Evaluation of Rhizobacterial Isolates for Their Antagonistic Effects against Various Phytopathogenic Fungi

Yun Seok Kim1   Sang woo Kim2   Kabir Lamsal2   Youn Su Lee2,*   

Abstract

This study was conducted to evaluate five different strains of rhizobacterial isolates viz. PA1, PA2, PA4, PA5 and PA12 for biological control against Colletotrichum acutatum, C. coccodes, C. gloeosporioides, C. dematium, Botrytis cinerea, Rhizoctonia solani, Sclerotinia minor and Fusarium sp. In vitro inhibition assay was performed on three different growth mediums,potato dextrose agar (PDA), tryptic soy agar (TSA), and PDA-TSA (1:1 v/v) for the selection of potential antagonistic isolates. According to the result, isolate PA2 showed the highest inhibitory effect with 65.5% against C. coccodes on PDA and with 96.5% against S. minor on TSA. However, the same isolate showed the highest inhibition with 58.5% against C. acutatum on PDA-TSA. In addition, an in vivo experiment was performed to evaluate these bacterial isolates for biological control against fungal pathogens. Plants treated with bacteria were analyzed with phytopathogens and plants inoculated with phytopathogens were treated with isolates to determine the biological control effect against fungi. According to the result, all five isolates tested showed inhibitory effects against phytopathogens at various levels. Mode of action of these rhizobacterial isolates was evaluated with siderophore production, protease assay, chitinase assay and phosphate solubilizing assay. Bacterial isolates were identified by 16SrDNA sequencing, which showed that isolates PA1 and PA2 belong to Bacillus subtilis, whereas, PA4, PA5, and PA12 were identified as Bacilus altitudinis, PaeniBacillus polymyxa and Bacillus amyloliquefaciens, respectively. Results of the current studysuggest that rhizobacterial isolates can be used for the plant growth promoting rhizobacteria (PGPR) effect as well as for biological control of various phytopathogens.

Acknowledgements

This research was supported by Ministry of Agriculture,Food and Rural Affairs (Project No. 111155-3). We would like to appreciate to the financial support.

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