Soybean phytophthora root rot: Phytophthora sojae races in Indiana and factors affecting disease resistance
Abstract
Phytophthora root rot of soybeans caused by Phytophthora sojae has been one of the most important diseases throughout the soybean growing areas of the United States and Canada since the 1950's. Documenting the current physiological diversity of P. sojae and the role of factors affecting disease resistance are important in reducing yield losses due to this disease. Prevalence and distribution of P. sojae races in Indiana, and the role of peroxidase activity and manganese (Mn) in disease resistance were studied. Twenty-seven P. sojae races from 63 counties in Indiana were identified from 1993-1995. Races 1 and 3 were the most prevalent, identified from 62 and 65% of the counties, respectively. Also, races virulent on soybeans with the Rps1-k were identified from 65% of the counties. The role of peroxidase activity and manganese content in race-specific resistance and non-race-specific resistance were studied using selected races of P. sojae and Rps genes in two genetic backgrounds. Data for peroxidase activity in hypocotyl tissue were obtained with a soybean peroxidase capture assay (SPCA). Manganese content was analyzed using micro-X-ray absorption near edge structure (XANES) spectroscopy. Peroxidase activity at 72 hours after inoculation was generally higher in resistant Rps race-specific reactions than in susceptible reactions, and peroxidase activity was somewhat higher in Williams (cultivar with non-race-specific resistance) than Harosoy isolines. In contrast, total manganese content increased in all inoculated soybeans regardless of disease reaction (resistant vs. susceptible) and genetic background (Williams vs. Harosoy).
Degree
Ph.D.
Advisors
Abney, Purdue University.
Subject Area
Plant pathology|Botany
Off-Campus Purdue Users:
To access this dissertation, please log in to our
proxy server.