Abstract:Objective To provide a theoretical basis for developing microbiome-based ecological control strategies against citrus Huanglongbing (HLB), a devastating bacterial disease seriously threatening the global citrus industry.Methods Rhizosphere soil samples from both HLB-infected and healthy citrus trees in Yizhang County, Hunan Province, were investigated. Using 16S rRNA gene and ITS region amplicon sequencing, we systematically analyzed the impact mechanism of HLB on the rhizosphere micro-ecosystem.Results The results showed that HLB infection significantly reduced the organic matter (6.65 g/kg) and available phosphorus (7.25 mg/kg) content of the rhizosphere soil compared with that of the healthy plants, and triggered a significant decrease in the alpha diversity of bacterial communities and a significant increase in the alpha diversity of fungal communities (P<0.05). Beta diversity analysis showed that HLB significantly altered the structure of the microbial communities. Specifically, the relative abundance of pro-biotic bacteria such as Pseudomonadota and Gemmatimonadota decreased, while oligotrophic Acidobacteriota and Chloroflexota were significantly enriched. In fungal communities, the abundance of saprophytic fungi in the phyla Ascomycota and Basidiomycota increased by 5.32% and 7.38%, respectively, while the phylas Rozellomycota and Mortierellomycota decreased by 12.30% and 3.23%, respectively. HLB disrupted the rhizosphere microbial balance by inhibiting Rozellomycota, leading to excessive proliferation of saprophytic fungi and weakening the system’s disease resistance. Analysis at the order level further revealed that beneficial bacterial groups such as Burkholderiales and Hyphomicrobiales were significantly depleted, whereas stress-adaptive groups like Ktedonobacterales showed significant proliferation. PICRUSt2 analysis revealed that HLB disturbed the structure of the citrus rhizosphere bacterial community via metabolic pathways and genetic information processing. HLB also utilized saprophytic and ectomycorrhizal fungi to maintain soil health.Conclusion This study revealed that HLB affects soil microecological balance by remodeling the structure and function of citrus rhizosphere microorganisms, and the results may provide a theoretical basis for the development of ecological prevention and control strategies for HLB based on microbiome regulation.
