Effects of Tobacco-Wheat (Sweet Potato) Strip Rotation on Occurrence of Tobacco Fusarium Root Rot

To investigate the effect of tobacco-wheat (sweet potato) strip rotation on the occurrence of tobacco Fusarium root rot and the soil microbial community structures, two treatments were established, i. e., continuous cropping of tobacco (SC) and tobacco-wheat (sweet potato) strip rotation (RC), and the field incidence of Fusarium root rot was surveyed. The structure and composition of the rhizosphere soil microbial community in tobacco were analyzed, along with the microbial interactions. Spearman correlation analysis was used to assess the relationship between soil microbial community parameters and disease index. Thus the effects of different cropping patterns on the occurrence of tobacco Fusarium root rot were clarified. Main results are as follows. (1) Tobacco-wheat (sweet potato) strip rotation significantly reduced the disease index (DI) of root rot in continuous cropped flue-cured tobacco (44.2% lower than that of continuous cropping). (2) Strip rotation significantly altered the composition and structure of the rhizosphere microbial community in flue-cured tobacco. Compared with continuous cropping, the relative abundance of Fusarium spp. reduced by 49.5%. (3) Compared with continuous cropping, the microbial co-occurrence network in the rhizosphere soil under rotation exhibited greater stability, with the modularity index increasing by 4.53%. (4) The disease index (DI) of root rot was significantly and positively correlated with the relative abundance of Fusarium spp., the bacterial and fungal community structures, and microbial co-occurrence network diameter, respectively, while significantly negatively correlated with fungal community richness, evenness, and network modularity index, respectively. In conclusion, tobacco-wheat (sweet potato) strip rotation significantly enhances the stability of the rhizosphere soil microbial network, reduces the relative abundance of Fusarium spp., and suppresses the occurrence of Fusarium root rot.