|Cochran, A - PURDUE UNIVERSITY|
Submitted to: Phytopathology
Publication Type: Abstract Only
Publication Acceptance Date: June 22, 1999
Publication Date: N/A
Technical Abstract: Phytophthora sojae which causes root rot and extensive yield loss in soybeans is a genetically diverse pathogen throughout primary soybean producing regions of the U.S. It is important to both soybean producers and breeders to be aware of race frequency and distribution of P. sojae. Previous Indiana reports in the 1990s suggest races 1, 3, 4, 7, 13, 25, 28, ,33, 43, and 44 occur most frequently. During 1996 and 1997, 289 isolates of P. sojae were obtained from 360 soybean fields in 70 Indiana counties. Eighteen of the 45 races or pathotypes reported in the U.S. were identified using the soybean Rps-differentials (1a, 1b, 1c, 1d, 1k, 3a, 6, 7). Rps virulence data for the isolates from each county suggest Rps gene combinations (1k or 1c + 3a or 6) will control races identified in 95-98% of the counties. Control of P. sojae races using individual Rps resistance genes would be less than 70% with the exception of Rps3a which would control 83% based on the Indiana P. sojae data.