Mechanism of Resistance to the Colorado Potato Beetle in Wild Solanum Species

Abstract

Field and laboratory experiments were used to measure several fitness parameters of the Colorado potato beetle, Leptinotarsa decemlineata (Say), when maintained on foliage of 7 resistant Solanum species. The relatively low mortality of adults and larvae, the reduced oviposition, and the low proportion of adults recovered 2 d after release on S. berthaultii, but with a larval development time similar to that of potato ( Solanum tuberosum L.), support the semiochemical-based nature of S. berthaultii resistance as described in the literature. Results very similar to those obtained with S. berthaultii were obtained on S. tarijense, suggesting that both species have a similar mode of resistance. The results obtained with S. capsicibaccatum were also similar to S. berthaultii. The absence of trichomes on S. capsicibaccatum indicated that the mechanism of resistance is probably based on different chemicals. S. jamesii, S. polyadenium, and S. trifidum produced high mortality of adults and larvae, and low egg production, indicating the presence of a toxic substance or of a strong feeding deterrent. S. pinnatisectum produced high larval mortality but adult mortality was relatively low indicating that the factor of resistance might be less effective or have a different effect on adults.