Induction of Disease Resistance Using Fluorest Pseudomonas

Abstract

Ragi, a highly nutritious millet, is susceptible to more than twenty pathogens newlineThe most dreadful among them is Magnaporthe grisea (Hebert) Barr., which is highly newlinevirulent causing the blast disease resulting in an annual yield loss of ~ 80 %. This study newlineaims at inducing disease resistance in ragi plants with plant growth promoting newlinerhizobacteria (PGPR) as inducers. The present study initiated with the isolation and newlinescreening of fluorescent Pseudomonas, a group of PGPR, from different rhizospheres. newlineThe 136 isolates were short-listed to twelve based on the plant growth promoting traits, newlinewhich were used to induce resistance in otherwise susceptible ragi seeds (Indaf 9). newlineForty-day old plants raised from primed seeds were challenge inoculated with the newlinespores of M. grisea, and the plants were scored for disease incidence after 20 days post newlineinoculation based on symptomatology. Untreated (mock) control was maintained newlinethroughout the study. Disease resistance with high significance was observed in primed newlineplants, with the isolate JUPW121 followed by JUPC113 to that of control plants. newlinePathogenesis-related (PR) proteins detected were significantly high at initial hours of newlinechallenge inoculation regulating disease protection. This is the first report on the newlinetemporal accumulation of PR protein in ragi plants against M. grisea. The two isolates newlineJUPC113 and JUPW121 were sequenced and were known to be Pseudomonas newlineaeruginosa, with the accession numbers - KX010601 and KX010602 respectively. Indepth study on the mechanism involved during induction of resistance was carried out newlineby investigating the regulation of the antioxidant-mediated defense response and the newlinephenylpropanoid pathway. The role of primary and secondary metabolites were also newlinestudied through metabolomic analysis. This is the first report on the role of tyrosine newlineammonia lyase (isoenzyme of PAL), in the phenylpropanoid pathway during induction newlineof resistance in primed ragi seedlings. Results of the hypersensitive response and newlinehistochemical studies supported the biochemical analysis and greenhouse studies, newlineindicating a positive regulation of host defense response through seed priming. This newlinestudy suffices the role of rhizobacteria in induction of resistance, as it reveals the newlinemechanism for sustainable, eco-friendly and economical approach for plant disease newlinemanagement.