Potential Use of Soil Bacteria Associated with Potato Rhizosphere as Bio-control Agents for Effective Management of Bacterial Wilt Disease

Potato has a crucial role to play in maintaining food security worldwide as it has high nutritive qualities and ratio of yield productivity to soil occupation. Despite the importance of the plant, its production is constrained by several biotic and abiotic stresses. Key among them is the bacterial wilt disease caused by Ralstonia solanacearum, with enormous yield losses. Existing management strategies have not been effective owing to the diversity of the pathogen with vast variation in host range. This study aimed at bio-prospecting for the potential of rhizopheral bacteria as biocontrol agents against potato bacterial wilt disease. The pathogen was isolated from plants showing typical symptoms of the disease and the obtained isolates were subjected to biochemical and molecular techniques of identification to confirm their status as Ralstonia solanacearum. In the course of bioprospecting, a total of 62 bacteria isolates were obtained from potato rhizosphere by serial dilution methods using broad spectrum media: nutrient agar and tryptic soy agar. Then, 20 isolates were selected based on their association with healthy plants for antagonistic tests using dual culture assay. During the in vitro screening, 5 bacteria species were identified to be highly antagonistic against four R. solanacearum strains. These antagonists were further tested in vivo for plant growth promoting traits and disease suppression ability. The results revealed that Bacillus cereus, Bacillus subtilis, Paenibacillus spp, Providencia rettgeri and Providencia vermicola were dominantly active in potato rhizosphere causing resistance to bacterial wilt disease. The isolates Bacillus cereus and Bacillus subtilis were also observed to have several plant growth promoting traits. These findings could provide baseline information for development of biocontrol strategies with the potential antagonists reported.