Systemic acquired resistance to Phytophthora infestans in tomato and the role of pathogenesis related proteins

Systemic resistance was induced in tomato by infecting the lower leaves with Phytophthora infestans . The level of this resistance increased over a period of 7 days from induction and stayed at the elevated level for at least a further 7 days. Changes in acid soluble proteins and chitinase activity were induced systemically by the infection and increased in parallel with systemic resistance. β1,3-glucanase was not induced systemically. Four varieties of tomato with different basic levels of susceptibility to P. infestans were found to develop systemic resistance to the same level. PR-protein fractions were tested in vitro for their antifungal activity against P. infestans . Their antifungal activity was found to increase during the experimental period in parallel with systemic acquired resistance.