Abstract: Phyllosphere microorganism play a critical role in plant disease resistance, yet their response mechanisms under pathogen infection require further exploration. This study investigated the structural and functional dynamics of phyllosphere microbial communities in healthy and infected leaves of Camellia sinensis cv. ‘Zhirenzao’ to elucidate their responses to pathogen invasion and potential roles in disease defense. In this study, we collected healthy and infected leaves, and analyzed them by high-throughput gene sequencing and microbiome analysis to identify primary pathogens, delineate bacterial and fungal community structures, and predict microbial functions. The results reveal that Fusarium and Pestalotia were the dominant pathogenic genera in the infected leaves A (IA) and B (IB), respectively. Both bacterial and fungal α-diversity were significantly higher in the infected leaves compared to those of healthy leaves (P<0.05), and the β-diversity analysis also reveals significant structural differences. In terms of species composition, the healthy leaves were dominated by Proteobacteria (79.9%), while the infected leaves were mainly composed of both Proteobacteria and Actinobacteria. Within the fungal communities, Dothideomycetes was a co-dominant class, while the infected leaves were dominated by Sordariomycetes, Agaricomycetes and Eurotiomycetes. LEfSe analysis further identified the significant differentiating species: the healthy leaves were dominated by potentially beneficial microbes like Trichococcus and Pseudomonas, whereas the infected leaves were primarily composed of pathogenic genera including Didymella, Plectosphaerella, Fusarium and Pestalotia. The results from functional prediction demonstrate that microbial functions in the healthy leaves were enriched for photosynthesis and carbon fixation pathways, while the infected leaves exhibited significant increase in pathways for bacterial chemotaxis, flagellar assembly and butyrate metabolism. FUNGuild annotation further reveals an increase in the proportion of plant pathogens, plant saprotrophs and wood saprotrophs in the diseased leaves, potentially reshaping the phyllosphere microbial community, where the proliferation of pathogens and decline of beneficial microbes may collectively impair host resistance. These findings provide a theoretical framework for understanding phyllosphere microbial functions in plant-pathogen interactions and establish a scientific basis for developing biocontrol strategies against tea plant diseases.

Key words: Camellia sinensis, phyllosphere microorganism, high-throughput sequencing, functional prediction