LOCAL AND SYSTEMIC PROTECTION AGAINST PHYTOPHTHORA-INFESTANS INDUCED IN POTATO AND TOMATO PLANTS BY JASMONIC ACID AND JASMONIC METHYL-ESTER

Jasmonic acid (JA) and jasmonic methyl ester (JME) are plant lipid der ivatives that have been postulated to play a role in plant wound and p athogen responses. Here we report that JA and JME applied as foliar sp rays to potato (cv. Bintje or Alpha) or tomato (cv. Baby) plants prote cted them against a challenge infection with Phytophthora infestans. L ocal protection against P. infestans isolates S49 or MR1 was evident i n plants treated with as low as 62.5 mu g (similar to 0.3 mu mol)/ml, whereas systemic protection was evident in plants treated with jasmona tes at 1000 mu g (similar to 4.8 mu mol)/ ml. Jasmonates at 4.8 mu mol /ml did not inhibit fungal mycelial growth in agar cultures. JA and JM E stimulated direct germination of sporangia in vitro and on planta. S DS-PAGE (sodium dodecyl sulfate-polyacrylamide gel electrophoresis) an alysis of acid-soluble proteins of treated tomato leaves revealed enha nced levels of two proteinase inhibitors and similar to 24- and 29- to 30-kDa proteins. Jasmonates did not induce phytoalexin synthesis in t reated potato or tomato plants. Systemin did not protect either potato or tomato from the blight fungus. We speculate that metabolites induc ed by jasmonates are responsible for the protection against P. infesta ns.