The greenbug, Schizaphis graminum (Rondani), is a serious pest of sorghum and small grains in the Southern Plains of the United States. Use of resistant cultivars is the major integrated pest management strategy for controlling greenbugs. However, greenbug-resistant sorghums developed through breeding are constantly challenged by the rapid occurrence of new biotypes that overcome the plant resistance. As a result, new resistant sorghums need to be developed, and insecticides must be used to combat this pest when sorghums resistant to the predominant biotype are not available. To begin to understand greenbug counter-defense mechanisms, we used a high-throughput AFLP fingerprinting method to examine genetic divergence among eight greenbug biotypes. Clustering analysis, based on 1775 scored AFLP markers, clearly showed that biotypes able to infest sorghum fields (biotypes C, E, I and K) share higher polymorphism among themselves than with non-sorghum biotypes. Our results suggest that a common genetic factor(s) responsible for high fitness on sorghum exists among the sorghum greenbug biotypes, enabling them to predominate and thrive in near-monocultural sorghum fields. Understanding this commonly shared genetic basis for fitness among sorghum greenbug biotypes may have great impact on enhancing host plant resistance.
Species 1: Homoptera Aphididae Schizaphis graminum (greenbug)
Keywords: Biotype, AFLP
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