Characterization and diversity of rhizobia nodulating prominent arid legumes of Thar desert of India

Abstract

A study was conducted to assess the characteristics and diversity existing in rhizobia nodulating leguminous trees (Acacia senegal and Prosopis cineraria) and crops (Cyamopsis tetragonoloba or guar and Vigna aconitifolia or moth bean) of arid zone of India. Sixty eight rhizobial cultures isolated from root nodules were characterized at phenotypic and molecular level. Sixty percent of the isolates were classified as fast or very fast growers and 88.5% of the colonies formed on YEMA medium plates were wet and gummy. Majority of the isolates did not grow on acidic pH (6 or below). PCR of 16S rDNA and sequencing led to identification of 25 representative isolates. A dendrogram developed based on partial 16S rDNA sequences delineated not only different genera of isolated rhizobia but also different species/strains indicating diverse nature of root nodule bacteria in hot arid soil environment. Genotypic and morphological associations were found to be independent of geographical affiliations.