Analysis Of The Virulence And Genetic Diversity Of Phytophthora Sojae

Soybean Phytophthora root rot caused by Phytophthora sojae is one of the most devastating diseases of soybean. In China, soybean yield losses caused by this disease have become more and more serious since it was first reported in the northeastern China in the 90s. Recently soybean disease investigation indicated that, nine provinces of China have occurred soybean phytophthora root rot and the most serious were Northeast ,Yellow River and Huaihe River Basins. Four main aspects of this study as followed:1. 79 soil samples were collected from 25 cities or counties of Heilongjiang, Heinan, Anhui, Hubei provinces and Xinjiang Autonomous Region, respectively, were identified the present of P. sojae by using modified leaf disc baiting technique. 18 positive soil samples were indetified, including 6 from Heilongjiang province, 2 from Hennan province, 3 from Anhui province and 7 positive soil samples from Xinjiang Autonomous Region whereas, no P. sojae were isolated from Hubei province.2. The virulence types of 81 isolates of P. sojae were identified using 13 differential hosts, the results indicated, virulence composition of P. sojae population was complex in China, there were great virulence difference among different areas, different fields, or in the same field. 56 virulence types were identified among the 81 isolates, and they were all difference from the virulence types which have been reported. Cluster based on the virulence indicated, variations among the isolates from Heilongjiang province were higher and they were divided into four groups, while variations among isolates from Anhui province were smaller and they were in the same subgroup in 0.832 similarity coefficient.3. Genetic variation in 103 isolates of P. sojae, including 81 isolated in 2007 and conservated in the lab, was analyzed by AFLP marker. Using 25 AFLP primers, fingerprint patterns were generated from each isolate. The data were analyzed using NTSYS-PC 2.1 software and could be concluded that 103 isolates could be divided into 7 groups and the genetic diversities of the isolates from Anhui, Xinjiang, Henan were low, while others'were high. There were relationships between AFLP fingerprint patterns and the distribution of different isolates.4. Using modified hypocotyl inoculation technique, resistance of 19 soybean cultivars or lines from Xinjiang to 7 isolates of P. sojae were identified, more than half of the P. sojae isolates had virulence to resistant genes Rps1a,Rps1d,Rps2,Rps3c,Rps4,Rps5,Rps6,Rps7, while few had virulence to Rps1c and Rps1k, that was to say, soybean cultivars or lines could be used as resistant sources.