青稞根际优良联合固氮菌的筛选及鉴定

为筛选获得对青稞具有促生性能的联合固氮菌，从西藏不同地区青稞根际采集土壤样品，以Ashby无氮培养基进行菌株分离，利用凯氏定氮法测定分离物的固氮量，通过培养皿纸上萌发法测定其对青稞种子萌发和幼苗生长的影响，根据菌株形态、理化特性和16SrDNA序列分析进行固氮菌株的鉴定。结果表明：从西藏高寒地区青稞根际分离获得的72株联合固氮菌，和CK相比，氮增量为0.30～26.07 mg·L^-1，其中有10个菌株的固氮量较高，氮增量为17.01～26.07 mg·L^-1。种子萌发和幼苗生长试验表明：10株菌中6株菌的综合促生效果较好，即菌株20-2、22-5、23-3、26-1、35-2和39-5。和CK相比，种子萌发率提高了-7.14%~25.00%，茎粗提高了1.53%~13.74%，株高提高了-9.52%~7.60%，根长提高了9.41%~38.09%，须根数提高了-11.26%~12.57%，鲜重提高了-4.97%~57.73%。经过多相分类鉴定，这6株菌分属于根瘤菌属、类芽孢杆菌属、无色杆菌属和假单胞菌属。

Screening and identification of superior associative nitrogen fixing bacteria in rhizosphere of Hordeum vulgare

In order to screen the combined nitrogen-fixing bacteria, which can promote barley growth, soil samples were collected from the rhizosphere of barley in different regions of Tibet. The strains were isolated on Ashby nitrogen-free medium. The fixed nitrogen content of the isolates was determined by Kjeldahl method. The germination of barley seeds and seedlings were determined by the method of culture dish paper germination. According to the strain morphology, physical and chemical characteristics, and 16S rDNA sequence analysis, nitrogen-fixing strains were identified. The results showed that 72 strains of associative nitrogen-fixing bacteria were isolated from barley rhizosphere in Tibet. The fixed nitrogen amount was between 0.30~26.07 mg·L^-1, of which 10 strains had higher nitrogen-fixing amount. Compared with CK, the fixed nitrogen amount increased by 17.01~26.07 mg·L^-1. The results of seed germination and seedling growth test showed that 6 of the 10 strains had better comprehensive promoting effect, namely strains 20-2, 22-5, 23-3, 26-1, 35-2 and 39-5. Compared with CK, seed germination rate increased by -7.14%~25.00%, stem diameter increased by 1.53%~13.74%, plant height increased by -9.52%~7.60%, root length increased by 9.41%~38.09%, fibrous root number increased by -11.26%~12.57%, fresh weight increased by -4.97%~57.73%. The six strains belonged to Rhizobium, Bacillus, Achrobacter and Pseudomonas.