Isolation, characterization and study of multi-faceted plant growth promoting traits of Rhizobium from root nodules of faba bean (Vicia faba L.) grown in acid soil of Eastern Himalaya

The present study reported the isolation and purification of root nodule Rhizobium from 18 different faba bean accessions and their characterization and study of multifaceted plant growth promoting (PGP) traits. The colony morphology, cell shape, cell wall reaction, and biochemical assays of 18 isolates were found to be similar to the reference strain Rhizobium leguminosarum MTCC 99, which is very close to R. leguminosarum biovar viceae. PCR amplification and sequence analysis of 16S rRNA gene of the Rhizobia isolates showed that the isolated strains were R. leguminosarum biovar viceae. The isolates RhFaba104, RhFaba130 and RhFaba134 could maintain cell growth even at a lower pH of 4.0. Among the 18 isolates, RhFaba130 possessed the maximum ability for phosphate dissolution from FePO4 (0.20 μg P ml-1 h-1), mineralization from Na-phytate (0.70 μg P ml-1 h-1), production of IAA (1.55 μg ml-1 h-1), Zn dissolution efficiency (176) and fixation of nitrogen (9.2 μg NH4-N per g CMC). The isolate RhFaba130 was the most efficient in terms of in-culture multifaceted PGP traits.