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Biological control activity of rice rhizosphere bacteria and their interactive effects with silica treatment against sheath blight of rice.

Jhonson Leonard: Louisiana State University

<div>Sheath blight of rice caused by the soil-borne fungus<em> Rhizoctonia solani</em> is one of the devastating diseases of rice worldwide. Bacteria isolated from diverse parts of the rice plant have the ability to inhibit the development of sheath blight. Silica has been found to potentiate defense enzyme activity in rice, thus led to the reduction of the progression of sheath blight lesions. This study aims to develop new biocontrol agents and cultural practices with silica fertilizer for disease management of sheath blight. Bacteria were isolated from rice rhizosphere and pure-cultured on Luria Broth Agar amended with 40 µg/ml of cycloheximide, and screened for their antifungal activity against <em>R. solani</em> on Potato Dextrose Agar plates. Among the 534 bacterial isolates tested, forty-nine isolates suppressed the development of <em>R. solani</em> in culture media. In the anti-fungal bioassay, the highest significant inhibition zone values range from 1.03 to 1.29 cm. These bacteria are being identified through 16s rDNA sequencing, and further tested for their <em>in vivo</em> activities in greenhouse and field assays. The additive or synergistic activity of selected bacteria in combination with different amounts of silicate slag, a silica fertilizer obtained as a by-product of the steel and iron industry, will be presented.</div>