Investigation Of The Genetic Diversity Of Phytophthora Capsici In China Using A Universal Fluorescent Labelling Method

Phytophthora capsici is an important oomycete pathogen threatening the vegetable production in China, but very little is known about its population structure. The objective of the present study was to evaluate the genetic diversity of 49 P. capsici isolates obtained from 2007 to 2014 at nine provincial locations in China. Isolates were assessed for mating type, metalaxyl resistance and simple sequence repeat (SSR) genotype. Mating-type analyses of the isolates showed that both mating types were present in all of the sampled production regions, and the mating-type frequency in the total Chinese population did not deviate significantly from a 1:1 ratio. Responses of isolates to the fungicide metalaxyl indicated the presence of intermediate resistance to metalaxyl among the field population. A universal fluorescent labelling method was adapted in this study to improve the efficiency of SSR genotyping. Microsatellite genotyping of the isolates using seven SSR markers revealed 44 unique multilocus genotypes. Genetic analyses indicated the existence of two genetic clusters within Chinese P. capsici collection. Clonal reproduction may play a more prominent role in Yunnan Province, but non-existence of repeated genotypes and existence of both mating types throughout all regions suggest outcrossing and sexual recombination likely play an important role in the overall epidemiology in China. Future studies would include expanded scale sampling at single regions over multiple years to better define the genetic diversity of P. capsici in China.