Abstract
Producing high-quality table grapes is becoming a challenge in the warmer area of the world due to the global increase in temperature, which negatively affects anthocyanin biosynthesis and other fruit quality attributes. Nanotechnology is a growing field that can be a very useful tool to improve crop productivity and sustainability. The red color is one of the major fruit quality parameters that determine table grape marketability. This study aimed to investigate the role of the zinc element in improving the marketable characteristics of Crimson seedless (Vitis vinifera L.) table grape berries i.e., color, firmness, total soluble solids and sugars; besides its role in activating PAL and SOD enzymatic systems. Additionally, this paper investigated the additive advantages of zinc when applied in nanometric form. Five concentrations of zinc oxide nanoparticles, ZnO NPs (0, 25, 50, 100 and 250 ppm), were compared to zinc oxide in mineral form at a concentration of 250 ppm to investigate their effects on the marketable characteristics of Crimson seedless grape cultivar. The treatments were applied as foliar spray on three-year-old Crimson seedless vines grafted on Richter 110 rootstock grown in one of the major table grape production area in Egypt. The experiment was arranged in completely randomized block design and each vine was sprayed with five letters of the solution. The use of the lowest concentration (25 ppm) of ZnO NPs achieved the highest significant enzyme activity (PAL and SOD). Moreover, the T.S.S, sugars and anthocyanin content in berries increased significantly in association of decreasing acidity. On the other hand, the use of a 50 ppm concentration led to an increase in fruit firmness. Collectively, our data showed that 25 ppm of zinc nanoparticles improved PAL and SOD enzymes activity, improved red coloration in table grape and was more effective than the 250 ppm zinc oxide mineral form.
Highlights
Crimson seedless (Vitis vinifera L.) grape cultivar is a late red cultivar and has excellent fruit qualities, good natural flavor, as well as strong and crispy berries [1]
The goal of this work was to evaluate the influence of Zinc Oxide Nanoparticles (ZnO NPs) as foliar spray on enzymatic activity and marketable characteristics including color, TSS, sugars and firmness of Crimson seedless table grape
Zinc oxide nanoparticles were synthesized by co-precipitation method at alkaline pH Plants 2021, 10, xuFsOiRngPEuErReRaEaVsIEaWstabilizing and reducing agent as previously described
Summary
Crimson seedless (Vitis vinifera L.) grape cultivar is a late red cultivar and has excellent fruit qualities, good natural flavor, as well as strong and crispy berries [1]. Under some warmer area, such as in Egypt, the cultivar shows a problem in inadequate coloring development of berries, which is one of the main fruit quality parameters [2] and a key factor in determining fruit marketability [3]. Anthocyanin pigment is responsible for Crimson seedless table grape berry coloration. This pigment is negatively affected by climate and differences between day and night temperature during the veraison stage [5] and it is affected by the low altitude [6,7]. Various reasons for inferior color development in table grapes have been reported for the conditions prevalent in Egypt, such as high temperature [8,9]) and vigorous growth with dense, shaded canopies [10,11]. The dynamics of anthocyanins and enzyme phenylalanine ammonia-lyase (PAL) activity suggested that PAL is an essential enzyme for their biosynthesis [12]
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