Geographic origin and wheat variety shape microbial and functional profiles of brewing wheat for Daqu fermentation

Wheat is the primary raw material for traditional Baijiu Daqu fermentation, yet its role as a carrier of functional microbiota and its contribution to Daqu quality remain poorly understood.

A total of 135 wheat samples representing five geographic regions and nine cultivars were subjected to sensory evaluation, physicochemical analysis, and 16S rRNA gene and ITS amplicon sequencing. Microbial community composition, predicted functional potential, and their associations with wheat quality traits were analyzed using PICRUSt2, Mantel tests, and correlation analyses.

Sensory evaluation indicated that the cultivation environment had a greater impact on Daqu quality than wheat cultivar, with wheat from the Dayi region and the MM916 cultivar exhibiting the most favorable characteristics. Sequencing identified 1,732 bacterial and 484 fungal amplicon sequence variants (ASVs), revealing significant geographic and varietal differences in microbial communities, while core taxa dominated by Pseudomonadota and Basidiomycota were consistently detected across all samples. Functional prediction suggested that microbial communities were primarily enriched in metabolic pathways, particularly carbohydrate metabolism, energy metabolism, and cofactor and vitamin metabolism. Spatial variation was observed in starch and sucrose metabolism, acetoin biosynthesis, and enzymes such as β-glucosidase and alcohol dehydrogenase. Wheat quality traits, especially protein, starch, and wet gluten content, were significantly associated with microbial composition and predicted functions. Thirty-two genera, including Sphingomonas, Pedobacter, and Martelella, showed strong correlations with these quality traits.

Geographic origin and wheat cultivar jointly shape the microbial communities and functional potential of brewing wheat, providing pre-existing microbial resources that may influence early Daqu fermentation and flavor formation. These findings offer a microbiome-based framework for evaluating and selecting high-quality wheat for Baijiu production.