Abstract: To understand the microcosmic effect of difenoconazole in the control of tobacco brown spot，the toxicity of difenoconazole to Alternaria alternata was determined by the mycelial growth rate test，and the phyllosphere microorganisms community structure and metabolic functions of both diseased and healthy tobacco leaves during different application periods were determined by Illumina high⁃throughput sequencing and Biolog metabolic phenotype techniques，respectively.Results showed that difenoconazole had a potent inhibitory activity against A.alternata，with an average EC₅₀ value for inhibiting mycelial growth of 0.17 mg/L.At the early occurrence stage of the disease，phyllosphere fungi in both diseased and healthy leaves were Ascomycota and Basidiomycota dominance at phylum level，the dominant fungal genera were Altemaria，Cladosporium and Symmetrospora.At the phylum level，the dominant bacteria were Proteobacteria and Firmicutes，and the dominant bacteria genera were Pantoea and Pseudomonas.After the application of difenoconazole WDG 900 g/ha，the relative abundance of the phyllosphere fungus Altemaria in diseased tobacco leaves decreased at 5 and 15 d，increased at 10 d after application，the relative abundance of Cladosporium continued to decrease after application，and the relative abundance of the phyllosphere Didymella in both diseased and healthy tobacco leaves decreased at 5 and 10 d and increased at 15 d after application，the relative abundance of the remaining flora also showed irregular increases and decreases.The relative abundance of Pantoea，Massilia，and Sphingomonas in the phyllosphere of diseased tobacco leaves decreased at 5 and 10 d and increased at 15 d after application，while the relative abundance of Pseudomonas kept increasing after application.The phyllosphere microorganisms metabolic activity of diseased tobacco leaves was weaker than that of healthy tobacco leaves，and the phyllosphere microorganisms in the diseased tobacco leaves were weaker in the metabolism of L⁃threonine，D，L⁃α⁃glycerol，α⁃ketobutyric acid，α⁃cyclodextrin carbon sources，while stronger metabolic activity of healthy tobacco leaves was found for all tested carbon sources except for α⁃ketobutyric acid and 2⁃hydroxy benzoic acid carbon sources.The treatment of difenoconazole decreased the microorganisms metabolic activity of both diseased and healthy tobacco leaves，and the activity gradually recovered with the application time.In summary，the application of difenoconazole can inhibit the growth of A.alternata，change the community structure of phyllosphere microorganisms in diseased leaves，and rapidly reduce the metabolic activity of phyllosphere microorganisms.

Key words: Tobacco brown spot, Difenoconazole, Phyllosphere microecology, Alternaria, Metabolic function

摘要： 为了解苯醚甲环唑防控烟草赤星病的微观效果，采用菌丝生长速率法测定了苯醚甲环唑对烟草赤星病菌的毒力，并采用Illumina高通量测序与Biolog代谢表型技术分别测定了药剂应用后感病与健康烟叶组织叶际微生物群落结构和代谢功能。结果表明，苯醚甲环唑对烟草赤星病菌菌丝生长具有较强的抑制作用，其半数最大效应质量浓度（EC₅₀）均值为0.17 mg/L。病害发生初期，感病与健康烟叶叶际真菌的优势菌门是子囊菌门和担子菌门，优势菌属为链格孢属、枝孢霉属、Symmetrospora；细菌优势菌门是变形菌门和厚壁菌门，优势菌属为泛菌属、假单胞菌属。施用苯醚甲环唑水分散粒剂900 g/hm²后，感病烟叶叶际真菌链格孢属相对丰度在施药后5、15 d降低，施药后10 d增加，枝孢霉属相对丰度在施药后持续降低，感病和健康烟叶叶际亚隔孢壳属相对丰度在施药后5、10 d降低，施药后15 d增加，其余菌群的相对丰度也呈现不规律的增减。感病烟叶叶际细菌泛菌属、马赛菌属、鞘脂单胞菌属相对丰度在施药后5、10 d降低，施药后15 d均上升，假单胞菌属相对丰度在施药后一直保持上升状态。感赤星病烟叶叶际微生物代谢活性弱于健康烟叶，感病烟叶叶际微生物对L-苏氨酸、D，L-α-甘油、α-丁酮酸、α-环式糊精碳源代谢较弱；健康烟叶对除α-丁酮酸和2-羟基苯甲酸碳源外的所有供试碳源代谢活性均较强。苯醚甲环唑处理降低了感病与健康烟叶叶际微生物的代谢活性，其代谢活性随着施药时间的延长均逐渐恢复。综上，施用苯醚甲环唑能抑制烟草赤星病的病原菌生长，改变感赤星病烟叶叶际微生物的群落结构，快速降低叶际微生物的代谢活性。

关键词: 烟草赤星病, 苯醚甲环唑, 叶际微生态, 链格孢属, 代谢功能