Phylogenetic diversity of indigenous Rhizobium trapped from the natural habitat of Pisum sativum L. in eastern and central Algeria

Abstract

The nitrogen-fixing symbiosis fixation between legumes and Rhizobium helps the plant to survive and to compete effectively on nitrogen poor soils. The soil environment attached to the root system is characterized by intense microbial activity. This work aimed to study the diversity of indigenous rhizobia living in the rhizosphere of forage pea in eastern and central Algeria. Bacteria were trapped in vitro from collected soils. They were isolated from nodules by direct isolation or by bacterial trapping, and tested for nodulation. Further characterization was carried out to identify the isolates. Ninety-four isolates were obtained. Thirty-four were rhizobial strains that could, with two exceptions, establish root-nodule symbioses with the host plant. Different profiles of susceptibility to rhizobiophages indicated that the majority of isolates were likely to be members of the Rhizobium leguminosarum group of species. The strains revealed diverse plasmid profiles, and diverse restriction patterns of cpn60 gene amplicons and on Southern blot analysis of nodABC genes. Sequences of 16S rRNA gene showed that all isolates exhibited 99.85% identity with R. leguminosarum sv. viciae USDA 2370T, R. laguerreae FB206T and R. anhuiense CCBAU 23252T. Analysis of cpn60 sequences revealed two groups. One of them clustered with ≤99% identity with R. laguerreae FB403. The second was clustered with ≤99% identity with R. laguerreae FB206T. Our findings suggest that the isolates may belong to the species R. laguerreae.