Stress response in the soybean aphid (Aphis glycines Matsumura)

The rapid spread and immense agricultural damage inflicted by the soybean aphid (Aphis glycines Matsamura) have made this invasive species the single most important arthropod pest of soybeans in N. America. With initial efforts heavily focused on chemical and biological control strategies, we currently lack a basic understanding of what environmental factors limit aphid population growth and range expansion. In addition, despite exposure to a broad range of potentially stressful environmental conditions, soybean aphids thrive wherever soybeans are found, suggesting current populations may harbor significant adaptive genetic variation. The current research characterizes the soybean aphid response to three environmental stressors (heat, starvation and an aphid resistant soybean variety). Specifically, we investigate 1) clonal variation in response to these stressors and 2) both short and long-term effects of stress exposure. Survival and offspring production were measured for clonal populations exposed to extreme heat (34C), starvation, soybean plants with the defense gene Rag2, and optimal control conditions (24C, plants lacking Rag2) for 72 hours. In addition, a subset of individuals were removed at 48hrs and placed under optimal conditions (24C) to monitor lifetime fecundity and longevity. Overall, we found that aphid clonal lines significantly varied in response to all stresses and in some cases we identified stress resistant clones, suggesting the adaptive potential of current populations could contribute to future outbreaks. In addition, we found that 48hrs exposure to stress significantly reduced lifespan and reproductive output, indicating long-term stress effects could limit aphid population growth in the field.