THE EFFECT OF LIGHT-INTENSITY ON COLORADO POTATO BEETLE RESISTANCE AND FOLIAR GLYCOALKALOID CONCENTRATION OF 4 SOLANUM-CHACOENSE CLONES

Controlled environment experiments were used to determine the effect of light intensity on levels of glycoalkaloids and resistance to the Colorado potato beetle (CPB), Leptinotarsa decemlineata Say, in Solanum chacoense Bitter clones that synthesized acetylated glycoalkaloids, the leptines. Plants were grown under two light intensities, 50 or 250-mu-mol m-2S-1, and bioassayed for CPB resistance by placing neonate larvae on excised foliage. Larval development stage and mortality were recorded after four days. The leptine-synthesizing clones responded to the increase in light intensity with a 2-4 fold increase in level of foliar leptines. Larval development rate on foliage from plants grown under high light intensity was reduced and larval mortality increased. Results showed a significant (p < 0.05) effect of light on glycoalkaloid synthesis and CPB resistance.