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ARS Home » Midwest Area » West Lafayette, Indiana » Crop Production and Pest Control Research » Research » Publications at this Location » Publication #151391

Title: EVALUATION OF SOYBEAN DIFFERENTIALS FOR THEIR INTERACTION WITH PHYTOPHTHORA SOJAE

Author
item DORRANCE, A - OHIO STATE UNIVERSITY
item JIA, H - OHIO STATE UNIVERSITY
item Abney, Thomas

Submitted to: Plant Health Progress
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/5/2004
Publication Date: 3/9/2004
Citation: Dorrance, A.E., Jia, H., Abney, T.S. 2004. Evaluation of soybean differentials for their interaction with phytophthora sojae. Plant Health Progress. 0309(1). Available: http://www.plantmanagementnetwork.org/sub/php/research/2004/psojae/

Interpretive Summary: Yield losses due to Phytophthora root rot are a major problem for U.S. soybean producers. New insights about sources for resistance genes in soybean varieties (soybean differentials) used to control and verify specific races of Phytophthora sojae are identified in this study. Information is available about soybean differentials and disease resistance conferred by Rps genes, but researchers utilizing the information regularly experience problems. For instance, differences in reactions for isolates of P. sojae have been reported. This may be due to changes in virulence in the pathogen or to different sources of resistance in a soybean differential. To determine the current status of soybean differentials available to researchers, we evaluated seed sources from the USDA Soybean Germplasm Collection, Purdue University and Ohio State University with five races of P. sojae from Indiana and Ohio. Races 1, 3, 4, 7, and 25 had the expected reaction on all three sets of soybean differentials for Rps1b, Rps1c, Rps1k, Rps 2, Rps3a, Rps4, Rps5, Rps6, Rps7, and on differentials Harlon, L59-731 and Union for Rps1a. Differentials L88-8470 for Rps1a and L93-3312 for Rps1d did not have the expected response. Differences in Rps2 for Races 4 and 25 could be attributed to the geographic source of P. sojae isolates, as virulence to this allele has not been used to characterize P. sojae races. This information will permit pathologists and breeders to deploy, recommend, and emphasize control strategies that can minimize substantial yield losses.

Technical Abstract: Soybean differentials, each containing a different resistance allele (Rps), are used to characterize races of Phytophthora sojae. Surveys in different soybean production regions have used different sets of soybean differentials, thought to carry the same Rps alleles. Isolates of P. sojae, originating from different regions, have been reported to have different reactions when evaluated on the differentials with the same Rps allele. The objective of this study was to determine if different sources of the Rps gene or the differentials themselves were responsible for this variation. Five races of P. sojae from both Ohio and Indiana were evaluated on soybean differential sources from the USDA Soybean Germplasm Collection, USDA-ARS Purdue University and The Ohio State University using the hypocotyl inoculation test. Races 1, 3, 4, 7, and 25 had the expected reaction on all three sets of soybean differentials for Rps1b, Rps1c, Rps1k, Rps 2, Rps3a, Rps4, Rps5, Rps6, Rps7, and on differentials Harlon, L59-731 and Union for Rps1a. Differentials L88-8470 for Rps1a and L93-3312 for Rps1d did not have the expected response. Differences in Rps2 for Races 4 and 25 could be attributed to the geographic source of the isolate, as virulence to this allele has not been used to characterize P. sojae races. All of the races had a resistant reaction on Rps3b and Rps3c; therefore these differentials should be screened with additional isolates. Differentials for the fourteen Rps alleles that represent different maturity groups are recommended.