Solanum berthaultii Hawkes is used in some potato breeding programs because of its resistance to insects. This close relative of Solanum tuberosum L. may eventually be introduced as a hybrid with the potato, in the geographic distribution of the Colorado potato beetle. To evaluate the fate of such a resistant variety derived from S. berthaultii, the biological performance and the genetic potential for adaptation of the Colorado potato beetle on S. berthaultii has been evaluated. Survival, developmental time, prepupal weight, fecundity, and egg weight were the fitness parameters considered. Survival and fecundity were reduced and more variable on S. berthaultii than on S. tuberosum, but developmental time and prepupal weight were similar on both plant species. The egg weight was not affected by the plant species or the parentage and did not influence the larval fitness parameters. For all the fitness parameters studied, except egg weight, a significant effect of the "Host × Sire" component was observed, indicating a difference in the effect of the plant species between insect families. However, this interaction had an additive genetic basis only for fecundity and possibly survival. Fecundity had a significant additive genetic component only on S. berthaultii. The important covariance of the survival between plant species and the negative covariance between fecundity and survival on S. berthaultii support the hypothesis that the Colorado potato beetle would have a lower rate of increase on S. berthaultii. Our results indicated that specialization of the Colorado potato beetle on S. berthaultii is possible but should not influence its performance on S. tuberosum.
HOST PLANT ADAPTATIONS AMONG GEOGRAPHIC POPULATIONS OF THE COLORADO POTATO BEETLE