Suppression of Fusarium moniliforme in Rice by Rice-Associated Antagonistic Bacteria.

The potential of antagonistic bacteria from paddy water, rhizosphere soils, sclerotia, and rice plants to control "bakanae" caused by Fusarium moniliforme was assessed. Experiments were conducted to determine the in vitro antibiosis and effect of bacteria on seed germination. Out of 441 isolates, 113 were inhibitory to mycelial growth of the pathogen. Bacterial strains were classified into three groups based on effect on seed germination: (i) those that promoted germination and enhanced seedling vigor; (ii) those that had no effect on germination; and (iii) those that were deleterious and inhibited germination. Bacterization of naturally infected seeds reduced bakanae incidence in seedbox and seedbed tests. In a seedbed experiment with IR 58 seeds soaked in suspensions of bacterial strains, bakanae incidence and disease control ranged from 0.9 to 6.8% and 71.7 to 96.3%, respectively. From the 3 years of field trials, 10 strains reduced bakanae. Five strains consistently reduced bakanae, but the other five exhibited variable effects among trials. Specificity of suppression by antagonistic bacteria against different pathogenic isolates of F. moniliforme from various locations in the Philippines was observed.