Effect of shading and ethephon on the anthocyanin composition of 'Crimson seedless' (Vitis vinifera L.)

[摘要] ENGLISH ABSTRACT: 'Crimson Seedless' is currently one of the most important and popular table grapecultivars produced in South Africa, and as such it is of great economic value for tablegrape producers. Major concerns with 'Crimson Seedless' is that it is prone toinadequate colouring, and with increased yields the berry size decreases. An additionaldifficulty is that methods used to increase berry size, further impede berry colouring. Aplant growth regulator (PGR) commonly used in table grape production, to enhancecolour formation, is ethephon (2-chloro-ethyl-phosphonic acid, 2-CEPA). In recent yearssignificant research has been done on the effect of sunlight on anthocyanin productionin grapes, although this has primarily been on wine grape cultivars. Currently, there islimited knowledge on the effect of sunlight on table grapes, and how this might influencetheir anthocyanin composition and content. The effect of ethephon on colour of grapesand other fruit have been extensively researched and well documented. However, theeffect of ethephon on the anthocyanin composition of 'Crimson Seedless' is not wellknown. The current study aimed to explore the effect of sunlight (by matter of exclusion)and management practices, namely defoliation and ethephon application, on theanthocyanin profile and content of 'Crimson Seedless'. Four different treatments wereapplied to two 'Crimson Seedless' vineyards, the first site located in Paarl, and thesecond in De Doorns. The treatments were: 1. Naturally exposed bunches, 2. Exposedbunches treated with ethephon, 3. Bunches kept in shade boxes, 4. Shaded bunchestreated with ethephon. At the De Doorns site an additional defoliation treatment wassuperimposed over the above treatments. An HPLC technique was modified for theseparation and detailed profiling of 'Crimson Seedless' anthocyanins and was used toanalyse the effect of the reported treatments on the anthocyanin profile of berry skins.The predominant anthocyanin in 'Crimson Seedless' is peonidin-3-glucoside (Pn-gluc),and this was found to be significantly increased only by ethephon application, and wasnot altered by sunlight or leaf removal. The responses of the other anthocyanin typesvaried according to the respective treatments applied. However, a general observationwas that ethephon application more consistently increased the concentration ofanthocyanins in berry skins than did sunlight. Leaf removal had the least significanteffect on anthocyanin concentration.

[发布机构] Stellenbosch University