Abstract
Eleven strains that formed symbiotic root nodules on Alhagi sparsifolia, designated previously as genospecies II, were identified as a new lineage of Mesorhizobium (Alphaproteobacteria) that could be differentiated from all previously recognized species of the genus Mesorhizobium by using 16S rRNA gene sequences (<97.8 % similarity), DNA–DNA hybridization (<45 %), dnaJ, dnaK, recA, glnA, nifH, nodA and nodC gene sequences, fatty acid profiles (C18 : 1ω7c, 35 %;11-methyl C18 : 1ω7c, 30 %) and numerical taxonomy. These strains are therefore considered to represent a novel species, for which the name Mesorhizobium alhagi sp. nov. is proposed, with isolate CCNWXJ12-2T (=ACCC 15461T=HAMBI 3019T) as the type strain.