Beyond biotypes: soybean aphid biology and the surprising durability of aphid-resistance in soybean

Monday, October 20, 2014 - 4:10pm
Event Type: 

Adam Varenhost will be presenting his Ph. D. defense as a part of the Department of Entomology's fall semester seminar series.

Event will be located in E164 Lagomarcino Hall.

Abstract: The soybean germplasm contains several genes that provide resistance to the soybean aphid, Aphis glycines Matsumura, (Rag-genes). These genes can limit A. glycines population growth and prevent yield loss. However field tests of Rag-containing soybean are never free of aphids. Despite the genetic bottleneck that A. glycines passed through on the way to North America and the sparse commercial use of Rag genes, several virulent biotypes are found in North America that survive on Rag-soybean. The potential for both virulent and avirulent biotypes to co-occur on both aphid-resistant and susceptible soybeans is present in North America. Host suitability can be affected when herbivore conspecifics with varying levels of virulence co-infest a shared host plant (i.e. induced susceptibility). In a series of experiments, Rag-genes efficacy was reduced when infested with varying combinations of A. glycines biotypes. Virulent biotypes reduced the capacity of Rag genes to protect the plant from avirulent biotypes. This obviation of resistance persisted for 5 days after virulent biotypes were removed from the plant. Further complicating the relationship between aphids and Rag-containing plants is the fitness costs associated with virulence to Rag genes. Combined, these features of the aphid-plant system (induced-susceptibility, obviation of resistance, fitness costs) can contribute to reducing the advantage that virulent biotypes enjoy within this system. These factors should preserve the efficacy of Rag-genes if they are used commercially.