Effects of jasmonic acid and of an elicitor from Ceratocystis fimbriata f.sp platani on the accumulation of phytoalexins in leaves of susceptible and resistant plane trees

Jasmonic acid and a glycoprotein elicitor produced by Ceratocystis fimbriat a f sp. platani, the canker stain agent, were tested for induction of couma rin phytoalexin accumulation in detached leaves of resistant (Platanus occi nentalis) and susceptible plane trees (Platanus acerifolia and P. occidenta lis). It was shown that leaves responded by different levels of phytoalexin accumulation after fungal elicitor treatment. The phytoalexins were excret ed from elicited leaf tissues and accumulated in elicitor-containing drople ts on the leaf surface. The highest level was found in leaves of resistant tree. Furthermore, pretreatment of leaves by jasmonic acid, sprayed before elicitor application, induced a further enhancement in phytoalexin accumula tion which was higher in leaves of susceptible trees without any change in the ratio of the three phytoalexins, scopoletin, umbelliferone and xanthoar nol. However, jasmonic acid did not mimic biotic stress by itself. It only increased the response of leaf cells to fungal elicitor leading to an activ ation of coumarin metabolism. (C) 1999 Elsevier Science Ireland Ltd. All ri ghts reserved.