Abstract
Thirty-one nodulating rhizobium strains were collected from root nodules of spring and winter type faba bean cultivars grown in micro ecoarea, i.e. the same field in Chengdu plain, China. The symbiotic efficiency and phylogeny of these strains were studied. Effectively nitrogen fixing strains were isolated from both winter type and spring type cultivars. Based on phylogenetic analysis of 16S rRNA gene and concatenated sequence of atpD, glnII and recA genes, the isolates were assigned as Rhizobium anhuiense and a potential new Rhizobium species. The isolates were diverse on symbiosis related gene level, carrying five, four and three variants of nifH, nodC and nodD, respectively. Strains carrying similar gene combinations were trapped by both winter and spring cultivars, disagreeing with the specificity of symbiotic genotypes to reported earlier faba bean ecotypes.
Highlights
Biological nitrogen fixation (BNF) is important for agriculture worldwide
Based on the phylogenetic analysis of nodD gene, faba bean symbionts were divided into groups roughly related to the division of winter and spring faba bean ecotypes [2]
Rhizobial bacteria were isolated from four spring type and eleven winter type faba bean cultivars grown in a single field in Chengdu plain (Table 1)
Summary
Biological nitrogen fixation (BNF) is important for agriculture worldwide. Legume-rhizobia symbiosis accounts 60% of the total BNF [1, 2]. Rhizobia form nodules on the roots or stems of the host plant. Faba bean is grown worldwide as a source of protein and starch [3]. Besides yielding food and fodder, faba bean provides assimilated nitrogen to other crops grown in crop rotation [5]. Faba bean is considered as a selective legume. Previous reports indicated that the isolations from faba bean root nodules contain Rhizobium leguminosarum symbiovar viciae and trifolii, R. etli, R. fabae, R. laguerreae, R. mesosinicum, R. anhuiense and Agrobacterium tumefaciens [8,9,10,11,12,13,14]. The symbiotic genotype of the PLOS ONE | DOI:10.1371/journal.pone.0167804 December 9, 2016
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