Physiological and phylogenetic analysis of rhizobia isolated from Acacia nilotica L.

Abstract

The legume-rhizobia relationship is known to be a beneficial symbiosis in the direction of agriculture. The present investigation was aimed to isolate and characterize five rhizobia isolates from woody legume tree; Acacia nilotica L. Physiological properties of all five isolated strains were similar. However, on the basis of nitrogen fixation test, only two isolates were symbiotic and the other three were non- symbiotic. Therefore, for phylogenetic analysis, only two isolates were subjected to 16S rRNA gene sequencing for strains. Hence, the DNA was isolated from the well grown bacterial cultures. Amplified DNA was sequenced for 16S rRNA. The phylogenetic tree was constructed and bacterial isolates were identified as rhizobia. Isolate first showed strong homology with Mesorhizobium loti and isolate second showed intermediate with Rhizobium leguminosarum and Rhizobium hainanense. For the confirmation of nitrogen fixing ability of isolates, nifH gene was amplified. Application of effective rhizobia strains as biofertilizers to improve legume production is an important approach in sustainable agriculture.

Key words: Legume, rhizobia, physiological, phylogenetic, biofertilizers.