Data Sheet 1_Do soil microbes regulate citrus fruit quality through soil nutrient availability?.doc

The relationship between soil microbes and citrus fruit quality is not fully understood at the moment. In this study, we collected citrus fruit and soil samples from fifteen orchards with generally similar planting conditions and soil profiles. Fruits were categorized into three quality types, namely, SL (small-weight and low Vitamin C), SH (small-weight and high Vitamin C), and BH (big-weight and high Vitamin C), respectively, based on PCA analysis. The results indicated significant differences (P < 0.05) were observed in the relative abundances of Acidobacteriia, Deltaproteobacteria, and Tremellomycetes at class level. Bacterial α-diversity showed no significant differences, whereas fungal communities exhibited significant differences in Shannon and Simpson index. Significant differences in β-diversity were observed among the groups. Microbial co-occurrence network analysis revealed a higher proportion of positive correlations in the BH group, suggesting stronger microbial cooperation. Redundancy analysis (RDA) demonstrated that fruit weight was influenced by soil pH, organic matter, and alkali-hydrolysable nitrogen as well as fungal Shannon and Simpson indices. Soil microbial taxa and available phosphorus significantly affected fruit quality indicators such as Vitamin C (Vc) content, titratable acidity, and soluble solids content. We propose that the diversity, composition, and co-occurrence networks of soil microbiota collectively influence soil nutrient availability. This nutrient availability, in turn, acts as a key determinant of citrus fruit quality.当前学界对土壤微生物与柑橘果实品质之间的关联尚未完全阐明。本研究从15个种植条件与土壤剖面大体相近的果园采集了柑橘果实及土壤样品。基于主成分分析（PCA），将果实划分为三类品质类型：SL（单果重量小且维生素C含量低）、SH（单果重量小但维生素C含量高）以及BH（单果重量大且维生素C含量高）。结果显示，在纲分类水平上，酸杆菌纲（Acidobacteriia）、δ-变形菌纲（Deltaproteobacteria）与掷孢酵母纲（Tremellomycetes）的相对丰度存在显著差异（P < 0.05）。细菌α多样性未呈现显著差异，而真菌群落的Shannon指数与Simpson指数则存在显著差异。各组间的β多样性同样存在显著差异。微生物共现网络分析表明，BH组的正相关占比更高，提示其微生物间的协作关系更为紧密。冗余分析（RDA，Redundancy Analysis）结果显示，果实重量受到土壤pH值、有机质、碱解氮以及真菌Shannon指数与Simpson指数的影响。土壤微生物类群与有效磷则显著影响维生素C（Vc）含量、可滴定酸度及可溶性固形物含量等果实品质指标。本研究提出，土壤微生物群落的多样性、组成及共现网络共同调控土壤养分有效性，而该养分有效性反过来成为决定柑橘果实品质的关键因素。