Abstract:

【Objective】 Plant growth-promoting rhizobacteria play an important role in promoting plant growth and development, improving the soil microenvironment, and aiding the development of sustainable forestry practices. The functional bacteria in the rhizospheric soil of Phyllostachys edulis, and their effects on seedling growth were investigated to provide a scientific basis for the development and utilization of new microbial resources from bamboo, improving the productivity of bamboo forests, and enhancing the functions of ecosystem services.【Method】The rhizosphere soil of P. edulis was selected as the research object, and the rhizosphere bacteria were isolated using traditional dilution culture methods. A phylogenetic tree based on the 16S rRNA gene sequences was constructed using the maximum-likelihood method. In vitro functional evaluation was performed based on the functional plates and specific color changes. The effects of the functional strains on the germination of P. edulis seeds and the growth of seedlings were finally investigated with re-inoculation experiments.【Result】 A total of 39 rhizosphere bacterial strains from 23 genera belonging to 12 families under three phyla, were isolated and cultured. Actinomycetota and Bacillaceae were the dominant phylum and family with relative abundances of 41.0% and 25.6%, respectively. Functional analysis of the 39 bacterial strains revealed that 20 and three strains were capable of producing IAA (indole-3-acetic acid) and siderophores, while five and three strains were capable of dissolving potassium and inorganic phosphorus, respectively, and seven strains were capable of mineralizing organic phosphorus. The strain SD2N7 was capable of simultaneously producing IAA, dissolving inorganic phosphorus and potassium, and mineralizing organic phosphorus. Based on the physiological and biochemical characteristics and the 16S rRNA gene alignment, strain SD2N7 was identified as Rahnella woolbedensis. The re-inoculation experiments revealed that strain SD2N7 could significantly shorten the germination period of P. edulis seeds and promote the elongation of the roots and leaves of P. edulis seedlings.【Conclusion】 There were abundant functional microbial resources in the rhizosphere soil of P. edulis, which were capable of producing IAA or siderophores, dissolving phosphorus and potassium, and performing other functions. The back-grafting test additionally demonstrated that strain SD2N7 significantly promoted seed germination and the growth of P. edulis seedlings.

Key words: Phyllostachys edulis, plant growth-promoting rhizobacteria (PGPR), isolation and cultivation, Rahnella, function assessment