Well-developed root systems and a nitrogen-rich rhizosphere recruit key bacterial taxa to resist disease invasion of field crop

Crop rotation patterns have important effects on crop growth and disease occurrence, but there is a lack of understanding of how crop root systems and inter-root environments affect the bacterial communities involved in plant disease resistance under different crop rotation patterns. In this study, two crop rotation patterns, tobacco-rice (TR) and tobacco-maize (TM), were set up in a tobacco growing region of southern China, and the differences in soil bacterial communities and the mechanisms of their influence on the occurrence of tobacco diseases were investigated under the two rotation patterns. The results showed that the disease incidence rate of tobacco under TR crop rotation was low, only 4.92 %, while the incidence rate under TM crop rotation was as high as 34.44 %. The bacterial genera affecting the disease incidence of tobacco were identified through microbial network and correlation analysis, and a total of 12 genera were identified as significantly correlated with the disease incidence rate of tobacco in the soil layers of 0–10 cm and 10–20 cm. Of these, four genera (Acidothermus, Chujaibacter, Rhodanobacter, and Nitrospira) were significantly and negatively correlated with the incidence rate, and also more abundant in the bacterial community of TR. Soil nitrogen nutrients and pH were the main soil factors influencing the differences in bacterial communities between the two rotation patterns. Partial least squares path model (PLS-PM) analysis revealed that the key bacterial taxa directly influenced the disease incidence of tobacco in both the 0–10 cm and 10–20 cm soil layers. Interestingly, the key bacterial taxa were directly influenced by soil nutrients in the 0–10 cm soil layer and by the tobacco root system in the 10–20 cm soil layer. In summary, nitrogen-rich nutrients and well-developed plant root systems are conducive to shaping soil bacterial communities with disease-resistant properties, reducing the disease incidence of tobacco. This study also provides new research perspectives for sustainable agricultural development and crop disease control.