Abstract:

This study aimed to explore the epidemic regularity and influencing factors of bacterial wilt in Yibin tobacco area，and provide technical support for tobacco bacterial wilt prevention and control. Through field survey and systematic investigation，the rhizosphere soil with different incidence of tobacco bacterial wilt was collected，and the differences of soil physicochemical properties and microbial communities between rhizosphere soils of diseased and healthy tobacco plants were measured and analyzed. The results showed that：（1）Bacterial wilt in Yibin tobacco-growing area began sporadic onset from late May to early June，and reached its peak in early July. The epidemic rate of bacterial wilt increased with the increase of rainfall. The cultivation methods and varieties had great influence on the occurrence of bacterial wilt of flue-cured tobacco，and the crop rotation for more than 3 years could significantly （p<0.05） reduce the occurrence of bacterial wilt. The flue-cured tobacco varieties Chuanyan 101 had the best resistance to bacterial wilt，Xiangyan 7 and Zhongyan 106 followed. It was found that the incidence and disease index of bacterial wilt in Junlian County and Junxian County ranged from 0 to 18.80% and 0 to 9.91，respectively，with the highest incidence in Junlian County and Gongxian County.（2）In terms of soil physical and chemical properties，soil pH value，organic matter，available potassium，available phosphorus，exchangeable calcium and exchangeable magnesium contents were higher in the rhizosphere soil of healthy tobacco plants，and alkali-hydrolyzable nitrogen contents were higher in the rhizosphere soil of diseased tobacco plants. Correlation analysis showed that the occurrence degree of bacterial wilt was positively correlated with soil alkali-hydrolyzable nitrogen content，but negatively correlated with soil pH value，organic matter，available potassium，available phosphorus，exchangeable calcium and exchangeable magnesium contents.（3）In terms of rhizosphere microbial community，the relative abundance of Actinobacteriota， Gemmatimonadota and Sphingomonas in uninfected rhizosphere soil was higher than that in diseased rhizosphere soil，while the relative abundance of Ralstonia was much lower than that in severely infected rhizosphere soil. In summary，farming system，rainfall，varieties，soil pH value，organic matter，available potassium，available phosphorus，exchangeable calcium，exchangeable magnesium contents and relative abundances ofActinobacteriota，Gemmatimonadota，Sphingomonas in rhizosphere soil in Yibin tobacco-growing area were important factors affecting the occurrence of bacterial wilt，while alkali-hydrolyzable nitrogen content，temperature and altitude were secondary factors.

Key words: tobacco bacterial wilt, rhizosphere soil, soil physical and chemical property, microbial community