IN VITRO ANTAGONISM OF RESIDENT RHIZOBACTERIA, BACILLUS AMYLOLIQUEFACIENS SUBSP. AMYLOLIQUEFACIENS AGAINST THE BACTERIAL BLIGHT PATHOGEN OF BT COTTON

Author(s): Raut LS and Hamde VS

Abstract: Bacterial blight is one of the most important yield-reducing diseases of Bt cotton caused by Xanthomonas axonopodis pv. malvacearum. The present work was undertaken to search for efficient biocontrol agents from resident microflora of soil as an alternative for chemical management. 114 resident rhizobacterial isolates were screened in vitro antagonistic activity against bacterial blight pathogen using cross plate technique. Among the tested rhizobacterial isolates, six isolates showed antagonistic activity. The highest antagonism was exhibited by rhizobacterial isolate RLS19. Based on the inhibitory activity, the rhizobacterial isolate RLS19 was selected for further investigation. The rhizobacterial isolate RLS19 was later identified as Bacillus amyloliquefaciens subsp. amyloliquefaciens by 16S rRNA sequence analysis. To study antagonistic mechanism, the rhizobacterial isolate was evaluated for production of non-volatile metabolites and volatile metabolites. B. amyloliquefaciens subsp. amyloliquefaciens was able to produce non-volatile diffusible metabolites and showed 32 mm zone of inhibition around the well. Also, the GC-MS analysis of cell free culture filtrate reveals the presence of three volatile metabolites i.e. Pyrrolo[1,2-a]pyrimidine-2,6-dione, hexahydro- , 2,5-Piperazinedione, 3,6-bis(2-methylpropyl)- and Acetamide, N-methyl-N-[4-(3-hydroxypyrrolidinyl)-2-butynyl]-. Based on these results Bacillus amyloliquefaciens subsp. amyloliquefaciens can be served as good microbial control candidate for control of bacterial blight pathogen of Bt cotton.

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