Potatoes Rhizosphere Bacteria Analysis And Multi-functional Azotobacter Screening

Potato (Solanum tuberosum L.) position in the country’s food production is increasingly important. With the rising market demand, but our potato yield level is not high, the increasingly serious soil-borne diseases, Therefore, study on nitrogen fixation, disease resistance,stress tolerance, growth-promoting potential of nitrogen-fixing bacteria is important. In this study, rhizosphere soil and root samples were as the research object. Potato rhizosphere soil bacterial community composition, isolation and identification roots of nitrogen-fixing bacteria, and to study its nitrogen fixation, dissolved phosphorus, and other growth-promoting function and disease resistance were studied for the development of micro-organisms fertilizers provide excellent strain resources.1. In this study, we determined the composition and abundance of potato rhizosphere microbes in soil samples using the pyrosequncing technology. The total of 29461 valid sequences belonged to the 13 gates and Actinobacteria, Proteobacteria, Bacteroidetes, Acidobacteria were the dominant gates.2. In this study, we isolated 150 bacteria from rhizosphere soil and root samples of potato. Through the screening of the growth on nitrogen-free medium plates and genetic testing nifH, we obtained 72 nitrogen-fixing bacteria. Based on 16S rDNA sequence,72 nitrogen-fixing strains belonged to 18 genera and the genus of Arthrobacter, Bacillus, Microbacterium, Pseudomonas and Rhizobium were the dominant bacteria. The results show that the among the 72 nitrogen-fixing bacteria, all bacteria have the nitrogenase activities of 0.072 ± 0.036-16.206 ± 5.253 nmol-mg-1·h-1; 18 the ACC deaminase positive strains with 2.069 ± 0.299-42.12 ± 5.946 μmol mg protein-1 h-1 were screened; 40 strains were able to degrade organic phosphorus and 8 bacteria were able to degrade inorganic phosphorus; 3 strains can restrain the growth of Fusarium wilt of potato fungi (Fusarium solani) MLS-QB and 10 strains can restrain the growth of potato blight fungus (Fusarium oxysporum) MLS-OF; 62 bacteria were able to produce IAA; total of 17 nitrogen-fixing bacteria had multi-function. By greenhouse experiments, strains MLS-1-6, MLS-4-8, MLS-1-7, MLS-7-7, MLS-5-3, MLS-1-15, GWR3, MLS-1-9 and MLS-5-2 can significantly promote the growth of potato seedlings. Using physiological and biochemical assays and Biolog method, these 17 multi-functional nitrogen-fixing bacteria were identified.