The Mechanism of a Multifunctional Strain of Streptomyces sp. on the Growth of Pinus massoniana Seedlings

Research into the mechanism by which Streptomyces enhances plant growth and soil microecological environment provides a theoretical basis for the development of bio-fertilizer with growth-promoting and stress-resistance effect. The growth-promoting functions of Streptomyces NJ10 were studied under pure culture conditions; a combination of chemical analyses and high-throughput sequencing techniques was used to determine the growth indices, soil physico-chemical indices, and rhizosphere microbial diversity of Pinus massoniana seedlings under potting conditions. The results showed that the NJ10 strain has various growth-promoting functions, including nitrogen fixation, inhibition of plant pathogens, and oxalate degradation. Inoculation with the NJ10 strain increased the seedling height, aboveground biomass, and mycorrhizal infection rate by 23.3%, 40.7%, and 36.7% (p < 0.001), respectively. This resulted in a decrease of the oxalate content and an increase in the carbonate content in soil. Inoculation with NJ10 significantly increased the relative abundance of beneficial bacterial genera such as Azoarcus, Steroidobacter, and Rhizorapis in rhizosphere soil of P. massoniana. Prediction of fungal functional types revealed an absolute dominance of saprotrophic fungal groups in the soil, with a significant decrease in the relative abundance of pathotroph-saprotroph and pathotroph fungi. In conclusion, the NJ10 strain is a multifunctional growth-promoting bacterium, which can promote the growth of P. massoniana, and improve the soil environment. Furthermore, it affects the microbial function of rhizosphere soil by nitrogen fixation, inhibition of plant pathogens, oxalate degradation, and stimulation of mycorrhizal formation. This study provides a theoretical basis for the development of microbial fertilizers with growth-promoting and stress-resistance effects.