Effect of flavonoids and a citrus-derived biostimulant on grape ripening: from cell cultures to field trials

Abstract

Climate change is disrupting grape ripening kinetics, causing a critical decoupling between technological and phenolic maturity in Vitis vinifera L. This shift often leads to wines with excessive alcohol and poor color, a major hurdle for the industry. While elicitors like methyl jasmonate1,2 have been studied, their field adoption remains low. We hypothesized that naringenin—a key intermediate in the phenylpropanoid pathway found abundantly in citrus waste—could bridge this gap, offering a sustainable solution within a circular economy framework. This study evaluates the potential of naringenin and naringin to stimulate anthocyanin biosynthesis in cell cultures and tests the field efficacy of a citrus-derived biostimulant on the composition of Garnacha and Tempranillo grapes and wines. Initially, Vitis vinifera L. cv. Gamay cell cultures were treated with 1.5 mM naringenin and naringin, both individually and combined. We monitored cell viability to ensure no toxicity and quantified anthocyanin accumulation, followed by a preliminary RNA-seq analysis to detect shifts in global gene expression. Subsequently, a biostimulant was extracted from grapefruit peels using Subcritical Water Extraction (SWE) and applied to field plots of cv. Garnacha and cv. Tempranillo. All replicates were harvested when control grapes reached 21 °Brix and analyzed individually via the Cromoenos method. Finally, we performed microvinifications and assessed the resulting wines through standard oenological analysis and sensory triangle tests. Cell culture trials proved that these flavonoids are non-toxic and result in a synergistic increase in anthocyanins, accompanied by clear changes in the global transcriptomic profile. In the vineyard, however, the biostimulant did not significantly increase anthocyanin levels or the Total Polyphenolic Index (TPI) in grapes or wine. Interestingly, a consistent and significant reduction in ethanol content was observed in the treated wines compared to controls. While naringenin effectively modulates the flavonoid pathway in vitro, its field application did not enhance color under our study conditions. However, the observed reduction in ethanol suggests that citrus-derived biostimulants are a promising, eco-friendly tool for managing grape ripening and wine balance in a warming climate.

References

1. Gil, R; Improving phenolic and chromatic characteristics of Monastrell, Merlot and Syrah wines by using methyl jasmonate and benzothiadiazole; Oeno One; 51 (1)