易贡茶树根际固氮菌的筛选及促生作用研究OA

This study aimed to isolate and screen elite nitrogen-fixing bacterial strains with multiple plant growth-promoting(PGPR)traits from the rhizosphere of tea plants in the high-altitude Yigong tea area of Xizang,identify their phylogenetic positions,and evaluate their application potential,so as to provide resources and a theoretical basis for developing specialized microbial inoculants for high-altitude tea plantations.Nitrogen-fixing bacteria were isolated using the dilution plate method with Ashby's nitrogen-free medium.Nitrogenase activities of the strains were measured by the acetylene reduction assay.Strain identification was based on morphological,physiological,biochemical characteristics and 16 S rDNA sequence analysis.The abilities of the strains to solubilize phosphate,release potassium,produce siderophores,synthesize indole-3-acetic acid(IAA),as well as their salt tolerance were further determined.Pot experiments using tea plants(the host plants),maize and rapeseed were conducted to verify the practical growth-promoting effects of the strains.The results show that ten nitrogen-fixing bacterial strains were isolated and screened from the tea rhizosphere soil,exhibiting nitrogenase activities ranging from 20.06 to 23.71 nmol·mg-1·h-1.The strains MZ-4-74,SC-5-67,MZ-2-5 and FX-2-86 were Serratia odorifera.The strains FX-3-48,FX-4-31,FX-4-73 and MZ-3-16 were Serratia fonticola.The strains FX-2-66 and FX-3-66 were Pseudomonas koreensis and Acinetobacter calcoaceticus,respectively.Functional characterization reveals that all 10 strains could solubilize potassium,8 strains possessed phosphate solubilizing ability,9 strains could produce siderophores,and 7 strains could synthesize IAA.Among them,FX-3-48,FX-2-86 and SC-5-67 exhibited strong salt tolerance.The pot experiment results demonstrate that inoculation with all strains significantly promoted the growth of tea,maize and rapeseed seedlings.The FX-3-48 treatment shows the most pronounced effect,increasing the fresh weight,stem diameter,plant height,and root length of tea seedlings by 330.77％,61.54％,86.09％,and 94.53％,respectively,compared to the CK control.The rhizosphere of tea plants in Yigong in Xizang area harbors abundant nitrogen-fixing bacterial resources with multiple plant growth-promoting functions.The screened strains exhibit significant potential for development into microbial inoculants,holding great importance for promoting green production in high-altitude tea plantations.