Over-summering and biotypic diversity of Schizaphis graminum (Homoptera: Aphididae) populations on noncultivated grass hosts
2003
Anstead, J.A. | Burd, J.D. | Shufran, K.A.
Greenbug, Schizaphis graminum (Rondani), populations over-summering on noncultivated grass hosts may be implicated in early fall infestations in wheat. The purpose of this study was to examine the relationship between over-summering greenbugs on noncrop hosts and fall infestations on wheat. Since greenbug populations on noncultivated hosts may also act as reservoirs of virulence genes, the biotypes of collected aphids were also determined. The grass species present at three sites (two in Oklahoma and one in Kansas) were identified and a species richness curve was generated. Greenbugs were collected at these sites and their hosts and biotypes determined. At Hays, KS, a persistent over-summering greenbug population lead to an early fall infestation in wheat. At the sites in Oklahoma, where over-summering greenbugs were not detected, the fall infestation occurred 3 months later. Biotypes G, I, K, and a new biotype (i.e., previously undescribed) were found on noncultivated hosts at Hays, but only biotypes I and K were found on the cultivated wheat. Finding a new biotype supports the hypothesis that biotypic diversity (new combinations of virulence genes) is generated and maintained on noncultivated grasses, which may then act as reservoirs of virulence genes found in populations on crops.
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