Differential induction of defence related proteins in melon seedlings infected with Didymella bryoniae and upon treatment with BTH, salicilic acid and methyl-jasmonate.

In the present study we have analysed the differential induc tion of defence proteins in necrotic and rotting lesions on melon seedlings infected by Didvmella brvoniae and upon exogenous application of the plant hormones salicylic acid and jasmonate and the synthetic activator BTH. Different pathogenesis re lated (PR) proteins including 1 ,3-glucanase (PR2), chitinase (PR3) and peroxidase (PR9) isoforms were analysed by isoelecric focusing and immunoblotting of total protein ex tracts. A differential induction of most of these proteins was observed in infected melon hypocotyls and after chemical treat- ments. In particular. two chitinase isoforms are differentially induced upon infection and treatment with BTH, Our results suggest that particular PRs are related to the defence mecha nisms during pathogen colonisation of melon seedlings following different signalling pathways