Strategic assessment of multiple plant growth promotion traits for shortlisting of fluorescent Pseudomonas spp. and seed priming against ragi blast disease

Biocontrol and induction of resistance through rhizosphere microflora against plant pathogens is a major area of interest. Fluorescent Pseudomonas (FPs), the highly noted diverse rhizospheric bacteria which are widely used for disease management in various plant–pathogen systems. Management of ragi blast disease by Magnaporthe grisea is a major challenge because of its wide host specificity. The present study is intended towards isolation of FPs for priming ragi seeds which could induce resistance against blast disease. They were characterized for PGP traits (production of indole acetic acid and siderophore, phosphate solubilisation, biofilm formation and cyanogenesis) and their antagonistic behaviour against M. grisea. Selection of the potential isolates was based on quantitative PGP traits through a nonparametric analysis. Principal Co-ordinate Analysis based on PGP traits classified 136 isolates into two clusters. Twelve best isolates were used for further studies on induction of resistance by seed priming under greenhouse conditions, followed by challenge inoculation with M. grisea. The isolate JUP121 showed best disease protection when compared to the control plants. Out of twelve treatments, four showed significant disease resistance under greenhouse conditions, which were further validated by biochemical determinants. A time course study on the accumulation of pathogenesis related (PR) proteins (β-1,3-glucanase and chitinase) was carried out which showed significant results on priming.