PHYTOALEXINS IN RICE - PYRICULARIA-ORYZAE INTERACTION - FACTORS AFFECTING PHYTOALEXIN PRODUCTION

Phytoalexin production in Oryza sativa-Pyricularia oryzae relationship as influenced by nitrogen fertilization and chemicals including growt h regulators, the fungal toxin, alpha-picolinic acid and a systemic no n-fungicidal blast controlling agent, probenazole was examined on deta ched leaf blade segments of blast susceptible (cv. Karuna) and resista nt (cv. IR 8) rice cultivars with drop-diffusate technique. Nitrogen f ertilization did not influence the production of phytoalexin. Gibberel lic acid and indoleacetic acid accelerated senescence of detached leaf blade segments to a lesser extent than abscisic acid. However, these growth regulators did not affect the phytoalexin production. alpha-Pic olinic acid induced the accumulation of phytoalexin in the leaf blade segments of resistant cultivar, but not in those of susceptible cultiv ar. Probenazole markedly enhanced the accumulation of phytoalexin in b oth cultivars.