Effect of water deficit and severe shoot trimming on the composition ofVitis vinifera L. Merlot grapes and wines

Abstract

Background and Aims:In recent years, increasing summer temperature, coupled with reduced and erratic rainfall during the growing season, has induced accelerated fruit ripening in several regions, resulting in an undesirable increase in wine alcohol concentration. This study was designed to evaluate the impact of canopy and water management on grape sugar and flavonoid accumulation, with the goal of reducing wine alcohol concentration while conserving or enhancing the concentration of phenolic substances. Methods and Results: In 2011 and 2012, two irrigation treatments (I -irrigated and DI -deficit irrigated) and two canopy heights (HC -high canopy and SC -short canopy) were applied in a Merlot vineyard. No interactions between treatments were observed, and thus independent results were obtained; DI berries had significantly higher sugar concentration (+5%) than that of I in both years and higher wine alcohol concentration only in 2012. Short canopy berries had lower sugar concentration (−4%) and lower wine alcohol (−8%) (only in 2011) than that of HC. Anthocyanins and tannins in berry and wine were increased by water deficit and not affected by severe trimming. Conclusions: Deficit irrigation did not reduce berry sugar concentration and wine alcohol concentration but did enhance desirable wine attributes. Berry sugar concentration and alcohol concentration in wine were reduced by SC in one of the two seasons. Water deficit and severe trimming showed independent effects on berry composition. Significance of the Study: Severe canopy reduction at early stages of ripening can reduce sugars without affecting the accumulation of anthocyanins in Merlot. Conversely, DI applied before veraison, despite promoting anthocyanins accumulation, may also increase berry sugar concentration at harvest.

Impact of Leaf Removal, Applied Before and After Flowering, on Anthocyanin, Tannin, and Methoxypyrazine Concentrations in ‘Merlot’ (Vitis vinifera L.) Grapes and Wines

“…Article study in 'Merlot' indicated that even significant reductions of this ratio (from 1.5 to 1.0 m 2 /kg) do not have any significant effect on anthocyanin accumulation in the berry, 22 suggesting a lack of relationship between the LA/Y ratio and anthocyanin accumulation in this variety. Besides the total amount of anthocyanin, environmental cues, and viticultural practices can also affect the anthocyanin profile, i.e., the relative abundance of the different anthocyanins.…”

“…Sensory analyses of the wines were performed as described in Herrera et al 22 considering the following attributes: color (color intensity and hue), taste (acidity, bitterness, astringency, and minerality), aroma (intensity, fruity, herbaceous, and spicy), and…”

“…14,15 As for tannin content, our data support the results of previous studies indicating that viticultural practices have a limited effect on skin and seed tannin content. 14,22,35 Both leaf-removal treatments affected the concentration of MPs during berry development; at harvest, significantly lower values were measured in LRAF berries ( Table 2). The MP concentration in the berry can be affected by multiple factors, specifically light and temperature, 2,9,36−39 crop level, 40 vigor, and high leaf area-to-yield ratio.…”

Preveraison Water Deficit Accelerates Berry Color Change in Merlot Grapevines

“…13°13´E; elevation 88 m asl), in an 18-year-old Merlot vineyard grafted onto SO4 rootstock. The experimental site and design has been described in detail (Herrera et al 2015). Briefly, to maintain the vines under a fully controlled water regime, four 85 m-long rows were covered with an ethylene-vinyl-acetate film using a five m high, open-side tunnel structure.…”

“…Each treatment was replicated four times in experimental plots of 10 vines each in a completely randomized design. Vine water status was estimated weekly using midday measurements of Ψ stem as described (Herrera et al 2015).…”