Synthesis of a grapevine phytoalexin in transgenic tomatoes (Lycopersicon esculentumMill.) conditions resistance againstPhytophthora infestans

Stilbene synthase occurs in several plant species and synthesizes the stilbene phytoalexin trans-resveratrol using substrates commonly present in plants. The formation of stilbenes is considered to be a component of general defence mechanisms against pathogens in plants. Two genes from the grapevine (Vitis vinifera) coding for stilbene synthase were transferred to tomato (cv. Vollendung) by means ofAgrobacterium tumefaciens.Southern blot and Northern blot analyses demonstrated that both genes were stably integrated into the tomato genome and were expressed in transgenic regenerants and their progeny after fungal infection, wounding, induction with elicitor, and u.v. irradiation. The accumulation of the phytoalexin trans-resveratrol, the product of stilbene synthase, was detectable shortly after fungal inoculation, resulting in a significant increase in the resistance of transgenic tomato toPhytophthora infestans.A similar accumulation of resveratrol occurred after inoculation withBotrytis cinereaandAlternaria solani,but no significant increase in resistance was observed in transgenic tomato plants.