Biotypic Status of Russian Wheat Aphid (Homoptera: Aphididae) Populations in the United States

Abstract

Baseline information on the biotypic status of Russian wheat aphid, Diuraphis noxia (Kurdjumov), populations in the United States prior to the commercial planting of Russian wheat aphid-resistant small grains is reported. Ten Russian wheat aphid clones, collected from 5 states, were evaluated for biotypic variation on 4 wheat, Triticum aestivum L., and 2 barley, Hordeum vulgare L., germplasm entries. Although minor statistical differences were detected in measurements of chlorosis, root weight, aphid numbers, and aphid weight among some clones, host responses to Russian wheat aphid infestation among the 10 clones were similar. No genotypic differences were detected among the aphid clones based on random amplified polymorphic DNA profiles. Ten years after its introduction to the United States and before the commercial release of resistant cultivars, the Russian wheat aphid has not exhibited biotypic variation like that found in another cereal aphid, Schizaphis graminum (Rondani). It has been previously shown that Russian wheat aphid populations from other parts of the world exhibit considerable biotypic variation. Thus, with the threat of future introductions into the United States, Russian wheat aphid should be periodically monitored for biotypic variation, before and after the deployment of resistant cultivars.