Isolation and Screening of Effective and Affinity Strains of Growth-Promoting Bacteria from Cotton Rhizosphere

Abstract:

To screen effective and affinity plant growth-promoting rhizobacteria strains (PGPR) that can react with cotton lectin from cotton rhizosphere, we isolate nitrogen-fixation bacteria, phosphate-releasing bacteria and potassium-releasing bacteria from cotton rhizosphere by Ashby medium, phosphate-releasing bacteria medium and potassium-releasing bacteria medium, respectively. The strains were re-screened by cotton lectin labeled with fluorescein isothiocyanate. According to their ability of nitrogen-fixation, p-releasing and K-releasing in pure culture condition, 2 strains of nitrogen-fixation bacteria, 2 strains of phosphate–releasing bacteria and 2 strains of potassium-releasing bacteria were inoculated as microbial fertilizers in pot experiment of cotton, respectively. About 20%~30% strains of PGPR had positive reaction with cotton lectin labeled by FITC among the PGPR. Study showed that the numbers of PGPR in cotton rhizosphere were about 10 times of those of controls sterilized. Pot test data suggested the 6 strains have certain affinity with cotton and can propagate in cotton rhizosphere. Through preliminary identification of 6 affinity strains, the strain of N1111 was identified as Azotobacter and N2121 was classified as Derxia. P2126 and P1108 were Xanthomonas and Pseudomonas, respectively. K2204 and K2116 were Bacillus.