Exploring soybean germplasm for resistance to Aphis glycines

Soybean aphid (Aphis glycines) has rapidly spread through the Midwest causing consistent yield losses on soybean since its introduction. Rag1, a gene that confers resistance to the soybean aphid by antibiosis mechanism has been isolated before. However, the consistency of the resistance conferred by Rag1 gene across different locations is unknown. We compared yield and aphid reproduction on Rag1 genotype and in a closely related susceptible line. These field trials were conducted at three different locations in Iowa, Minnesota and Illinois. Seed yield in RAG1 line was not significantly different across these locations despite different aphid pressure. The yield of the susceptible line was reduced with increased aphid pressure. Single gene resistance, however, can be easily overcome by a pest and we observed significant soybean aphid populations (greater than 250 per plant) on RAG1 containing plants. Therefore, we measured resistance (aphid numbers per plant) on 13 soybean varieties across five different locations in Iowa, Illinois, Wisconsin and Michigan. Results showed a significant location by line interaction. Cluster and grouping analysis were conducted to evaluate the potential utility of these lines for soybean aphid management.