Submitted to: Crop Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 6/10/2006
Publication Date: 12/10/2006
Citation: Ferro, C.R., Hill, C.B., Miles, M.R., Hartman, G.L. 2006. Evaluation of soybean cultivars with the Rps1k gene for partial resistance and tolerance to Phytophthora sojae. Crop Science. 46(6):2427-2436. Interpretive Summary: Phytophthora root rot (PRR) is a soilborne disease that primarily attacks the roots of soybean plants. Partial resistance and tolerance can be used to augment complete resistance. In this study, partial resistance and tolerance to two compatible races of Phytophthora sojae were identified in private commercial cultivars possessing the complete resistance gene Rps1k. Many of the private cultivars had a high level of partial resistance in the greenhouse and in the field; however, resistance measurements in the greenhouse were not correlated with yield. Most of the private cultivars appeared to be consistently tolerant to PRR in the field based on yields of plants in inoculated and non-inoculated plots. This information is useful to commercial seed companies, soybean growers and consultants.
Technical Abstract: Phytophthora root rot (PRR) is a soilborne disease caused by Phytophthora sojae that primarily attacks the roots of soybean plants. Race-specific resistance (complete resistance genes), partial resistance (limits pathogen colonization and plant damage), and tolerance (suffering no significant yield loss when infected) have been found. The objectives in this study were to identify partial resistance and field tolerance to two races of P. sojae compatible with the Rps1k gene in private commercial cultivars. Partial resistance and tolerance to compatible P. sojae races 28 and 30 were identified in private commercial cultivars. Many of the private cultivars had a high level of partial resistance in the greenhouse, not significantly different from the incompatible cultivar A3302 possessing the Rps1c gene, for percentage of control of root and top mass, plant height, and root and plant disease ratings. A high degree of partial resistance was also expressed in the field for yield; however, resistance measurements in the greenhouse were not correlated with yield. The percentage of control for plant height at the growth stage R6 in the field was significantly correlated with the percent of control for yield in three experiments (r=0.39, 0.57, and 0.62). Most of the private cultivars appeared to be consistently tolerant to PRR because there was not a significant difference in yield between inoculated treatments with or without Apron fungicide seed applications.