Effects of Rag1 soybeans on the development and performance of noctuid larvae

Rag1-resistant soybeans, Glycines max Merr., are known to produce antibiosis against soybean aphid, Aphis glycines Matsumura (Hemiptera: Aphididae).  But we do not fully understand how the Rag1 gene affects other soybean pests.  Our research evaluated how resistant soybeans affect noctuid larvae using four nutritional indices.  Factors measured included relative growth rate, approximate digestibility, and efficiency of conversion of ingested and digested materials.  Data were collected using four Lepidoptera: fall armyworm, Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae); corn earworm, Helicoverpa zea (Boddie) (Lepidoptera: Noctuidae); soybean looper, Chrysodeix includens (Walker) (Lepidoptera: Noctuidae); and velvetbean caterpillar, Anticarsia gemmatalis Hübner (Lepidoptera: Noctuidae).  All tests used resistant and susceptible soybeans.  Results indicated that resistant soybeans had a negative effect on the relative growth rate of S. frugiperda, H. zea and A. gemmatalis.  Helicoverpa zea was able to more effectively digest susceptible soybeans, while A. gemmatalis had the most effective digestion of a Rag1-resistant line over all others.  For A. gemmatalis, the efficiency of conversion of digested materials was lowest on a Rag1-resistant soybean line.  These data indicate that in some cases, Rag1 soybeans have negative effects on noctuid species.