Contribution of jasmonic acid to resistance against Phytophthora blight in Capsicum annuum cv. SCM334

Defense responses were investigated in the leaves of a cultivar of pepper, Capsicum annuum (cv. SCM334) resistant to Phytophthora blight. Jasmonic acid (JA) increased in the resistant cultivar immediately after inoculation with the pathogen, Phytophthora capsici, but as the levels of JA later decreased, levels of salicylic acid (SA) increased and were subsequently accompanied by hypersensitive response (HR)-mediated cell death in SCM334. Simultaneously, expression patterns of JA- and HR-related genes were analyzed. The mRNA of catalase and peroxidase (suppressing HR generation) disappeared, while the mRNA of OPR3 (encoding JA synthesis reductase) was detected in SCM334 specifically. JA-mediated defense appears to be crucial in the resistance of pepper plants against P. capsici.