Abstract
ABSTRACT ‘Rubi’ table grape has wide acceptance of the consumer market due to its affordable price and attractive color as a function of the accumulation of anthocyanins. However, environmental conditions do not always favor the suitable accumulation of these pigments, resulting in commercial devaluation and nutritional depreciation of fruits. Thus, the present study aimed to investigate the effect of application of different ethephon concentrations, associated or not with CaCl2 application, on the skin color and quality of ‘Rubi’ grape berries. First, specific traits of berries treated with 0, 200, 400, 600, 800 mg L-1 ethephon associated with 1.5% CaCl2 solution were evaluated and pH, titratable acidity (TA), soluble solids (SS), berry firmness, total and reducing soluble sugars, and anthocyanin and flavonol levels were analyzed. This first stage of evaluation revealed no changes in total sugar levels, firmness, SS, TA, SS/TA ratio, and flavonol levels, while changes were detected regarding reducing sugar and anthocyanin levels. Thus, in the second stage, the following variables were evaluated: SS, TA, reducing sugar levels, anthocyanin levels, phenylalanine ammonia lyase (PAL) and glutathione S-transferase (GST) activity of ‘Rubi’ grape berries treated with 0, 200, 400, 600, 800 mg L-1 ethephon, associated or not with 1.5% CaCl2 solution. The results of the present study indicate that ethephon associated with CaCl2 can contribute to improve the post-harvest quality of ‘Rubi’ grape, since this association increased the accumulation of anthocyanins due to the higher activity of PAL and GST, related to biosynthesis and storage of antocyanins, respectively, and increased the levels of reducing sugars (at low ethephon concentrations), not changing other quality aspects. Therefore, a single ethephon application from 200 mg L-1 associated with the application of 1.5% CaCl2 at the final ripening stage, when bunches present from 30 to 50% skin color coverage, was sufficient to produce satisfactory results regarding skin color improvement of ‘Rubi’ grape berries.
Highlights
The Brazilian grape industry is concentrated in a few regions, being especially important in the state of Rio Grande do Sul, in the ‘Serra Gaúcha’ region, where almost the entire production is for processing, and it is essentially produced by smallholder family farmers
Among the varieties of table grapes, ‘Rubi’ (Vitis vinifera L.) has wide acceptance of the consumer market due to its affordable price and attractive color, since its commercial quality is firstly attributed to its typical red color (HIRATSUKA et al, 2001; LI et al, 2002)
There were no changes in the levels of total sugars, firmness, SS, titratable acidity (TA), SS/TA ratio, and flavonols (Table 1)
Summary
The Brazilian grape industry is concentrated in a few regions, being especially important in the state of Rio Grande do Sul, in the ‘Serra Gaúcha’ region, where almost the entire production is for processing, and it is essentially produced by smallholder family farmers. Anthocyanins are pigments responsible for such reddish color (ROBERTO et al, 2012; YAMAMOTO et al, 2015). They belong to the class of flavonoids and play an important ecological role in several plant species, attracting pollinators to flowers, seed dispersers in fruits, in addition to their synthesis in several other plant organs in response to stresses like prolonged exposure to UV light (KOYAMA et al, 2014). Anthocyanins may exhibit anticancer, anti-inflammatory, antioxidant, pharmacological, and chemoprotective effects (MIAO et al, 2016)
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