Copies of author's previously published articles inserted. Bibliography: leaves 143-167. Temperature may affect fruit-set in grapevines through its effect on the development of the flowers up to flower opening and on pollination, be it on the germination of the pollen and the growth of the pollen tube, or on the post-fertilisation growth of the ovule.

Copies of author's previously published articles inserted. / Bibliography: leaves 143-167. / xvi, 176 leaves, [17] leaves of plates : ill. (chiefly col.) ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Temperature may affect fruit-set in grapevines through its effect on the development of the flowers up to flower opening and on pollination, be it on the germination of the pollen and the growth of the pollen tube, or on the post-fertilisation growth of the ovule. / Thesis (Ph.D.)--University of Adelaide, Dept. of Horticulture, Viticulture and Oenology, 1996

Thesis (PhD(Agric))--Stellenbosch University, 2012 / ENGLISH ABSTRACT: Field spectroscopy was used to study leaf composition and selected factors (including canopy growth manipulation and water status changes) that may impact on it in a Vitis vinifera cv. Shiraz vineyard, showing considerable variability in vigour. Temporal and spatial variability in leaf composition were incorporated into measurements by analysing leaves in different shoot positions and at different developmental stages during three different growing seasons. Irrigation and canopy manipulation treatments were also imposed in order to provide new insights into assessing the grapevine leaf and possibly also the canopy growth and ageing dynamics as well as pigment content, as a basis of executing a generally non-destructive measurement approach. Despite large climatic differences between the seasons, canopy size seemed of crucial importance in determining grapevine water relations in the grapevines from the different canopy manipulation treatments. Drastic compensation effects in terms of secondary shoot growth also followed the canopy reduction treatment. Despite this, canopy microclimate was apparently improved, considering the results from light measurements as well as the ripening dynamics in the reduced canopies. Reduced canopies also seemed to display a different canopy composition, in favour of secondary growth. This could have impacted positively on water use efficiency as well as ripening, due to higher photosynthetic efficiency of these leaves during the ripening stages. The reduced canopy treatments offered the possibility of attaining technological ripeness at an earlier stage and at comparatively lower potential alcohol levels. This study illustrated the relevance of considering the vegetative development of the grapevine, along with leaf ageing in the canopy, when conducting calibrated non-destructive measurements of leaf pigments, structure and water content. The relevance of using multivariate techniques in leaf spectroscopy was shown. This can be applied and simplified to aid in non-destructive leaf pigment, structure and water content estimation in future studies. Even with the general variation encountered in this vineyard, predictions of the major pigments in grapevine leaves were within acceptable error margins. Further work is required to improve the modelling of xanthophylls, which may require non-linear multivariate techniques. Logistical shoot growth modelling was used in leaf age estimation and classification, which made it possible to simplify statistical analysis of the leaf parameters mentioned. Practical application of the modelled and predicted parameters was shown for a specific period in season two by comparing the reaction of different treatments to developing water deficits. The results indicated that several parameters, with special mention of the carotenoid:chlorophyll ratio and chlorophyll a:b ratio, can be monitored on young and old leaves in the canopy in order to monitor developing water deficit stress. The modelled parameters, however, did not seem to be sensitive enough to allow specific prediction of predawn leaf water potential values. Specific leaf mass, equivalent water thickness, total specific leaf mass as well as leaf chronological age were successfully predicted from leaf spectral absorbance data, and this may be useful in future work on quantifying leaf adaptation to the micro-environment within the canopy. / AFRIKAANSE OPSOMMING: Veldspektroskopie is gebruik om blaarsamestelling en spesifieke faktore (insluitend lowergroei manipulasie en waterstatus veranderinge) wat ‘n impak kan hê in ‘n Vitis vinifera cv. Shiraz wingerd, met beduidende variasie in groeikrag, te ondersoek. Ruimtelike, asook tydsgebonde, variasie in blaarsamestelling is geïnkorporeer in die metings deur blare van verskillende lootposisies en vir verskillende ontwikkelingstadia gedurende drie verskillende groeiseisoene te meet. Besproeiings- en lowermanipulasie behandelings is ook uitgevoer om die dinamiek van blaar- en lowergroei, veroudering, asook pigmentinhoud te bestudeer binne die konteks van die uitvoering van ‘n nie-destruktiewe meetstrategie. Ondanks groot klimaatsverskille tussen die seisoene, blyk lowergrootteverskille belangrik te wees in die bepaling van wingerdstok-waterverhoudings in die verskillende lowermanipulasie behandelings. Drastiese kompensasiereaksies ten opsigte van sylootgroei is waargeneem in reaksie op die gereduseerde lowerbehandeling. Indien die resultate van ligmetings en druifrypwording in die gereduseerde lowerbehandeling in ag geneem word, is lowermikroklimaat egter steeds verbeter. Hierdie behandeling het oënskynlik ook veranderde lowersamestelling gehad, tot voordeel van sylootgroei. Dit kon moontlik ‘n positiewe invloed gehad het op waterverbruikseffektiwiteit asook druifrypwording, as gevolg van moontlike hoër fotosintetiese effektiwiteit van die blare gedurende die rypwordingstadia. Die gereduseerde lowerbehandeling het die moontlikheid gebied om tegnologiese rypheid by ‘n vroeër datum te bereik, met moontlike laer alkoholvlakke in die wyn. Hierdie studie het die belangrikheid beklemtoon om die vegetatiewe ontwikkeling van die wingerdstok in ag te neem wanneer gekalibreerde nie-destruktiewe metings van blaarpigmente, blaarstruktuur asook waterinhoud onderneem word. Die belang van multi-variant meettegnieke in blaarspektroskopie is aangetoon. Dit kan verder vereenvoudig word ter ondersteuning van niedestruktiewe meting van blaarpigment, -struktuur en -waterinhoudsbepaling in toekomstige studies. Selfs met die variasie wat in die wingerd voorgekom het, was die voorspellings van die vlakke van die belangrikste pigmente wat in wingerdblare aangetref word binne aanvaanbare foutgrense. Opvolgwerk is nodig om die modellering van xanthofil te verbeter, aangesien dit moontlik nielineêre multi-variant analise mag benodig. Logistiese groeimodellering is gebruik om blaarouderdom te bepaal en te klassifiseer, wat dit moontlik gemaak het om statistiese analise te vereenvoudig vir die genoemde blaarparameters. Die praktiese toepassing van die gemodelleerde en voorspelde parameters is aangetoon vir ‘n spesifieke gedeelte in seisoen twee, deur die reaksie van verskillende behandelings op toenemende watertekorte te bestudeer. Resultate het aangetoon dat verskeie parameters, met spesifieke klem op die karotenoïed:chlorofil verhouding, asook die chlorofil a:b verhouding, gemoniteer kan word op jong en ouer blare in die lower ten einde ontwikkelende waterstrestoestande te identifiseer. Die gemodelleerde parameters was egter klaarblyklik nie sensitief genoeg vir akkurate voorspelling van voorsonsopkoms-waterpotensiaalvlakke nie. Spesifieke blaarmassa, ekwivalente waterdikte, totale spesifieke blaarmassa, sowel as blaarouderdom kon suksesvol voorspel word deur gebruik te maak van absorpsieblaarspektroskopie, wat nuttig kan wees in toekomstige studies wat handel oor die kwantifisering van blaaraanpassing by die mikro-omgewing binne ‘n wingerdlower.

Thesis (MscAgric (Viticulture and Oenology))--University of Stellenbosch, 2007. / A common phenomenon in most South African vineyards, especially in the Western Cape region, is that of within vineyard variation. This variation phenomenon is caused by an array of controllable and non-controllable factors that interact with each other to affect vine vigour. Controllable factors can be managed by the grape grower, while the non-controllable factors have to be managed in the planning process in order not to negatively affect productivity or product quality. The main goal of any grape grower is to optimise vine performance in an attempt to achieve the best possible yield while at the same time allowing vines to optimally ripen grapes towards optimal wine quality. A grape grower has to use every possible means and technique available to him in order to manage his vineyards in such a manner as to achieve this goal. In the past, it was difficult to visualize the extent and distribution of vigour variation in vineyards, but with modern technological improvements in the field of remote sensing, grape growers are able to identify and specify different vigour levels within a vineyard. When remote sensing is applied in a vineyard, the grape grower can identify certain areas that may need more specific attention than others. Consequently, managerial decisions based on detailed information can be made in an attempt to improve the general condition and performance of a vine. Not only can the acquired information be used to plan managerial actions throughout the season, but it can also be used to plan and devise harvest strategies. Some areas in a vineyard may be at a certain point in the ripening process and need to be harvested, while grapes from other areas still need to develop the wanted flavours. One managerial action applied at véraison by some grape growers, is that of crop thinning. Different vigour areas can now be subjected to various crop thinning actions in an attempt to determine the best crop load for a vigour level. With this in mind, two studies were launched to firstly investigate the interaction between vine vigour and harvest dates; and secondly to investigate the interaction between vine vigour and crop load and how their combined interaction might influence a vine’s characteristics, grape composition and wine quality. Vigour variation was firstly identified through multispectral aerial imagery, and then visually verified by visits to the experimental vineyards. The multispectral aerial image was then “orthorectified” in order to produce a classified multispectral image. The image was classified through different colour codes that were assigned to the different vigour levels to clearly distinguish between them. A series of vegetative and reproductive measurements were conducted to try and establish if any correlations could be obtained of the interaction between vine vigour, different harvest dates and crop loads. In order to verify differences in vine vigour, underlying causes were also determined through soil analyses of which chemical analysis, bulk density, porosity, as well as root penetration and distribution were determined. Vegetative measurements that were conducted for both studies indicated good correlations between the different vigour levels and the image classifications. The results also identified the effect that topping (mechanical or manual) had on the main and lateral leaf areas. Reproductive measurements throughout the season, in the form of berry sampling, showed changes in berry composition and accentuated the effects of the different treatments, which could also be confirmed through sensorial analysis of the wines. The results also emphasized the need to not only make use of one of two chemical parameters to identify grape ripeness, but to incorporate a number of parameters, such as sugar, pH and acid levels. From the varying grape chemical characteristics, a wine style can be identified that might carry the approval of the winemaker for the production of a specific type of wine. Soil studies of both vineyards also gave important evidence for the causes of vigour variation. The data collected will hopefully provide grape growers with information that will enable them to make educated decisions concerning grape production and how vigour, in conjunction with different harvest dates and crop loads, will enable them to produce fruit of good quality and, so doing, improve their financial position.

Thesis (MScAgric (Viticulture and Oenology))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: Grapevine water status is considered to be the most important factor limiting plant growth and production in the Mediterranean zones. In these regions with limited summer rainfall and limited water resources for irrigation grapevines may experience water deficits for an extended period of time. The demand of water for agriculture is constantly increasing, and will continue to do so due to the rise in the world population and to the effects of climate change on rainfall and evaporative demand in these regions. The Western Cape wine region is also classified as Mediterranean and grapevines grown in this region are often exposed to water “stress” conditions due to high evaporative demand and low water availability in the soil. Plant water status of grapevines may dependent on, amongst other factors, the water potential of soil layers close to the root system, canopy size and evaporative demand. The canopy size of a grapevine can inherently be seen as a measure of grapevine vigour, and vigour variation among grapevines within a vineyard is a common phenomenon in the Western Cape. The importance of the contributions from several factors causing vigour variation within vineyards is still a subject of debate. This may be largely ascribed to the significant amount of variability in vineyards that researchers have to deal with during viticultural studies. However, the recent advances in remote sensing technology have established new methods to assess grapevine vigour variability. In the face of the recognized variation within vineyards and the importance of a sustained grapevine water status, for wine grape productivity and -quality, it is alarming to think that a vineyard block is generally managed as a homogeneous entity when it comes to irrigation scheduling. What is more alarming is the assumption that grape, juice and wine quality will be homogeneous throughout a vineyard block – even without irrigation. With this in mind, a study was conducted to study the interaction between grapevine vigour and grapevine water status within a commercial vineyard with variable vigour by implementing various irrigation regimes. Vigour variation was identified through multispectral aerial imagery and plant-based water status determinants were used to assess grapevine water status in plots of differing vigour within the vineyard. Soil water status was also assessed, and vegetative growth quantified to ultimately determine the variability in vigour and its possible contribution to the variability through the water status of the plant. Reproductive growth was monitored continually before evaluating the effect of water status and grapevine vigour on grape composition and subsequent wine quality. The various methods used to evaluate grapevine vigour showed good correspondence. Pruning mass measured at the end of the season confirmed leaf area measurement (main leaves and lateral leaves) during vegetative growth, and corresponded well, in terms of main vigour classifications with the NDVI images collected. Berry weight and volume responded to the various classifications, with a decrease in water deficits from one classification to the next accompanying an increase in berry weight and volume. Analyses of the berry composition and wines showed statistically significant differences between the classifications. This was found for sugar content per berry, total phenols, total red pigment, malic acid, nitrogen and pH for the grape juice analyses. Wine pH and total acidity also differed significantly. / AFRIKAANSE OPSOMMING: In die Mediterreense sones word plantwaterstatus beskou as `n hooffaktor wat groei en produksie van `n wingerdstok negatief beinvloed. In hierdie sones kan wingerdstokke vir lang periodes `n tekort aan water ervaar a.g.v `n tekort aan reënwater gedurende die somer en lae beskikbaarheid van besproeingswater. Die vraag na water vir landbou is ook konstant besig om toe te neem in dié sones en die tendens sal voorduur a.g.v die groei in die wêreldbevolking, die effek van klimaatsveranderig op reënvalpatrone en die hoë verdampingsfaktor. Die wingerd- en wynstreek van die Wes-Kaap word ook geklassifiseer as Mediterreens en wingerdstokke in hierdie streek ervaar dikwels waterspanning wat deur hoë evapotranspirasie en min beskikbare grondwater veroorsaak word. Van die faktore wat die waterstatus van `n wingerdstok bepaal is onder andere die waterpotensiaal van die grondlae rondom die wortelstelsel, die grootte van die wingerdlowerraamwerk en die evapotranspirasiebehoefte. Die omvang van `n wingerdstok se lower binne die prieel word beskou as `n aanduiding van wingerdstokgroeikrag en variasie in groeikrag tussen wingerdstokke is `n algemene verskynsel in die Wes-Kaap. Die rangorde, wat die effek van die verskeie faktore wat groeikragvariasie tussen wingerdstokke bepaal, word steeds gedebatteer. Die debat kan groottendeels toegeskryf word aan die beduidende hoeveelheid variasie tussen wingerde waarmee navorsers te doen kry in wingerdkundige studies. Hoewel, met onlangse vordering aangaande afstandswaarnemingstegnologie is daar nou nuwe metodes beskikbaar om wingerdgroeikrag te evalueer. Dit is kommerwekend om te dink dat `n wyndruifwingerd normaalweg as `n homogene eenheid bestuur word as dit kom by besproeiing. Veral met die wete dat groeikragvariasie tussen wingerde algemeen erken en aangeteken word, en dat volhoubare waterstatus van `n wingerdstok van kardinale belang is vir produksie en kwaliteit van wyndruiwe. Die aanname dat wyndruiwe, die sap- en ook wynkwaliteit homogeen sal wees regdeur `n wingerdblok is egter meer kommerwekkend. Na aanvang van dié denke is daar `n studie geloods om die interaksie tussen wingerdstokgroeikrag en wingerdstokwaterstatus te evalueer. Met die studie is verskeie besproeiingsregimes aangebring binne `n kommersiële wingerd wat interne groeikragvariasie tentoonstel. Groeikragvariasie was geïdentifiseer deur middel van multispektrale lugfotos terwyl die wingerdstok se waterstatus geëvalueer is met behulp van plantgebaseerde metings in die verskillende groeikragareas. Die waterstatus van die grond is geëvalueer tesame met die vegetatiewe groei van die wingerd sodat die groeikragvariasie en die invloed van die plantwaterstatus op die groeikrag bepaal kon word. Die reproduktiewe groei is deurlopend gemonitor voor die effek van wingerdstokwaterstatus en wingerdstokgroeikrag op druifsamestelling en wynkwaliteit bepaal is. Daar was `n goeie ooreenkoms tussen die verskeie metodes wat gebruik is om wingerdgroeikrag te bepaal. Snoeimassa aan die einde van die seisoen was ooreenkomstig met die blaaroppervakte (hooflootblare en sylootblare) wat tydens vegetatiewe groei gemeet is, en het ook goed korreleer, met die multispektrale lugfotos se hoof groeikragklassifikasie. Korrelgewig en -volume het reageer op die verskeie besproeiingsregimes, en daar was `n toename in korrelgewig en -volume saam met die afname in watertekort van een regime tot `n ander. Daar was beduidende verskille tussen die verskeie klassifikasies t.o.v. korrelsamestelling analise en wynevaluasie. Die suikerinhoud per korrel, totale fenole, totale rooi pigment, appelsuur, stikstof en pH het verskil in druiwesap analises. Die pH en suur van die wyne het ook beduidend verskil.

Thesis (MScAgric)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: Phenolic compounds are important quality indicators of a red wine, as they can contribute to the colour of a young red wine, colour stability during ageing as well as astringency, bitterness, body and overall mouthfeel properties. Wine composition is commonly influenced by winemaking and viticultural practices. In South Africa it often happens that vines are excessively vigorous, resulting in canopies that are too dense, which in turn could have a negative effect on the quantity and quality of the grapes produced. Viticultural practices such as judicious canopy management and irrigation are designed to control vine vigour and yield, thus improving fruit ripening and colour development. Artificial shading and water deficit have been reported to have an influence on the sensory properties of red wine as well as on the flavonoid composition. These effects are dependent on a number of factors, however, including the season, cultivar, light intensity, and the extent and timing of water deficit. There is limited research on the possible interactive effects of grapevine water deficits and canopy manipulation on grape and wine flavonoid composition in Shiraz, as well as the relationships between berry and wine composition. We thus investigated the effect of canopy reduction in combination with water deficit on the phenolic and colour composition of Shiraz grapes at different levels of ripeness, and in their corresponding wines after alcoholic and malolactic fermentation as well as after six months’ ageing. This study found that it is possible to improve the phenolic composition of grapes and wine by shoot removal, and some of the tendencies in the wines were also observed after the ageing period. If the shoot removal is not performed at a very early stage, sunburn damage can occur and this will result in berries with a lower mass and volume at harvest due to excessive exposure without the berry having adapted to the imposed conditions. Harvesting at different ripeness levels also affected the chemical and phenolic composition of the grapes and resulting wines. The water deficit effect on most phenolic parameters measured in the grapes and wine was not as prominent as that of the canopy manipulation treatment. This study improved our understanding of how an improvement in the canopy microclimate of Shiraz could be reflected in the phenolic composition of wines, along with a potentially important effect of harvesting date. On this basis it may be possible to attain a specific wine style. Harvesting at a ripe stage, for example, could result in the production of wines with higher colour density and astringency, while unripe grapes could result in wines with higher levels of perceivable fresh berry attributes. In particular, canopy reduction could increase the astringency and body of wines made from grapes subjected to water deficit. / AFRIKAANSE OPSOMMING: Fenoliese verbindings is belangrike kwaliteitsparameters van rooiwyn, aangesien dit kan bydra tot die kleur van ‘n rooiwyn, kleurstabiliteit tydens veroudering sowel as frankheid, bitterigheid en mondgevoel. ‘n Wyn se fenoliese samestelling word algemeen bepaal deur wynmaak- en wingerdkundige praktyke. In Suid-Afrika gebeur dit gereeld dat wingerde uitermatig groeikragtig is, wat lei tot te digte lower wat sodoende ‘n negatiewe effek op kwantiteit en kwaliteit van die druiwe wat geproduseer word, het. Wingerdkundige praktyke soos oordeelkundige lowerbestuur en besproeiing is ontwerp om wingerdstokke se groeikrag en opbrengs te beheer, en sodoende vrugrypwording en kleurontwikkeling te verbeter. Kunsmatige beskaduwing en waterstres is gerapporteer om ‘n invloed te hê op die sensoriese eienskappe van rooiwyn sowel as op die flavonoïedsamestelling. Hierdie effekte is egter afhanklik van ‘n verskeidenheid faktore, insluitende die seisoen, kultivar, ligintensiteit en die mate en tyd van waterstres toegepas. Daar is beperkte navorsing op die moontlike interaktiewe effekte van waterstres en lowermanipulasie op die druif en wyn flavonoïedsamestelling in Shiraz, sowel as die verhoudings tussen druif en wyn samestelling. Ons het dus die effekte van lowerbestuur in kombinasie met waterstres op die fenoliese en kleursamestelling van Shiraz druiwe by verskillende rypheidsvlakke ondersoek, asook in hul ooreenstemmende wyne na alkoholieseen appelmelksuurfermentasie sowel as na ses maande veroudering. Hierdie studie het gevind dat dit moontlik is om die fenoliese samestelling van druiwe en wyn deur lootverwydering te verbeter, en sommige van die tendense is ook waargeneem in die wyn na die verouderingsperiode. Indien lootverwydering nie toegepas word by ‘n baie vroeë stadium nie, kan sonbrand voorkom en dit kan lei tot korrels met ‘n laer massa en volume by oes as gevolg van oormatige blootstelling sonder dat die korrel aangepas het by die spesifieke kondisies. Oes by verskillende rypheidsvlakke affekteer ook die chemiese en fenoliese samestelling van die druiwe en ooreenstemmende wyne. Die waterstreseffek op meeste van die fenoliese parameters gemeet in druiwe en wyn was nie so prominent soos dié van die lowermanipulasie behandeling nie. Hierdie studie het ons begrip verbeter van hoe ‘n verbetering van die lower mikroklimaat van Shiraz gereflekteer kan word op die fenoliese samestelling van die wyn, saam met ‘n potensiële belangrike effek van oesdatum. Op grond van hierdie basis is dit dus moontlik om ‘n spesifieke wynstyl te verkry. Oes by ‘n ryp stadium, byvoorbeeld, kan die produksie van wyn met ‘n hoër kleurdigtheid en frankheid tot gevolg hê, terwyl onryp druiwe wyne met hoër vlakke van waarneembare vars bessiekenmerke tot gevolg kan hê. Verlaging van lowerdigtheid kan veral die frankheid en mondgevoel van wyne gemaak van druiwe blootgestel aan waterstres, verbeter.

Thesis (MScAgric (Viticulture and Oenology))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: Cabernet Sauvignon is the most planted red cultivar in South Africa and the second most planted red cultivar in the Olifants River region. The cultivar is prone to vigorous growth with low yields. Excessive irrigation could accentuate these cultivar characteristics. Considering the foregoing, the aim of the study was to describe how Cabernet Sauvignon will react to climate, soil type (texture) and irrigation within the Lower Olifants River wine region to enable growers to make the right decisions regarding long term as well as short term cultivation practices. This study is part of a project carried out by the ARC Infruitec-Nietvoorbij at Stellenbosch to determine the effects of soil type and atmospheric conditions on yield and wine quality of Cabernet Sauvignon in different grape growing regions of South Africa. Similar studies are being carried out in the Orange River, Stellenbosch and Swartland regions of South Africa. The Lower Olifants River region could be divided into three climatic regions. Furthermore, two climatic regions is evident regarding the formation of grape wine colour and aromas. Proximity to the Atlantic Ocean would play an important role in a cultivar establishment policy. The variation in stem water potential (ΨS) could be related to soil water status expressed in terms of matric potential (ΨM). In the case of sandy soils, ΨS decreased substantially more as the ΨM decreased compared to the sandy loam soils. The reason could be that the unsaturated hydraulic conductivity in sandy soils decreased more rapidly as the ΨM decreased compared to the heavier soils. Thus could explain why the grapevines in the sandy soils experienced more water stress than the ones in the sandy loam soils at a given ΨM. Climate had a strong influence on grapevine water status with grapevines nearer to the ocean experiencing less water stress compared to the ones further inland. This was especially true for grapevines in the sandy soils. Vegetative growth and yield of grapevines in the sandy soils were more sensitive to water deficits compared to the ones in the sandy loam soils. For deficit irrigated grapevines in the sandy soils, vegetative growth and yield decreased by ca. 30% when ca. 55% less water was applied from flowering to harvest. Yield reduction were ca. 15% with no or very little influence on vegetative growth with ca. 80% reduction in water applied from flowering to harvest for grapevines in the sandy loam soils. The influence of soil texture on wine quality and style were evident under intensive irrigation as well as over different climatic regions. Overall sensorial potential wine quality of grapevines in sandy soils tended to be higher compared to the ones in the sandy loam soils. Deficit irrigation tended to increase wine colour intensity, irrespective of soil texture. Furthermore, deficit irrigation in sandy loam soils tended to increase wine fullness and the berry characteristics of the wine. Berry characteristics of wines from the sandy soils tended to be higher compared to the ones from the sandy loam soils. Too severe water deficits in sandy soils could be detrimental to wine quality. Climate tended to have an influence on wine style of grapevines in the sandy soils with wines produced further away from the ocean tended to have higher berry characteristics. Irrigation management could be a powerful tool to manipulate the grapevine in sandy soils. For grapevines the sandy loam soils in addition to regulated deficit irrigation, additional canopy management practices could be needed to improve wine quality. / AFRIKAANSE OPSOMMING: Cabernet Sauvignon is die mees aangeplante rooidruif kultivar in die Suid-Afrikaanse wynbedryf. In die Olifantsriver streek is dit naas Shiraz, die tweede mees aangeplante rooidruif kultivar. Cabernet Sauvignon is bekend as ‘n groeikragtige skaamdraer. Indien oorbesproei word, kan hierdie potensiële nadelige eienskappe nog meer na vore tree. Die doel van die studie is om die invloed van die klimaat, grond en besproeiing op Cabernet Sauvignon se vegetatiewe groei, produksie en wyngehalte in die Benede Olifantsrivier streek te bepaal. Hierdie inligting kan produsente help om ingeligte kortsowel as langtermyn besluite te maak rakende die verbouing van Cabernet Sauvignon. Hierdie studie vorm deel van ‘n breër studie in die Suid-Afrikaanse wynbedryf, gedryf deur die Landbou Navorsingsraad (LNR) Infruitec-Nietvoorbij, Stellenbosch om die invloed van atmosferiese toestande en grond op die produksie en wyngehalte van Cabernet Sauvignon te bepaal. Soortgelyke projekte word uitgevoer in die Oranjerivier, Stellenbosch en Swartland wynstreke. Die Benede Olifantsrivier streek kan verdeel word in drie klimaatstreke op grond van temperatuurdata. In terme van die ontwikkeling van druifkleur en aromas, kan die streek verdeel word in twee klimaatstreke. Die afstand vanaf die Atlantiese Oseaan kan ‘n belangrike rol speel in die ontwikkeling van ‘n kultivarriglynplan vir die streek. Grondwaterstatus, uitgedruk as die matrikspotensiaal (ΨM), kan aanleiding gee tot variasie in middag blaarwaterpotensiaal (ΨS) lesings. Die ΨS van die sand gronde verlaag vinniger soos die ΨM verlaag invergelyke met die sandleem gronde. Dit kan moontlik wees as gevolg van die verskil in die grond onversadigde hidroliese konduktiwiteit. Sand gronde se hidroliese konduktiwiteit verlaag vinniger soos die ΨM verlaag, invergelyke met sandleem gronde. Dit verklaar waarom wingerde in sand gronde by dieselfde ΨM, meer waterspanning ondervind as wingerde in sandleem gronde. Klimaat het ‘n invloed op die waterstatus van die wingerdstok. Wingerde nader aan die see het minder waterspanning ondervind invergelyke met wingerde wat verder in die binneland geleë is. Dit was veral die geval met wingerde in die sand gronde. Vegetatiewe groei en produksie van wingerde in die sand gronde is meer sensitief vir waterspanning as wingerde in die sandleem gronde. Tekortbesproeiing in die sand gronde het die groei asook produksie met ongeveer 30% verlaag deur ongeveer 55% minder water toe te dien vanaf blom tot oes. In teenstelling daarmee is die produksie van wingerde in die sandleem gronde met ongeveer 15% verlaag met geen tot baie min verlaging in die groeikrag. Ongeveer 80% minder water is toegedien vanaf blom tot oes. Grondtekstuur kan wyngehalte en -styl beïnvloed ten spyte van intensiewe besproeiing en klimaatsverskille. Sensoriese potensiële wyngehalte van wingerde in die sand gronde was beter invergelyke met dié van die sandleem gronde. Die wyne vanaf die sand gronde het ook geneig om oor meer bessie intensiteit te beskik as wyne vanaf die sandleem gronde. Tekortbesproeiing neig om die wynkleur intensiteit te verhoog, ongeag van grondtekstuur. Tekortbesproeiing in die sandleem gronde kan ook die volheid van die wyne verbeter, asook die bessie intensiteit van die wyn verhoog. Te hoë waterspanning in die sand gronde kan wyngehalte nadelig beïnvloed. Klimaat kan ook die wynstyl vanaf sand gronde beïnvloed met wyne verder vanaf die see wat oor meer bessie intensiteit beskik as wyne nader aan die see. Beheerde tekortbesproeiing kan as ‘n kragtige hulpmiddel gebruik word om wingerde in die sand gronde te manipuleer. Vir wingerde in die sandleem gronde, addisioneel tot beheerde tekortbesproeiing en normale loofbestuurspraktyke, kan ekstra loofbestuurspraktyke bv. die verwydering van sylootlote, dalk nodig wees om wyngehalte te verbeter.

Thesis (MScAgric (Viticulture and Oenology))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: Within-vineyard variability in vigour and water status commonly occurs in South African vineyards. Different soil types found over short distances are probably the main cause of vigour variability, while differences in grapevine water status are commonly induced by lateral water flow in the vineyard, blocked irrigation emitters and differences in soil water-holding capacity. These factors can cause heterogeneous ripening and differences in fruit quality between different parts of the vineyard, an aspect that needs to be avoided as far as possible in order to produce quality wines. Measurements of carbon isotope discrimination (CID) have proved to be a tool to assess grapevine physiology in order to study the effects of environmental parameters on leaf carbon dioxide (CO2) gas exchange and stomatal conductance (gs). Grapevine water deficit stress/strain in reaction to these environmental conditions can then be determined by observing the amount of 13C absorbed by plant material after discrimination of 13C has taken place, and this is influenced by the grapevine stress condition and can indicate water-use efficiency. In this study, the variability of grapevine water status and vigour was determined in order to quantify these parameters in different parts of the vineyard. Two separate trials were conducted, the first at Wellington, South Africa, where different irrigation regimes resulted in variability in grapevine water status between plots. The second trial was at Stellenbosch, South Africa, where plots were divided among different vigour classes and irrigation was applied in different quantities for different irrigation treatments. Within-vineyard variability in water status (Wellington and Stellenbosch) and vigour (Stellenbosch) were then quantified and the effects on some grapevine physiological parameters and berry composition were measured. The treatments in the Wellington trial led to differences in grapevine water status, which could be quantified by measurements of stem water potential (SWP) and leaf water potential (LWP). Soil variability also led to differences in grapevine vigour, which were quantified by measurements of pruning mass, leaf area and shoot length. The effect of the variability in grapevine water status on grapevine physiology was assessed by measuring CID, which was the main focus of the study. Other physiological measurements, such as gs and leaf and canopy temperature, were also conducted. The effect of these conditions on grape berry composition was also studied. In the Stellenbosch trial, soil water content, plant water status measurements (SWP, predawn LWP and LWP), physiological measurements (CID and gs) and berry size measurements were used to classify plots into water status treatments (“wet” and “dry” treatments). The effect of vigour differences was analysed separately from these treatments by using pruning mass as a covariate in the statistical analyses. The effect of vigour variability on the measurements was studied by looking at the effect of the covariate on the measurements, while shoot growth rate, shoot length and leaf area measurements were conducted as vegetative growth measurements. Differences in measurements were then studied between the treatments and between the vigour levels of the different plots. In the Wellington trial, plant water status was determined by irrigation, showing increased stress for treatments that received less irrigation. The differences in plant water status then caused differences in grapevine physiology between the treatments, leading to increased gs for increased irrigation. This of course influenced leaf internal CO2 and therefore CID, although CID was also clearly influenced by berry development. Berry size was influenced by irrigation, with larger berries found in wetter treatments, while berry chemical composition was influenced by the irrigation regime, with increased irrigation leading to increased pH and leading to trends showing increased total soluble solids and malic acid, and reduced total and tartaric acid and colour intensity. In the Stellenbosch trial, plots with higher vigour had increased shoot growth rate, longer shoots and increased leaf area, although topping influenced this. Wet treatment vines also showed slightly longer shoots and larger leaf areas. There were differences in soil water content between the wet and dry treatments, and this led to differences in plant water status. Vigour also influenced pre-dawn LWP, especially in the 2007 season, as higher-vigour vines struggled more to rehydrate through the night. Differences in plant water potential led to differences in grapevine physiology, with increased gs for vines from the wet treatment, while higher-vigour vines had slightly increased gs. The differences in gs led to gas exchange differences and therefore differences in CID, meaning that water status and vigour influenced CID. CID measurements illustrated the long term effect of water status on plant physiology, while measurements such as SWP illustrated the short term effects. CID measurements therefore proved to be accumulative over the season, in contrast to SWP measurements that were much more dependent on the current state of grapevine water status. Other physiological measurements showed that wet-treatment vines had higher photosynthetic rates and evapotranspiration and lower leaf temperatures, while higher-vigour vines had slightly increased evapotranspiration and decreased leaf temperatures. Wet-treatment vines had larger berries, while a higher vigour also led to slightly larger berries. Berry composition was influenced by treatment, where wet-treatment vines had increased pH and total soluble solids, while higher-vigour vines had increased juice pH and, in the 2008 season, decreased total soluble solids. Extremely stressed conditions did not show significant effects on plant water potential, but SWP measurements indicated slightly higher stress for the extremely stressed vines and LWP showed slightly less stressed conditions for these vines. Measurements of gs showed slightly lower values for the extremely stressed vines, while measurements of CID showed large significant differences, with the extremely stressed vines having measurements showing high stress. The measurement therefore indicated highly stressed conditions accurately, while other physiological measurements, such as photosynthetic rate, evapotranspiration and leaf temperatures, only showed trends and no significant differences. Measurements of stomatal conductance reacted to plant water status measurements throughout the diurnal measurement days, while CID only reacted slightly with gs changes during these days and was perhaps influenced more by berry chemical composition and development at this early stage of the season. Vigour and water status therefore influenced grapevine physiology, with a more direct effect by water status and an indirect effect by vigour due to microclimatic differences. This also influenced berry composition and therefore quality. In future studies, CID measurements should be done on juice from which organic acids have been removed in order to eliminate the effect of seasonal berry composition on the measurement. Measurements of CID proved to be an integrative, but sensitive, indicator of grapevine stress, especially at the end of the season. It might at best be useful as a post-harvest management tool for producers or grape buyers, especially for irrigation control, as has also been stated by Van Leeuwen et al. (2007). / AFRIKAANSE OPSOMMING: Binne-wingerd variasie in groeikrag en waterstatus is algemeen in Suid-Afrikaanse wingerde. Verskillende grondsoorte wat na aan mekaar voorkom, is seker een van die vernaamste oorsake van variasie in groeikrag, terwyl verskille in wingerdwaterstatus algemeen deur laterale watervloei in die wingerd, verstopte besproeiingspuite en verskille in grond waterhouvermoë geïnduseer word. Hierdie faktore kan aanleiding gee tot heterogene rypwording en verskille in vrugkwaliteit tussen verskillende dele van die wingerd, ‘n aspek wat so ver moontlik vermy moet word om kwaliteitwyne te kan produseer. Die meting van koolstof-isotoopdiskriminasie (KID) is bewys om as gereedskap te kan dien vir die assessering van wingerdfisiologie om die effekte van omgewingsparameters op blaar koolstofdioksied (CO2) - gasuitruiling en stomatale geleiding (gs) te bestudeer. Die stres/stremming as gevolg van ‘n watertekort in die wingerd in reaksie op hierdie omgewingstoestande kan dan bepaal word deur te kyk na hoeveel 13C deur die plantmateriaal geabsorbeer word ná 13C-diskriminasie plaasgevind het, en dít word deur die wingerdstrestoestande beïnvloed en kan ‘n aanduiding verskaf van die doeltreffendheid van waterverbruik. In hierdie studie is die variasie in wingerdwaterstatus en groeikrag bepaal om hierdie parameters in verskillende dele van die wingerd te kwantifiseer. Twee afsonderlike proewe is uitgevoer, die eerste by Wellington, Suid-Afrika, waar verskillende besproeiingsregimes gelei het tot verskille in die wingerdwaterstatus tussen persele. Die tweede proef was by Stellenbosch, Suid-Afrika, waar persele tussen verskillende groeikragklasse verdeel is en besproeiing in verskillende hoeveelhede vir verskillende besproeiingsbehandelings toegepas is. Binne-wingerd variasie in waterstatus (Wellington en Stellenbosch) en groeikrag (Stellenbosch) is toe gekwantifiseer en die effekte op sekere wingerd-fisiologiese parameters en korrelsamestelling is gemeet. Die behandelings in die Wellington-proef het gelei tot verskille in wingerdwaterstatus, wat deur metings van stamwaterpotensiaal (SWP) en blaarwaterpotensiaal (BWP) gekwantifiseer kon word. Grondverskille het ook gelei tot verskille in wingerdgroeikrag, wat deur metings van snoeimassa, blaaroppervlak en lootlengte gekwantifiseer is. Die effek van die variasie in wingerdwaterstatus op wingerdfisiologie is deur metings van KID bepaal wat die hooffokus van hierdie studie was. Ander fisiologiese metings, soos gs en blaar- en lowertemperatuur, is ook gedoen. Die effekte van hierdie toestande op die samestelling van die druiwekorrels is ook bestudeer. In die Stellenbosch-proef is grondwaterinhoud, metings van plantwaterstatus (SWP, voorsonopgang SWP en BWP), fisiologiese metings (KID en gs) en metings van korrelgrootte gebruik om die persele in waterstatusbehandelings (“nat” en “droë” behandelings) te verdeel. Die effek van verskille in groeikrag is apart van hierdie behandelings geanaliseer deur snoeimassa as ‘n kovariaat in die statistiese analises te gebruik. Die effek van groeikragvariasie op die metings is bestudeer deur ondersoek in te stel na die effek van die kovariaat op die metings, terwyl lootgroeitempo-, lootlengte- en blaaroppervlakmetings as metings van vegetatiewe groei uitgevoer is. Verskille in metings tussen die behandelings en tussen die groeikragvlakke van die verskillende persele is toe bestudeer. In die Wellington-proef is plantwaterstatus deur besproeiing bepaal, met verhoogde stres in behandelings waar daar minder besproeiing toegedien is. Die verskille in plantwaterstatus het dan verskille in wingerdfisiologie tussen die behandelings veroorsaak, wat gelei het tot ‘n verhoogde gs in die geval van verhoogde besproeiing. Dit het natuurlik ‘n effek op die interne CO2 van die blaar en dus op KID gehad, hoewel KID ook duidelik deur korrelontwikkeling beïnvloed is. Korrelgrootte is deur besproeiing beïnvloed, met groter korrels in die natter behandelings, terwyl die chemiese samestelling van die korrel deur besproeiingsregime beïnvloed is. Verhoogde besproeiing het pH verhoog en gelei na tendense wat verhoogde totale oplosbare vaste stowwe en appelsuur, en verminderde totale suur, wynsteensuur en kleurintensiteit getoon het. In die Stellenbosch-proef het persele met hoër groeikrag ook verhoogde lootgroeitempo, langer lote en verhoogde blaaroppervlak getoon, hoewel dit deur top beïnvloed is. Wingerdstokke van die nat behandeling het ook effe langer lote en groter blaaroppervlakke getoon. Daar was verskille in grondwaterinhoud tussen die nat en droë behandelings en dit het verskille in plantwaterstatus veroorsaak. Groeikrag is ook deur voor-sonopgang BWP beïnvloed, veral in die 2007-seisoen, aangesien stokke met hoër groeikrag meer gesukkel het om in die nag te rehidreer. Verskille in plantwaterpotensiaal het gelei tot verskille in wingerdfisiologie, met ‘n verhoogde gs vir stokke in die nat behandeling, terwyl stokke met hoër groeikrag ‘n effens verhoogde gs getoon het. Die verskille in gs het gelei tot verskille in gasuitruiling en dus verskille in KID, wat beteken dat waterstatus en groeikrag ‘n invloed op KID het. KID was meer verteenwoordigend van die langtermyneffekte van water status op plantfisiologie, terwyl metings soos SWP die korttermyneffekte weerspieël het. KID metings was dus akkumalatief oor die seisoen, terwyl SWP metings meer ‘n weerspieëling was van die huidige toestand van plantwaterpotensiaal. Ander fisiologiese metings het getoon dat stokke in die nat behandeling ‘n hoër fotosintesetempo en evapotranspirasie sowel as laer blaartemperature ondervind het, terwyl die stokke met hoër groeikrag effe verhoogde evapotranspirasie en verminderde blaartemperature getoon het. Stokke in die nat behandeling het groter korrels gehad, terwyl hoër groeikrag ook effens groter korrels veroorsaak het. Korrelsamestelling is deur die behandelings beïnvloed, met stokke in die nat behandeling wat verhoogde pH en totale oplosbare vaste stowwe getoon het, terwyl stokke met hoër groeikrag verhoogde pH van die sap en verminderde totale oplosbare vaste stowwe (laasgenoemde in die 2008-seisoen) gehad het. Uitermate toestande van stres het geen beduidende effekte op plantwaterpotensiaal getoon nie, hoewel SWP-metings effens hoër stres vir die uitermate gestresde wingerde getoon het en BWP effens minder gestresde toestande vir hierdie stokke getoon het. Metings van gs het effens laer waardes vir die uitermate gestresde stokke getoon, terwyl metings van KID groot noemenswaardige verskille getoon het, met die metings vir die uitermate gestresde wingerde wat hoër stres aangedui het. Dié meting het dus hoogs gestresde toestande akkuraat aangedui, terwyl ander fisiologiese metings, soos tempo van fotosintese, evapotranspirasie en blaartemperature net tendense en nie beduidende verskille aangedui het nie. Metings van stomatale geleiding het dwarsdeur die dae waarop daaglikse metings gedoen is op plantwaterstatusmetings gereageer, terwyl KID net effens met gs-veranderinge op hierdie dae gereageer het en moontlik meer deur die chemiese samestelling en ontwikkeling van die korrel in hierdie vroeë stadium van die seisoen beïnvloed is. Groeikrag en waterstatus het dus wingerdfisiologie beïnvloed, met ‘n meer direkte effek deur waterstatus en ‘n indirekte effek deur groeikrag as gevolg van mikroklimaatsverskille. Dit het ook korrelsamestelling en dus kwaliteit beïnvloed. In toekomstige studies moet KID-metings gedoen word op sap waarvan die organiese sure verwyder is om die effek van seisoenale korrelsamestelling op die meting uit te sluit. Metings van KID is getoon om ‘n integrerende, maar gevoelige, aanduider van wingerdstres te wees, veral aan die einde van die seisoen. Dit is ten beste miskien bruikbaar as naoesbestuursgereedskap vir produsente of druiwekopers, veral vir besproeiingsbeheer, soos ook reeds deur Van Leeuwen et al. (2007) aangedui is.