Screening And Identification Of Xinjiang Walnut Growth-promoting Rhizobacteria

The indigenous microorganisms in rhizosphere soil of Xinjiang walnut were chosen as the research object. The walnut rhizosphere soil gathered was separated and purified. some high-quality and efficient strains were screened, which had growth-promoting effect for walnut tree and could colonize stably in its rhizosphere. They could provide strain material for the development of specific walnut microbial fertilizer in the future.The rhizosphere soil gathered from Xinjiang walnut-producing areas of Aksu, Hotan and Kashgar was regarded as the material in the research. First, selective medium was used to separate the walnut growth-promoting rhizobacteria(phosphate-solubilizing bacteria,potassium bacteria, nitrogen-fixing bacteria and antagonistic bacteria). Second, the methods of dissolved phosphorus ring screening and liquid shake flask screening were used to measure its phosphate-solubilizing ability. Flame photometer method was used to measure its releasing ability. Total nitrogen difference method was used to measure its nitrogen-fixing ability.Confrontation experimental method was used to measure its antagonistic ability. Then, the field colonization experiments were conducted after induced by rifampicin, in order to ensure the stability of each capability. Finally, molecular identification relied on 16 S rDNA method.The results are as follows:1. By measuring the growth-promoting ability, 64 strains of PGPR were screened,including 14 strains of phosphate-solubilizing bacteria, 16 strains of potassium bacteria, 20 strains of nitrogen-fixing bacteria, 14 strains of antagonistic bacteria.2. After inducted by rifampicin resistance, 13 strains of phosphate-solubilizing bacteria,14 strains of potassium bacteria, 10 strains of nitrogen-fixing bacteria and 7 strains of antagonistic bacteria were selected.3. After the screened strains were conducted the field colonization experiments, the recycled strains were counted and measured their growth-promoting ability again. Eventually,11 strains of phosphate-solubilizing bacteria, 10 strains of potassium bacteria, 8 strains of nitrogen-fixing bacteria and 7 strains of antagonistic bacteria were screened.4. By using the method of 16 S rDNA, we identified that the phosphate-solubilizing bacteria belonged to 4 genera, and they were Microbacterium, Acinetobacter, Staphylococcus,Pseudomonas; the potassium bacteria belonged to 3 genera, and they were Microbacterium,Bacillus, Pseudomonas; the nitrogen-fixing bacteria belonged to 5 genera, and they were Rhizobium, Pseudomonas, Sinorhizobium, Arthrobacter, Bacillus; the antagonistic bacteria belonged to 3 genera, and they were Streptomyces, Bacillus, Pseudomonas. Among them,Pseudomonas was the dominant genera of the phosphate-solubilizing bacteria, the potassium bacteria and the antagonistic bacteria, but the dominant genera of the nitrogen-fixing bacteria was Rhizobium.