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Association of white clover (Trifolium repens L.) with rhizobia of sv. trifolii belonging to three genomic species in alkaline soils in North and East China
- Zhang, Jun Jie, Jing, Xiao Yan, de Lajudie, Philippe, Ma, Chuang, He, Pei Xin, Singh, Raghvendra Pratap, Chen, Wen Feng, Wang, En Tao
- Plant and soil 2016 v.407 no.1-2 pp. 417-427
- Rhizobium, Trifolium repens, alkaline soils, bacteria, biogeography, essential genes, multilocus sequence typing, nutrient content, phylogeny, ribosomal RNA, sequence homology, soil pH, surveys, symbiosis, China
- AIMS: Rhizobia associated with white clover (Trifolium repens) grown in alkaline soils of China have never been investigated. This is the first survey to report of their genetic and biogeographical diversity. METHODS: Nodule bacteria were isolated from white clover grown in alkaline soils (pH 8.18–8.99) in North and East China and were characterized by multilocus sequence analysis (MLSA) of the housekeeping genes (atpD, recA, and glnII), and phylogenies of 16S rRNA gene and symbiotic genes nodC and nifH. The biogeographic distribution of rhizobial species was analyzed in relation to the soil factors. RESULTS: A total of 83 new strains could be affiliated to Rhizobium that shared 100 % sequence similarity of 16S rRNA gene with R. leguminosarum, R. acidisoli, R. anhuiense, R. indigoferae, R. sophorae, and R. laguerreae. Three genospecies were further distinguished based on the housekeeping gene analysis among these new strains: R. anhuiense, R. leguminosarum, and a hypothetical novel Rhizobium genospecies. Highly conserved symbiotic genes corresponding to those of symbiovar trifolii in R. leguminosarum were observed among all the new strains. Unique rhizobial communities associated with white clover were detected in the tested alkaline soils, and soil characteristics such as pH and nutrient levels were estimated as the determinant factors. CONCLUSIONS: White clover established symbiosis with three Rhizobium genospecies harboring similar symbiotic genes in alkaline soils in China. Biogeographic pattern exists in clover rhizobia that was determined by the soil pH and nutrient levels.