Thesis (MScAgric (Viticulture and Oenology)--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: ‘Crimson Seedless’ is currently one of the most important and popular table grape
cultivars produced in South Africa, and as such it is of great economic value for table
grape producers. Major concerns with ‘Crimson Seedless’ is that it is prone to
inadequate colouring, and with increased yields the berry size decreases. An additional
difficulty is that methods used to increase berry size, further impede berry colouring. A
plant growth regulator (PGR) commonly used in table grape production, to enhance
colour formation, is ethephon (2-chloro-ethyl-phosphonic acid, 2-CEPA). In recent years
significant research has been done on the effect of sunlight on anthocyanin production
in grapes, although this has primarily been on wine grape cultivars. Currently, there is
limited knowledge on the effect of sunlight on table grapes, and how this might influence
their anthocyanin composition and content. The effect of ethephon on colour of grapes
and other fruit have been extensively researched and well documented. However, the
effect of ethephon on the anthocyanin composition of ‘Crimson Seedless’ is not well
known. The current study aimed to explore the effect of sunlight (by matter of exclusion)
and management practices, namely defoliation and ethephon application, on the
anthocyanin profile and content of ‘Crimson Seedless’. Four different treatments were
applied to two ‘Crimson Seedless’ vineyards, the first site located in Paarl, and the
second in De Doorns. The treatments were: 1. Naturally exposed bunches, 2. Exposed
bunches treated with ethephon, 3. Bunches kept in shade boxes, 4. Shaded bunches
treated with ethephon. At the De Doorns site an additional defoliation treatment was
superimposed over the above treatments. An HPLC technique was modified for the
separation and detailed profiling of ‘Crimson Seedless’ anthocyanins and was used to
analyse 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 was
not altered by sunlight or leaf removal. The responses of the other anthocyanin types
varied according to the respective treatments applied. However, a general observation
was that ethephon application more consistently increased the concentration of
anthocyanins in berry skins than did sunlight. Leaf removal had the least significant
effect on anthocyanin concentration. / AFRIKAANSE OPSOMMIMG: ‘Crimson Seedless’ is tans een van die belangrikste en gewildste tafeldruif cultivars wat
in Suid-Afrika verbou word en daarom is dit van groot ekonomiese waarde vir tafeldruifprodusente.
‘Crimson Seedless’ is egter daarvoor bekend dat dit te swak kleur (volgens
uitvoer spesifikasies) en tweedens is die cultivar geneig om kleiner korrels te ontwikkel
wanneer die oeslading vermeerder word. ‘n Addisionele probleem is dat die praktyke
wat in die industrie gebruik word om korrels te vergroot ‘n verdere negatiewe impak op
‘Crimson Seedless’ se kleur ontwikkeling kan veroorsaak. Die plant-groei-reguleerder
wat algemeen in tafeldruif verbouing gebruik word, ten einde beter gekleurde druiwe te
produseer, is ethephon (2-chloro-ethyl-phosphonic acid, 2-CEPA). In die laaste paar
jaar was daar baie navorsing gedoen oor die effek wat sonlig het op die antosianien
produksie van druiwe, maar navorsing was gefokus op wyndruif cultivars. Huidiglik is
daar beperkte tegniese kennis oor die effek wat sonlig op tafeldruiwe het, en hoe dit
moontlik die antosianien samestelling en inhoud kan beïnvloed. Daar is ook reeds
verskeie studies gedoen en data gepubliseer oor die invloed wat ethephon op die kleur
het van druiwe en ander vrugte, maar die invloed wat ethephon op die antosianien
samestelling van ‘Crimson Seedless’ het, is nie wel bekend nie. Die doel van hierdie
studie was om die effek van sonlig (deur uitsluiting) en bestuurspraktyke
(blaarverwydering en ethephon toediening) te bestudeer en hoe dit die antosianien
samestelling van ‘Crimson Seedless’ beïnvloed. Vier verskillende behandelings is
toegedien in twee ‘Crimson Seedless’ wingerde, die eerste proefperseel in die Paarl en
die tweede proefperseel in De Doorns. Die behandelings was: 1. Natuurlik blootgestelde
trosse, 2. blootgestelde trosse met ethephon, 3. Trosse met skadubokse omhul, 4.
Skaduboks trosse met ethephon. By De Doorns is ‘n addisionele blaarverwydering proef
bygebring. ‘n HPLC tegniek was aangepas om die antosianien samestelling en inhoud
van ‘Crimson Seedless’ te bepaal, en om die effek van die behandelings te ondersoek.
Die HPLC data het getoon dat peonodien-3-glukosied (Pn-gluc) die primêre antosianien
in ‘Crimson Seedless’ is met die hoogste inhoud van al die antosianiene. Pn-gluc was
betekenisvol beïnvloed deur ethephon toediening, terwyl die ander behandelings geen
betekenisvolle effekte daarop gehad het nie. Die effekte wat die ander antosianiene
gehad het, het gevarieer volgens die behandelings wat toegedien was. ‘n Algemene
observasie was dat ethephon toediening die antosianien konsentrasie in ‘Crimson
Seedless’ druiwe skille meer konsekwent vermeerder het as die sonlig blootstelling. Die
blaarverwydering het die minste betekenisvolle effek op die antosianien inhoud van
‘Crimson Seedless’ gehad.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/5337 |
| Date | 12 1900 |
| Creators | Human, Michael Adriaan |
| Contributors | Bindon, K. A., University of Stellenbosch. Faculty of Agrisciences. Dept. of Viticulture and Oenology. |
| Publisher | Stellenbosch : University of Stellenbosch |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | Unknown |
| Type | Thesis |
| Format | 95 p. : ill. |
| Rights | University of Stellenbosch |
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