Mechanism of resistance to the Colorado potato beetle in wild Solanum species

Field and laboratory experiments were used to measure several fitness param eters of the Colorado potato beetle, Leptinotarsa decemlineata (Say), when maintained on foliage of 7 resistant Solanum species. The relatively low mo rtality of adults and larvae, the reduced oviposition, and the low proporti on of adults recovered 2 d after release on S. berthaultii, but with a larv al development time similar to that of potato (Solanum tuberosum L.), suppo rt the semiochemical-based nature of S. berthaultii resistance as described in the literature. Results very similar to those obtained with S. berthaul tii were obtained on S, tarijense, suggesting that both species have a simi lar mode of resistance. The results obtained with S. capsicibaccatum were a lso similar to S, berthaultii. The absence of trichomes on S. capsicibaccat um indicated that the mechanism of resistance is probably based on differen t chemicals. S. jamesii, S. polyadenium, and S. trifidum produced high mort ality of adults and larvae, and low egg production, indicating the presence of a toxic substance or of a strong feeding deterrent. S, pinnatisectum pr oduced high larval mortality but adult mortality was relatively low indicat ing that the factor of resistance might be less effective or have a differe nt effect on adults.