Effects of systemic and contact fungicides on life stages and symptom expression of Phytophthora ramorum in vitro and in planta

Elliott, Marianne; Shamoun, Simon F.; Sumampong, Grace

doi:10.1016/j.cropro.2014.10.008

Cited by 18 publications

(12 citation statements)

References 41 publications

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“…Due to the large number of isolates assayed, we only tested the sensitivity of the pathogen at three mancozeb concentrations. Although this limitation does not allow us to calculate EC 50 , the half maximum effective concentration, accurately (Sebaugh, ), a rough estimate indicates that it ranges from 0.02 to 39.57 μg/ml with a mean of 12.79 μg/ml, which was within the ranges observed for A. alternata in other studies (Malandrakis et al., ) as well as for other pathogens (Elliott, Shamoun, & Sumampong, ; Rekanovic et al., ).…”

Section: Discussionsupporting

confidence: 60%

“…Trade‐offs resulting from negative pleiotropy with other ecological and life‐history traits of pathogens may counterbalance the selective advantages of resistant mutations even in the presence of the antimicrobials, hampering accumulation and spatiotemporal dynamics of mutants. This trade‐off is expected to be common (Hall, Gubbins, & Gilligan, ; Li & Xiao, ), particularly in nonspecific fungicides (Melnyk, Wong, & Kassen, ) such as mancozeb, due to the involvement of many genes across pathogen genomes in the evolution of resistance and may also explain the constraining selection in the adaptation of A. alternata to mancozeb as indicated by a significantly lower population differentiation in mancozeb tolerance than that of SSR marker loci as well as similar spatiotemporal patterns of mancozeb sensitivity observed across pathogen species (Elliott et al., ; Henríquez, Sarmiento, & Alarcón ).…”

Section: Discussionmentioning

confidence: 99%

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Slow and temperature‐mediated pathogen adaptation to a nonspecific fungicide in agricultural ecosystem

Zhu

et al. 2017

Evolutionary Applications

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The spread of antimicrobial resistance and global change in air temperature represent two major phenomena that are exerting a disastrous impact on natural and social issues but investigation of the interaction between these phenomena in an evolutionary context is limited. In this study, a statistical genetic approach was used to investigate the evolution of antimicrobial resistance in agricultural ecosystem and its association with local air temperature, precipitation, and UV radiation. We found no resistance to mancozeb, a nonspecific fungicide widely used in agriculture for more than half a century, in 215 Alternaria alternata isolates sampled from geographic locations along a climatic gradient and cropping system representing diverse ecotypes in China, consistent with low resistance risk in many nonspecific fungicides. Genetic variance accounts for ~35% of phenotypic variation, while genotype–environment interaction is negligible, suggesting that heritability plays a more important role in the evolution of resistance to mancozeb in plant pathogens than phenotypic plasticity. We also found that tolerance to mancozeb in agricultural ecosystem is under constraining selection and significantly associated with local air temperature, possibly resulting from a pleiotropic effect of resistance with thermal and other ecological adaptations. The implication of these results for fungicide and other antimicrobial management in the context of global warming is discussed.

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Section: Discussionsupporting

confidence: 60%

Section: Discussionmentioning

confidence: 99%

Slow and temperature‐mediated pathogen adaptation to a nonspecific fungicide in agricultural ecosystem

Zhu

et al. 2017

Evolutionary Applications

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“…Associations of mancozeb tolerance with difenoconazole tolerance (RGR and MRGR respectively) were evaluated by simple linear correlation [63]. Multiple linear regression analysis implemented in Matlab [34] was used to evaluate the association among mancozeb tolerance, difenoconazole tolerance and aggressiveness of isolates using the model: , where c is the intercept, y, x1 and x2 were lesion area, mancozeb tolerance and difenoconazole tolerance and b1 and b2 were regression coefficients for mancozeb and difenoconazole, respectively. Matlab [64] was also used to determine outliers which were discarded in parameter estimation and validation and to plot a figure showing the relationship among aggressiveness and fungicide resistance.…”

Section: Discussionmentioning

confidence: 99%

“…alternata isolates (3 out of 234) had an EC 50 value 10-fold greater than the baseline and therefore can be considered as candidate progenitors of future resistant genotypes [12,34]. Therefore, caution should be taken in practice to prevent amplification in the frequency of these genotypes.…”

Section: Sequestration Of the Antifungal Agents In Cell Membranes Andmentioning

confidence: 99%

Cross-resistance of the pathogenic fungus Alternaria alternata to fungicides with different modes of action

Yang

Ouyang

et al. 2019

Preprint

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Background: Cross-resistance, a phenomenon that a pathogen resists to one antimicrobial compound also resists to one or several other compounds, is one of major threats to human health and sustainable food production. It usually occurs among antimicrobial compounds sharing the mode of action. In this study, we determined the sensitivity profiles of Alternaria alternata , a fungal pathogen which can cause diseases in many crops to two fungicides (mancozeb and difenoconazole) with different mode of action using a large number of isolates (234) collected from seven potato fields across China. Results: We found that pathogens could also develop cross resistance to fungicides with different modes of action as indicated by a strong positive correlation between mancozeb and difenoconazole tolerances to A. alternata . We also found a positive association between mancozeb tolerance and aggressiveness of A. alternata , suggesting no fitness penalty of developing mancozeb resistance in the pathogen and hypothesize that mechanisms such as antimicrobial compound efflux and detoxification that limit intercellular accumulation of natural/synthetic chemicals in pathogens might account for the cross-resistance and the positive association between pathogen aggressiveness and mancozeb tolerance. Conclusions: The detection of cross-resistance among different classes of fungicides suggests that the mode of action alone may not be an adequate sole criterion to determine what components to use in the mixture and/or rotation of fungicides in agricultural and medical sects. Similarly, the observation of a positive association between the pathogen’s aggressiveness and tolerance to mancozeb suggests that intensive application of site non-specific fungicides might simultaneously lead to reduced fungicide resistance and enhanced ability to cause diseases in pathogen populations, thereby posing a greater threat to agricultural production and human health. In this case, the use of evolutionary principles in closely monitoring populations and the use of appropriate fungicide applications are important for effective use of the fungicides and durable infectious disease management.

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“…The diameter of the mycelial plug inoculum was subtracted and the two diameter measurements were averaged. Percent growth inhibition for each antimicrobial substance and concentration was calculated by dividing colony diameter in the treated plates by that in the control plates (no antimicrobial substance added) [ 38 ].…”

Section: Methodsmentioning

confidence: 99%

Biopesticide Activity from Drimanic Compounds to Control Tomato Pathogens

et al. 2018

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Tomato crops can be affected by several infectious diseases produced by bacteria, fungi, and oomycetes. Four phytopathogens are of special concern because of the major economic losses they generate worldwide in tomato production; Clavibacter michiganensis subsp. michiganensis and Pseudomonas syringae pv. tomato, causative agents behind two highly destructive diseases, bacterial canker and bacterial speck, respectively; fungus Fusarium oxysporum f. sp. lycopersici that causes Fusarium Wilt, which strongly affects tomato crops; and finally, Phytophthora spp., which affect both potato and tomato crops. Polygodial (1), drimenol (2), isonordrimenone (3), and nordrimenone (4) were studied against these four phytopathogenic microorganisms. Among them, compound 1, obtained from Drimys winteri Forst, and synthetic compound 4 are shown here to have potent activity. Most promisingly, the results showed that compounds 1 and 4 affect Clavibacter michiganensis growth at minimal inhibitory concentrations (MIC) values of 16 and 32 µg/mL, respectively, and high antimycotic activity against Fusarium oxysporum and Phytophthora spp. with MIC of 64 µg/mL. The results of the present study suggest novel treatment alternatives with drimane compounds against bacterial and fungal plant pathogens.

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Effects of systemic and contact fungicides on life stages and symptom expression of Phytophthora ramorum in vitro and in planta

Cited by 18 publications

References 41 publications

Slow and temperature‐mediated pathogen adaptation to a nonspecific fungicide in agricultural ecosystem

Slow and temperature‐mediated pathogen adaptation to a nonspecific fungicide in agricultural ecosystem

Cross-resistance of the pathogenic fungus Alternaria alternata to fungicides with different modes of action

Biopesticide Activity from Drimanic Compounds to Control Tomato Pathogens

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