Abstract: Streptomyces rochei D74 has good growth-promoting effects on a variety of crops. We investigated the growth-promoting effects of Streptomyces rochei D74 on strawberry and rhizosphere microbial community under facility-cultivated condition. The results showed that: 1) D74 treatment significantly increased the dry and fresh weights of roots at the flowering stage by 40.5% and 51.8%, respectively. The total length, total surface area and the number of root tips increased by 120.9%, 55.5%, and 57.1%, and the average diameter and total volume increased by 36.5% and 6.9%, respectively. 2) Fruit yield was improved by 111.4%, along with the increase of nutrient contents (soluble protein content by 32.0%; and vitamin C by 9.4%). 3) The total potassium and ammonium nitrogen at the fruiting stage were also significantly increased by 0.5% and 1.9% under the D74 treatment, while sucrase, urease, catalase, and acid phosphatase were enhanced by 35.5%, 163.8%, 86.5%, and 32.8%, simultaneously. 4) D74 treatment significantly reshaped the rhizosphere bacterial community and dramatically increased the diversity of bacterial and fungi communities, coupled with a enrichment of potential beneficial bacteria such as Sphingomonas and a reduction of the harmful bacteria Fusarium and Plectosphaerella. Soil enzyme activities in the root zone were positively correlated with the relative abundance of beneficial bacterial genera such as Sphingomonas after the application of D74. In conclusion, D74 treatment improved soil chemical properties, soil enzyme activity, as well as growth characteristics of strawberry in greenhouse, by enriching beneficial bacteria and decreasing the relative abundance of harmful bacteria, with consequences on both quality and yield.

Key words: Streptomyces rochei, strawberry, growth-promoting, soil microbial community