BIOCONTROL POTENTIAL OF QUORUM QUENCHING RHIZOBACTERIA AGAINST SOFT ROT PATHOGEN, Pectobacterium carotovorum subsp. carotovorum.
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Date
2022-02-15
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University of Agricultural Sciences, Bangalore
Abstract
Pectobacterium carotovorum subsp. carotovorum (Pcc) is a brute force pathogen
causing necrotic soft rot, virulence of which is induced by quorum sensing regulated
production of plant cell wall degrading enzymes. Quorum quenching (QQ) by the
disruption of the quorum sensing signals, the AHL molecules, is recently being proposed
as the strategy for the biocontrol of plant pathogens. Employing QQ based suppression of
plant pathogens with rhizobacteria, therefore, assumes a greater significance in the wake
of development of multidrug resistance in plant pathogens. To harness the potential of
QQ rhizobacteria in the biocontrol programme, ninety-six bacteria isolated from the
rhizosphere of crops cultivated in farms of GKVK were screened for their QQ ability
using the bioindicator Chromobacterium violaceum RU9. The in vitro screening yielded
twenty-four isolates with variable QQ efficiency. Out of 24 isolates, the isolate BMR17
recorded significantly higher QQ efficiency of 93% while BRR05, BBR58, BBR60,
BAR70, BAR75, BAR78, BAR79 and BFR83 exhibited efficiency between 86% and
92%. In vitro biocontrol assay of green gram seeds and in - vitro maceration attenuation
assay on Potato, Carrot, Radish and Cucumber evidenced that BRR05, BMR17, BMR22,
RAR39, BBR57, BAR79 and BFR86 showed efficient QQ biocontrol potential. The
isolates BRR05, BMR17 and BFR86 degraded different long chain and short chain AHL
molecules as revealed by HPLC chromatogram and heat map. Principal Component
Analysis of the plant growth and yield parameters of Green gram as influenced by the
inoculation of these three biocontrol isolates under greenhouse condition revealed that
BFR86 (Priestia megaterium) is the potent QQ biocontrol agent against the pathogen Pcc
followed by BMR17 (Staphylococcus hominis) and BBR57 (Priestia aryabhattai).