Plant growth promoting rhizobacteria suppress blast disease caused by Pyricularia oryzae and increase grain yield of rice

Plant growth promoting rhizobacteria are being widely utilized in agriculture due to their biopesticide and biofertilizer potential. The indigenous PGPR inhabiting certain hosts can act as potent bioinoculants due to their native habitat and acclimatization to the environment. Four hundred and fifty indigenous isolates were obtained from rice rhizosphere to assess their antagonism towards rice blast pathogen P. oryzae. Only 100 isolates showed antagonistic activity. Twenty out of 100 isolates inhibited the mycelium growth of P. oryzae by 30-65 % in vitro. Five strains, KFP-5, KFP-7, KFP-12, KFP-17 and KFP-18, showing 63-65 % antagonism towards P. oryzae, were tested for the production of biocontrol determinants and suppression of blast disease in rice plants. The antagonistic strains produced various biocontrol determinants such as the hydrolytic enzymes, protease, glucanase and cellulase with solubilization zone diameters of 10-19, 4.2-14.5 and 2-13.5 mm respectively and siderophores with zone diameter of 7-12 mm. The antagonistic strains also solubilized potassium, phosphorus and zinc from inorganic sources with solubilization zones of 2.1-3.2, 2.3-3.6 and 1.7-2.9 mm respectively. Three antagonistic strains, KFP-5, KFP-7 and KFP-17 significantly suppressed blast disease with a disease score 1.1-1.9 and increased yield of rice plants. The potent antagonistic strains were identified as members of the genus Bacillus by 16S rRNA gene sequencing.