Preference and performance of two lepidopteran species on Rag1 cultivars

The Rag1 gene in soybeans (Glycines max) is responsible for resistance to the invasive soybean aphid (Aphis glycines Matsumura). Soybeans expressing Rag1 were released in 2010 for commercial use. The effects of Rag1 on other insect pests of soybeans has yet to be explored. In 2011, we performed a laboratory experiment to evaluate the preference and performance of the fall armyworm Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae) and the corn earworm Helicoverpa zea (Boddie) (Lepidoptera: Noctuidae) on soybeans that contain the Rag1 gene. Our previous research indicated that Spodoptera frugiperda showed a preference for Rag1 soybeans, although it gained less mass as it developed on the same soybeans. For this series of experiments, we conducted choice and no-choice tests using two different Rag1 genetic lines and their respective near-isolines. Also, we compared the mass of both insect species after consuming either Rag1 soybeans or the near-isoline for seven days. We also evaluated relative growth rate, efficiency of conversion for digested food and ingested food. Our data addresses the potential for other agricultural pest insects to injure Rag1 soybeans.