Pathotypes of Phytophthora sojae and their distribution in Jilin, China

A nine-year survey on pathotypes of Phytophthora sojae from 2007 to 2015 throughout Jilin Province of China was conducted. A total of 219 single-zoospore isolates of P. sojae that came from 250 commercial soybean fields in 25 counties were tested for their virulence phenotypes by using eight soybean differentials representing eight Rps alleles. The investigation showed that Phytophthora root rot (PRR) or P. sojae is mainly distributed in northeast Jilin. A total of 91 pathotypes were identified from 219 isolates, in which 34 matched the virulence formula of 15 known races, and two races (races 28 and 30) were identified in China for the first time. The highest isolation frequency was 6.4% found for race 8, followed by race 3 and race 1, each representing 4.6% and 4.1% of the isolates. The isolation frequencies of the remaining 12 races (races 0, 4, 9, 13, 14, 23, 24, 25, 28, 30, 33, and 44) was less than 2.3%. In addition, nine intermediate reaction types (IRTs) were found (0.5–1.4% isolation frequency). The remaining 67 pathotypes that represented approximately 66% of the isolates were not identified to a race. The isolates each defeated zero to eight Rps genes, and 71.2% of the isolates defeated more than three Rps genes, indicating that virulence of the isolates in Jilin is moderately strong. Virulence frequency of the isolates to eight single Rps genes ranged from 20–77%. More than 57% of the isolates were virulent on Rps1a, Rps1b, Rps1d, Rps6, and Rps7 while less than 30% of the isolates were virulent on Rps1c, Rps1k, and Rps3a, indicating that Rps1c, Rps1k, and Rps3a were more effective than the other five Rps genes in Jilin at reducing infection of soybean by P. sojae.