如东田菁根瘤菌遗传多样性及高效促生菌株筛选

Genetic diversity of the Rhizobia and screening of highefficient growth-promoting strains isolated from Sesbania cannabina in Rudong County

【目的】研究江苏如东沿海滩涂田菁根瘤菌的遗传多样性和系统发育,筛选高效促生田菁根瘤菌。【方法】采用16S rRNA基因、持家基因(rec A、atp D、glnⅡ)、共生基因(nod A、nif H)的系统发育分析,并进行温室盆栽接种试验筛选高效菌株。【结果】分离到的32株田菁根瘤菌分布于Ensifer、Neorhizobium、Rhizobium,并与E.meliloti、N.huautlense、E.sesbaniae、R.pusense亲缘关系最近。共生基因nod A、nif H的系统进化分析结果基本一致,均与E.saheli最为相近。7株代表菌株均能耐受5%的Na Cl(W/V)浓度,其中YIC5082耐盐性最强,能够耐受6%的Na Cl。温室盆栽试验表明7株代表菌株均能与田菁有效结瘤固氮,其中6株菌显著提高了植株的株高和鲜重。【结论】江苏如东沿海滩涂田菁根瘤菌具有较丰富的遗传多样性,其中N.huautlense、E.meliloti为优势种。该地区的田菁根瘤菌多数具有较好的共生有效性及耐盐性,YIC5077促生效果最为突出,并表现出较强的固氮及结瘤能力,具有良好的应用前景。

[ Objective] To study the genetic diversity and phylogeny of Rhizobia isolated from Sesbania cannabina growing on the tidal fiat in Rudong County and screen high-efficient growth-promoting strains as Rhizobia inoculator to S. cannabina. [ Methods] Phylogenetic analyses were based on 16S rRNA gene, housekeeping genes （recA, atpD, glnH） and symbiotic genes （nodA, nifH）. The growth-promoting efficiency was tested by plant inoculation assay on S. cannabina in greenhouse. [ Results ] The 32 isolates belonged to Ensifer, Neorhizobium, Rhizobium, and most closely related to E. meliloti, N. huautlense, R. pusense. The phylogenies of nodA and nifH were congruent, and most closely related to E. saheli. The 7 representative isolates were resistant to high concentration of NaC1 （5% , W/V） , and YIC5082 grew well in TY medium with 6% NaC1. In plant inoculation assay, all the 7 representative isolates were effective on symbiotic nitrogen fixation, and 6 out of the 7 isolates significantly enhanced the fresh weight and height of plants. [ Conclusion] Rhizobia isolated from S. cannabina growing on the tidal flat in Rudong County showed rich genetic diversity. N. huautlense and E. meliloti were the dominant species. Most of the isolates showed fine growth-promoting efficiency and salt tolerance. YIC5077 showed the best growth-promoting efficiency, good nodulation and nitrogen fixation abilities, which has promising potential applications as Rhizobia inoculator to S. cannabina.