Exploring the evolution of sugars and volatile compounds in Marselan grape berries under water stress

Abstract

The coordination between sugar and aroma compounds concentration in grape berries under water stress still unclear. Here, the field grown ‘Marselan’ (Vitis vinifera L.) vines were submitted to two levels of water stress (T1: −0.40 MPa ≤ Ψ_PD < −0.20 MPa; T2: −0.60 MPa ≤ Ψ_PD < −0.40 MPa₎ from 20 to 120 days after anthesis across two consecutive vintages (2021, 2022). The concentration of bound aroma compounds was promoted at ripe stage under T1, with a particularly significant increase in bound higher alcohols. In the PCA analysis, we found that the influences caused by weather conditions between two vintages were larger than those between treatments, the cooler weather promoting the concentration of aroma compounds. According to the OPLS-DA analysis, the concentration of bound benzyl alcohol, 1-heptanol, α-terpineol, 1-octen-3-ol and 1-hexanol was closely related to that of sugar. Furthermore, T1 promoted the expression of sugar transporters, glycosyl transferase and higher alcohol concentration at the veraison stage; in particular, the expression of VvSUC12 was highly correlated with the concentration of bound alcohols. Taking all findings into consideration, T1 could be more favorable to increase the bound alcohols concentration by upregulating the β-D-glucose transport.