Purpose To investigate the effects of grape powdery mildew on the grape phyllosphere microbiota, and to evaluate the diversity and community structure of fungi and bacteria on healthy and diseased grape leaves, providing references for precise disease control and the development of new biocontrol agents for grape diseases.
Methods Vitis vinifera cv. ‘Red Globe’ was selected as the research object. During the powdery mildew epidemic period, healthy leaves were collected as the control group (CK), while symptomatic leaves served as the diseased group (NE). Microbial omics combined with bioinformatics analysis were employed to compare phyllosphere fungal and bacterial diversity and community structure between the two groups.
Results After the occurrence of grape powdery mildew, the number of fungi from class to species level and bacteria from phylum to species level increased; fungal alpha diversity and richness decreased, whereas bacterial alpha diversity and richness showed non-significant increases (P>0.05). Principal coordinate analysis indicated extremely significant differences in fungal beta diversity between groups (P<0.01), while bacterial community structure remained statistically unchanged. After the occurrence of powdery mildew, the relative abundance of Ascomycota, Erysiphe and Peniophora significantly increased (P<0.05). The dominant bacterial phyla were Firmicutes, Proteobacteria, and Actinobacteriota, with no significant difference between before and after disease occurred. However, beneficial genera including Paenibacillus, Streptomyces, Alistipes, and Pandoraea significantly decreased in relative abundance. Plant pathogen-wood saprotrophs (Peniophora, Stemphylium), fungal parasite-undefined saprotrophs (Vishniacozyma, Papiliotrema, Bullera, Saitozyma, Hannaella), and plant pathogens (Erysiphe, Gibberella) were significant increased (P<0.05). Bacterial functional annotation indicated that: In the NE group, the pathways of catechol degradation Ⅲ (ortho-cleavage), aromatic compound degradation via β-ketoadipate, arginine/ornithine/proline interconversion, and octane oxidation were significantly upregulated, while mannan degradation pathway was downregulated (P<0.05).
Conclusion Powdery mildew exerts greater disruptive effects on bacterial networks than fungal networks, characterized by increased connectivity but reduced stability and modularity in bacterial communities. Pathogenic fungi significantly proliferates while stress-resistance-related bacterial metabolic pathways are suppressed. The antagonistic Streptomyces sp. VAI-40 isolated from the phyllosphere significantly inhibites Botrytis cinerea and Alternaria solani.
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