Role of steroidal glycoalkaloid alpha-tomatine in host-plant resistance of tomato to Colorado potato beetle

The role of the steroidal glycoalkaloid alpha-tomatine in the hostplant resistance of tomato to the Colorado potato beetle, Leptinotarsa decemlineata (Say) was examined in short- (24 hr; using first- and fourth-instar larvae) and long-term (first-instar larvae reared through the prepupal stage) feeding experiments. Consumption rate, growth rate, efficiency of conversion of ingested food to body mass, and survival were compared for L. decemlineata provided foliage from susceptible (Lycopersicon esculetum Mill. cv. Walter), resistant (L. hirsutum f. glabratum C.H. Mull accession PI 134417), and F1 hybrid plants. Values obtained for dietetic indices were regressed against corresponding values for alpha-tomatine content of foliage provided to larvae. Differences in dietetic indices could not be attributed to variation in foliar alpha-tomatine content despite a long-standing literature showing the ex planta alpha-tomatine inhibits feeding and growth by L. decemlineata