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 derivatives that have been postulated to play a role in plant wound and pathogen responses. Here we report that JA and JME applied as foliar sprays to potato (cv. Bintje or Alpha) or tomato (cv. Baby) plants protected them against a challenge infection with Phytophthora infestans. Local protection against P. infestans isolates S49 or MR1 was evident in 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 jasmonates 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 JME stimulated direct germination of sporangia in vitro and on planta. SDS-PAGE (sodium dodecyl sulfate-polyacrylamide gel electrophoresis) analysis of acid-soluble proteins of treated tomato leaves revealed enhanced levels of two proteinase inhibitors and similar to 24- and 29- to 30-kDa proteins. Jasmonates did not induce phytoalexin synthesis in treated potato or tomato plants. Systemin did not protect either potato or tomato from the blight fungus. We speculate that metabolites induced by jasmonates are responsible for the protection against P. infestans.