Enhanced Nitrogen Fixing in Sesbania grandiflora by Azospirillum (BPL7) sp. Isolated from Godavari Belt Region, Andhra Pradesh, India

Abstract

Biological nitrogen fixation is the key to sustain productivity in agriculture, horticulture and forestry. Among several biological nitrogen fixers, Azospirillum is the free-living bacterium, which is involved in the nitrogen fixation, promoting the lateral root formation and in some cases they form nodules in the roots. Efficient nitrogen fixing, Azospirillum BPL7 strain was isolated from the Godavari belt region of Andhra Pradesh. Out of 19 strains isolated, the BPL7 strain had shown better growth-promoting characteristics and nitrogen fixing activity in five test plants viz. Sesbania grandiflora, Zea mays, Oryza sativa, Sesamum indicum and Solanum melongena plantlets under laboratory conditions. The morphological, biochemical and physiological characteristics in comparison with type strain Azospirillum brasilense (NCIM No. 5135) has proved it as an Azospirillum sp. The nature of oxidation and fermentation of different carbon compounds by Azospirillum BPL7 strain matched with that of the type strain. Moreover, the biometric observations viz. shoot and root length, shoot and root dry weight and nitrogen fixation among all the plants reflected that a few plants have dominated while a few were equivalent and still a few were inferior to the type strain is clearly expounded in the results. Therefore, upon observation of the results pertaining to the various characteristics in comparison with type strain and plant growth promoting aspects related to S. grandiflora, the isolated strain Azospirillum BPL7 was confirmed as Azospirillum brasilense and found to be the best nitrogen fixing bacteria among all the isolates including the type strain.