Phylogenetic analysis of 23S rRNA gene sequences of some Rhizobium leguminosarum isolates and their tolerance to drought

The phylogenetic relationships among thirteen Rhizobium leguminosarum bv. viciae isolates collected from various geographical regions were studied by analysis of the 23S rRNA sequences. The average of genetic distance among the studied isolates was very narrow (ranged from 0.00 to 0.04) and the studied isolates formed two main groups based on cluster analysis. The isolates were tested for their growth on YMA medium supplemented with concentrations 10, 20 and 30% of polyethylene glycol plus control. All isolates exhibited good drought-tolerant efficiencies at 10% PEG. While most of the isolates could not tolerate up to 20% PEG, isolates of Rlv6, Rlv9, Rlv12 and Rlv13 tolerated up to 20% PEG.