Impact of Bacillus subtilis and Pseudomonas fluorescens beneficial bacterial agents on soil-borne diseases, growth, and economics of continuous cropping of flue-cured tobacco

Employing beneficial bacteria as fungicides is an effective strategy for improving crop and soil health. Despite its effectiveness, the investigation of appropriate beneficial bacterial candidates for tackling the challenges posed by the continuous cropping of field tobacco remains a neglected area. This study addressed this gap by conducting field experiments at two distinct sites to ascertain the effects of introducing beneficial bacterial agents (CK, devoid of bacterial agent; B, Bacillus subtilis agent; P, Pseudomonas fluorescens agent; and a mixture of both bacterial agents [B + P]) on soil-borne pathogen abundance, disease occurrence, and economic effects in the context of the continuous cropping of flue-cured tobacco. The results revealed that the application of bacterial agents (B, P, and B + P) contributed to varying degrees of reduction in the relative abundance of Fusarium spp. within the continuous cropping flue-cured tobacco soil, while enhancing the abundance of Bacillus spp. and Pseudomonas spp. Notably, the B + P treatment demonstrated a superior performance. In terms of disease management, B + P treatment significantly inhibited the incidence of black shank disease and root black rot disease by over 50.0%, with a significant reduction in severity exceeding 34.3%. The relative control effects reached 48.7%–66.7% and 39.1%–63.2%, respectively. In addition, the mixed application of bacterial agent (B + P) exerted a substantial positive influence on various agronomic attributes of flue-cured tobacco, such as leaf dimensions, leaf count, and dry matter accumulation. Chemical component contents and economic parameters, such as yield, high-quality tobacco leaf proportion, and medium-to high-quality tobacco leaf proportion, also demonstrated excellent enhancement. This comprehensive improvement ultimately achieved disease mitigation and increased yield. Overall, the integration of B. subtilis and P. fluorescens can improve soil health and promote crop growth. The mixed application strategy (B + P) is an effective approach for mitigating soil-borne diseases, augmenting yields, and elevating economic returns.