Differential sensitivity of rice pathogens to growth inhibition by flavonoids

Abstract

Differential sensitivity of the major pathogens of rice, Xanthomonas oryzae pv. oryzae, Pyricularia oryzae and Rhizoctonia solani to inhibition by certain flavonoids was tested using paper disc/liquid culture and spore germination assays. Naringenin, the first intermediate of the flavonoid pathway, displayed growth inhibition of Xanthomonas strains and spore germination of P. oryzae. On the other hand, no such inhibition was found with Rhizoctonia solani. Crude extracts of leaf and pericarp tissues of a fully purple pigmented rice cultivar, Purpleputtu, also showed growth inhibition of Xanthomonas.The sensitivity of rice pathogens to growth inhibition by flavonoids was highly variable. Naringenin showed growth inhibition of Xanthomonas as well as Pyricularia. The anthocyanin extract from leaves of rice was found to be inhibitory to Xanthomonas.