Objective To elucidate the microbiological mechanisms through which long-term straw return influences the severity of bacterial diseases in paddy fields, thereby providing a theoretical basis for precise disease prevention and control.

Method Based on a long-term field location experiment in Huizhou, Guangdong Province, this study implemented three treatments: 1.3 times the amount of full straw returned (S30, with a seasonal application rate of 8425 kg·hm⁻²), full straw returned (CKS, with a seasonal application rate of 6,400 kg·hm⁻²), and no straw returned (CK). Using metagenomic sequencing, we systematically compared the dynamics of soil bacterial community structure and the relative abundance of key pathogenic species (including Burkholderia glumae, Xanthomonas oryzae, and Dickeya oryzae) under different straw management practices, and examined their relationships with environmental factors through correlation analysis.

Result Straw returning significantly enhanced the species richness of soil bacterial communities (P<0.05) and altered their structural composition. Among the detected phyla, Proteobacteria, Chloroflexi, and Acidobacteria were identified as the dominant taxa, and their relative abundances were significantly influenced by both the amount of returned straw and the growth stages of rice. Redundancy analysis confirmed that soil pH served as a key environmental factor driving shifts in community structure (P = 0.024) . Straw returning generally reduced the abundance of three pathogenic bacteria during the tillering stage. It also lowered the disease severity indices for bacterial leaf blight, leaf streak, and panicle blight of rice, though not significantly, and even carried a potential risk of increasing foot rot incidence. At the maturity stage, S30 significantly increased the abundance of B. glumae and X. oryzae, while the relative abundance of D. oryzae was markedly reduced. Additionally, S30 significantly promoted the aggravation of bacterial leaf blight and raised the incidence of leaf streak and foot rot. In contrast, CKS showed no significant negative impact on the occurrence of most bacterial diseases. Its disease incidence was only slightly higher than that of CK, and the disease index performance remained relatively moderate. Correlation analysis revealed that at maturity, the abundances of Burkholderia and Xanthomonas were significantly positively correlated with soil pH, while at the tillering stage, Dickeya abundance showed a strong association with soil available phosphorus content.

Conclusion Long-term straw returning is altering the soil microenvironment, resulting in dual specificity on the type and growth stage of bacterial diseases in rice. At the tillering stage, it reduced the disease indices of bacterial leaf blight, leaf streak, and panicle blight, though not significantly, while even increasing the risk of bacterial foot rot. At maturity, however, straw returning promoted different bacterial diseases depending on the amount applied. Among the treatments, S30 showed the most pronounced effects, providing a scientific basis for ecologically sustainable management of bacterial diseases in rice.