Using wasps as a tool to restore a functioning vine grape mycobiota and preserve the mycobial "terroir"

Abstract

In the last one-hundred years, the exponential expansion of wine making has artificialized the agricultural landscape as well as its microbial diversity, spreading human selected Saccharomyces cerevisiae strains. Evidence showed that social wasps can harbor a significant fraction of the yeast phenotypic diversity of a given area of wine production, allowing different strains to overwinter and mate in their gut. The integrity of the wasp-yeast ecological interaction is of paramount importance to maintain the resilience of microbial populations associated to wine aromatic profiles. In a field experiment, we verified whether Polistes dominula wasps, reared in laboratory and fed with a traceable S. cerevisiae strain, could be a useful tool to drive the controlled yeast dispersion directly on grapes. The demonstration of the biotechnological potential of social insects in organic wine farming lays the foundations for multiple applications including maintenance of microbial biodiversity and rewilding vineyards through the introduction of wasp associated microbiomes.

Figure 1

Experiment vineyard and study design. (a) Field setting, with experimental vineyard lines (L5, L6, and L8) covered with nets and L7 net-free. (b) Scheme of the treatments and samples collection, with details on timings and metabarcoding and metabolomics analyses.

Figure 2

Mycobiota characterization of the experimental vineyard. (a) S. cerevisiae relative abundance in all samples grouped according to the different environment (laboratory and experimental vine plant rows); (b) observed alpha diversity; (c) beta diversity—PCoA on weighted UniFrac distances; the boxplots on the right and above the PCoA plot report the distribution of samples, grouped according to the vineyard row, along the first and second coordinate, respectively. *Wilcoxon–Mann–Whitney p-value < 0.05.

Figure 3

Fungal OTUs with relative abundances significantly differ in the analyzed samples. The relative abundance of each fungal taxon was compared by means of Negative Binomial distribution analysis among samples grouped according to the vineyard of origin or wasps reared in the laboratory. *Wald test p-value corrected by multiple testing < 0.05; the black triangles indicate, among the groups of samples connected by the horizontal line, which group bears the highest abundance of the taxon.

Figure 4

Volatile compounds significantly differing among fermentations grouped according to the vineyard row originating the grapes. Color legend indicates samples collected at different time points during fermentation. *Wilcoxon–Mann–Whitney p-value < 0.05.

Figure 5

Correlations among fungal and volatile compounds abundances in fermenting musts from the studied vineyard rows. Significant Spearman correlations (r > 0.5, p-value < 0.05) with the most abundant fungi are shown, the complete list of correlations is reported in Supplementary Figs. 6–8 and Supplementary Table 5.