Streptomyces rochei D74 Improves Tobacco Growth and Quality by Regulating the Rhizosphere Microecological Community

Shiyu Wang¹Lumin Zhang²Jiaxin Liu¹Yongxian Xu²Yingnan Li¹Kun Huang²Hangxian Lai¹Junxiang Pu²Xiaoyu Geng²Zhixin Yang²Qiao Guo^1*Shuanglü Shan^2*

• ¹Northwest A&F University, Yangling, China
• ²Honghe Branch of Yunnan Tobacco Company, Mile, China

Streptomyces rochei D74 promotes growth and enhances quality in crops such as wheat and tomato. However, its potential role and optimal application method in tobacco production remain unclear. This study for the first time investigated the effects of S. rochei D74 with different application methods on tobacco growth and quality, soil physicochemical properties, and rhizosphere microbial community structure. S. rochei D74 was applied via basal application (BA), foliar spray (FS), and their combination (BA-FS) under field conditions. Results showed that different microbial treatments promoted tobacco growth compared to the control, as exemplified by notable increases in plant height (by 5.3~10.5%) and stem girth (by 7.0~15.6%), while also reducing the proportion of low-grade leaves (by 10.2~28.4%, p < 0.05). Particularly, the BA-FS treatment achieved the highest leaf yield and output value, alongside elevating the contents of total nitrogen (by 29.0~36.2%) and total alkaloids (by 34.3~66.8%) in C3F and B2F grade leaves, increasing the potassium-to-chlorine ratio, and reducing carbohydrate accumulation (e.g., starch). There were corresponding improvements in soil available nutrient contents, including nitrogen, manganese, phosphorus, and iron. Microbial treatments resulted in a lower relative abundance of Fusarium in the fungal community, despite not causing a significant shift in bacterial α-diversity. Microbial treatments increased the proportion of positive correlations in bacterial networks and heightened the complexity of fungal networks , thereby likely fostering more cooperative microbial interactions that supported improved nutrient acquisition and plant growth. Mantel analysis revealed that fungal and bacterial community abundances strongly influenced soil nutrient contents and tobacco leaf quality. The findings indicate that combined root and foliar application of S. rochei D74 optimally improves tobacco growth and quality by modifying microecological conditions in rhizosphere soil.