Pseudomonas aeruginosa GSE 18 inhibits the cell wall degrading enzymes of Aspergillus niger and activates defence-related enzymes of groundnut in control of collar rot disease

Abstract

Pseudomonas aeruginosa GSE 18, reduced the pre-emergence rotting and post-emergence wilting of groundnut by >60% in A. niger-infested potting mixture. Bacterial seed treatment induced the rapid accumulation of defence-related enzymes like chitinase, β-1,3-glucanase, peroxidase and phenylalanine ammonia lyase (PAL) in groundnut seedlings compared with the control. Activities of these enzymes were significantly (P=0.01) higher in GSE 18-treated seedlings than the control, with activation of PAL being the highest (>2-fold). Cell-free culture filtrate of P. aeruginosa GSE 18 inhibited the in vitro production of polygalacturonase and cellulase by A. niger up to 77% and 68%, respectively, 6 days after inoculation. Thus, activation of host defence responses and inhibition of fungal cell wall-degrading enzymes appear to play a significant role in the biocontrol activity of GSE 18 in collar rot of groundnut.