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Distinctive Mesorhizobium populations associated with Cicer arietinum L. in alkaline soils of Xinjiang, China

Zhang, Jun Jie, Lou, Kai, Jin, Xiang, Mao, Pei Hong, Wang, En Tao, Tian, Chang Fu, Sui, Xin Hua, Chen, Wen Feng, Chen, Wen Xin
Plant and soil 2012 v.353 no.1-2 pp. 123-134
Cicer arietinum, Mesorhizobium ciceri, Mesorhizobium mediterraneum, alkaline soils, chickpeas, genes, genetic variation, host plants, intergenic DNA, nucleic acid hybridization, restriction fragment length polymorphism, ribosomal RNA, sequence analysis, China
BACKGROUND AND AIMS: Rhizobia associated with chickpea in the main chickpea production zone of Xinjiang, China have never been investigated. Here, we present the first systematic investigation of these rhizobia’s genetic diversity and symbiotic interactions with their host plant. METHODS: Ninety-five isolates obtained from chickpea nodules in eight alkaline-saline (pH 8.24–8.45) sites in Xinjiang were characterized by nodulation test, symbiotic gene analysis, PCR-based restriction fragment length polymorphism (RFLP) of the 16S rRNA gene and 16S–23S rRNA intergenic spacer (IGS), BOX-PCR, phylogenies of 16S rRNA and housekeeping genes (atpD, recA and glnII), multilocus sequence analysis (MLSA) and DNA–DNA hybridization. RESULTS: All 95 isolates were identified within the genus of Mesorhizobium. Similarities less than 96.5% in MLSA and DNA–DNA hybridization values (<50%) between the new isolates and the defined Mesorhizobium species, and high similarities (>98%) of symbiotic genes (nodC and nifH) with those of the well studied chickpea microsymbioints Mesorhizobium ciceri and Mesorhizobium mediterraneum were found. CONCLUSIONS: Chickpea rhizobia in alkaline-saline soils of Xinjiang, China, form a population distinct from the defined Mesorhizobium species. All these chickpea rhizobia in Xinjiang harbored symbiotic genes highly similar to the type strains of two well-studied chickpea rhizobia, M. ciceri and M. mediterraneum, evidencing the possible lateral transfer of symbiotic genes among these different rhizobial species. On the other hand, chickpea may strongly select rhizobia with a unique symbiotic gene background.