Systemic acquired resistance in tomato against Phytophthora infestans by pre-inoculation with tobacco necrosis virus

Inoculation of the two bottom leaves (1 and 2) of tomato plants (Lycopersicon esculentum) cv. Vollendung with tobacco necrosis virus (TNV) induced systemic resistance against late blight disease caused by Phytophthora infestans SDS PAGE of acid soluble proteins extracted from TNV-inoculated plants showed accumulation of six pathogenesis-related proteins in inoculated leaves ii and 2) and in upper leaf tissue (leaf 3). Western blot analysis with antisera raised against different pathogenesis-related proteins of tomato and tobacco revealed that four of these proteins were P14, AP24, chitinase and beta-(1,3)-glucanase. An in vitro study of the antifungal activity of these pathogenesis-related proteins showed that only the basic fraction has direct antifungal activity toward Phytophthora infestans. The induction of systemic resistance was accompanied by an increase of peroxidase activity in inoculated leaves as well as in upper leaf tissue (leaf 3). On the other hand, significant increase in the activity of beta-(1,3)-glucanase was observed only in leaves inoculated with tobacco necrosis virus. Leaf tissue analysis of induced plants showed that inoculation with TNV resulted in the induction of three new peroxidase and one beta-(1,3)-glucanase isozymes. (C) 1997 Academic Press Limited.