Glycoalkaloid responses of potato to Colorado potato beetle defoliation.

Two experiments were conducted to measure the glycoalkaloid concentrations of potato tubers in response to Colorado potato beetle and manual defoliation. For plants defoliated by Colorado potato beetles, there was a significantly greater production of glycoalkaloids than in control plants and manually defoliated plants for both skin and inner tissue of tubers in experiment 1. In experiment 1, there was a 58.1% and 48.3% increase in glycoalkaloids in skin and inner tissue of tubers, respectively, from plants defoliated at high levels by Colorado potato beetles compared to control plants. In experiment 2, although a significant difference in glycoalkaloid concentration was not observed among the treatments, the skin and inner tissue of tubers from plants defoliated at high levels by Colorado potato beetles increased glycoalkaloid concentration by 23.4% and 14.5%, respectively, compared to tubers from control plants. In experiment 1, the concentration of tuber extract required to reduce Chinese hamster ovary (CHO) cellular proliferation by 50% was 10-fold less for the skin versus the inner tissue, indicating that skin tissue was more toxic under the in vitro conditions of this assay.