A FEEDING DETERRENT FOR THRIPS-PALMI KARN Y (THYSANOPTERA, THRIPIDAE)FOUND IN TOMATO LEAVES - ISOLATION AND IDENTIFICATION

Despite its polyphagous nature, Thrips palmi does not really attack to mato plants. In efforts to elucidate the chemical basis responsible fo r the tomato's resistance, a crystalline compound possessing strong an tifeeding activity for this insect species was isolated from tomato le aves by means of methanol extraction, water/butanol partition, silica gel chromatography, and preparative high-performance liquid chromatogr aphy. According to responses to certain test reagents, qualitative and quantitative LC profiles of component sugars, melting point, specific rotation, UV-, IR-, MS-, H-1-NMR- and C-13-NMR-spectra, the compound was identified as alpha-tomatine, a known steroidal glycoalkaloid in t omato plants. The immunity of tomato plants to T. palmi is explained s olely by the occurrence of alpha-tomatine, because T. palmi does not u se airborne information (attractants/repellents) to avoid tomato leave s, and tomato leaves apparently provide the required phagostimulants a nd nutrients.