Viticultural parameters and enological performance of six Merlot clones in two contrasting vintages

Abstract

Context and purpose of the study 

Vitis vinifera L. and other Vitis have high genetic variations for cultivars or varieties. Many countries carried out strong efforts creating new clones of varieties, mainly focusing on plants free of viruses and other grapevine diseases, but also on different agronomical and enological characteristics of the plants. The aim of this study was to evaluate six clones of Merlot in the traditional viticulture of southeastern Brazil, focusing on distinct characteristics of yield, enological potential of grapes and wine typicality, in order to improve wine quality.

Material and methods

Six Merlot clones grafted onto Paulsen 1103 rootstock were planted in 2018, and evaluated in two consecutive vegetative cycles (2021 and 2022), analyzing viticultural and enological parameters. The 2021 vintage was characterized as wet in the beginning and dry close to the harvest date; the 2022 vintage was dry in the beginning and very dry at the end. Vines were trained on vertical shoot positioning (VSP), trellised in bilateral cordons, with 1 m spacing between plants and 2.5 m between rows. The experimental design was a randomized block, with four replicates of twelve plants each per clone per treatment. French and Italian breeding programs developed the evaluated clones: INRA-ENTAV 181 (standard, already used in the region by many wineries), R12, VCR 1, VCR 101, ENTAV 348 and ENTAV 519. Viticultural parameters evaluated were days until budburst, days until flowering, days until maturation, days until harvest, total cycle, yield per vine, and yield per hectare, in both vintages, taking as reference the solstice day (June 21^st). From each experimental unit, two hundred berries were collected at harvest, to determine enological parameters and 20 kg of grapes per treatment were gathered for winemaking. Wines were elaborated in an experimental scale, according to classical protocols. After bottling, wines were analyzed to determine classical parameters and phenolic compounds. Results are shown as the mean of two vintages.

Results

Significant differences were observed for all clones, in all phenological stages, except for days of flowering, yield per vine and yield per hectare. The climatic condition was different and influenced all parameters, except in days for maturation. Clone Merlot R12 was the earliest to be harvested, at 167.6 days, followed by VCR1, ENTAV 519 and VCR101, ENTAV 348, and the last was clone ENTAV 181, at 176.0 days. Yield was not significantly different between clones, but vintage has a significant effect, with higher values observed in 2021. Grape composition varied in total soluble sugars, higher in clones ENTAV 181 and ENTAV 348, followed by other four clones. No differences were observed in pH and titratable acidity. Wines had significant differences in alcohol degree, total titratable acidity, color intensity, and total phenol index (TPI), while no differences were observed to the other parameters. Clones VCR1 and ENTAV 181 had the highest alcohol degree, while ENTAV 348, VCR1, and R12 had greater TPI. These results bring new alternatives for producers and wineries, showing the importance to choose between clones with different agronomical and enological characteristics, mainly increasing the harvest period, as well as the possibility to elaborate young or aging wines.