Effect of different viticultural techniques on the qualitative and quantitative characters of cv. Xinomavro under vineyard conditions in Naoussa

Abstract

In order to counteract the various effects of climate change on the physiology of the grapevine and on the quality of the grapes leading to the wine produced, many different approaches have been proposed. The aim of this study was to assess the effect of different cultivation techniques on the quantitative and qualitative characters of the grapes of cv Xinomavro, during the cultivation season 2019-2020. The experimental vineyard is located in Giannakochori, Naoussa (Greece), where the vines are trained in bilaterally cordon-trained (bilateral Royat) and plant density of 4000 vines/ha. The following viticultural techniques were evaluated on two different sub-plots of the vineyard: (i) the effect of two training systems (Lyre-shaped training system – bilateral Royat) on the southern side of the rows (vineyard orientation W-E), (ii) the effect of two planting densities (4000 and 10000 vines/ha). In all samples, the sugar content of the must was calculated using a refractometer, the active acidity (pH) using a pH meter and the total acidity using a sodium hydroxide solution (NaOH). Mechanical analysis of the grapes of all the samples under study was performed. The weight of thirty (30) berries, the weight of the grape and the length and width of the berries and the grapes of each sample were measured. The use of a spectrophotometer quantified the content of grape's skin in total anthocyanins, total phenolics, condensed tannins, total ortho-diphenols, total flavonoids, total flavanols, total flavonols and flavones and their antioxidant capacity with the use of FRAP and DPPH methods. The use of high-performance liquid chromatography (HPLC) identified the most important anthocyanins and acids found in grapes. The measurements in the grape seeds were made on the same compounds as the skins, except for total and individual anthocyanins. Differences in sugars and active acidity of the must as well as in phenolic compounds were observed during the various treatments. The training systems also exhibited differences: the grapes originating from the Lyre-shaped training system showed higher concentration of total soluble solids and tannins, while those originating from the bilateral Royat recorded higher pH. The right side of the vines, which was more exposed to higher temperatures (due to southern wind), recorded higher concentrations in most phenolic compounds. Planting density recorded differences in almost all measurements and especially in total and individual anthocyanins. Moreover, the results showed increased concentration in skin tannins, in total soluble solids, pH, and higher concentration of total phenolics and flavonoids, thus making the wine coming from these grapes ideal for maturing and ageing.