Prospecting Beneficial Microsymbiont Associated with Root Nodules of Crop Legumes of North-Eastern India, Nagaland

The present study isolates and characterizes the root nodule microsymbiont of five crop legumes: Canavalia gladiata (Jacq.) DC, Dolichos lablab L., Phaseolus lunatus L., Phaseolus vulgaris L. and Vigna unguiculata (L.) Walp. From 69 isolates, 21 with distinct Random Amplified Polymorphic DNA (RAPD)-fingerprints were identified to diverse taxa through 16S rRNA sequencing. Enterobacter was the predominantly identified taxa. Seventeen isolates were evaluated for their morpho-biochemical and plant growth-promoting properties. All isolates exhibited auxin and gibberellic acid production; however, phosphate solubilizing activity was limited to a few. The bacteria showed a highly variable metabolic and enzyme activity profile suggesting functional specialization determined by the plant host. Inoculation of PLLUM5 (Enterobacter spp.) promotes the growth of non-host plants, namely, rice and soybean, which agrees with the phytohormone production. Significant increases in biomass and lateral roots were observed in the inoculated plants compared to the control. The identified root nodule microsymbiont has potential application as a wide host-range bio-inoculum in agriculture.