Trigonella arcuata-associated rhizobia—an Ensifer (Sinorhizobium) meliloti population adapted to a desert environment

Abstract

With the aim of systematically investigating rhizobia associated with the Trigonella arcuata—an ephemeral legume native to the Gurbantunggut Desert—66 bacterial strains were isolated from root nodules and characterized with PCR-based RFLP of 16S rRNA and nodC genes, RFLP of ribosomal IGS, BOX-PCR, and sequencing of housekeeping (16S rRNA, recA, atpD) and symbiotic (nodC and nifH) genes, numerical taxonomy and nodulation tests. The T. arcuata rhizobia were classified as Ensifer (Sinorhizobium) meliloti, but the 10% differences in nodC and nifH gene sequences and the 20% phenotypic dissimilarity demonstrated that the T. arcuata rhizobia have divergently evolved from the E. meliloti reference strains. Although they shared several other hosts under laboratory conditions, the studied rhizobial population seems adapted to their natural environment based upon their wide range of resistance to desert conditions. All these data indicate that T. arcuata rhizobia are a valuable source of rhizobial inoculants for bioremediation of arid areas.