Browsing by Author "Samuels, Liam Jay"

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    Characterization of cv. Cabernet Sauvignon (Vitis vinifera L.): the contribution of Ecklonia maxima seaweed extract
    (Stellenbosch : Stellenbosch University, 2022-12) Samuels, Liam Jay; Blancquaert, Erna; Setati, Mathabatha Evodia; Stellenbosch University. Faculty of Agrisciences. Dept. of Viticulture and Oenology.
    ENGLISH ABSTRACT: Conventionally grape cultivation makes use of chemical fertilizers and synthetic pesticides to sustain growth and ensure fruit production ultimately resulting in more resistant grapevines to pests and diseases. However, their application also imposes a negative impact on human health and the environment. Therefore, agricultural sustainability is increasingly encouraged to ensure food safety and the conservation of the environment. In this regard viticulture is urgently seeking alternative solutions to increase sustainability. Biostimulants is a novel and sustainable tool which may be a good alternative to reduce the chemical-dependency typical of conventional cultivation practices, thereby supporting eco-friendly methods to increase agricultural outputs, via fruit quality, and resistance to abiotic stress. Biostimulants is the term given to a range of products, of natural origin, known to promote vegetative and reproductive growth as well as increase tolerance against biotic and abiotic stress. Seaweed extracts, a sub-category of biostimulants, have been highlighted as one of the most promising groups of biostimulants for use in viticulture. Commercial seaweed extract products are often derived from Ascophyllum nodosum (often located on the coasts of the North Atlantic), with studies on its effects on plant physiology being very popular and well-researched. The South African species, Ecklonia maxima, and its effects on wine grapes, is however under researched. The aim of this study was to evaluate the influence of Ecklonia maxima (EM) seaweed extract on vine physiology, grape and wine quality within in the South African viticultural context on Vitis vinifera L. Cabernet Sauvignon. Foliar applications of a commercial Ecklonia maxima seaweed extract biostimulant, under the trade name Kelpak ®, were conducted before flowering, at fruit set and at véraison under two irrigation scenarios ((i) irrigated and (ii) non-irrigated). Grapevine photosynthetic capacity, chlorophyll content and water status were not impacted by the application of Ecklonia maxima. Leaf area and fruit composition were positively impacted by the treatments. The combination of EM applications and irrigation resulted in significantly higher leaf area. Furthermore, the leaf area continuously increased throughout the season which is the first study to report this finding. The latter resulted in increased concentrations of sugars, organic acids, amino acids and phenolic content in grape berries. Surprisingly, the increased concentrations of the metabolites at harvest were not reflected in the wine parameters (final alcohol content (%), wine pH and total acidity and phenolic content) made in this study. This suggests that fermentation kinetics altered the extraction of these metabolites. Our findings correspond with that of the use of Ascophylum nodosum which resulted in increased fruit quality. The study was only conducted in one season and subsequent seasons should be conducted to have a clear understanding of the photosynthetic, water use, and metabolic pathways induced when using Ecklonia maxima. Furthermore, Ecklonia maxima should be used in conjunction with conventional farming to enhance grapevine functioning and fruit quality.