Plant growth promoting rhizobacterial (PGPR) bioconsortia mediates induction of defense-related proteins against infection of root rot pathogen in mulberry plants

The mixture of Pseudomonas fluorescens isolate Pf1 and Py15 and Bacillus subtilis isolate 16 (Bs16) was found to protect mulberry plants from root rot disease caused by Macrophomina phaseolina. Induction of defense-related proteins and chemicals by the mixture of Pf1, Py15 and Bs16 against challenge inoculation with M. phaseolina in mulberry were studied. The activity of defense enzymes peroxidase (PO), polyphenol oxidase (PPO), phenylalanine ammonia lyase (PAL), beta-1, 3-glucanase, chitinase and defense chemical total phenols were found to be significantly higher in combined application of biocontrol agents Pf1 + Py15 + Bs16 followed by Pf1 + Bs16, Pf1 + Py15 and Py15 + Bs16 treated plants when compared to individual treatments and control. The SDS-PAGE analysis of protein in biocontrol agents treated plant showed eight proteins with molecular weight of 14, 23, 30, 35, 45, 50, 60 and 98 kDa. In healthy plants only six proteins (excepting 14 and 98 kDa) appeared in biocontrol agents treated plant two additional new proteins appeared. These results suggest that induction of defense enzymes involved in phenyl propanoid pathway and accumulation of total phenols and PR-proteins might have contributed to restriction of invasion of M. phaseolina in mulberry roots.