Comparative analysis of rhizosphere microbial community structure in leaf blight-resistant and -susceptible plum cultivars

【Objective】Plum (Prunus salicina Lindl.), a woody plant of the Rosaceae family, is rich in organic acids, vitamins, carotenoids, proteins, and mineral elements such as iron and calcium. The Zhenzhu Li plum cultivated in Tian'e County, Guangxi, is an important local economic crop. However, leaf blight severely affects its yield and fruit quality, posing a major challenge to the sustainable development of the plum industry. Field observations revealed that the Mihuang Li cultivar exhibits strong resistance to leaf blight, whereas Zhenzhu Li is susceptible. This study aims to compare the rhizosphere microbial community compositions as well as the functional differences between the resistant (Mihuang Li, TA) and susceptible (Zhenzhu Li, TB) cultivars under the same environmental conditions, aiming to elucidate the mechanisms underlying the high disease resistance of Mihuang Li and to identify potential antagonistic microorganisms, thus providing theoretical and technical support for developing an ecological control system against plum leaf blight.【Methods】The experiment was conducted in a Zhenzhu Li plum orchard in Tian'e County, Hechi City, Guangxi. Rhizosphere soil samples were collected from three healthy trees per cultivar (TA and TB) around the canopy drip line in four directions. Samples were processed for DNA extraction, and high-throughput sequencing of bacterial 16S rRNA (V3-V4 region) and fungal ITS regions was performed on the Illumina MiSeq PE300 platform (Majorbio BioPharm Technology Co., Ltd., Shanghai, China). PCR amplicons were purified, quantified, and sequenced (2 × 300 bp). Data were analyzed using QIIME for diversity metrics, PICRUSt2 for COGbased bacterial functions, FUNGuild for fungal guilds, and IBM SPSS Statistics 21 for statistical comparisons (Duncan's multiple range test, P＜0.05).【Results】At the bacterial phylum level, the dominant phyla in the TA rhizosphere were Proteobacteria, Actinobacteriota, Acidobacteriota, and Chloroflexi, with Verrucomicrobiota and WPS-2 uniquely detected in TA. In contrast, TB was dominated by Actinobacteriota, Proteobacteria, Acidobacteriota, and Chloroflexi, with Bacteroidota and Methylomirabilota uniquely detected. At the genus level, TA showed higher relative abundances of Bradyrhizobium and Acidothermus, whereas TB was enriched in Arthrobacter. For fungi, TA was dominated by Ascomycota, Basidiomycota, and Mortierellomycota, while Rozellomycota was uniquely detected in TB. At the genus level, Trichoderma, Apiotrichum, and Solicoccozyma were detected only in TA, whereas TB showed higher relative abundances of Fusarium, Neocosmospora, and Chordomyces. COG-based functional prediction showed that TA had higher relative abundances of functional categories related to cell motility, secondary metabolite biosynthesis, lipid metabolism, and energy production and conversion, whereas TB exhibited higher abundances of categories associated with cytoskeleton formation, RNA processing, carbohydrate metabolism, and defense mechanisms. FUNGuild analysis revealed that TA rhizosphere fungi were mainly classified as saprotrophic guilds, while TB harbored a higher proportion of plantpathogenic guilds.【Conclusion】The rhizosphere microbial community of the resistant cultivar Mihuang Li (TA) differs significantly from that of the susceptible cultivar Zhenzhu Li (TB) in both composition and predicted function. TA harbors beneficial microorganisms such as Bradyrhizobium and Trichoderma, which exhibit strong saprotrophic activity and potential antagonism against pathogens, as well as enrichment in metabolic pathways related to energy production and secondary metabolism. These features may contribute to enhanced host resistance by maintaining rhizosphere ecological balance and suppressing pathogen colonization. In contrast, the TB rhizosphere community is dominated by potential pathogens (Fusarium, Gibberella) and decomposers, making it more prone to disease occurrence. Overall, this study reveals the potential role of rhizosphere microbial communities in the formation of leaf blight resistance in P. salicina, providing theoretical support for the screening of antagonistic microbes and the development of microbe-based disease control strategies in plum orchards.