Study On Nitrogen Fixation, Disease Resistance And Plant Growth Promotion Of Bacteria From Rhizosphere

Study on nitrogen fixation, disease resistance and plant growth promotion of bacteria from rhizosphere has important significance because energy shortage, soil borne diseases and environmental stress are serious problems of agricultural production. One hundread and two nitrogen-fixing bacteria collected from 10 provinces over China were studied. Some strains with relative high nitrogenase activity, plant pathogenic fungi resistance, ACC deaminase activity and environment adapt ability were found. Most of these potential strains belong to Paenibacillus and Bacillus, and extensively colonized in geography and crops with no specificity. These strains hold a good prospect for future applications. The results in detail are as follows:Nitrogen fixation potential and distribution: 102 nitrogen fixing bacteria were tested for their nitrogenase activity with acetylene reduction assay (ARA). The nitrogenase activities of 46 strains were higher than the reference strain Azotobocter chroococcum ACCC11103 (9.741nmol/h·mg), and 4 strains were significant at the 0.05 level. Taxonomic distribution of test strains was in Paenibacillus and Bacillus, showed significant diversity on the distribution regarding to geography and crops, and have high potential of nitrogen fixation. Geography distribution of these strains shows relative concentrated, and has an average distribution regarding to crops. 14 strains of test strains were detected nifH gene, 13 were simlar to Paenibacillus sp.with similarity higher than 97%, 1 was similar with Burkholderia vietnamiensis 99% with similarity.Plant pathogenic fungi resistance potential and distribution: Confrontation method was used to screen antagonistic bacteria against plant pathogenic fungus, 8 strains have been found have the ability and belong to Bacillus, Burkholderia, Paenibacillus, Pseudomonas 4 genera . Geography distribution of these strains concentrated at Beijing, Neimeng and Heilongjiang, from rhizosphere of 6 crops. Taxonomic and geography distribution of these strains were relative concentrated.Growth promotion potential and distribution: 20 strains were found ACC deaminase positive. They belong to 9 genera of Bacillus, Paenibacillus, Rhizobium, Agrobacterium, Burkholderia, et al. They were from rhizosphere of 6 crops in 5 provinces of Beijing, Neimeng, Heilongjiang, Hebei, et al. Growth promotion characteristics of these strains showed significant diversity on the distribution regarding to taxonomic, geography and crops.Carbon utilization, phosphate solubilization and Inoculation test: Most test strains showed strong carbon source utilization. Strains 7016 and 7163 could solubilize inorganic phosphate and 7009, 7016 and so on could solubilize organic phosphate. 12 strains showed high adapt ability to harsh environment. Inoculation had positive effect on pakchoi growth and increased fresh weight. 23 strains showed significant increase at 0.05 level compared with control.