Objective To investigate the antagonistic activity of Bacillus amyloliquefaciens X60 against tobacco phyllosphere microorganisms and its effects on the phyllosphere microbial community of tobacco. Methods Bioactivity assays were conducted to evaluate the antagonistic effects of B. amyloliquefaciens X60 against 20 species of pathogenic fungi, 15 species of non-pathogenic fungi, 2 specialized forms of pathogenic bacteria, and 15 species of non-pathogenic bacteria. Amplicon sequencing was employed to assess the influence of this strain on the phyllosphere microbial community structure. Results B. amyloliquefaciens X60 exhibited strong antagonistic activity (inhibition rates of 60.00%-80.00%) against 13 species of pathogenic fungi (e.g., Rhizopus oryzae) and 12 species of non-pathogenic fungi (e.g., Trichoderma harzianum). Moderate antagonism (inhibition rates of 10.00%-59.00%) was observed against 7 species of pathogenic fungi (e.g., Alternaria tenuissima) and 3 species of non-pathogenic fungi (e.g., Thielavia microspora). Significant antibacterial activity (inhibition zone diameter >20 mm) was detected against 2 specialized forms of pathogenic bacteria (Pseudomonas syringae pv. tabaci and pv. angulata) and 7 non-pathogenic bacteria (e.g., Exiguobacterium). After application, X60 showed the control efficacy of 52.35% against tobacco leaf spot. Following treatment, the relative abundance of Pantoea—a genus of opportunistic bacteria dominating the infected tissue—increased, whereas bacterial diversity and richness initially declined and then recovered. Fungal richness decreased throughout the observation period, while fungal diversity exhibited a transient decrease followed by a rebound. The relative abundance of phytopathogenic fungi declined from 44.87% to 6.71%. Conclusion B. amyloliquefaciens X60 possesses a broad antimicrobial spectrum and exerts strong antagonistic activity against 25 fungal and 9 bacterial species colonizing the tobacco phyllosphere. Under field conditions, the strain provided 52.35% control of tobacco leaf spot and significantly reduced the abundance of foliar phytopathogens, demonstrating the potential as a biocontrol agent for the management of this disease.
| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |