A study to investigate the potentiality of a biostimulant made by Fabaceae tissues and rich in triacontanol (long-chain alcohol) to enhance grapevine resilience under drought stress

The primary objective of this research was to investigate the potential benefits of a Fabaceae-based product rich in triacontanol (a long-chain alcohol) applied to Vitis vinifera cv. Merlot, on key physiological and productive parameters of grapevines under controlled water stress conditions. Specifically, the study focused on evaluating parameters such as photosynthetic activity, water use efficiency, and yield quality, while also monitoring the grapevines' physiological responses to water stress. By elucidating the effects of this treatment, the findings aim to contribute to developing innovative and sustainable solutions for modern viticulture. The experiment involved 40 Merlot grapevines grafted onto Kober 5BB rootstock. The vines were divided into two experimental groups: untreated control (NT) and treatment (T1), with 20 plants per group (4 replicates per group; 52 m² per plot) following a randomized block design. Net photosynthetic rate (A), stomatal conductance (gs), transpiration rate (E), and internal CO₂ concentration (ci) were measured on three replicates per treatment (8 leaves per treatment) between 8:30 and 10:30 a.m. on fully expanded, healthy leaves between the 5th and 10th internodes of a central shoot. A portable photosynthesis system (Li-6400XT, Li-Cor Inc.) was used with a photosynthetic photon flux density (PPFD) of 1,200 µmol m⁻² s⁻¹, CO₂ concentration set to 400 µmol mol⁻¹, and relative humidity (RH) maintained at 65%. The qualitative parameters of the grape skin were also evaluated with rapid field spectroscopic and rheological systems. T1 showed a significant improvement in WUE compared to NT, while NT recorded higher evapotranspiration (E), indicating greater water loss in untreated plants. Furthermore, all analysed genes exhibited significantly higher activation in T1 plants compared to NT. This suggests that the treatment triggered molecular mechanisms associated with water stress resistance. Finally, no differences were observed in total polyphenol concentration in grape skins between T1 and NT during the phenolic ripening curve, suggesting the treatment did not influence secondary metabolite accumulation under the tested conditions. In conclusion, T1 (Fabaceae-based product rich in triacontanol) appears to offer significant advantages in managing water stress by improving WUE and activating stress-response genes, making it a promising tool for sustainable viticulture. However, its neutral impact on polyphenol content warrants further investigation to understand its broader implications for fruit quality and marketability.