The phenolic profile of red grape berries is a key quality factor and several techniques have been applied to increase the accumulation of those compounds in berries¹. In the last decade, research on the topic has focused mainly on innovative agronomical techniques, such as the application of bioelicitors in order to enhance phenolic content². Plants interact with diverse microbial communities inside the roots and in the rhizosphere,phyllosphere and carposphere³. Plant biosynthetic products, like secondary metabolites, affect this interaction; thus, the exogenous application of resistance elicitors and phytohormones trigger the secondary metabolism and promote the biosynthesis of specific compounds that can alter the structure of the associated microbial communities^{4 5}.

In an open field experiment (Muses Valley, Askri, Viotia, Greece), biostimulants were applied to Vitis vinifera L. Mouhtaro grape vines at three time points during veraison (400 mg/L ΑΒΑ, 0.3 mM, BTH and 0.3 % CHT, all in aqueous solutions). Grapes were harvested at optimum sugar maturity to produce red wine. Conventional analysis for total phenolic content and anthocyanins was carried out on the harvested grapes. Standard wine analyses recommended by OIV were used on grape and wine (pH, alcoholic content, total acidity). Additionally, total phenolic index and total anthocyanins and tannins by precipitation with a methyl cellulose assay were measured in wines. More details can be found in Miliordos et al. (2021)⁶.

The carposhere biofilm of the epiphytic microbial communities were washed with sterile PBS and detached with 4 cycles of 2 min pulse sonication at 120 kHz followed by vortex. Total genomic DNA was extracted from biofilm pellets with the DNeasy Power soil DNA isolation kit following the manufacturer’s protocol (MoBio Laboratories, Carlsbad, CA, USA). Prokaryotic and fungal communities were analysed by amplicon sequencing analysis with Illumina HiSeq 2x250bp. The V4 region of the 16S rRNA gene was analysed for prokaryotes (515f - 806r primer pair) and the ITS2 region for fungi (fITS7 - ITS4 primer pair). Bioinformatic analysis was performed with DADA2 and α- & β- diversity analysis with phyloseq R packages v. 1.38.0. Final differences in the abundance of microbial members of the prokaryotic and fungal community between the treatments (Control, CHT, BTH, ABA) was tested using linear discriminant analysis (LDA) and effect size analysis (LEfSe). More details can be found in Miliordos et al. (2021)⁷.

Sensory trials were carried out using 12 trained assessors (equal representation of the two genders) with the majority having professional experience in the wine industry at least two years of experience in red wine tasting. Samples were served in ISO standard glasses 3591 and coded with a randomised three-digit number⁸. The evaluation consisted in describing eight descriptors quantitatively using a scale of 1 to 10 (lowest to highest intensity) for the following characteristics: Colour, Overall Aroma, Strawberry, Sour Cherry, Blackberries, Vegetal Aroma, Spiciness, Vanilla, Red Flowers and Caramel.

Differences in the microbial communities were observed after the application of the plant activators (Figure 1).

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This research was co-funded by the European Regional Development Fund of the European Union and Greek national funds through the Operational Program Competitiveness, Entrepreneurship and Innovation, under the call RESEARCH–CREATE–INNOVATE (project code: T1EDK- 04200 (MU-SA).

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