Biological Control of Blast Disease of Rice (Oryza sativa L.) with Antagonistic Bacteria and Its Mediation by a Pseudomonas Antibiotic.

Abstract

Rice plant associated microorganisms both Pseudomonas spp. and Bacillus spp. were isolated and tested for antagonism against the rice blast fungus Pyricularia oryzae Cav. Field test of four selected strains in an upland rice farm in the Philippines afforded significant leaf blast reduction with rice var. UPLRi-5. Strain 7-14, identified as P. fluorescens was most effective. The crude extract prepared from this strain provided 70-100% inhibition of conidial germination at 1.0ppm. The antiblast extract also protected IR 50 rice seedlings from infection of P. oryzae. Evidence suggested that siderophore was unlikely to be involved in the mechanism of strain 7-14 in its antagonism against the rice blast fungus. In vitro test showed that inhibition of P. oryzae by strain 7-14 was not reversed by Fe amendments. Thus, the antiblast antibiotic, instead of siderophore production from Pseudomonas strain 7-14 protected rice seedlings from infection by P. oryzae.