Leaf physical and chemical features influence selection of plant genotypes by Hessian fly.

Abstract

To identify features of plants that mediate host selection behavior in the Hessian fly, we established the ranking of six grasses by ovipositing females and then ran choice tests with plant models that incorporated physical and/or chemical features of the six grasses. In tests with real plants, egg counts revealed the following ranking: 18ITSN triticale > Otane hexaploid bread wheat > Fleet barley > PND tetraploid durum wheat > 3424 hexaploid bread wheat > Awapuni oat. On all six grasses, the adaxial side of the leaf received more eggs than the abaxial side. In tests with green paper models treated with extracts of the six grasses, egg counts were similar to egg counts on real plants. In tests with models that incorporated a molded resin imprint of an abaxial or adaxial leaf surface, egg counts on adaxial models, but not abaxial models, again were similar to egg counts on real plants. In two final tests a factorial design was used to compare the effects of the chemical and physical features of two pairs of grasses: (1) two bread wheats, Otane and 3424; and (2) a bread wheat and an oat, Otane and Awapuni. In the two tests, the effects of the physical features of the models were at least as important as the effects of the chemical features.