Thesis (PhDAgric)--Stellenbosch University, 1971. / ENGLISH ABSTRACT: The object of this anatomical study was to collect scientific data on the effect of Metoidogyne hapta Chitwood, 1949, on the roots of the following grapevine cultivars viz: Vitis vinifePa L. cvs. Steen and White French and the root-stocks, Jacquez, 1202 C, 99 R, Salt.Creek and Dogridge. These cultivars differed widely in their resistance to M. hapta attacks. In the roots of Steen, White French, Jacquez and 1202 C the formation of multinucleate syncytia by the destruction of the walls of groups of cells often occurred. In Salt Creek, Dogridge and 99 R roots, syncytia were observed in the stele only. The formation o,f abnormal xylem as a result of nematodal activities was a common occurrence. In the roots of these latter three cultivars, M. hapta could not complete its life cycle. Salt Creek, Dogridge, 99 R and often Steen formed a wound periderm which prevented the nematodes from reaching the xylem. Histological changes were often induced in advance of the invading nematodes. / AFRIKAANSE OPSOMMING: Die doel met hierdie anatomiese studie was om wetenskaplike inligting te versamel aangaande die uitwerking van Metoidogyne hapta Chitwood, 1949, op enkele cultivars van wingerdstokke,te wete Steen en Fransdruif van Vitis vinifera L. en die onderstokke Jacquez, 1202 C, 99 R, Salt Creek en Dogridge. Hierdie cultivars het onderling baie verskil in hul weerstandvermoe teen M. hapta. Ten gevolge van die vernietiging van die wande van selgroepe, in die wortels van Steen, Fransdruif, Jacquez en 1202 C, is veelkernige sinsiete (Eng. syncytia) gevorm. In die wortels van Salt Creek, Dogridge en 99 R, is sinsiete net in die sentrale silinder waargeneem. Die vorming van abnormale xileem weens nematodiese bedrywighede was 'n baie algemene verskynsel. M. hapta kon in laasgenoemde drie cultivars nie sy lewenskringloop voltooi nie. In Salt Creek, Dogridge, 99 R en dikwels ook in Steen, is wondperiderm gevorm, waardeur die nematodes verhinder was om die xileem te bereik. Die indringende nematodes het voor hulle uit dikwels histologiese veranderinge in die wortels teweeggebring.

Thesis (MScAgric)--Stellenbosch University, 2004. / ENGLISH ABSTRACT: The effect of shoot heterogeneity on vegetative and reproductive growth parameters, vine physiology and grape composition was investigated in a ShirazlRichter 99 vineyard. Comparisons between underdeveloped (typically shorter and less ripened at véraison) and normally developed shoots in both shaded (non-manipulated) and well-exposed (manipulated) canopies were made. Compared to underdeveloped shoots, normal shoots had a larger total leaf area, due to the higher occurrence of secondary shoots as well as larger leaves on primary and secondary shoots. Since the photosynthetic activity of the leaves from normal shoots was higher than those from underdeveloped shoots, higher levels of carbohydrates were produced and stored in the former. Starch was more evenly distributed over the length of the whole shoot in normally developed shoots compared to underdeveloped shoots. Normally developed shoots were longer and thicker in diameter than underdeveloped shoots. The larger clusters of the normally developed shoots are evidence of their more favourable total leaf area per gram berry mass. Berries from the normally developed shoots were smaller at five weeks after véraison than those from underdeveloped shoots, displaying a higher skin to pulp ratio and therefore higher anthocyanin and total phenolic extraction potential for winemaking. The smaller clusters and fewer berries per cluster found for the underdeveloped shoots indicate an imbalance between vegetative and reproductive growth initiated during the vegetative growth phase and continued during the ripening period. The peculiar absence of statistically significant differences in grape composition between normally and underdeveloped shoots indicates that assimilates needed for berry ripening of the latter originated in organs other than the leaves [e.g. from adjacent normal shoots and the rest of the permanent structure of the vine (cordon, trunk, roots)]. The larger differences in berry size that occurred between shoot types in the shaded compared to the well-exposed canopies may be evidence for this. The photosynthetic activity of shoots was lower in shaded than in exposed canopies. The total carbohydrate production of the normal shoots in shaded canopies seemed insufficient to supply in the ripening needs of the shoot itself, their own clusters as well as the ripening of stem tissue and clusters of the underdeveloped shoots in the canopy. This is illustrated by the lower levels of starch that accumulated in the normal shoots from shaded compared to that of exposed canopies. Vine shoot heterogeneity clearly leads to visible and physiological imbalances that would impact negatively on grape and wine quality as well as production costs and should therefore be avoided on any terroir. / AFRIKAANSE OPSOMMING: In hierdie studie is die effek van heterogene lootontwikkeling in die lower van 'n ShirazlRichter 99 wingerd ondersoek. Vergelykings is getref tussen normale en onderontwikkelde lote in beskadude en blootgestelde lowers ten opsigte van hul vegetatiewe en reproduktiewe groeieienskappe, fisiologiese aktiwiteit en druifsamestelling en -gehalte. 'n Groter totale blaaroppervlak het by die normaalontwikkelde lote voorgekom as gevolg van die groter aantal sekondêre lote en groter primêre en sekondêre blare. Aangesien die blare van die normaal ontwikkelde lote fotosinteties meer aktief was as dié van onderontwikkelde lote, het die eersgenoemde lote groter hoeveelhede koolhidrate geproduseer en gestoor. Styselopberging het meer eweredig oor die lengte van die normale lote plaasgevind. Laasgenoemde lote was ook heelwat langer en dikker in deursnee as die onderontwikkelde lote. Die gunstiger totale blaaroppervlak per korrelmassa verhouding van die normale lote is duidelik weerspieêl in die groter trosse, terwyl die kleiner korrels (en dus die groter dop:pulp verhouding) op 'n groter potensiaal vir kleur- en fenolekstraksie tydens die wynbereidingsproses dui. Die kleiner trosse en kleiner aantal korrels per tros wat by die onderontwikkelde lote gevind is, dui op 'n wanbalans tussen die vegetatiewe en reproduktiewe groei van die loot wat tydens die vegetatiewe groeifase van die wingerdstok geïnisieer is en tydens die rypwordingsperiode voortgesit is. Die vreemde afwesigheid van enige statisties betekenisvolle verskille in druifsamestelling tussen die normale en onderontwikkelde lote dui daarop dat die verbindings wat vir die rypmaking van trosse op onderontwikkelde lote aangewend is, waarskynlik van ander wingerdorgane (bv. naasliggende lote, kordonarms, stam, wortels) as die spesifieke loot se blare afkomstig was. Die waarneming dat die korrelgroottes van normale en onderontwikkelde lote meer van mekaar verskil het in die beskadude as blootgestelde lowers, kan moontlik as bewys hiervoor dien. Die fotosintetiese aktiwiteit van beide loottipes was laer in die skaduryke lowers. Die koolhidrate wat deur normaalontwikkelde lote in skadu-Iowers geproduseer is, was oênskynlik onvoldoende vir die rypmaking van die loot self, die spesifieke loot se trosse, asook die trosse en lootweefsel van naasliggende onderontwikkelde lote. Hierdie bewerings word gerugsteun deur die laer vlakke van styselakkumulasie wat by die normale lote in beskadude lowers gevind is. Aangesien heterogene lootontwikkeling en -groei duidelike sigbare en fisiologiese wanbalanse in die wingerdstok tot gevolg het wat negatief op druifsamestelling, wyngehalte en produksiekoste inwerk, behoort dit in kommersiêle wingerde vermy te word.

Thesis (MSc)--University of Stellenbosch, 2004. / ENGLISH ABSTRACT: Arbuscular mycorrhizal (AM) C-costs in grapevines were investigated. Since both dormant vines and AM colonisation rely on stored C for initial growth, AM colonisation costs would therefore compete with plant growth for available C reserves. The aims of this study were to assess the host C economy during AM development and the subsequent C-costs of N and P uptake, as well as the effects of C costs on host growth. This was evaluated in two separate experiments; one assessing the symbiotic influence on the C costs of fungal establishment and nutritional benefits, whilst the other one evaluated the effects of the symbiosis on host growth and nutrient productivities. This study has shown that AM acts as a C sink, competing with the host for available C. Past work on the AM sink effect has focused mainly on the movement of photosynthetic C below ground to support the AM fungus. This however, does not take into account the effect that stored C will have on the C economy of the plant and symbiosis. The role of stored C becomes even more crucial when working with deciduous plants that rely on stored C for new growth at start of a growing season. It has been reported that stored C in AM plants is remobilized at the start of a growing season and then the C reserves are refilled towards the end of the season, when the plants enter dormancy. The initial costs of AM fungal colonisation were borne by the above-ground C reserves, at the expense of new growth in host plants. These costs were offset once the plateau phase was reached, and the depleted reserves started to refill. Once established, the active symbiosis imposed a considerable below ground C sink on host reserves. In spite of these costs, the improved P nutrition of AM roots was achieved with a more efficient C-use. This concurs with other findings, that of the belowground C allocated to AM roots, a greater part is used by AM respiration and a smaller part for P uptake. The C costs of the AM fungal phase of rapid development can be seen as negative to root growth and shoot development. These negative effects may continue for a period of time, even during the plateau phase of fungal development. Once the AM symbiosis is fully established, the host growth and development is then improved to a greater extent than in non-AM plants. From this study it can be concluded that AM growth directly competes with host development, but the symbionts revert to a beneficial partnership once it is fully established. / AFRIKAANSE OPSOMMING: Die C koste van arbuskulêre mikorisa (AM) in wingerdstokke is ondersoek. Beide rustende wingerdstokke en AM koloniseering is afhanklik van gestoorde C vir aanvanklike groei. AM kolonisering sou dus met plantgroei kompeteer vir beskikbare C reserwes. Die doelstellings van hierdie ondersoek was eerstens om die C-ekonomie van die gasheer tydens AM ontwikkeling en die gevolglike Ckostes van N en P opname te bepaal en tweedens sowel as die invloed van C veranderings op gasheergroei vas te stel. Hierdie is in twee afsonderlike eksperimente ondersoek: een om die simbiotiese invloed op die C-kostes van swam-vestiging en voedingsvoordele te bepaal, terwyl die ander die uitwerking van simbiose op gasheergroei en voedings doeltreffenheid evalueer het. Die ondersoek het bewys dat AM, as ‘n C-sink, kompeteer met die gasheer vir beskikbare C. Vorige werk oor die AM sink-effek het hoofsaaklik gefokus op die afwaartse beweging van fotosintetiese C om die AM-swam ondergronds te ondersteun. Die werk neem egter nie in ag wat die effek van gestoorde C op die C-ekonomie van die plant en simbiose sou wees nie. Die rol van gestoorde C is selfs nog meer belangrik wanneer met bladwisselende plante gewerk word, omdat sulke plante op gestoorde-C vir nuwe groei aan die begin van die groeiseisoen staatmaak. Dit is op rekord dat gestoorde C in bladwisselende plante by aanvang van die groeiseisoen gemobiliseer word en dat die C-reserwes teen die einde van die seisoen wanneer die plante rustyd nader, weer hervul word. Die aanvanklike kostes van AM kolonisering is deur die bogronds C-reserwes, ten koste van nuwe groei van die gasheerplante, gedra. Hierdie kostes herstel sodra die plato-fase bereik is, waar die uitgeputte reserwes begin hervul het. As die aktiewe simbiose eers gevestig is, sal dit as ‘n onderg P-voeding van AM wortels verkry wordrondse C-sink vir gasheer optree.Hierdie C verbruik word egter as doeltreffend beskou aangesien verbeterde. Dit is bekend dat ‘n groter deel van die ondergrondse C geallokeer word aan AM-wortels, deur middel van AM respirasie en P-opname. Die C-kostes van die AM-fungus tydens die fase van vinnige ontwikkeling, kan ‘n negatiewe effek op wortel- en lootontwikkeling hê. Hierdie negatiewe uitwerking kan vir ‘n tydperk voortdeur, selfs gedurende die plato-fase van fungi-ontwikkeling. Sodra die AM-simbiose volledig gevestig is, word gasheergroei en ontwikkeling tot ‘n groter mate verbeter as in plante sonder AM-fungi. Hierdie ondersoek het bewys dat AM groei direk met gasheerontwikkeling kompeteer, maar dat die simbiose ‘n voordelige vennootskap vorm sodra dit volledig gevestig is.

Thesis (MSc)--Stellenbosch University, 1959. / ENGLISH ABSTRACT: no abstract available / AFRIKAANSE OPSOMMING: geen opsomming

Thesis (MScAgric (Soil Science))--University of Stellenbosch, 2007. / This study forms part of an ARC Nietvoorbij research project on the long-term effect of different groundcover management practices in vineyards. This study concentrated on the root distribution of the vines after different groundcover practices were used for one decade. The vineyard on the research farm of the Agricultural Research Council at Robertson, South Africa, was divided into 56 equally distributed trail blocks, 14 treatments with four replicas each. For the study Chardonnay cultivar on 99 Richter rootstock was used. This study concentrated on only eight treatments. The eight different cover crop practices consisted of the mechanical treatment, chemical treatment, straw mulch treatment, permanent cover crop treatment and four annual cover crop treatments. The annual cover crop treatments consisted of triticale cover crop that was sprayed with an herbicide before bloom, a triticale cover crop that was left to die naturally, a grazing vetch cover crop that was sprayed with an herbicide before bloom and a grazing vetch cover crop that was left to die naturally. The vineyard was established in November 1992 while the different treatments started in April 1993. Root studies were conducted during the 2002/2003 season. In this study the auger method was used to determine root density (mm/cm³). The root density was correlated with data from the penetrometer studies, yield and shoot mass collected during the same season.

Thesis (MScAgric)--Stellenbosch University, 1966. / ENGLISH ABSTRACT: no abstract available / AFRIKAANSE OPSOMMING: geen opsomming

Thesis (MScAgric)--Stellenbosch University, 1963. / ENGLISH ABSTRACT: no abstract available / AFRIKAANSE OPSOMMING: geen opsomming

Thesis (MScAgric)--Stellenbosch University, 1992. / One microfiche copy / ENGLISH ABSTRACT: The possibility of harvesting grapes at an earlier stage of maturity, based on differences in glucose and fructose concentration which influence the sweetness of grapes, was investigated. Although differences between cultivars were found the extent was not such that a specific cultivar could be selected in order to harvest at a lower sugar concentration, but with the same sweetness. Certain characteristics of table and wine grape cultivars with respect to anatomical composition and skin penetration resistance (SPR) were also investigated in order to ascertain the extent to which grapes would resist external damage, and to what extent turgor and skin thickness contributed to SPR. Daily variances in SPR confirm that not only skin strength, but also the turgor of the grape berry contributed to SPR. Skin penetration resistance seems to be a good criterion of the extent to which cultivars would resist external damage, because it is based on the toughness of the skin and the turgor of the berry. / AFRIKAANSE OPSOMMING: Die moontlikheid van vroeer oes op grond van verskille in die glukose- en fruktosekonsentrasie wat 'n invloed op die soetheid van druiwe mag he, is ondersoek. Daar is gevind dat die verskille wat tussen cultivars voorkom nie van so 'n grootte-orde is dat 'n spesifieke cultivar geselekteer kan word ten einde by 'n laer totale suiker, maar by dieselfde soetheidsgraad, te kan oes nie. Verder is sekere eienskappe van tafel- en wyndruifcultivars t.o.v. anatomiese samestelling en doppenetrasieweerstand (DP\V) ondersoek om die moontlike weerstand teen eksterne beserings en die mate waartoe turgor en dopdikte 'n invloed daarop mag uitoefen, _vas te stel. Daaglikse variasie in DPW het bevestig dat die DPW nie alleen afhanklik is van dopsterkte nie, maar ook van die turgor van die korrel. Doppenetrasieweerstand blyk 'n goeie maatstaf te wees vir die mate waartoe cultivars weerstand hied teen sekere eksterne beserings omdat dit gebaseer is op dopsterkte en turgor van die korrel.

Thesis (MSc) -- Stellenbosch University, 1975. / No abstract available

Thesis (PhD)--University of Stellenbosch, 2003. / ENGLISH ABSTRACT: Grapevine leafroll-associated virus-3 is one of ten members of the C/osteroviridae that are known to infect grapevine. Nine of these viruses are associated with grapevine leafroll disease, of which GLRaV-1 and GLRaV-3 are the most important and widespread. Members of the C/osteroviridae are unique amongst the viruses, as it is the only known family whose members encode a heat shock protein 70 kOa homolog (Hsp70h). The Hsp70h is a movement protein (MP) that is required for the active translocation of the virion structure through the plasmodesmata into adjacent cells. Broad-spectrum resistance to unrelated viruses can be obtained by a pathogen-derived resistance (POR) strategy that is based on the expression of a dysfunctional MP in plants. The Hsp70h has two distinct domains. The N-terminal two thirds of the protein is an ATPase domain and shares high homology with the ATPase domains of all Hsp70h proteins from the C/osteroviridae and Hsp70 proteins from the prokaryote and eukaryote kingdoms. Conserved amino acids are found in the ATPase domain and are required for the positioning of the ATP at the catalytic site for ATP hydrolysis. The C-terminal domain is variable and the function of this domain in the Closteroviridae is not known. In prokaryote and eukaryote Hsp70 proteins, the C-terminal domain is required for protein-protein interactions. The American NY-1 isolate of GLRaV-3 has been sequenced and POR strategies have been attempted with the coat protein, divergent coat protein and replicase genes, but not with a dysfunctional form of the hsp70h gene. In this study, double-stranded RNA was isolated from a commercial vineyard with unknown virus status, but with distinct grapevine leafroll symptoms, and from two grapevine sources of known virus status, one with mild and one with severe symptoms. The GLRaV-3 hsp70h gene was amplified by RT-PCR from the dsRNA and the gene sequence was analysed. The hsp70h gene from the three virus sources contained more than 94% nucleotide sequence homology to the NY-1 isolate and the conserved amino acids required for ATPase activity were present. The hsp70h gene isolated from GLRaV-3 from a commercial Stellenbosch vineyard showing clear leafroll symptoms was selected for further work and was subjected to site-directed mutagenesis to engineer four point mutations in the gene. These four mutations resulted in the substitution of Asn for Asp", Gly for Thr1O, Lys for Glu 174 and Asn for Asp 197. The wild type (WT) and mutated (Mut) forms of the hsp 70h genes were cloned into a bacterial expression vector. Expression of both the WT- and Mut-Hsp proteins was achieved, and the protein was expressed in the insoluble inclusion bodies. All attempts to refold and isolate active proteins from the inclusion bodies were unsuccessful. Attempts to increase the concentration of soluble protein within the expressing bacteria were unsuccessful. Due to the lack of active protein, biochemical tests on the ATPase activity of the WT- and Mut-Hsp proteins could not be conducted. The wt- and mut-hsp genes were cloned into a plant expression vector for transformation into tobacco plants. These transformations were successful and gave rise to 22 Km' and 18 Km' plants from the WT- and Mut-Hsp constructs respectively. Two plant lines, M5 and M10, transformed with the mut-hsp transgene construct, appeared to have a high level of resistance to the challenging potato X potexvirus, whereas all the other tested plants were susceptible to the challenging virus. It was thus shown that a dysfunctional form of the GLRaV-3 Hsp70h could provide resistance to an unrelated virus in tobacco. / AFRIKAANSE OPSOMMING: Wingerdrolblaar-geassosieerde virus 3 (GLRaV-3) is een van 10 lede van die Closteroviridae wat wingerd kan infekteer. Nege van die virusse is met wingerdrolblaar geassosieer. Die GLRaV-1 en GLRaV-3 is die belangrikste en mees wyd verspreide lede van die rolblaar-geassosieerde Closteroviridae. Lede van die Closteroviridae is uniek in die opsig dat die virusse vir 'n 70 kDa-homoloë hitteresponsproteïen (Hsp70h) kodeer. Die Hsp70 is 'n bewegingsproteïen (MP) wat belangrik is vir die translokasie van die virus deur die plasmodesmata na die naasliggende sel. Breë-spektrum weerstand teen onverwante virusse kan behaal word deur 'n patogeen-afgeleide weerstandstrategie (POR), wat op die uitdrukking van 'n disfunksionele MP wat in plante uitgedruk word, gebaseer is. Die Hsp70hproteïen het twee gebiede. Die N-terminale gebied is In ATPase-gebied en toon hoë homologie met ander ATPase-gebiede van Hsp70h-proteïene van die Closteroviridae, asook die prokariotiese en eukariotiese koninkryke. Gekonserveerde aminosure wat belangrik is vir die posisionering van ATP in die katalitiese domein vir ATP-hidrolise is in die ATPase-gebied gevind. Die C-terminale gebied is variërend en die funksie van die gebied in die Closteroviridae is onbekend. In prokariotiese en eukariotiese Hsp70h-proteïene is die C-terminale gebied belangrik vir proteïenproteïen interaksies. Die nukleotiedvolgorde van die Amerikaanse NY-1-isolaat van GLRaV-3 is al bepaal en POR-strategieë is ook op die kapsiedproteïen, uiteenlopende kapsiedproteïen en die replikasie-proteïen uitgevoer, maar nog nie op 'n disfunksionele vorm van die Hsp70h-geen nie. In hierdie studie is dubbelstring-RNA (dsRNA) van 'n kommersiële wingerd met onbekende virusstatus wat rolblaarsimptome toon, geïsoleer, asook van twee wingerde met 'n bekende virusstatus, een met ligte en een met strawwe simptome. Die GLRaV-3 hsp70h-geen is met hulp van die polimerasekettingreaksie-metode (PKR) vanaf die dsRNA geamplifiseer en die geen se nukleotiedvolgorde is bepaal. Die hsp 70-gene van drie verskillende wingerde het meer as 94% homologie met die NY-1-isolaat getoon. Die gekonserveerde aminosure wat vir ATPase-aktiwiteit belangrik is, was teenwoordig. Die hsp70h-geen van GLRaV-3, wat uit 'n kommersiële wingerd met duidelike rolblaarsimptome in die Stellenbosch-gebied geïsoleer is, is vir verdere navorsing gekies en dit is aan setel-gerigte mutagenese blootgestelom vier mutasies van die geen te bewerkstellig. Die gevolg van hierdie vier mutasies was die verandering van Asn na Asp", Gly na Thr1o, Lys na Glu174 en Asn na Asp197. Die wilde (WT) en veranderde (Mut) vorms van die hsp-gene is in 'n bakteriese uitdrukkingsvektor gekloneer. Uitdrukking van beide die WT- en die Mut-Hspproteïene is behaal, maar die proteïene was in die onoplosbare fraksie geleë. Pogings om die onoplosbare proteïene te isoleer en in 'n aktiewe oplosbare vorm te verkry, was onsuksesvol. Verdere pogings om die proteïene in die oplosbare fraksie van die bakteriese ekspressiesisteem uit te druk, was ook onsuksesvol. As gevolg van die gebrek aan aktiewe proteïen kon biochemiese toetse nie op die ATPaseaktiwiteit van die WT- en Mut-Hsp proteïne gedoen word nie. Die wt- en mut-hsp-gene is ook in In plantekspressievektor gekloneer vir transformasie in tabakplante. Hierdie transformasies was suksesvol en het aanleiding gegee tot 22 kanamisienbestande (Km') en 18 Km' plante vanaf die WT- en Mut-Hspkonstrukte onderskeidelik. Twee plantlyne, M5 en M10, wat met die mut-hsptransgene getransformeer is, het 'n hoë vlak van weerstand teen die infekterende aartappelvirus X getoon in vergelyking met ander plante wat met die virus geïnfekteer is. Daar is dus bewys gelewer dat 'n disfunksionele vorm van die GLRaV-3 Hsp70h weerstand kan bied teen 'n onverwante virus in tabak.