Exploring Plant Growth Promoting Potential of Non Rhizobial Root Nodules Endophytes of Vigna radiata1

Abstract

Plant growth promoting (PGP) rhizobacteria exert beneficial effects and may establish as endophytes in their hosts. Here, plant growth promoting traits of 26 non rhizobial and one fungal endophyte previously isolated from Vigna radiata rootnodules were assessed for IAA and siderophore production, Phosphate solubilization and hydrolytic enzymes production. Most bacterial endophytes improved seedling vigor index while fungal endophyte (Macrophomina phaseolina) lacked all PGP traits. Endophytes Ml, M10 and M15 were most influential in improving Seedling Vigor Index. Three endophytes having multiple PGP traits with maximum siderophore production: 46.77 μg mL–1 (Bacillus anthracis; Ml), IAA production: 10.81 μg mL–1 (Paenibacillus taichungensis; M10) and phosphate solubilization: 134.483 μg mL–1 (Paenibacillus xyla nilyticus; M15) significantly increased root length (RL), shoot length (SL), number of lateral roots (NLR)and plant dry weight (DW) when inoculated/co inoculated with E. adhaerens (native rhizobia) to V. radiata in a small field trial. M10 inoculation produced longest RL while Ml when coinoculated with E. adhaerens produced highest SL and NLR. Ml inoculation or coinoculation was most effective in improving dry weight of mature plants. Most of the endophytes coinoculated with E. adhaerens improved growth parameters. We report that non rhizobial endophytes with PGP traits in combination with native rhizobia can be prospective candidates for use as biofertilizer.