Preliminary Analysis Of Genetic Diversity Of Phytophthora Sojae In China

Phytophthora root rot of soybean caused by Phytophthora sojae is a destructive soilborne disease,since it was first found in the Northeast China in 1991,P.sojae has been gradually found all over the country,and has become a major threat to soybean production.In this study, diseased soybean samples were collected from Xinjiang and Northeast China.A total of 179 P.soja isolates were obtained and subjected genetic diversity analysis using CAPS and SSR markers.The result as follows:1.A total of 391 root rot soybean samples were collected from Xinjiang and Northeast China,of which 205 were infected with P.soja.A total of 137 Psojae were isolated from both fresh infected tissues and heavily infected tissues using our developed procedure.We improved the isolation procedure and achieved up to 31%isolation efficiency.2.Four model P.sojae strains representing four major genotypes were used to develop CAPS and SSR makers for the analysis of the genetic diversity of P.sojae populations.3.Analysis of the genetic diversity of 179 P.sojae strains showed that,there were 41 P.sojae strains shared the four major genotypes.However,different banding patterns were identified in Chinese population,indicating that some variations distinct from four major genotypes occurred in Chinese population.Cluster analysis 179 P.sojae isolates into 7 UPGMA groups at the level of 80%genetic similarity,including Northeast isolates being distributed in 7 groups,and Xinjiang population in 4 groups.The average Shannon's Information index of the Northeast population was 0.45,higher than that of Xinjiang(0.34), suggesting that the Northeast population had higher level of genetic diversity than Xinjiang population.The Nei's genetic identity between two populations was 0.9935.All genotypes in Xinjiang population were found in the Northeast population,while there were 3 genotypes in the Northeast population were not detected in Xinjiang population.These suggest that P.sojae in Xinjiang was likely introduced from Northeast China.