Abstract
In viticulture, various techniques can be used to improve productivity, tolerance to biotic or abiotic stress, the quality of grapes and wines such as the use of plant regulators and biostimulants. Thus, the objective of this work was to evaluate the effect of application of abscisic acid (S-ABA),Ascophyllum nodosum (A. nodosum)seaweed extract andAloe vera (A. vera)gel on phenolic composition and chromatic characteristics of grapes from the 'Cabernet Sauvignon' variety. The experiment was conducted in a commercial vineyard in Campo Largo - Paraná, in two consecutive seasons, 2017/18 and 2018/19, involving the following treatments: 1) control; 2) (S-ABA) 400 mg/L; 3) S- ABA 600 mg/L; 4)A. veragel 200 mL/L; 5)A. veragel 400 mL/L; 6) seaweed extract 0.2 mL/L; 7) seaweed extract 0.4 mL/L. Two applications were performed with the seaweed extract andA.gel when the bunches were atveraisonstage (50 and 75% of grape berries with coloration). Total anthocyanins content, total polyphenols content and activity of phenylalanine ammonia-lyase (PAL), polyphenoloxidase and peroxidase enzymes were assessed in the berries skin. Total anthocyanins, individual anthocyanins and total polyphenol contents as well as lightness, chroma and hue angle were analyzed in the corresponding wines. S-ABA increased the content of anthocyanins and total polyphenols, as well as the activity of PAL in the first season.A. nodosum(AN) seaweed extract increased the total polyphenol content, total anthocyanins content and PAL in the berry skin of 'Cabernet Sauvignon' variety. S-ABA increased the total polyphenol content and anthocyanins in wine, as well as theA. nodosum, in at least one of the evaluated seasons.
Highlights
The color of red grapes’ skin results from the synthesis of anthocyanins and degradation of chlorophyll (Deng et al, 2019)
The ABA600 (S-ABA 600 mg/L) treatment was significantly higher than the others for the total anthocyanins content in the first season (2017/18), while the two tested doses of A. nodosum (AN02 0.2 mL/L; AN04 0.4 mL/L) were higher than the other treatments in the second season (2018/19)
The AV400 treatment obtained the highest value for phenylalanine ammonia-lyase (PAL) activity in the first season, followed by AV200 (A. vera 200 mL/L) treatment and the doses of A. nodosum, differing statistically from the other treatments
Summary
The color of red grapes’ skin results from the synthesis of anthocyanins and degradation of chlorophyll (Deng et al, 2019). Anthocyanins are water-soluble flavonoid compounds, and their concentration and diversity determine the intensity and stability of color in both grape berries and wines (Sun et al, 2019). Seaweed-based extracts have been used as a sustainable tool to improve plant abiotic stress tolerance and increase fruit quality (Calvo et al, 2014; Santaniello et al, 2017), in particular the biosynthesis of flavonoids (Cai et al, 2012; Fan et al, 2014; Santaniello et al, 2017). Studies on the effect of these extracts on secondary metabolism compounds, fundamental to grape and wine quality, are still scarce. Salvi et al (2019) tested the application of Ascophyllum nodosum (AN) in ‘Sangiovese’ variety, and the results indicated that the seaweed extract improved the ecophysiological characteristics, as well as increased the content of total sugars and polyphenols in dry and hot years
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