Population genetic structure of rubber tree powdery mildew pathogen (Erysiphe quercicola) from China

Abstract

In order to manage agricultural pathogens, it is crucial to understand the population structure underlying epidemics. Rubber tree powdery mildew, caused by Erysiphe quercicola, is a serious threat to rubber plantations worldwide especially in subtropical environments including all rubber tree growing regions in China. However, the population structure of the pathogen is uncertain. In this study, 16 polymorphic microsatellite markers were used to genotype powdery mildew samples from the main rubber tree growing regions including Yunnan (YN), Hainan (HN), western Guangdong (WG) and eastern Guangdong (EG). YN had higher genotypic diversity (Simpson’s indices), genotypic evenness, Nei's gene diversity, allelic richness and private allelic richness than the other regions. Cluster analysis, DAPC analyses, pairwise divergence and shared MLGs analyses all showed that the YN differed significantly from the other regions. The genetic differentiation was small among the other three (HN, WG and EG) regions. Analysis of molecular variance indicated that the variability among regions accounted for 22.37% of the total variability. Genetic differentiation was significantly positively correlated (Rxy = 0.772, P = 0.001) with geographic distance. Linkage equilibrium analysis suggested possible occurrence of sexual recombination although asexual reproduction predominates in E. quercicola. The results suggested that although significant genetic differentiation of E. quercicola occurred between YN and the other regions, pathogen populations from the other three regions lacked genetic differentiation.