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Evaluation of Bacillus and Pseudomonas strains for bio-control activities on sheath blight and bacterial panicle blight of rice

Ateet Maharjan: Louisiana State University Agricultural Center

<div>Sheath blight (ShB - caused by <em>Rhizoctonia solani</em>) and bacterial panicle blight (BPB - caused by <em>Burkholderia glumae</em>) are economically important rice diseases in Louisiana and other rice-growing regions. Fungicides and oxolinic acid are applied to manage ShB and BPB, respectively, but these chemical methods are not sustainable economically and ecologically. To develop alternative biotic materials for disease management, rice-associated bacteria were screened based on their antagonistic activities against the pathogens by growth-inhibition plate assays, and three strains each of <em>Bacillus </em>spp. and <em>Pseudomonas </em>spp. were selected for evaluation in the field for ShB and BPB, respectively. Rice plants were artificially inoculated with <em>R. solani</em> at the tillering stage, while <em>B. glumae</em> was inoculated at 30% heading. Selected antagonistic bacteria were applied via spraying on the sheath (for ShB) or panicles (for BPB) of plants 24 h after inoculation. A field trial in 2017 revealed that one <em>Bacillus</em> strain REB 711, significantly suppressed ShB development compared to the untreated control, although it was less effective than the fungicide azoxystrobin. Efficacy of the <em>Pseudomonas</em> strains for suppression of BPB could not be determined in the field trial due to low disease pressure. Related research activities include characterization of the antimicrobial compounds from the bio-control agents and combined application of bio-control agents.</div>