文冠果根系固氮菌的分离与鉴定

Isolation and Identification of Nitrogen Fixing Bacteria in the Root System of Xanthoceras Sorbifolium

目的文冠果在栽培情况下部分植株生有根瘤,如果能从其中分离出共生固氮菌,则有助于改善文冠果在农林边际地造林用的养分供给,促进产业发展。方法用Ashby(无氮)、YMA(有氮)、高氏一号(有氮)和高氏一号(无氮)等4种培养基,将有根瘤和无根瘤文冠果根系分别研磨,低速离心,取上清液,分别涂布于培养基培养,并分离纯化得到菌株,并对无氮培养基上分离纯化出来的菌株进行16S rDNA全序列测序鉴定。结果从文冠果有根瘤和无根瘤根系中共分离出20株内生菌,其中6株为固氮菌。从有根瘤的文冠果根系上分开出4株能够固氮的内生菌,其中2株经鉴定为新菌种,另外2株因为生长缓慢,未鉴定。从无根瘤的文冠果根系中分离出2株固氮菌,经鉴定均为新菌种。结论文冠果具根瘤根系和无根瘤根系中均存在固氮菌和根瘤菌,且至少有1个根瘤菌新种和1个根癌农杆菌新种被发现。

Objective Some plants of Xanthoceras sorbifolium have root nodules under cultivation.If symbiotic nitrogen fixing bacteria can be isolated from them,it will help to improve the nutrient supply of Xanthoceras sorbifolium for afforestation in agricultural and forestry marginal land and promote industrial development.Methods In this study,the roots of Xanthoceras sorbifolium with and without root nodules were ground and centrifuged at low speed with Ashby(nitrogen free),YMA(nitrogen free),Gaoshi No.1(containing nitrogen)and Gaoshi No.1(nitrogen free)media.The supernatant was coated on the culture medium respectively,and the strains were isolated and purified.The strains isolated and purified on the nitrogen free medium were identified by 16S rDNA sequencing.Results A total of 20 strains of endophytic bacteria were isolated from the nodule and non-nodule roots of Xanthoceras sorbifolium,of which 6 were nitrogen fixing bacteria.Four strains of endophytic bacteria capable of nitrogen fixation were isolated from the root system of Xanthoceras sorbifolium with root nodules,two of which were identified as new strains,and the other two were not identified because of their slow growth.Two strains of nitrogen fixing bacteria were isolated from the root system of Xanthoceras sorbifolium without root nodules,which were identified as new strains.Conclusion Nitrogen fixing bacteria and rhizobia were found in both nodule and non-nodule roots of Xanthoceras sorbifolium,and at least a new rhizobia strain and a new A.tumefaciens strain were found.