rarely been followed up with experimentation. In order to understand what factors affect the evolution of resistance, and to use this information to design effective resistance management strategies, more experimental studies are required.

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 Resistance to the SDHI Fungicides Boscalid and Fluopyram in Podosphaera xanthii Populations from Commercial Cucurbit Fields in Spain

2021 ◽  
Vol 7 (9) ◽  
pp. 733
Author(s):  
Alejandra Vielba-Fernández ◽  
Álvaro Polonio ◽  
Laura Ruiz-Jiménez ◽  
Antonio de Vicente ◽  
Alejandro Pérez-García ◽  
...  
Keyword(s):  
Management Practices ◽  
Rapid Development ◽  
Resistance Management ◽  
Leaf Disc ◽  
Lamp Assay ◽  
Primary Control ◽  
Podosphaera Xanthii ◽  
Growing Seasons ◽  
Development Of Resistance ◽  
Plant Assays

Powdery mildew is caused by Podosphaera xanthii, and is one of the most important diseases that attacks Spanish cucurbit crops. Fungicide application is the primary control tool; however, its effectiveness is hampered by the rapid development of resistance to these compounds. In this study, the EC50 values of 26 isolates were determined in response to the succinate dehydrogenase inhibitor (SDHI) fungicides boscalid and fluopyram. From these data, the discriminatory doses were deduced and used for SDHI resistance monitoring during the 2018 and 2019 growing seasons. Of the 298 isolates analysed, 37.9% showed resistance to boscalid and 44% to fluopyram. Although different phenotypes were observed in leaf disc assays, the resistant isolates showed the same phenotype in plant assays. Compared to sensitive isolates, two amino acid changes were found in the SdhC subunit, A86V and G151R, which are associated mostly with resistance patterns to fluopyram and boscalid, respectively. Furthermore, no significant differences were observed in terms of fitness cost between the selected sensitive and resistant isolates analysed here. Lastly, a loop-mediated isothermal amplification (LAMP) assay was developed to detect A86V and G151R mutations using conidia obtained directly from infected material. Our results show that growers could continue to use boscalid and fluopyram, but resistance management practices must be implemented.

scholarly journals The Usefulness of Fungicide Mixtures and Alternation for Delaying the Selection for Resistance in Populations of Mycosphaerella graminicola on Winter Wheat: A Modeling Analysis

2013 ◽  
Vol 103 (7) ◽  
pp. 690-707 ◽  
Author(s):  
P. H. F. Hobbelen ◽  
N. D. Paveley ◽  
R. P. Oliver ◽  
F. van den Bosch
Keyword(s):  
Winter Wheat ◽  
Management Strategies ◽  
Resistance Management ◽  
Mycosphaerella Graminicola ◽  
Decay Rates ◽  
Response Curves ◽  
Resistance Risk ◽  
Modes Of Action ◽  
Development Of Resistance ◽  
Concurrent Use

A fungicide resistance model (reported and tested previously) was amended to describe the development of resistance in Mycosphaerella graminicola populations in winter wheat (Triticum aestivum) crops in two sets of fields, connected by spore dispersal. The model was used to evaluate the usefulness of concurrent, alternating, or mixture use of two high-resistance-risk fungicides as resistance management strategies. We determined the effect on the usefulness of each strategy of (i) fitness costs of resistance, (ii) partial resistance to fungicides, (iii) differences in the dose-response curves and decay rates between fungicides, and (iv) different frequencies of the double-resistant strain at the start of a treatment strategy. Parameter values for the quinine outside inhibitor pyraclostrobin were used to represent two fungicides with differing modes of action. The effectiveness of each strategy was quantified as the maximum number of growing seasons that disease was effectively controlled in both sets of fields. For all scenarios, the maximum effective lives achieved by the use of the strategies were in the order mixtures ≥ alternation ≥ concurrent use. Mixtures were of particular benefit where the pathogen strain resistant to both modes of action incurred a fitness penalty or was present at a low initial frequency.

scholarly journals Fitness of Herbicide-Resistant Weeds: Current Knowledge and Implications for Management

Plants ◽  
2019 ◽  
Vol 8 (11) ◽  
pp. 469 ◽  
Author(s):  
Vila-Aiub
Keyword(s):  
Life History ◽  
Herbicide Resistance ◽  
Management Practices ◽  
Current Knowledge ◽  
Resistance Management ◽  
Fitness Cost ◽  
Plant Fitness ◽  
Resistance Mutations ◽  
Fitness Costs ◽  
Wide Range

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.

scholarly journals Are crop and detailed physiological models equally "mechanistic" for predicting the genetic variability of whole plant behaviour? - the nexus between mechanisms and adaptive strategies

2020 ◽  
Author(s):  
F Tardieu ◽  
I S C Granato ◽  
E J Van Oosterom ◽  
B Parent ◽  
G L Hammer
Keyword(s):  
Genetic Variability ◽  
Growth And Yield ◽  
Specific Response ◽  
Response Curves ◽  
Evaporative Demand ◽  
Physiological Mechanisms ◽  
Physiological Models ◽  
Crop Models ◽  
Whole Plant ◽  
Developmental Traits

Abstract Tailoring genotypes for the variety of environmental scenarios associated with climate change requires modelling of the genetic variability of adaptation mechanisms to environmental cues. A large number of physiological mechanisms have been described and modelled, e.g. at transcript, metabolic or hormonal levels, but they remain to be assembled into whole-plant and canopy models. A 'bottom-up' approach combining physiological mechanisms leads to a near-infinite number of combinations and to an unmanageable number of parameters, so more parsimonious approaches are required. We propose that natural selection has constrained the large diversity of mechanisms into consistent strategies, in such a way that not all combinations of mechanisms are possible. These constraints, and resulting feedbacks, result in integrative 'metamechanisms', e.g. response curves of traits to environmental conditions, measurable via high throughput phenotyping, and resulting in robust and stable equations with heritable genotype-dependent parameters. Examples are provided for the responses of developmental traits to temperature, for the response of growth and yield to water deficit and evaporative demand, and for the response of tillering to light and temperature. In these examples, it was inoperative to combine upstream mechanisms into whole-plant mechanisms, whereas the evolutionary constraints on the combinations of physiological mechanisms renders possible the use of genotype-specific response curves at plant or canopy levels. These can be used for a new generation of crop models capable of simulating the behavior of thousands of genotypes. This has significant consequences for plant modelling and its use in genetics and breeding.

scholarly journals Moderate levels of 5-fluorocytosine cause the emergence of high frequency resistance in cryptococci

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Yun C. Chang ◽  
Ami Khanal Lamichhane ◽  
Hongyi Cai ◽  
Peter J. Walter ◽  
John E. Bennett ◽  
...  
Keyword(s):  
Cellular Uptake ◽  
High Frequency ◽  
Antifungal Agent ◽  
Inhibitory Concentration ◽  
Glucuronic Acid ◽  
Rapid Development ◽  
Acid Synthesis ◽  
Transcriptional Factor ◽  
Development Of Resistance ◽  
Acid Accumulation

AbstractThe antifungal agent 5-fluorocytosine (5-FC) is used for the treatment of several mycoses, but is unsuitable for monotherapy due to the rapid development of resistance. Here, we show that cryptococci develop resistance to 5-FC at a high frequency when exposed to concentrations several fold above the minimal inhibitory concentration. The genomes of resistant clones contain alterations in genes relevant as well as irrelevant for 5-FC resistance, suggesting that 5-FC may be mutagenic at moderate concentrations. Mutations in FCY2 (encoding a known permease for 5-FC uptake), FCY1, FUR1, UXS1 (encoding an enzyme that converts UDP-glucuronic acid to UDP-xylose) and URA6 contribute to 5-FC resistance. The uxs1 mutants accumulate UDP-glucuronic acid, which appears to down-regulate expression of permease FCY2 and reduce cellular uptake of the drug. Additional mutations in genes known to be required for UDP-glucuronic acid synthesis (UGD1) or a transcriptional factor NRG1 suppress UDP-glucuronic acid accumulation and 5-FC resistance in the uxs1 mutants.

scholarly journals Seed production of barnyardgrass (Echinochloa crus-galli) in response to time of emergence in cotton and rice

2011 ◽  
Vol 150 (6) ◽  
pp. 717-724 ◽  
Author(s):  
M. V. BAGAVATHIANNAN ◽  
J. K. NORSWORTHY ◽  
K. L. SMITH ◽  
P. NEVE
Keyword(s):  
United States ◽  
Seed Production ◽  
Herbicide Resistance ◽  
Crop Production ◽  
Integrated Management ◽  
Resistance Management ◽  
Simulation Models ◽  
Effective Resistance ◽  
Southern United States

SUMMARYThe spread of herbicide resistance in barnyardgrass (Echinochloa crus-galli(L.) Beauv.) poses a serious threat to crop production in the southern United States. A thorough knowledge of the biology of barnyardgrass is fundamental for designing effective resistance-management programmes. In the present study, seed production of barnyardgrass in response to time of emergence was investigated in cotton and rice, respectively, in Fayetteville and Rohwer, Arkansas, over a 2-year period (2008–09). Barnyardgrass seed production was greater when seedlings emerged with the crop, but some seed production was observed even if seedlings emerged several weeks after crop emergence. Moreover, barnyardgrass seed production was highly variable across environments. When emerging with the crop (0 weeks after crop emergence (WAE)), barnyardgrass producedc. 35 500 and 16 500 seeds/plant in cotton, andc. 39 000 and 2900 seeds/plant in rice, in 2008 and 2009, respectively. Seed production was observed when seedlings emerged up to 5 WAE (2008) or 7 WAE (2009) in cotton and up to 5 WAE (2008, 2009) in rice; corresponding seed production wasc. 2500 and 1500 seeds/plant in cotton, andc. 14 700 and 110 seeds/plant in rice, in 2008 and 2009, respectively. The results suggest that cultural approaches that delay the emergence of barnyardgrass or approaches that make the associated crop more competitive will be useful in integrated management programmes. In the context of herbicide resistance management, it may be valuable to prevent seed return to the seedbank, irrespective of cohorts. The findings are vital for parameterizing herbicide resistance simulation models for barnyardgrass.

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