Thesis (MScAgric (Viticulture and Oenology))--University of Stellenbosach, 2010. / ENGLISH ABSTRACT: Cabernet Sauvignon, the most planted red wine cultivar in South Africa, is prone to vigorous
growth with low yields. The aim of the study was to describe how Cabernet Sauvignon
grapevines react to climate and irrigation within the Swartland region. Such knowledge would
assist growers in decisions regarding long term as well as short term cultivation practices. This
study was part of a larger project carried out by the Infruitec-Nietvoorbij institute of the
Agricultural Research Council at Stellenbosch to determine effects of soil type and climate on
yield and wine quality of Cabernet Sauvignon. The larger project was carried out in selected
grape growing regions, i.e. Stellenbosch, Swartland, Lower Olifants River and Lower Orange
River.
Due to the proximity to the Atlantic Ocean, the study area in the Swartland region could
be divided into two climatic regions for viticulture. Grapevines near Philadelphia closer to the
ocean experienced less water constraints compared to those further inland near Wellington.
Variation in stem water potential could also be related to soil water matric potential. Climate
tended to have a more pronounced effect on the grapevine response to water constraints
further inland than closer to the ocean. Vegetative growth, berry size and yield depended on
water constraints experienced by the grapevines. In the warmer climate, severe constraints
reduced yield.
In the warmer climate, grapes started to ripen earlier than those in the cooler climate.
Sugar concentration (mg/mL) was highest where grapevines experienced moderate water
constraints. These seemingly balanced grapevines had the highest sugar accumulation,
probably due to optimum photosynthesis and carbohydrate utilization. Low water constraints
increased vegetative growth which could have been a sink for sugar loading. In addition to
sugar loading, degree Balling (°B) increases could also have been due to a concentration effect
where water constraints reduced berry volume. Therefore, °B is probably not a representative
indicator of grapevine functioning.
Anthocyanin biosynthesis, as quantified on a per berry basis, showed that sugar and
anthocyanin could be co-regulated, with anthocyanin biosynthesis reaching a plateau when the
sugar content per berry reached 200 mg/mL to 220 mg/mL. At véraison, the most intense grape
colour occurred where grapevines experienced moderate water constraints, i.e. single drip line
at Wellington and no irrigation at Philadelphia. However, at harvest grapes from the cooler
climate tended to have more intense colour and higher phenolics, indicating that lower
temperatures favoured anthocyanin biosynthesis. These results supported earlier findings that
grapevine water status influences berry volume and dynamics of berry ripening.
Water constraints tended to increase sensorial wine colour intensity, as well as wine
fullness. Moderate water constraints at both localities resulted in the best sensorial wine quality.
Yet there were indications that too severe water constraints could be detrimental to wine quality. Irrigation can be used to manipulate grapevine growth in warmer climates, but might be less
effective in cooler climates. In warmer climates, moderate water constraints required to achieve
balanced grapevine functioning can be obtained with single drip irrigation, but this might not be
the case in cooler climates. / AFRIKAANSE OPSOMMING: Cabernet Sauvignon, die mees aangeplante rooiwynkultivar in Suid-Afrika, is geneig tot kragtige
groei met lae opbrengste. Die doelwit van hierdie studie was om te beskryf hoe Cabernet
Sauvignon-wingerdstokke reageer op klimaat en besproeiing in die Swartland-streek. Hierdie
kennis sal kwekers help wanneer hulle besluite moet neem oor langtermyn sowel as korttermyn
verbouingspraktyke. Hierdie studie was deel van ‘n groter projek deur die Infruitec-Nietvoorbij
Instituut van die Landbounavorsingsraad op Stellenbosch om die effekte van grondtipe en
klimaat op die opbrengs en wynkwaliteit van Cabernet Sauvignon te bepaal. Die groter projek is
in geselekteerde wingerdverbouingstreke uitgevoer, nl. Stellenbosch, Swartland, Benede
Olifantsrivier en Benede Oranjerivier.
As gevolg van die nabyheid daarvan aan die Atlantiese Oseaan kon die studiegebied in
die Swartland-streek in twee klimaatstreke vir wingerdbou verdeel word. Wingerdstokke by
Philadelphia, wat nader aan die oseaan is, het minder waterstremming ervaar as dié verder
binnelands naby Wellington. Veranderinge in stamwaterpotensiaal hou moontlik ook verband
met die grondwater- matrikspotensiaal. Klimaat het ‘n groter effek op die reaksie van die
wingerdstok op waterstremming verder binnelands as nader aan die oseaan. Vegetatiewe groei,
korrelgrootte en opbrengs was afhanklik van die waterstremminge wat deur die wingerdstokke
ervaar is. In die warmer klimaat het die ernstige stremminge opbrengs verminder.
In die warmer klimaat begin druiwe vroeër ryp word as in die koeler klimaat.
Suikerkonsentrasie (mg/ml) was die hoogste waar wingerde matige waterstremming ervaar het.
Hierdie skynbaar gebalanseerde wingerdstokke het die hoogste suikerakkumulasie vertoon,
moontlik as gevolg van optimum fotosintese en koolhidraatverbruik. Lae waterstremming het
vegetatiewe groei verhoog, wat ook ‘n vraagpunt vir suikerlading kon wees. Benewens
suikerlading kon verhogings in grade Balling (°B) ook moontlik aan ‘n konsentrasie-effek
toegeskryf word in terme waarvan waterstremming die korrelvolume verminder het. °B is dus
moontlik nie ‘n verteenwoordigende indikator van wingerdstokfunksionering nie.
Antosianienbiosintese, soos gekwantifiseer op ‘n per-korrel basis, het getoon dat suiker
en antosianien saam gereguleer kon word, en dat antosianienbiosintese ‘n plato bereik het
wanneer die suikerinhoud per korrel 200 mg/mL tot 220 mg/mL was. By deurslaan het die mees
intense druifkleur voorgekom waar die wingerdstokke matige waterstremming ervaar het, d.w.s.
enkel druplyn op Wellington en geen besproeiing op Philadelphia. Teen oes was die druiwe in
die koeler klimate egter geneig om meer intense kleur en meer fenole te bevat, wat aandui dat
laer temperature antosianienbiosintese bevoordeel. Hierdie resultate ondersteun vroeër
bevindings dat die waterstatus van die wingerdstok ‘n invloed op korrelvolume en die dinamika
van korrelrypwording het.
Waterstremming neig om die sensoriese wynkleurintensiteit te verhoog, asook die
volheid van die wyn. Matige waterstremming op beide liggings het aanleiding gegee tot die beste sensoriese wynkwaliteit. Tog was daar aanduidings dat waterstremming wat te straf was,
nadelig kon wees vir wynkwaliteit. Besproeiing kan gebruik word om wingerdgroei in warmer
klimate te manipuleer, maar is moontlik minder effektief in koeler klimate. In warmer klimate kan
die matige waterstremming wat benodig is vir gebalanseerde wingerdstokfunksionering, verkry
word deur enkel drupbesproeiing, maar dit is moontlik nie die geval in koeler klimate nie.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/5292 |
| Date | 23 November 2010 |
| Creators | Mehmel, Tara Olivia, Van Heerden, Tara Olivia |
| Contributors | Myburgh, P. A., Deloire, A. J., 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 |
| Format | 172 p. : ill. |
| Rights | University of Stellenbosch |
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