山西黄芪根际固氮菌的分离与应用

Isolation and application of nitrogen-fixing bacteria in rhizosphere of Astragalus membranaceus Bunge in Shanxi

[目的]对黄芪道地产区山西浑源的黄芪根际固氮细菌进行了分离鉴定,并应用于黄芪栽培中以观察其固氮能力,旨在筛选并获得能够促进黄芪生长的固氮菌,为降低黄芪生产成本提供依据。[方法]采用Ashby无氮培养基初筛获得了120个自生固氮菌株;进一步用固氮培养基对初筛所得菌株进行复筛,根据固氮能力、菌落生长速度等特征,获得了2株具有较强固氮能力的菌株t16和t21;通过细菌鉴定系统和16SrRNA序列分析对其进行分类鉴定。另外还用全N差值法检测了t16和t21浸泡黄芪种子后的固氮活性。[结果]t16和t21分别属于Rhizobiumsp.和Sinorhizobiumsp.。经两株菌发酵液浸泡后,培养30d分别能够增加黄芪幼苗含氮量14.23%-18.67%和13.10%-18.77%。其中含菌量为106个·mL-1的t16发酵液和含菌量为108个·mL-1的t21发酵液效果最好,折算每公顷30d的固氮量达2.25kg。[结论]山西黄芪根际固氮菌具有较大的开发利用潜力。

[Objective]Astragalus membranaceus Bunge （AMB） is an important herb that has been used in traditional Chinese medicine for centuries, and Hunyuan County of Shanxi province is one of the most important planting bases for AMB. Nitrogen fertilizer input for AMB production in China is very high. It is essential to reduce nitrogen fertilizer in- put and thus cultivation cost while achieving a high yield for sustainable and environmentally friendly AMB production. Research on biological nitrogen fixation has increased significantly because of its potential importance to the economy and the environment. AMB plants can obtain nitrogen from biological nitrogen fixation via diazotrophs. The aim of this work was to screen and identify nitrogen-fixing bacteria from the rhizosphere of AMB cultivated in Hunyuan County, Shanxi province, and to demonstrate their potential for nitrogen fixation with AMB as well as plant growth promotion. [Methods] 120 nitrogen fixing strains were isolated from soil samples using Ashby nitrogen free medium. Two strains of them, t16 and t21, with strong ability of nitrogen fixation were screened out according to the ability of nitrogen fixa- tion, growth speed and other characteristics in further screening with nitrogen fixing medium. To demonstrate their potential for nitrogen fixation with AMB and growth promotion activities, the bacterial liquid of the two isolates were used to soak AMB seeds and inoculate into AMB seedlings for 30 d at 28~C in a growth cabinet. [Results] Based on morphological detection, physiological and biochemical detection and 16S rRNA gene sequence analysis, the two strains of t16 and t21 were identified as Rhizobium sp. and Sinorhizobium sp. , respectively. Both of the two strains signifi- cantly promoted the growth of AMB seedlings. They also increased the nitrogen contents of dry weight by 14.23% to 18.67% and 13.10% to 18.77%, respectively, compared with the uninoculated controls. The bacterial liquids of T16with 106 mL 1 and T21 with 108 mL-1 have the best effect. The conversion amount of nitrogen fixing in 30 days is a- bout 2.25 kilograms per hectare. EConclusiong These promising nitrogen fixation bacteria isolates from the rhizosphere of AMB showed potential to promote AMB production via nitrogen fixation and other plant growth promoting functions. This will improve AMB production efficiency and reduce the environmental pollution that results from AMB production.