The Population Genetic Diversity Of Phytophthora Infestans In Gansu Province

Potato late blight, caused by Phytophthora infestans (Mont.) de Bary, is still a devastating disease on potato production. The structure and variation of Phytophthora infestans population are associated with disease occurrence and epidemics. Therefore, understanding of the potential genetic variation in the pathogen population is essential for developing effective disease control strategies. The total potato production in China ranks the first in the world, and Gansu province is among the most suitable regions for potato growth and have been the most important potato producer including the seed production. In this research, disease samples were collected and pathogen isolated in 2008 and 2009 in Gansu. The isolated P. infestans were determination for mating types and analyzed for the genetic diversity using a set of 8 SSR markers. The main results are as follows:1. A total of 246 P. infestans isolates in 2008 and 2009 were isolated.2. Of the 246 obtained isolates, 181 were determined for mating types including 119 being A1 mating type and 62 A2. The frequency of A2 mating type varies in different areas, being 87% in Anding, 25% in Zhangxian, 21% in Zhuanglang and 13% in Weiyuan, respectively. The frequency of the A2 mating type in 2008 and 2009 were 26% and 40%, respectively, suggesting widespread and increased presence of A2 mating type in Gansu Province.3. SSR primers genotyping led to the identification of 22 genotypes among 70 isolates from 2008, of which two dominant genotypes comprised 30% and 49% isolates, respectively. A total of 87 genotypes were detected in 176 isolates of 2009. The genotype diversity varies among different regions, with Weiyuan being the most diverse which comprises 54% genotypes in 2009. A total of 105 genotypes were detected from 246 P. infestans isolates in 2008 and 2009. The ratio of genotype number/isolate number increased from 30% in 2008 to 49% in 2009. This study showed that the genetic diversity of P. infestans populations in Gansu Province is relatively high. The dramatic changes in P. infestans genotypes between different years suggested that seed tubers are likely an important primary source of pathogen inoculum that contribute to late blight epidemics. The detection of the same P. infestans genotypes in different areas suggested exchanges the pathogen populations. The overlapping of the same P. infestans genotypes in different years in the same region suggested overwintering of the pathogen.The research will contribute to the understanding of P. infestans life cycle and epidemic of potato late blight in Gansu.