Study on the relationship between bacterial wilt and rhizospheric microbial diversity of flue-cured tobacco cultivars

Bacterial wilt caused by Ralstonia solanacearum, is one of the serious soil-borne diseases in flue-cured tobacco production areas in China. However, it was found that the occurrence of bacterial wilt not only varied with different cultivars but also varied with various sites even under the condition of planting the same variety. It suggests that the occurrence of bacterial wilt could be controlled by regulating soil microorganism and the growth environment. Therefore, the relationship between microorganism's diversity in the rhizosphere and actual incidences were evaluated on the number of symptomatic plants and the functional diversity of soil microorganisms in field trials on two sites. The results showed that the incidence of bacterial wilt in the same cultivar was varied between the two experimental sites. However, the same trend was found in the number of rhizospheric microbes among the three varieties except for fungi. Also, a good relationship was found between the number of pathogens, microbial functional diversity in the rhizosphere, and actual incidences. The utilization intensity of carbohydrates, amino acids, carboxylic acids, polymers, amines, and carbon utilization of rhizospheric soil microbial community was negatively related with the occurrence of bacterial wilt while it was on the opposite for the utilization intensity of phenolic acids. The results revealed that the mechanism for resistance in flue-cured tobacco was directly associated with the number of pathogenic microorganisms in rhizosphere and the diversity of rhizospheric microbes. By improving the diversity of rhizospheric microbes, the incidence of tobacco bacterial wilt disease can be reduced.