Abstract
Knowledge of the evolution of fungicide resistance is important in securing sustainable disease management in agricultural systems. In this study, we analyzed and compared the spatial distribution of genetic variation in azoxystrobin sensitivity and SSR markers in 140 Phytophthora infestans isolates sampled from seven geographic locations in China. Sensitivity to azoxystrobin and its genetic variation in the pathogen populations was measured by the relative growth rate (RGR) at four fungicide concentrations and determination of the effective concentration for 50% inhibition (EC50). We found that all isolates in the current study were sensitive to azoxystrobin and their EC50 was similar to that detected from a European population about 20 years ago, suggesting the risk of developing azoxystrobin resistance in P. infestans populations is low. Further analyses indicate that reduced genetic variation and high fitness cost in resistant mutations are the likely causes for the low evolutionary likelihood of developing azoxystrobin resistance in the pathogen. We also found a negative correlation between azoxystrobin tolerance in P. infestans populations and the mean annual temperature of collection sites, suggesting that global warming may increase the efficiency of using the fungicide to control the late blight.
Highlights
Knowledge of the evolution of fungicide resistance in pathogen populations is important for planning strategies to increase the effective use of fungicides and reduce the costs of plant disease management
Numerous transposable elements distributed around functional genes in the P. infestans genome[28,29] may allow the pathogen to generate large amounts of genetic variation to cope with frequent changes in fungicide initiatives; and an epidemic mode of population development[30] adopted by the pathogen could ensure its ability to preserve allelic combinations that are well adapted to existing fungicides while retaining the pathogen’s ability to generate novel allelic combinations that may offer an evolutionary advantage to counter the introduction of new fungicides[31]
The objectives of this study were to: i) monitor the spatial distribution of azoxystrobin sensitivity in field populations of P. infestans occurring in the main Chinese potato cropping regions; ii) investigate the relative role of genetics and plasticity in determining azoxystrobin resistance; and iii) infer the main evolutionary forces driving the evolution of azoxystrobin resistance in P. infestans by comparing spatial distributions of genetic variation in SSR marker loci and azoxystrobin sensitivity
Summary
Knowledge of the evolution of fungicide resistance in pathogen populations is important for planning strategies to increase the effective use of fungicides and reduce the costs of plant disease management. Temperature is one of the most important environmental parameters with crucial impacts on all biotic and abiotic processes[13,14,15] It can affect the evolutionary landscape of pathogens[16,17], toxicity of chemicals[18,19] and interactions between pathogens and chemicals. Potato late blight caused by Phytophthora infestans (Mont) de Bary is among the most important plant diseases in the world. It is infamous as the under-lying cause of the Irish potato famine of the 1840s but still is the most devastating disease globally[25], in regions of moderate temperature and high humidity. The objectives of this study were to: i) monitor the spatial distribution of azoxystrobin sensitivity in field populations of P. infestans occurring in the main Chinese potato cropping regions; ii) investigate the relative role of genetics and plasticity in determining azoxystrobin resistance; and iii) infer the main evolutionary forces driving the evolution of azoxystrobin resistance in P. infestans by comparing spatial distributions of genetic variation in SSR marker loci and azoxystrobin sensitivity
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