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 morphological and genetic mechanisms associated with the whitefly and tomato plant that may explain observed variations in resistance patterns. Leaf 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 dense trichomes positioned close to the stem terminus. Leaf trichome density also explained a significant portion of the variance in whitefly oviposition rates among commercial cultivars. Cultivars with low trichome densities sustained less whitefly oviposition than did cultivars with high trichome densities. There was no relationship between leaf trichome densities and whitefly oviposition rates on wild tomatoes. High levels of resistance were observed on Lycopersicon hirsutum Humb, and Bonpl. and L. pennellii (Corr.) D'Arcy. The patterns of trichome-based resistance among the commercial cultivars were validated in held choice tests and greenhouse population studies. Six genetically distinct tomato lines were generated by introgression of a single L. pennellii chromosome into L. esculentum Miller. The genetic information that confers resistance in L, pennellii Is spread across at least 5 different chromosomes, but a substantial portion likely resides on a single chromosome.