Multifarious antagonistic potentials of rhizosphere associated bacterial isolates against soil borne diseases of Tomato

Biological control of soil borne plant pathogens is a potential alternative strategy to agrochemicals that are harmful to human health and the environment. Thus the present study focuses on the screening of indigenous soil isolates with multiple traits related to biocontrol of Xanthomonas, Fusarium oxysporum and Rhizoctonia solani. Rhizosphere soils were collected from different areas of Bangalore in India. Out of 12 actinomycetes and 51 bacterial isolates that were isolated, 1 actinomycete and 3 bacterial isolates showed maximum antagonistic activity against Xanthomonas spp (13- 20%) and Fusarium oxysporum (25-76%), Rhizoctonia solani (55- 83%) by dual culture technique. These isolates were identified as B. subtilis, P. aeruginosa, Streptomyces spp and P. fluorescens. The four isolates were further screened for PGPR traits. P.aeruginosa p6 showed positive for all PGPR traits and antagonism due to siderophore and HCN production. B.subtilis B2 showed mycolytic enzymes mediated antagonism. Streptomyces sp. 9p and P. fluorescens R showed concurrent production of both mycolytic enzymes and PGPR traits. All the four isolates showed increase in seed germination in the range of 28 to 71% when compared to control (14%). Present study reports the PGPR potential and biocontrol ability of the strains which can be used as biofertilizers as well as biocontrol agents.

Author(s): B. Sasirekha, Ashwini and Srividya Shivakumar*

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