Deterministic vs. stochastic: Fungal assembly driven by grape cultivar dictates divergent wine aromas in spontaneous...

This study investigates how grape cultivar drives fungal community assembly during spontaneous fermentation in Penglai, China, and its impact on wine flavor differentiation. Using high-throughput sequencing, volatile analysis, neutral community model (NCM), null model, and Spearman correlations, we tracked fungal succession and flavor metabolites. Findings revealed Saccharomyces dominated Marselan (MS) grape skins, while Cladosporium dominated Cabernet Franc (CF) skins. MS wines contained significantly elevated concentrations of C6 alcohols, fatty acids, and phenolics, contributing herb and baking aromas, whereas CF wines were characterized by dominant esters and terpenes, intensifying floral and spicy. In MS, Saccharomyces and Kazachstania drove key flavors. In CF, Saccharomyces and Hanseniaspora were primary flavor drivers. Deterministic processes governed fungal assembly in MS, while stochastic processes dominated in CF. This research quantifies, for the first time in wine fermentation, the ecological mechanisms of cultivar-driven microbial assembly. It reveals the cascading pathway: Cultivar → Fungal Community Dynamics → Metabolic Network → Flavor Differentiation. These findings provide critical evidence for the microbial basis of terroir and offer significant implications for directing spontaneous fermentation practices.