Geographic Distribution and Intrabiotypic Variability of Four Soybean Aphid Biotypes

Soybean aphid (Aphis glycines) is an invasive species in North America. For more than a decade, scientists have been working on host plant resistance, but the frequent identification of aphid isolates resistant (virulent) to soybean [ Glycine max (L.) Merr.] traits has caused concern amongst stakeholders interested in aphid control. To explore the diversity and distribution of these virulent aphids, we sampled soybean fields throughout the north-central United States and southern Canada from 2011 through 2013. We evaluated soybean aphid performance on soybean cultivars containing Rag1, Rag2, and Rag3 loci and categorized them per standard biotypes. The soybean aphid biotypes were widely distributed across the sampled region. We also used the performance test scores to study the outliers and unexpected results according to biotype. Intrabiotypic variability is common in North America.