Induction of Systemic Resistance by Mixtures of Rhizobacterial Isolates against Pythium aphanidermatum

The efficacy of seven Rhizosbacterial isolates was tested for their ability to inhibit the growth of Pythium aphanidermatum, the causal agent of turmeric rhizome rot. In vitro studies revealed that Pseudomonas flurocense (PF25) and Bacillus megaterium (BM29) showed the highest inhibition of Mycelial growth (72.4%; 76.2%) of P. aphanidermatum. Both the antagonists were compatible with each other and they were tested alone and together in vivo for the control of P. aphanidermatum. Besides, the induction of defense-related enzymes such as peroxide (PO), polyphenoloxidase (PPO), phenylalanine ammonialyase (PAL), B1, 3-glucanase and the accumulation of phenolics in turmeric rhizomes due to the application of bioagents were also studied. Combined application of Rhizobacteria and challenge inoculated with P. aphanidermatum recorded maximum induction of defense- related enzymes and accumulation of phenolics compared with individual application. This study suggests that the increased induction of defense - related enzymes (4 to 5 fold) and phenolic content (6 fold) due to combination treatment of bioagents might have involved in the reduction of rhizome- rot incidence and in turn increased the plant growth and yield of turmeric.