INVOLVEMENT OF POLYAMINES, DIAMINE OXIDASE AND PEROXIDASE IN RESISTANCE OF CHICKPEA TO ASCOCHYTA-RABIEI

Peroxidase (POD, EC 1.11.1.7), diamine oxidase (DAO, EC 1.4.3.6) activ ities and polyamine levels have been investigated in stems, untreated or inoculated with conidia of Ascochyta rabiei, obtained from chickpea cultivars, respectively susceptible (<Calla>) and resistant (<Sultano >) to an isolate of the fungus. DAO activity and cadaverine content ar e constitutively higher in the fourth internode of resistant cultivar Sultano as compared with the cultivar Calia. Germination of conidia, d evelopment of hyphae and formation of appressoria were found to be sim ilar in the two cultivars. POD and DAO activities and putrescine level increased markedly after infection in both cultivars as compared with control plants, with a greater enhancement of both enzyme activities and diamine level in <Sultano>. Apparent histochemical activities of b oth DAO and POD were detected in the lignosuberized barriers set up by cortical and pith parenchyma cells in response to pathogen invasion. The barriers are thicker and wider in resistant plants. In addition to these responses, the two cultivars showed different histological feat ures. The resistant cultivar Sultano has a higher number of xylem elem ents and xylem parenchyma cells as compared with <Calia>. Results obta ined suggest that the structural organization of xylem tissues, polyam ine metabolism and peroxidase activity may have a role in the resistan ce of the cultivar Sultano to A. rabiei.