A Feeding Deterrent for Thrips palmi KARNY (Thysanoptera

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