Study on the mechanism of biological control of tobacco bacterial wilt with different green manures

Tobacco bacterial wilt (Ralstonia solanacearum, Rs) causes severe damage to tobacco production in the Guizhou Province. The investigation of the effects of suppressing bacterial wilt pathogens and improving soil microbial activity of different types of green manure will provide new ideas and methods for controlling tobacco bacterial wilt. In this study, 15 green manures suitable for planting in southwestern tobacco areas were selected. A pot simulation experiment was conducted to demonstrate the inhibitory effect of green manure on Rs in soil. UPLC-Q-TOF/MS was employed to identify and analyze the type and quantity of amino acids in the root exudates of different green manures, and fluorescence quantitative PCR was used to study the effects of root exudates on the population of Rs. High-throughput sequencing of soil microbes was performed to reveal the soil microbial community structure and functional genes in field experiments. As planting time increased, the number of Rs in the soil showed a downward trend. The inhibitory effect of mung bean root exudate on Rs was the strongest, with an inhibitory rate of 69.05%. The content of amino acids in the root exudates of February orchid was higher than that in any other green manure, while the amino acid content in rape was the lowest. The mung bean treatment had the highest tyrosine content, which was 54.74% higher than that of the lowest (oil rape). Glutamic acid and alanine contents in February orchids were significantly higher than those in other green manures. In addition, the serine content of hairy vetch was 33.19% higher than that of mung beans. After green manure was applied in the field, the control efficacy of bacterial wilt in mung bean treatments was as high as 55.61%. The relative abundance of Rs in the control rhizosphere soil was significantly higher than those in the green manure-planted soil, which were 4.35, 4.14, 2.90, and 2.29 times that of rape, hairy vetch, mung bean, and February orchid, respectively. The relative abundances of α-Proteobacteria, Haliangium, and Klebsiella were higher in the mung bean treatment than in other treatments. Soil functions such as amino acid metabolism, transcription, replication, and repair were enhanced after treatment with green manure. In summary, the root exudates of green manure significantly affected the population of Rs. After the application of green manure, the structure and function of soil bacterial microbial communities changed. Therefore, treatment of mung beans is suitable for the biological control of tobacco bacterial wilt. This research will explore a new approach for the green prevention and control of tobacco bacterial wilt.