Evaluation of the effect of regulated deficit irrigation on Vitis vinifera Cabernet-Sauvignon physiological traits and final fruit composition

Abstract

Context and purpose of the study – Climate change establishes challenges, as well as opportunities for many sectors, and markedly the wine sector. The wine industry plays a weighty role in Chile’s economy, where contributes considerably to the country financial development. Counting the vulnerability of the country to such changes, it is fundamental to enact preventive measures aiming at besting the resources management, above all water necessities for cultivated crops. Optimal irrigation in grapevines could be accomplished by means of physiological data based programming and final grape and wine chemical and sensory performance. This study aims to understand the impacts of different levels of deficit irrigation on a large amount of chemical markers from aroma to non-volatile compounds, and the final impact on sensory profile.   

Material and methods – A regulated deficit irrigation (RDI) experimental trial that was conducted in a commercial vineyard of Cabernet Sauvignon in the Maule valley in central Chile. Four regulated deficit irrigation (RDI regimes were employed in four replicated blocks to replenish different portions of evapotranspiration (ET) from pea-size stadium until harvest. These managements were conceived 100 % ET, 70 % ET, 50-100 % ET (50 % ET before veraison and 100 % ET afterward) and 25-100 % ET (25 % ET before veraison and 100 % ET afterward). The following parameters were measured: midday stem water potential (Ψstem), stomatal conductance (gs), vine and grapes growth, yield, quality of must. GSMS for norisoprenoid, terpene, C6s compounds and methoxypyrazines concentration and HPLC for anthocyanin and low molecular weight phenols was used. 

Results – Of definite interest were the outcomes from the grapes’ evolution monitoring, as we had expectations of an alteration in their development in RDI conditions. Apart from the mere berry size, which showed significant differences between the treatments and control, no other variations have been registered. Surprisingly, the °Brix degrees were very alike, indicating that a reduced water availability does not always imply a faster maturation of the sugars in the grapes, as opposed to previous investigations that shows that a conventional irrigation may imply a delay in sugar accumulation. These circumstances additionally, allowed us to harvest all of the four regimes at the same time, thus providing optimal comparison bases. Significant differences were found in several traits, from lower concentration of malic acid in RDI treatments to higher concentrations of anthocyanin and some specificflavonoids like quercetin and miricetins. In the case of aroma compounds, our partial results indicate a significant effect of the RDI in increasing the concentration of 3-Isobutyl-2-methoxypyrazine. This result might be linked to increased light interception in the RDI treatments, who tend to defoliate early in the season