VARIATION IN TRICHOME-BASED RESISTANCE TO BEMISIA-ARGENTIFOLII (HOMOPTERA, ALEYRODIDAE) OVIPOSITION ON TOMATO

Twenty commercial tomato cultivars and 7 Mild relatives of tomato were screened in the laboratory for resistance to the silverleaf whitefly Bemisia argentifolii Bellows & Perring. In addition, we examined morph ological and genetic mechanisms associated with the whitefly and tomat o plant that may explain observed variations in resistance patterns. L eaf trichome and position relative to the stem terminus were the best predictors of whitefly oviposition rates on tomato cultivars and their wild relatives. Higher oviposition rates occurred on leaves with dens e trichomes positioned close to the stem terminus. Leaf trichome densi ty also explained a significant portion of the variance in whitefly ov iposition rates among commercial cultivars. Cultivars with low trichom e densities sustained less whitefly oviposition than did cultivars wit h high trichome densities. There was no relationship between leaf tric home densities and whitefly oviposition rates on wild tomatoes. High l evels of resistance were observed on Lycopersicon hirsutum Humb, and B onpl. and L. pennellii (Corr.) D'Arcy. The patterns of trichome-based resistance among the commercial cultivars were validated in held choic e tests and greenhouse population studies. Six genetically distinct to mato lines were generated by introgression of a single L. pennellii ch romosome into L. esculentum Miller. The genetic information that confe rs resistance in L, pennellii Is spread across at least 5 different ch romosomes, but a substantial portion likely resides on a single chromo some.