scholarly journals Species hybridisation and clonal expansion as a new fungicide resistance evolutionary mechanism in Pyrenophora teres spp.

2021 ◽  
Author(s):  
Chala J Turo ◽  
Wesley J Mair ◽  
Anke Martin ◽  
Simon R Ellwood ◽  
Richard Oliver ◽  
...  
Keyword(s):  
Point Mutation ◽  
Protein Function ◽  
Fungicide Resistance ◽  
Resistance Management ◽  
Fungal Species ◽  
Net Blotch ◽  
High Genetic Diversity ◽  
Intergenic Regions ◽  
Natural Recombination ◽  
Genome Level

The barley net blotch diseases are caused by two fungal species of the Pyrenophora genus. Specifically, spot form net blotch is caused by P. teres f. sp. maculata (Ptm) whereas net form net blotch is caused by P. teres f. sp. teres (Ptt). Ptt and Ptm show high genetic diversity in the field due to intraspecific sexual recombination and hybridisation of the two species although the latter is considered rare. Here we present occurrence of a natural Ptt/Ptm hybrid with azole fungicides resistance and its implication to barley disease management in Australia. We collected and sequenced a hybrid, 3 Ptm and 10 Ptt isolates and performed recombination analyses in the intergenic and whole genome level. Eleven out of 12 chromosomes showed significant (P < 0.05) recombination events in the intergenic regions while variable recombination rate showed significant recombination across all the chromosomes. Locus specific analyses of Cyp51A1 gene showed at least four recombination breakpoints including a point mutation that alter target protein function. This point mutation did not found in Ptt and Ptm collected prior to 2013 and 2017, respectively. Further genotyping of fourteen Ptt, 48 HR Ptm, fifteen Ptm and two P. teres isolates from barley grass using Diversity Arrays Technology markers showed that all HR Ptm isolates were clonal and not clustered with Ptt or Ptm. The result confirms occurrence of natural recombination between Ptt and Ptm in Western Australia and the HR Ptm is likely acquired azole fungicide resistance through recombination and underwent recent rapid selective sweep likely within the last decade. The use of available fungicide resistance management tactics are essential to minimise and restrict further dissemination of these adaptive HR Ptm isolates.

Prevention and Detection of Fungicide Resistance Development in Rhizoctonia zeae from Soybean and Corn in Nebraska

2021 ◽  
Author(s):  
Nikita Gambhir ◽  
Srikanth Kodati ◽  
Matthew Huff ◽  
Flávio Silva ◽  
Olutoyosi Ajayi-Oyetunde ◽  
...  
Keyword(s):  
Fungicide Resistance ◽  
Resistance Management ◽  
Dry Weight ◽  
Geographic Region ◽  
Population Characteristics ◽  
Current Status ◽  
In Planta ◽  
Resistance Development ◽  
Rhizoctonia Zeae

The goal of this research was to advance the foundational knowledge required to quantify and mitigate fungicide resistance in Rhizoctonia zeae, the seedling disease pathogen of soybean and corn. In vitro sensitivity to azoxystrobin, fludioxonil, sedaxane, and/or prothioconazole was determined for 91 R. zeae isolates obtained mostly from soybean and corn fields in Nebraska. Isolates were sensitive to fludioxonil, sedaxane, and prothioconazole (EC50 < 3 µg/ml) and had a positively skewed EC50 distribution. Isolates were not sensitive to azoxystrobin in vitro (EC50 > 100 µg/ml) or in planta. Application of azoxystrobin did not significantly decrease disease severity or improve total dry weight of the soybean plants (P > 0.05). The risk of resistance development in R. zeae was estimated by characterizing its population structure. Eighty-one R. zeae isolates were genotyped using six microsatellite markers. Results showed that the population has a mixed mode of reproduction and is structured according to geographic region, suggesting limited dispersal. These population characteristics suggest that R. zeae has an intermediate risk of resistance development. Overall, this research established the current status of fungicide sensitivity in R. zeae in Nebraska and estimated its risk of resistance development, which can inform fungicide resistance management for R. zeae.

scholarly journals Fungicide Resistance Management Guidelines for the Control of Tomato Diseases in the Mid-Atlantic and Northeast Regions of the United States

2010 ◽  
Vol 11 (1) ◽  
pp. 32 ◽  
Author(s):  
Christian A. Wyenandt ◽  
Steven L. Rideout ◽  
Beth K. Gugino ◽  
Margaret T. McGrath ◽  
Kathryne L. Everts ◽  
...  
Keyword(s):  
United States ◽  
Fungicide Resistance ◽  
Resistance Management ◽  
The United States ◽  
Management Tool ◽  
Fresh Market ◽  
Management Guidelines ◽  
Control Programs ◽  
Action Committee ◽  
Tomato Diseases

Foliar diseases and fruit rots occur routinely on tomato, an important crop grown throughout the Mid-Atlantic and Northeast regions of the United States where it is produced for both fresh-market and processing. To enable these tomato growers to more effectively manage economically important diseases, a fungicide resistance management table has been developed which promotes the importance of understanding FRAC (Fungicide Resistance Action Committee) codes and provides an integrated pest management tool for tomato growers which will allow them to develop season-long disease control programs with an emphasis on fungicide resistance management. Accepted for publication 19 July 2010. Published 27 August 2010.

scholarly journals Double Mutations in Succinate Dehydrogenase Are Involved in SDHI Resistance in Corynespora cassiicola

2022 ◽  
Vol 10 (1) ◽  
pp. 132
Author(s):  
Bingxue Sun ◽  
Guangxue Zhu ◽  
Xuewen Xie ◽  
Ali Chai ◽  
Lei Li ◽  
...  
Keyword(s):  
Succinate Dehydrogenase ◽  
Point Mutation ◽  
Single Point ◽  
Resistance Management ◽  
Site Directed Mutagenesis ◽  
Single Point Mutation ◽  
Single Mutation ◽  
Corynespora Cassiicola ◽  
Double Mutation ◽  
Mutation Analyses

With the further application of succinate dehydrogenase inhibitors (SDHI), the resistance caused by double mutations in target gene is gradually becoming a serious problem, leading to a decrease of control efficacy. It is important to assess the sensitivity and fitness of double mutations to SDHI in Corynespora cassiicola and analysis the evolution of double mutations. We confirmed, by site-directed mutagenesis, that all double mutations (B-I280V+D-D95E/D-G109V/D-H105R, B-H278R+D-D95E/D-G109V, B-H278Y+D-D95E/D-G109V) conferred resistance to all SDHI and exhibited the increased resistance to at least one fungicide than single point mutation. Analyses of fitness showed that all double mutations had lower fitness than the wild type; most of double mutations suffered more fitness penalties than the corresponding single mutants. We also further found that double mutations (B-I280V+D-D95E/D-G109V/D-H105R) containing low SDHI-resistant single point mutation (B-I280V) exhibited higher resistance to SDHI and low fitness penalty than double mutations (B-H278Y+D-D95E/D-G109V) containing high SDHI-resistant single mutations (B-H278Y). Therefore, we may infer that a single mutation conferring low resistance is more likely to evolve into a double mutation conferring higher resistance under the selective pressure of SDHI. Taken together, our results provide some important reference for resistance management.

scholarly journals Succinate dehydrogenase inhibitor (SDHI) fungicide resistance prevention strategy

2011 ◽  
Vol 64 ◽  
pp. 119-124 ◽  
Author(s):  
A.H. McKay ◽  
G.C. Hagerty ◽  
G.B. Follas ◽  
M.S. Moore ◽  
M.S. Christie ◽  
...  
Keyword(s):  
New Zealand ◽  
High Risk ◽  
Succinate Dehydrogenase ◽  
Fungicide Resistance ◽  
Fungal Pathogens ◽  
Resistance Management ◽  
Resistance Development ◽  
Development Of Resistance ◽  
Action Committee ◽  
Succinate Dehydrogenase Inhibitor

Succinate dehydrogenase inhibitor (SDHI) fungicides are currently represented in New Zealand by eight active ingredients bixafen boscalid carboxin fluaxapyroxad fluopyram isopyrazam penthiopyrad and sedaxane They are either currently registered or undergoing development in New Zealand for use against a range of ascomycete and basiodiomycete pathogens in crops including cereals ryegrass seed apples pears grapes stonefruit cucurbits and kiwifruit These fungicides are considered to have medium to high risk of resistance development and resistance management is recommended by the Fungicide Resistance Action Committee (FRAC) in Europe Guidelines are presented for use of SDHI fungicides in New Zealand to help avoid or delay the development of resistance in the fungal pathogens that they target

scholarly journals Fungicide resistance characterised across seven chemical classes in a Botrytis cinerea population isolated from Australian vineyards

2021 ◽  
Author(s):  
Lincoln A. Harper ◽  
Scott Paton ◽  
Barbara Hall ◽  
Suzanne McKay ◽  
Richard P. Oliver ◽  
...  
Keyword(s):  
Adverse Effect ◽  
Botrytis Cinerea ◽  
Fungicide Resistance ◽  
Chemical Control ◽  
Management Strategies ◽  
Resistance Management ◽  
Gray Mold ◽  
Chemical Groups ◽  
Important Disease ◽  
Selection Of

AbstractGray mold, caused by Botrytis cinerea, is an economically important disease of grapes in Australia and across grape growing regions worldwide. Control of this disease relies heavily on canopy management and the application of single site fungicides. Fungicide application can lead to the selection of fungicide resistant B. cinerea populations, which has an adverse effect on the chemical control of the disease. Characterising the distribution and severity of resistant B. cinerea populations is needed to inform resistance management strategies. In this study, 725 isolates were sampled from 75 Australian vineyards during 2013 – 2016 and were screened against seven fungicides with different MOAs. The resistance frequencies for azoxystrobin, boscalid, fenhexamid, fludioxonil, iprodione, pyrimethanil and tebuconazole were 5, 2.8, 2.1, 6.2, 11.6, 7.7 and 2.9% respectively. Nearly half of the resistant isolates (43.7%) were resistant to more than one of the fungicides tested. The frequency of vineyards with at least one isolate simultaneously resistant to 1, 2, 3, 4 or 5 fungicides was 19.5, 7.8, 6.5, 10.4 and 2.6%.Resistance was associated with previously published genotypes in CytB (G143A), SdhB (H272R/Y), Erg27 (F412S), Mrr1 (D354Y), Os1 (I365S, N373S + Q369P, I365S + D757N) and Pos5 (P319A, L412F). Expression analysis was used to characterise fludioxonil resistant isolates exhibiting overexpression (6.3 - 9.6-fold) of the ABC transporter encoded by AtrB (MDR1 phenotype). Novel genotypes were also described in Mrr1 (S611N, D616G) and Cyp51 (P357S). Resistance frequencies were lower when compared to most previously published surveys of both grape and non-grape B. cinerea resistance. Nonetheless, continued monitoring of critical chemical groups used in Australian vineyards is recommended.

scholarly journals Mixtures as a Fungicide Resistance Management Tactic

2014 ◽  
Vol 104 (12) ◽  
pp. 1264-1273 ◽  
Author(s):  
Frank van den Bosch ◽  
Neil Paveley ◽  
Femke van den Berg ◽  
Peter Hobbelen ◽  
Richard Oliver
Keyword(s):  
At Risk ◽  
Disease Control ◽  
Fungicide Resistance ◽  
Management Strategies ◽  
Resistance Management ◽  
Relative Effect ◽  
Resistance Evolution ◽  
Modes Of Action ◽  
Selection For ◽  
Effective Life

We have reviewed the experimental and modeling evidence on the use of mixtures of fungicides of differing modes of action as a resistance management tactic. The evidence supports the following conclusions. 1. Adding a mixing partner to a fungicide that is at-risk of resistance (without lowering the dose of the at-risk fungicide) reduces the rate of selection for fungicide resistance. This holds for the use of mixing partner fungicides that have either multi-site or single-site modes of action. The resulting predicted increase in the effective life of the at-risk fungicide can be large enough to be of practical relevance. The more effective the mixing partner (due to inherent activity and/or dose), the larger the reduction in selection and the larger the increase in effective life of the at-risk fungicide. 2. Adding a mixing partner while lowering the dose of the at-risk fungicide reduces the selection for fungicide resistance, without compromising effective disease control. The very few studies existing suggest that the reduction in selection is more sensitive to lowering the dose of the at-risk fungicide than to increasing the dose of the mixing partner. 3. Although there are very few studies, the existing evidence suggests that mixing two at-risk fungicides is also a useful resistance management tactic. The aspects that have received too little attention to draw generic conclusions about the effectiveness of fungicide mixtures as resistance management strategies are as follows: (i) the relative effect of the dose of the two mixing partners on selection for fungicide resistance, (ii) the effect of mixing on the effective life of a fungicide (the time from introduction of the fungicide mode of action to the time point where the fungicide can no longer maintain effective disease control), (iii) polygenically determined resistance, (iv) mixtures of two at-risk fungicides, (v) the emergence phase of resistance evolution and the effects of mixtures during this phase, and (vi) monocyclic diseases and nonfoliar diseases. The lack of studies on these aspects of mixture use of fungicides should be a warning against overinterpreting the findings in this review.

scholarly journals Using Epidemiological Principles to Explain Fungicide Resistance Management Tactics: Why do Mixtures Outperform Alternations?

2018 ◽  
Vol 108 (7) ◽  
pp. 803-817 ◽  
Author(s):  
James A. D. Elderfield ◽  
Francisco J. Lopez-Ruiz ◽  
Frank van den Bosch ◽  
Nik J. Cunniffe
Keyword(s):  
High Risk ◽  
Disease Control ◽  
Fungicide Resistance ◽  
Total Yield ◽  
Resistance Management ◽  
Careful Consideration ◽  
Low Risk ◽  
Model Parameterization ◽  
Grapevine Powdery Mildew ◽  
Label Dose

Whether fungicide resistance management is optimized by spraying chemicals with different modes of action as a mixture (i.e., simultaneously) or in alternation (i.e., sequentially) has been studied by experimenters and modelers for decades. However, results have been inconclusive. We use previously parameterized and validated mathematical models of wheat Septoria leaf blotch and grapevine powdery mildew to test which tactic provides better resistance management, using the total yield before resistance causes disease control to become economically ineffective (“lifetime yield”) to measure effectiveness. We focus on tactics involving the combination of a low-risk and a high-risk fungicide, and the case in which resistance to the high-risk chemical is complete (i.e., in which there is no partial resistance). Lifetime yield is then optimized by spraying as much low-risk fungicide as is permitted, combined with slightly more high-risk fungicide than needed for acceptable initial disease control, applying these fungicides as a mixture. That mixture rather than alternation gives better performance is invariant to model parameterization and structure, as well as the pathosystem in question. However, if comparison focuses on other metrics, e.g., lifetime yield at full label dose, either mixture or alternation can be optimal. Our work shows how epidemiological principles can explain the evolution of fungicide resistance, and also highlights a theoretical framework to address the question of whether mixture or alternation provides better resistance management. It also demonstrates that precisely how spray tactics are compared must be given careful consideration.[Formula: see text] Copyright © 2018 The Author(s). This is an open access article distributed under the CC BY 4.0 International license .

Sensitivity and Resistance Risk Assessment of Puccinia striiformis f. sp. tritici to Triadimefon in China

Plant Disease ◽  
2021 ◽  
Author(s):  
Gangming Zhan ◽  
Fan Ji ◽  
Jun Zhao ◽  
Yue Liu ◽  
Aihong Zhou ◽  
...  
Keyword(s):  
Point Mutation ◽  
Fungicide Resistance ◽  
Puccinia Striiformis ◽  
Germination Rate ◽  
Detection Methods ◽  
Cross Resistance ◽  
Maximal Effect ◽  
Baseline Sensitivity ◽  
Resistance Risk ◽  
Wide Range

Wheat stripe rust, caused by Puccinia striiformis f. sp. tritici (Pst), is a destructive disease of wheat that seriously threatens production safety in wheat-producing areas worldwide. In China, the disease has been largely controlled with fungicide triadimefon. Although high levels of fungicide resistance in other fungal pathogens have been reported, failure to control Pst with any fungicides has seldomly been reported and fungicide sensitivity of Pst has not been evaluated in China. The distribution of triadimefon-resistant Pst isolates was investigated in the present study. The baseline sensitivity of 446 Pst isolates across the country to triadimefon was determined, and the concentration for 50% of maximal effect (EC50) showed a unimodal distribution curve, with a mean value of 0.19 μg mL-1. The results indicated a wide range of sensitivity to triadimefon, with more insensitive isolates collected from Pst winter-increasing areas and northwest over-summering areas, whereas more sensitive isolates were collected from southwest over-summering areas and epidemic areas of Xinjiang and Tibet. The majority of the tested Pst isolates were sensitive to triadimefon; only 6.79% had developed varying degrees of resistance. Characterization of parasitic fitness revealed that the triadimefon-resistant isolates exhibited strong adaptive traits in urediniospore germination rate, latent period, sporulation intensity, and lesion expansion rate. Positive cross-resistance was observed between triadimefon and tebuconazole or hexaconazole, but not between pyraclostrobin or flubeneteram. The point mutation Y134F in the 14α-demethylase enzyme (CYP51) was detected in triadimefon-resistant isolates. A molecular method (Kompetitive Allele Specific PCR) was established for the rapid detection of Y134F mutants in the Pst population. Two genotypes with one point mutation Y134F conferred resistance to triadimefon in Pst. The risk of resistance to triadimefon in Pst may be low to moderate. This study provided important data for establishment of high throughput molecular detection methods, fungicide resistance risk management, and the development of new target fungicides.

Advances in understanding the epidemiology, molecular biology and control of net blotch and the net blotch barley interaction

2021 ◽  
pp. 477-524
Author(s):  
Anke Martin ◽  
◽  
Barsha Poudel ◽  
Buddhika Amarasinghe Dahanayaka ◽  
Mark S. McLean ◽  
...  
Keyword(s):  
Molecular Biology ◽  
Fungicide Resistance ◽  
Net Blotch ◽  
Sources Of Resistance ◽  
Breeding Programs ◽  
Barley Cultivars ◽  
Sexual And Asexual Reproduction ◽  
And Control ◽  
Different Sources ◽  
Durable Disease Resistance

Net blotches are the most widely distributed foliar diseases of barley worldwide, causing significant losses in grain yield. They occur as net form net blotch, caused by Pyrenophora teres f. teres and spot form net blotch caused by P. teres f. maculata. Both sexual and asexual reproduction play a role in the P. teres disease cycles leading to changes in genetic variation of populations. Breeding programs have to keep pace with pathogenic changes and ensure different sources of resistance are present in current barley cultivars. Knowledge of the genetic architecture and genes involved in virulence is thus vital to increase the durability of net blotch resistance in barley cultivars. This chapter explores the molecular biology, life-cycle and epidemiology of the net blotch fungi and discusses the key challenges we are facing in managing the net blotches using both fungicide resistance and breeding strategies to achieve durable disease resistance in barley.

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