Thesis (MSc)--Stellenbosch University, 2002. / ENGLISH ABSTRACT: The cultivation of table grapes in the warmer areas of South Africa, indeed worldwide, is complicated by rest breaking problems in spring due to delayed budbreak. In order to overcome these problems rest breaking agents, mainly hydrogen cyanamide, are applied. However, instead of alleviating the problem, additional problems such as uneven budbreak and reduced production are often induced. This study was initiated to further understand the physiological processes occurring during budbreak and how the application of hydrogen cyanamide influences these processes. The following aspects were investigated in this study: a. The effect of hydrogen cyanamide on tissue cytokinin (specifically zeatin riboside) levels of Sultanina table grape vines after application at different times before natural budbreak was studied over two seasons. In 1997, hydrogen cyanamide was applied at three weeks before induced budbreak and in 1998 at six weeks before induced budbreak. One year-old canes were sampled weekly after hydrogen cyanamide application, divided into distal and proximal sections, then further divided into buds, bark and wood tissues and the zeatin riboside (ZR) levels determined. A relatively high amount of chilling coupled to late hydrogen cyanamide application in 1997 led to a large effect on ZR release, but did not lead to significant shifting of the budbreak pattern. Zeatin riboside peaks were observed in buds, internode wood and bark of treated vines compared to control vines. The peaks were higher in distal portions compared to proximal portions in all tissues. The relatively lower chilling and earlier application of hydrogen cyanamide in 1998 had a larger effect on the budbreak pattern while the bud ZR peak was shifted earlier. The distal portion bud ZR . peak was again higher than the proximal portion bud ZR peak. In 1997, as sampling was not initiated early enough, bud ZR peaks were only observed after budbreak, while in 1998 bud ZR peaks were observed before and after budbreak. The effect of these ZR increases on the development of inflorescence primordia, subsequent bunch development and ultimately production, are discussed. b. Free xylem sap was sampled at cane and spur pruned lengths from unpruned canes of Sultanina from budswell until after budbreak in 1999 and from three table grape cultivars, i.e Sultanina, Alphonse Lavalleé and Sunred Seedless, in 2001 and ZR levels determined. The ZR levels in the buds of these three table grape cultivars, pruned to different cane lengths were also determined. One year old canes of these cultivars, were each pruned to long canes (14 buds) and short spurs (2 buds). The ZR content in buds of these canes at distal and proximal positions were determined weekly from budswell until after budbreak in 1999. Xylary ZR peaks occurred before 50% budbreak. Spur xylary ZR levels of all three cultivars followed a similar pattern, although at lower ZR levels than that of the canes. This is similar to previous studies on xylary ZR levels of apple shoots. The high levels of free ZR found in xylem sap at the distal portions of canes support the hypothesis of a cumulative ZR build-up effect as cane length increases. Spur pruning resulted in earlier budbreak and a higher final budbreak than cane pruning. The proximal portions of shoots, whether spur pruned or the proximal portions of canes, showed elevated ZR levels in all cultivars. This difference in ZR levels in bud tissue of different portions of the cane would suggest a difference in ZR consumption or turnover. The results of this study have important management implications for the cultivation of vines in warmer areas in which hydrogen cyanamide is used to alleviate budbreak problems. / AFRIKAANSE OPSOMMING: Die verbouing van tafeldruiwe in die warmer gebiede van Suid-Afrika, soos straks wêreldwyd, word bemoeilik deur rusbreekprobleme in die lente weens vertraagde bot. Rusbreekmiddels, meestal waterstofsiaanamied, word gevolglik toegedien om hierdie probleme te probeer oorkom. In plaas van opheffing van die probleem, veroorsaak hierdie toedienings somtyds addisionele probleme soos ongelyke bot en verlaagde produksie. Hierdie studie is aangepak om die fisiologiese prosesse wat tydens bot plaasvind, beter te verstaan, asook hoe die toediening van waterstofsiaanamied hierdie prosesse beïnvloed. Die volgende is in hierdie studie ondersoek: a. Die invloed van waterstofsiaanamied op lootweefsel sitokinien (naamlik zeatin ribosied, ZR) vlakke van 'n Sultanina tafeldruif wingerd is oor twee seisoene ondersoek na toediening op verskillende tye voor bot. Waterstofsiaanamied is in 1997 drie weke en in 1998 ses weke voor geïnduseerde bot toegedien. Een jaar oue lote is weekliks gemonster na waterstofsiaanamied toediening, verdeel in apikale en basale gedeeltes en verder verdeel in ogies, bas en houtweefsel en die ZR vlakke bepaal. Relatief hoër vlakke koue, gekoppel met later watersiaanamied toediening het in 1997 tot 'n groot effek op ZR vlakke gelei, maar het nie die botpatroon wesentlik verskuif nie. Zeatin ribosied pieke is waargeneem in ogies, internode hout en bas van behandelde wingerd in vergelyking met kontrole wingerd. Die pieke was hoër in apikale gedeeltes in vergelyking met basale gedeeltes in alle weefsels. Die relatief laer koue en vroeër toediening van waterstofsiaanamied in 1998 het 'n groter effek op die botpatroon gehad, terwyl die ogie ZR piek vroeër geskuif is. Die apikale gedeelte se ogie ZR piek was weereens hoër as die basale gedeelte se ogie ZR piek. Monstering was nie vroeg genoeg begin in 1997 nie, aangesien ogie ZR pieke slegs na bot waargeneem is, terwylogie ZR pieke in 1998 voor en na bot waargeneem is. Die effek van hierdie verhoging in ZR vlakke op die ontwikkeling van blom primordia, daaropvolgende tros ontwikkeling en uiteindelik produksie, is bespreek. b. Vry xileemsap is gemonster van langdraer en kortdraer gedeeltes van ongesnoeide lote van Sultanina vanaf ogieswel tot na bot in 1999 en vanaf drie tafeldruif kultivars, naamlik Sultanina, Alphonse lavalleé en Sunred Seedless, in 2001 en die ZR vlakke bepaal. Die ZR vlakke van ogies van hierdie drie kultivars, gesnoei tot verskillende lootlengtes is ook bepaal. Eenjarige lote van hierdie kultivars is gesnoei tot langdraers (14 ogies) en kortdraers (2 ogies). Die ZR vlakke in ogies geleë op apikale en basale gedeeltes van hierdie lote is weekliks in 1999 bepaal vanaf ogieswel tot na bot Xileemsap ZR pieke is waargeneem voor 50% bot. Kortdraer xileemsap ZR vlakke het 'n soortgelyke patroon as die langdraers gevolg vir al drie kultivars, alhoewel teen laer ZR vlakke as die langdraers. Hierdie waarneming is soortgelyk aan vorige studies op xileemsap ZR vlakke van appel lote. Die hoë ZR vlakke gevind in die xileemsap van die apikale gedeeltes van lote ondersteun die hipotese van 'n kumulatiewe opbou van ZR soos die lengte van die loot toeneem. Die snoei van lote as kortdraers het gelei tot vroeër bot en 'n hoër finale bot persentasie as die snoei van langdraers. Die basale gedeeltes van lote het verhoogde ZR vlakke in al drie kultivars getoon, onafhanklik van die feit dat dit vanaf die kortdraer of die basale gedeelte van 'n langdraer was. Hierdie verskil in ZR vlakke in ogie weefsel van verskillende gedeeltes van die loot impliseer 'n verskil in ZR verbruik of omset. The resultate van hierdie studie het belangrike bestuursimplikasies vir die verbouing van wingerd in warmer gebiede, waar waterstofsiaanamied gebruik word om botprobleme te oorkom.

Thesis (MScAgric (Soil Science))--University of Stellenbosch, 2008. / In order to produce table grapes of export quality economically, irrigation must be practised conservatively without adversely affecting the crop. To use water as conservatively as possible effective irrigation scheduling practices must be applied. The highest water use efficiency (WUE) is only possible if irrigation scheduling practices lower the amount of water applied, while at the same time they increase the yield. The first aim of this project is to investigate whether current irrigation practices make efficient use of water by comparing irrigation requirements determined using theoretical models with actual irrigation applied for two seasons (2005/6 and 2006/7). Secondly, the effect of cumulative irrigation on the chemical status of soil in 16 blocks was investigated to establish whether nutrient leaching as a result of differential water use may have had an influence on yield. Six blocks (three dripper and three microsprinkler blocks) were selected and irrigation requirements were determined using evaporation pan calculations, SAPWAT and Vinet and compared with actual irrigation applications. Furthermore, a yield-irrigation index (kg/m3) and an income-irrigation index (R/m3) were determined for each of the six blocks and compared. To investigate the effect of cumulative water use on the chemical status of the soils of 16 blocks, soil samples were taken and analysed for pH (1M KCl), EC (1:5); soluble cations and anions (Ca, Mg, Na, K, SO4, NO3, and Cl), ammonium acetate extractable cations (Ca, Mg, Na and K) and micro elements (Zn, Fe, Mn, Cu and B). The irrigation requirements predicted by the different irrigation scheduling methods are variable. For Vinet, the irrigation requirement determined for microsprinkler irrigation is much higher than that determined using the evaporation pan or SAPWAT approaches. Comparison of the irrigation applied to each of these blocks does not clarify whether any irrigation scheduling takes place. Results showed a relationship between the yield-irrigation index and income-irrigation index. It has not however been verified whether this relationship is statistically significant.

Thesis (MscAgric (Viticulture and Oenology))--University of Stellenbosch, 2007. / Regal Seedless is a white, seedless grape which has the potential to become a profitable cultivar for the table grape producer since it has the advantages of early season harvesting and inherently large berries. There is, however, a downside to this cultivar, namely the seasonal occurrence of an unacceptable, astringent taste. This negative taste affects the demand by local and international markets. The astringency perception is due to the presence of phenolic compounds. It is well known that the phenolic composition and concentration change during the ripening of the grape. Different postharvest treatments are applied to fresh fruit like persimmons to remove astringency. These treatments include the use of carbon dioxide, nitrogen and ethanol. The aim of this study was to determine the optimum maturity level for Regal Seedless where the phenolic concentration is the lowest and the astringent taste acceptable. The use of postharvest treatments to manipulate the taste and the phenolic content, were also investigated. The effect on other quality parameters like total soluble solids (TSS), pH and total titratable acidity (TTA) were also evaluated.

Thesis (MScAgric) -- University of Stellenbosch, 2002. / ENGLISH ABSTRACT: The table grape industry is a major contributor to the South African economy, directly through foreign earnings from this predominantly export-based industry, as well as indirectly through the employment of thousands of people. It is a growing industry and consists of several production areas. The fastest growing table grape production area in South Africa is the Lower Orange River area, which produces some of the earliest grapes in the Southern Hemisphere. The biggest river in South Africa irrigates this area and it has an extreme climate characteristic of semi-desert areas. This area is considered to be optimal for the production of high quality, early, white seedless grapes. Previously, this area was predominantly planted to Sultanina vines for the purpose of raisin production. When seedless table grapes became a consumer preference, the producers very successfully converted their production practices to yield export quality seedless grapes from the established Sultanina vineyards. Extensive new plantings as well as re-plantings occurred in this area, also including newer cultivars from local and overseas breeding programmes. Being a viticultural and economical hot-spot, the Lower Orange River area is attracting much attention as a table grape production area and it also formed the backdrop to this study. The cultivar profile is changing in the area and it is projected that Sultana-, Regal-, Prime Seedless and Sugraone will be the four major early, white seedless cultivars in 2005. Based on this knowledge and prompted by a lack of information regarding production costs and general profitability of the new cultivars, this study was initiated in the form of a comparative analysis between the four mentioned cultivars spanning the early, middle and late regions of the Lower Orange River area. The approach used extracted information regarding cultural input costs (specifically labour as man-hours and the consequent costs) per manipulation performed in the vineyards. This approach is different from the more general method of obtaining input costs for a specific area based on combined mean values, often not distinguishing between cultivars. The specific aims of the study included a comparative analysis of input costs for production cultural practices per main manipulation action, as well as a comparative analysis taking into account productivity, value and extraordinary costs related to each of the four cultivars. To this end, 22 experimental plots were identified for use in the study. Collaboration of the production managers of each of the experimental plots were procured and information regarding production costs per manipulation and productivity of each cultivar and experimental plot were extracted from their own record keeping systems or from documents provided to the production managers. The value (price achieved) of the various cultivars for the 2001/2002 table grape season were put into perspective by using data from a survey which included information regarding payments for the various cultivars during the season in the Lower Orange River area. Information regarding fruit and vine royalties was obtained from the various plant breeders' rights holders of the various cultivars, where applicable. Primary descriptions of each experimental plot concerning general cultivation practices and information regarding the specific season were used to qualify results obtained from the various blocks. Several complicating factors impacted on the study and specifically the subsequent analyses of the results. Some of the factors were already identified as complicating factors in the planning stage of the study and were mostly linked to the recent introduction of two of the cultivars to the Orange River area. From the data gathered and the analyses performed it became clear that it would be difficult to discern significant differences (where significant is defined as PS0.10), but clear trends were observed and indications obtained. Based on the input cost analyses of this study it is proposed that mature Prime Seedless will have the highest labour input and cultural production cost of the four cultivars, followed by Sugraone. The labour input and the cost for the production cultural practices studied for young Prime Seedless vines were very high in comparison to the mature Sultana Seedless and Sugraone vines, especially for the canopy management and bunch manipulation actions. Prime Seedless was especially prone to the set of small and uneven berries, which lead to very high labour input requirements and subsequent cost for bunch manipulations. Sugraone is also known for the set of small and uneven berries in the Lower Orange River area, especially in difficult climatic seasons, also requiring high labour input for bunch manipulations. The initial indication is that mature Sultana- and Regal Seedless will require similar labour inputs for cultural production practices. The fact that Regal Seedless does not require expensive gibberellic acid (GA) applications, or girdling for thinning and berry enlargement purposes, is a tremendous advantage from a production cost point of view. Accordingly, initial indications are that Regal Seedless will have the lowest cultural production cost of the four cultivars. Regal Seedless was prone to the set of uneven berries during the year of study and accordingly it is suspected that this factor will ultimately determine the labour requirements and cultural production input cost, especially in difficult climatic seasons. The labour input and ultimately the cultural production cost for Sultana Seedless will be determined by the correct timing and concentration of the GA applications for thinning and berry sizing. Sultana Seedless and Sugraone produced high yields during the 2001/2002 table grape season in the Lower Orange River area. Yield information from the various experimental plots confirmed that there is little to choose between the two cultivars in terms of yield when cultivation conditions and practices are optimal. Large variation was observed in the yield results from the Regal- and Prime Seedless experimental plots. This is largely due to the recent introduction of the cultivars to the area and the consequent scarcity of blocks of these cultivars that are in full production. It was impossible to identify clear trends in terms of the future productivity of mature Regal- and Prime Seedless, but some indications of labour inputs could be extracted and qualified. Early maturing Prime Seedless and Sugraone performed very well in terms of price, especially in the harvest period prior to week 50. This advantage of high prices early in the season is, however, not always applicable to early cultivars in the later maturing regions of the Lower Orange River area. Later during the season, after week 50, when the supply of table grapes to the overseas markets has increased sharply, Sultana Seedless is usually the best performer in terms of price of the four cultivars. The ultimate price obtained by a cultivar is to a large extent determined by supply and demand, quality and acceptance of the specific cultivar. This study and its outcomes have a strong regional (Lower Orange River) and local (South Africa) impact and the specific results will undoubtedly be valuable to the producers, exporters and other role-players with vested interest in the cultivars studied or in table grape production per se. The methodology adopted in this study, however, is of broader interest and dearly shows the advantage of having detailed and qualified information regarding cultivation practices and bringing it in relation to the labour and consequent costs required per action. This should lead to more business intelligence and realistic planning on the producer side when decisions regarding the choice of a cultivar for a specific production area with a particular marketing scope have to be made. This study has also paved the way for similar studies, specifically with regard to the detailed description of the methodology that was established. Knowledge of the problems experienced in this study provides a useful reference for the planning and execution of similar studies. / AFRIKAANSE OPSOMMING: Die tafeldruifindustrie dra grootskaals by tot die Suid- Afrikaanse ekonomie: regstreeks deur middel van buitelandse valuta vanaf hierdie hoofsaaklik uitvoer-gebaseerde industrie, asook indirek deur werkverskaffing aan duisende mense. Dit is 'n vinnig groeiende industrie en bestaan uit verskeie produksie-areas waarvan die Benede-Oranjerivierarea, waar van die vroegste druiwe in die suidelike halfrond geproduseer word, tans die meeste groei toon. Die grootste rivier in Suid-Afrika vloei deur hierdie gebied wat deur uiterste klimaatstoestande, soortgelyk aan die van semi-woestyngebiede, gekenmerk word. Hierdie gebied is baie gunstig vir die produksie van hoë-gehalte, vroeë, wit pitlose druiwe. In die verlede is hoofsaaklik Sultanina vir die produksie van rosyne in hierdie gebied verbou. Namate pitlose tafeldruiwe voorkeur begin geniet het onder verbruikers wêreldwyd, het produseerders in die area hul verbouingspraktyke suksesvol aangepas vir die produksie van uitvoergehalte tafeldruiwe vanaf die grootskaalse, reeds gevestigde Sultanina-wingerde. Uitgebreide aanplantings en heraanplantings, wat nuwe cultivars van plaaslike en oorsese teelprogramme ingesluit het, is in hierdie gebied gedoen. Die vinnige groei in tafeldruifaanplantings en -uitvoere, asook die ekonomiese impak van die industrie in die Benede-Oranjeriviergebied, het die afgelope aantal jaar sterk op die voorgrond getree en het gevolglik gedien as agtergrond vir hierdie studie. Die cultivarprofiel in dié area is besig om te verander en volgens vooruitskattings gaan Sultana, Regal, Prime Seedless en Sugraone die vier prominente vroeë, wit, pitlose tafeldruifcultivars in 2005 wees. Gebaseer op hierdie feit en na aanleiding van 'n behoefte aan meer inligting met betrekking tot produksiekostes en algemene winsgewendheid van die nuwe cultivars, is 'n vergelykende studie aangaande die vier genoemde cultivars in die Benede-Oranjeriviergebied geloods. Die benadering wat gedurende die studie gevolg is, het inligting aangaande produksie-insetkoste (spesifiek arbeid in man-ure en gevolglike koste) per manipulasie onttrek. Hierdie benadering verskil van die meer algemene metodiek om insetkoste-inligting van 'n spesifieke area van gekombineerde gemiddelde waardes te verkry. Met so 'n benadering word gewoonlik geen onderskeid tussen cultivars getref nie. Die spesifieke doelwitte van hierdie studie het 'n vergelykende analise aangaande die insetkoste van die produksiepraktyke per hoofmanipulasie/aksie ingesluit, asook 'n analise waar produktiwiteit, waarde en buitengewone koste van die vier cultivars in ag geneem is. In totaal is 22 eksperimentele persele gebruik in die studie. Samewerking van die produksiebestuurders van die onderskeie esperimentele persele is verkry ten opsigte van die verskaffing van inligting oor produksiekoste per manipulasie, en die produktiwiteit per cultivar en eksperimentele perseel. Die produksiebestuurders het die nodige dokumente ontvang om die inligting te onttrek, of kon die inligting verskaf soos dit in hul rekordhoudingsisteem voorgekom het. Die waarde (prys behaal) van die onderskeie cultivars vir die 2001/2002-seisoen is in perspektief gestel deur gebruik te maak van 'n opname wat in die Benede Oranjeriviergebied plaasgevind het. Hierdie opname het inligting oor die uitbetalings van die onderskeie cultivars in die area vir die 2001/2002- seisoen ingesluit. Inligting rakende die stok- en vrugproduksie-tantieme is vanaf die onderskeie plantttelersregtehouers van die cultivars verkry. Primêre beskywings van die algemene verbouingspraktyke van elke eksperimentele blok en inligting oor die spesifieke seisoen is gebruik om die data wat vanaf die esperimentele persele verkry is, in perskektief te stel. Verskeie kompliserende faktore het die studie en die ontleding van data beïnvloed. Verskeie van hierdie faktore is reeds geidentifiseer met die beplanning van die studie en was meestal gekoppel aan die onlangse bekendstelling van Regal en Prime Seedless aan die Benede-Oranjeriviergebied. Na aanleiding van die data wat ingesamel en ontleed is, was dit duidelik dat dit moeilik sou wees om betekenisvolle verskille (waar "betekenisvol" as PS0.10 gedifinieer is) tussen die cultivars uit te lig, maar dat dit egter wel moontlik sou wees om aanvanklike indikasies en tendense te kry. Gebaseer op die insetkoste-ontleding van die studie blyk dit dat volwasse Prime Seedless die hoogste arbeidsinsetle en produksiekoste van die vier cultivars gaan hê, gevolg deur Sugraone. Die arbeidsinsetle en koste van die produksie-aksies wat van jong Prime Seedless bestudeer is, was baie hoog in vergelyking met volwasse Sultana Seedless- en Sugraone-stokke, veral ten opsigte van lowerbestuur en trosmanipulasies. Prime Seedless was veral geneig tot die set van klein, oneweredige korrels, wat tot baie hoë arbeidsinsetle en gevolglik koste vir trosmanipulasies gelei het. Sugraone is ook daarvoor bekend dat dit geneig is tot die set van klein, oneweredige korrels in die Benede-Oranjeriviergebied (veral in moeilike klimaatseisoene), wat gevolglik tot hoë arbeidsinstle vir trosmanipulasie lei. Die aanvanklike aanduiding is dat volwasse Sultana en Regal Seedless min of meer die dieselfde arbeidsinsetle vir verbouing sal vereis. Die feit dat Regal Seedless nie duur gibberelliensuur (GS)-behandelings vir blomtrosuitdunning of korrelvergroting benodig nie, is 'n enorme voordeel in terme van produksiekoste. Gevolglik is die aanvanklike aanduiding dat Regal Seedless die laagste produksieskoste van die vier cultivars sal hê. In die studiejaar was Regal Seedless egter geneig tot die set van onweredige korrels en gevolglik word verwag dat hierdie faktor uiteindelik die arbeidsinsetle en produsiekoste van die cultivar sal bepaal, veral in moeilike klimaatseisoene. Die arbiedsinsetle en produksiekoste van Sultana Seedless sal bepaal word deur die korrekte tydsberekening en konsentrasie van die GS-behandelings vir uitdunning en korrelvergroting. Sultana Seedless en Sugraone het gedurende die 2001/2002-seisoen hoë opbrengste in die Benede-Oranjeriviergebied geproduseer. Oesdata inligting van die onderskeie esperimentele persele het bevestig dat daar min te kies is tussen die twee cultivars in terme van produktiwiteit wanneer verbouingstoestande en -praktyke optimaal is. Groot variasie is egter waargeneem in die opbrengsresultate van die Regal en Prime Seedless. Dit is hoofsaaklik as gevolg van die onlangse bekendstelling van die twee cultivars in die area en dus ook die beperkte aantal blokke van die cultivars wat reeds in vol produksie was. Dit was dus onmoontlik om duidelike tendense in terme van die toekomstige produksie van volwasse Regal en Prime Seedless te identifiseer. Indikasies van arbeidsinsette en produksiekoste kon egter wel verkry word. Vroeg rypwordende Prime Seedless en Sugraone vaar baie goed in terme van die prys wat dit behaal, veral in die oesperiode voor week 50. Hierdie voordeel van hoë pryse behaal vroeg in die seisoen is egter nie altyd van toepassing op vroeë cultivars in die later rypwordende areas van die Benede-Oranjeriviergebied nie. Later in die seisoen (na week 50), wanneer die aanbod van tafeldruiwe op oorsese markte skerp toegeneem het, is Sultana Seedless gewoonlik die beste presteerder in terme van prys van die vier cultivars. Die uiteindelike prys wat deur cultivars behaal word, word tot 'n groot mate bepaal deur vraag en aanbod, kwaliteit en aanvaarding van die cultivar deur die verbruiker. Die studie en die uitkomste daarvan het 'n sterk streeks (Benede-Oranjerivier) en plaaslike (Suid-Afrika) impak, en die spesifieke resultate salongetwyfeld van waarde wees vir produseerders, uitvoerders en ander rolspelers met bestaande belange in die cultivars of vir tafeldruifproduksie as sulks. Die metodiek wat in hierdie studie gebruik is, is egter van breêr belang en wys duidelik die voordele daarvan om gedetailleerde en gekwalifiseerde inligting aangaande produksiepraktyke te hê, wat dit ook in verband bring met arbeid en gevolglike koste per aksie. Dit behoort te lei tot meer besigheidsintelligensie en realistiese beplanning deur die produseerder met betrekking tot cultivarkeuse vir 'n spesifieke produksiearea met 'n spesifieke bemarkings geleentheid. Hierdie studie het ook die weg gebaan vir soortgelyke studies, spesifiek ten opsigte van die gedetailleerde beskrywing van die metodiek wat gevestig is. Kennis van die probleme wat in hierdie studie ondervind is, kan dien as nuttige verwysing vir die beplanning en uitvoer van soortgelyke studies.

Thesis (PhD (Agric) (Conservation Ecology and Entomology))--University of Stellenbosch, 2006. / A study was performed to develop a generic pest monitoring system for sampling the main table grape pests in vineyards in the Hex River Valley, Western Cape Province of South Africa. The presence of phytophagous and predatory mites on cover crop plants was also investigated as this may contribute to biological control of the phytophagous mites in vines. Life table studies for Epichoristodes acerbella (Walker), an important phytosanitary pest, were conducted to determine whether or not this pest was sensitive to high temperatures. Information gained from the latter can also be used for breeding purposes in the possible future development of a sterile insect technique (SIT) programme to control this pest. The sampling system consisted of inspecting 20 plots of five vines per plot per one to two hectares. The top fork of each of the five vines per plot was examined for Planococcus ficus (Signoret) to a distance of within 30 cm of the stem, as well as the distal 15 cm of one cane per vine for the presence of P. ficus and damage caused by Phlyctinus callosus Boh. One bunch per vine was examined for insect damage or presence, and one leaf per vine for the presence of leaf infesting arthropods, such as Tetranychus urticae Koch, P. ficus and Frankliniella occidentalis (Pergande). Corrugated cardboard bands, tied around the stem of one vine per plot, were used to monitor activity of P. callosus. Blue sticky traps, at a density of four to five traps per one to two hectares, were used to monitor activity of F. occidentalis. Pheromone traps, at a density of one trap per one to two hectares, were used to monitor activity of P. ficus, E. acerbella and Helicoverpa armigera (Hübner). All the above-mentioned inspections were done at two-weekly intervals, except traps for E. acerbella and H. armigera, which were inspected weekly. In each of the rows in which the sample plots were situated, one leaf of each of the cover crop plant species was examined for the presence of phytophagous mites and their predators. The abundance and distribution of cover crop plants were determined using a co-ordinate sampling system. Cover crop sampling was done at monthly intervals. The current threshold for P. ficus is 2% stem infestation, which is reached when more than 65 males per pheromone trap are recorded. Counting mealybugs on the sticky pads in the pheromone traps is time consuming. However, the number of grid blocks on the sticky pad with males present can be counted. When P. ficus males are found in 27 blocks on the sticky pad, stem inspections should commence. Due to the spatial association between P. ficus bunch and stem infestation, stem infestation could give an indication of where bunch infestation could be expected. The use of blue sticky traps for predicting halo spot damage, caused by F. occidentalis, is not recommended. The presence of thrips on the vine leaves could not give an indication of where to expect bunch damage, since thrips on the leaves and halo spot damage were not spatially associated. A suitable sampling method for F. occidentalis still needs to be developed. The monitoring system described here can only provide information on the infestation status of the vineyard. For E. acerbella, H. armigera and P. callosus, the traps and cardboard bands could be used to identify vineyards where these pests are present and therefore, where phytosanitary problems may arise. The presence of P. callosus under the bands was spatially associated with P. callosus damage and could be used as an indicator of the latter. The presence of drosophilid flies in the bunches could not be used as an indicator of the presence of E. acerbella in the bunches. If 5% bunch damage is used as an economic threshold for E. acerbella and P. callosus, there will be a good chance of not under spraying if control measures are applied at 1% bunch damage. Epichoristodes acerbella favoured more moderate constant temperatures, with constant temperatures of 28°C and above being unfavourable for development. The economic threshold for Tetranychus urticae Koch is six mites per leaf, or if presence-absence sampling is used, 11 to 29% leaf infestation. Three important predatory mites, that kept T. urticae under control, were found in the Hex River Valley, namely Euseius addoensis (Van der Merwe & Ryke), Neoseiulus californicus (McGregor) and an undescribed phytoseiid in the genus Typhlodromus. Various cover crop plants served as hosts for T. urticae and predatory mites. The presence of these plants created suitable conditions for the survival of these mites and may have influenced their presence on the vine leaves. In the case of phytosanitary pests, both field and pack shed inspections can be used to conclude with a 99% degree of certainty that infestation levels in the pack shed will be 10% or less, since similar results for both methods were obtained. However, more than 20 plots will have to be inspected.

Thesis (MScAgric)--University of Stellenbosch, 2007. / ENGLISH ABSTRACT: The declaration of Namibia’s independence from South Africa in 1990 has seen the Namibian government aim to plan and implement development programmes that enhance a growing agricultural sector. The new government is facing challenges regarding the addressing of inequalities of income and the allocation and distribution of resources, which have resulted in implementation of the land reform programmes. On the international front, Namibia is a member country of various trade arrangements, such as the WTO, the SADC and SACU. The main driving force behind Namibia’s joining the international communities chiefly has been market access and trade policy reforms. The country’s agricultural sector, in particular the horticultural industry, in regards to table grape production, has been significantly affected by both domestic and regional policies, as well as by the WTO rules. The aim of this study is to determine the environmental factors that create a competitive advantage for the Namibian table grape industry in the international market. A detailed supply-chain analysis, augmented by Porter’s ‘diamond’ model, is used in this study to assess the determinants of the competitiveness of fresh table grapes. Interviews were conducted in informal, semi-structured questions. The questionnaires were mailed to several producers within the table grape-growing industry. Secondary information was obtained from reports, articles and research publications, among other sources. An expert assessment was used to verify information based on the reference methods. Consultations took place in the form of office visits and, in some cases, telephone interviews were held with different experts. The finding of the study shows that Namibia can supply the European markets during the northern hemisphere off-season with quality fresh table grapes. However, industry growth in the European Union (EU) market is constrained by limited free import quotas and high tariffs, specifically as regards seeded fresh table grapes, which are not exempt from such duties. Such constraints are in place despite Namibia’s meeting of international set quality standards, such as EUREPGAP. Moreover, there is potential for increasing supplies to the regional and Asian markets as well as the US market albeit to the lesser extent. Finally, Namibian fresh table grapes profitability is significantly affected by the high production and transaction costs incurred, as well as by the decline in business and the depreciation of the US Dollar against the Namibian Dollar. The study makes the general recommendation that producers should significantly reduce their transaction costs within the chain, by means of vertical co-ordination and integration. / AFRIKAANSE OPSOMMING: Met die verklaring van Namibië se onafhanklikheid van Suid-Afrika in 1990 het die Namibiese regering hulle dit ten doel gestel om ontwikkelingsprogramme te beplan en in werking te stel ten einde daardie land se groeiende landbousektor te versterk. Die nuwe regering moet tans uitdagings met betrekking tot inkomsteongelykhede en die toekenning en verspreiding van hulpbronne die hoof bied wat tot die inwerkingstelling van grondhervormingsprogramme aanleiding gegee het. Internasionaal is Namibië 'n lidland van verskeie handelsreëlings soos die Wêreldhandelsorganisasie (WHO), die Suider-Afrikaanse Ontwikkelingsgemeenskap (SAOG) en die Suider-Afrikaanse Doeane-unie (SADU). Die twee hooffaktore wat daartoe gelei het dat Namibië hom by die internasionale gemeenskappe skaar, is marktoegang en handelsbeleidhervormings. Die land se landbousektor, in besonder die tuinboukundige bedryf met die klem op tafeldruifproduksie, is aansienlik deur binnelandse en streeksbeleid asook deur die WHO-reëls geraak. Die doel van hierdie studie is om die omgewingsfaktore te bepaal wat in die internasionale mark aan die Namibiese tafeldruifbedryf 'n mededingende voordeel gee. Derhalwe gebruik die navorser 'n gedetailleerde aanvoerkettingontleding, ondersteun deur Porter se “diamantmodel”, om die beslissende faktore vir die mededingendheid van vars tafeldruiwe te evalueer. Onderhoude is met behulp van informele, semigestruktureerde vrae gevoer. Die vraelyste is aan verskeie produsente op die gebied van tafeldruifboerdery gepos. Sekondêre inligting is ook onder andere uit verslae, artikels en navorsingspublikasies verkry. Met behulp van 'n kundige evaluering is inligting op grond van die verwysingsmetodes geverifieer. Oorlegpleging met verskeie kundiges het in die vorm van kantoorbesoeke en in sommige gevalle deur middel van telefoononderhoude plaasgevind. Die studiebevinding toon dat Namibië die Europese markte gedurende die noordelike halfrond se tussenseisoen van gehalte- vars tafeldruiwe kan voorsien. Die uitbreiding van die bedryf in die Europese Unie (EU-) mark word egter deur beperkte gratis invoerkwotas en hoë tariewe aan bande gelê, in besonder met betrekking tot pitlose, vars tafeldruiwe wat nie van invoerbelasting vrygestel is nie. Hierdie beperkinge word opgelê ten spyte daarvan dat Namibië aan vasgestelde internasionale gehaltestandaarde soos EUREPGAP voldoen. Die moontlikheid bestaan boonop om lewering aan die streeks- en Asiatiese markte asook die VS-mark te verhoog, hoewel in 'n mindere mate. Laastens word die winsgewendheid van Namibiese vars tafeldruiwe beduidend deur hoë produksie- en transaksiekoste, asook deur die afname in sake en die waardevermindering van die Amerikaanse teenoor die Namibiese dollar geraak. Die studie maak die algemene aanbeveling dat produsente hulle transaksiekoste binne die ketting aansienlik met behulp van vertikale koördinering en integrasie moet verminder.

Submitted by Bruna Thaís Ferracioli Vedoato null (bruvedoato@hotmail.com) on 2016-09-26T18:10:20Z No. of bitstreams: 1 PRODUÇÃO, QUALIDADE FÍSICO-QUÍMICA E ATIVIDADE ANTIOXIDANTE DA UVA ‘NIAGARA ROSADA’ EM DIFERENTES PORTA-ENXERTOS - BRUNA VEDOATO - 2016.pdf: 1036201 bytes, checksum: 0630db78ae8c7fd17c72d0c15d0133c7 (MD5) / Approved for entry into archive by Felipe Augusto Arakaki (arakaki@reitoria.unesp.br) on 2016-09-27T18:08:37Z (GMT) No. of bitstreams: 1 vedoato_btf_me_bot.pdf: 1036201 bytes, checksum: 0630db78ae8c7fd17c72d0c15d0133c7 (MD5) / Made available in DSpace on 2016-09-27T18:08:37Z (GMT). No. of bitstreams: 1 vedoato_btf_me_bot.pdf: 1036201 bytes, checksum: 0630db78ae8c7fd17c72d0c15d0133c7 (MD5) Previous issue date: 2016-07-28 / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / A utilização de porta-enxerto está entre as inúmeras técnicas culturais visando à melhoria na produtividade e qualidade da uva. Particularmente na região de Jundiaí-SP há uma necessidade de maiores informações sobre a influência do porta-enxerto nos aspectos produtivos e na qualidade físico-química da uva ‘Niagara Rosada’. O objetivo desse trabalho foi avaliar o efeito de diferentes porta-enxertos na produção, curva de maturação, características físico-químicas e compostos fenólicos da videira ‘Niagara Rosada’. O experimento foi realizado na área experimental do Centro de Frutas do Instituto Agronômico de Campinas, em Jundiaí-SP, nos ciclos de produção de 2013 e 2014. Foram avaliadas a evolução da maturação das uvas; produção, produtividade e número de cachos por planta; massa fresca de cacho (MFC), engaço (MFE) e bagas (MFB); comprimento de cacho (CC), engaço (CE) e bagas (CB); largura de cacho (LB), engaço (LE) e bagas (LB); relação comprimento/largura de bagas; número de bagas por cacho; teor de sólidos solúveis (SS), pH, acidez titulável (AT) e relação SS/AT; conteúdo de clorofila total, antocianinas totais, carotenoides totais, polifenóis totais, flavonoides totais e atividade antioxidante nas uvas. Os dados de produção, análises físicas e químicas, compostos fenólicos e atividade antioxidante foram submetidos à análise de variância (teste F) e as médias comparadas pelo teste Tukey, a 5% de probabilidade. Os dados obtidos para evolução da maturação foram submetidos à análise de variância (teste F) e análise de regressão polinomial. Os porta-enxertos ‘IAC 766’ e ‘106-8 Mgt’ influenciaram apenas nos teores de sólidos solúveis no mosto da videira ‘Niagara Rosada’. O ciclo de produção de 2013 induziu maior produção e produtividade; comprimento de cachos; massa fresca, comprimento e largura de bagas; pH, relação SS/AT da cultivar Niagara Rosada sobre diferentes porta-enxertos. / The use of rootstock is among the many cultural techniques aimed at improving the productivity and quality of grapes. Particularly in Jundiaí-SP region there is a need for more information about the influence of rootstock in production aspects and the physical and chemical quality of the grape 'Niagara Rosada'. The aim of this study was to evaluate the effect of different rootstocks in the yield, physical and chemical characteristics, evolution of the maturation curve, phenolic compounds and antioxidant activity of 'Niagara Rosada' grapevine. The experiment was conducted in the experimental area of the Fruit Center of Campinas Agronomic Institute in Jundiaí-SP, in 2013 and 2014 production cycles. We evaluated the yield for both plant and area, number of bunches per plant; bunch (MFC), rachis (MFE) and berries (MFB) fress mass; bunch (CC), rachis (EC) and berries (CB) lenght; bunch (LB), stems (LE) and berries (LB) width; length/width ratio of berries; number of berries per cluster; soluble solids (SS), pH, titratable acidity (TA) and SS/AT ratio; evolution of the maturation curve; total chlorophyll, total anthocyanins, total carotenoids, total polyphenol, total flavonoid and antioxidant activity in grapes. The data of yield, physical and chemical analysis, phenolic compounds and antioxidant activity of the clusters were subjected to analysis of variance (F test) and the averages compared by Tukey test at 5% probability. For data obtained from berries of sampling for the maturation were subjected to analysis of variance (F test) and polynomial regression analysis. The 'IAC 766' and '106-8 Mgt' rootstocks interfered only in soluble solids content ensuring greater values. The 2013 production cycle induced higher production and productivity; length of bunches; fresh weight, length and width of berries; pH, SS / TA Niagara Rosada on different rootstocks.

Thesis (MScAgric)--University of Stellenbosch, 2006. / ENGLISH ABSTRACT: Phaeomoniella chlamydospora, Eutypa lata, Phomopsis, Phaeoacremonium, and Botryosphaeria spp. are important trunk disease pathogens that cause premature decline and dieback of grapevine. Previous research has focused primarily on wine grapes and the incidence and symptomatology of these pathogens on table grapes were largely unknown. A survey was therefore conducted to determine the status and distribution of these pathogens and associated symptoms in climatically diverse table grape growing regions. Fifteen farms were identified in the winter rainfall (De Doorns, Paarl and Trawal) and summer rainfall (Upington and Groblersdal) areas. Samples were taken in July and August 2004 from Dan-ben-Hannah vineyards that were 8 years and older. Distal ends of arms were removed from 20 randomly selected plants in each vineyard. These sections were dissected and isolations were made from each of the various symptom types observed: brown or black vascular streaking, brown internal necrosis, wedge-shaped necrosis, watery necrosis, esca-like brown and yellow soft wood rot, as well as asymptomatic wood. Fungal isolates were identified using molecular and morphological techniques. Pa. chlamydospora was most frequently isolated (46.0%), followed by Phaeoacremonium aleophilum (10.0%), Phomopsis viticola (3.0%), Botryosphaeria obtusa (3.0%), B. rhodina (2.2%), B. parva (2.0%), Fusicoccum vitifusiforme (0.6%), B. australis, B. dothidea and an undescribed Diplodia sp. (0.2% each), while E. lata was not found. Most of these pathogens were isolated from a variety of symptom types, indicating that disease diagnosis can not be based on symptomatology alone. Pa. chlamydospora was isolated from all areas sampled, although most frequently from the winter rainfall region. Pm. aleophilum was found predominantly in Paarl, while P. viticola only occurred in this area. Although B. obtusa was not isolated from samples taken in De Doorns and Groblersdal, it was the most commonly isolated Botryosphaeria sp., being isolated from Upington, Paarl and Trawal. B. rhodina occurred only in Groblersdal and B. parva in Paarl, Trawal and Groblersdal, while B. australis was isolated from Paarl only. The rest of the isolates (33%) consisted of sterile cultures, Exochalara, Cephalosporium, Wangiella, Scytalidium, Penicillium spp. and two unidentified basidiomycetes, which were isolated from five samples with yellow esca-like symptoms from the Paarl area. These findings clearly illustrate that grapevine trunk diseases are caused by a complex of fungal pathogens, which has serious implications for disease diagnosis and management. Protection of wounds against infection by any of these trunk disease pathogens is the most efficient and cost-effective means to prevent grapevine trunk diseases. However, previous research on the effectiveness of chemical pruning wound protectants has mostly focused on the control of Eutypa dieback only. Fungicide sensitivity studies have been conducted for Pa. chlamydospora, P. viticola and Eutypa lata, but no such studies have been conducted for the pathogenic Botryosphaeria species from grapevine in South Africa. Ten fungicides were therefore tested in vitro for their efficacy on mycelial inhibition of the four most common and/or pathogenic Botryosphaeria species in South Africa, B. australis, B. obtusa, B. parva and B. rhodina. Iprodione, pyrimethanil, copper ammonium acetate, kresoxim-methyl and boscalid were ineffective in inhibiting the mycelial growth at the highest concentration tested (5 μg/ml; 20 μg/ml for copper ammonium acetate). Benomyl, tebuconazole, prochloraz manganese chloride and flusilazole were the most effective fungicides with EC50 values for the different species ranging from 0.36-0.55, 0.07-0.17, 0.07-1.15 and 0.04-0.36 μg/ml, respectively. These fungicides, except prochloraz manganese chloride, are registered on grapes in South Africa and were also reported to be effective against Pa. chlamydospora, P. viticola and E. lata. Results from bioassays on 1-year-old Chenin Blanc grapevine shoots indicated that benomyl, tebuconazole and prochloraz manganese chloride were most effective in limiting lesion length in pruning wounds that were inoculated with the Botryosphaeria spp after fungicide treatment. The bioassay findings were, however, inconclusive due to low and varied re-isolation data of the inoculated lesions. Benomyl, tebuconazole, prochloraz manganese chloride and flusilazole can nonetheless be identified as fungicides to be evaluated as pruning wound protectants in additional bioassays and vineyard trials against Botryosphaeria spp. as well as the other grapevine trunk disease pathogens. / AFRIKAANSE OPSOMMING: Phaeomoniella chlamydospora, Eutypa lata, Phomopsis, Phaeoacremonium, en Botryosphaeria spesies is die mees belangrikste stamsiekte patogene wat agteruitgang en vroeë terugsterwing van wingerd veroorsaak. Voorafgaande navorsing het hoofsaaklik gefokus op wyndruiwe en die voorkoms en simptomatologie van hierdie patogene op tafeldruiwe is dus grootliks onbekend. ‘n Opname is gevolglik gedoen in verskillende klimaaatsareas waar tafeldruiwe verbou word om die voorkoms en verspreiding, asook die simptome geassosieer met hierdie patogene, te bepaal. Vyftien plase is geïdentifiseer in die winter- (De Doorns, Paarl en Trawal) en somer-reënval (Upington en Groblersdal) streke. Wingerde (8 jaar en ouer) met die kultivar Dan-ben-Hannah is gekies vir opname en monsters is gedurende Julie en Augustus 2004 geneem. Die distale deel van ‘n arm is verwyder vanaf 20 lukraak gekose plante in elke wingerd. Hierdie dele is ontleed en isolasies is gemaak vanuit elke simptoomtipe wat beskryf is, naamlik bruin en swart vaskulêre verkleuring, bruin interne nekrose, wig-vormige nekrose, waterige nekrose, esca-geassosieerde bruin en geel sagte houtverrotting en asimptomatiese hout. Identifikasie van die swamagtige isolate is gedoen op grond van morfologiese eienskappe en molekulêre tegnieke. Pa. chlamydospora is die meeste geïsoleer (46.0%), gevolg deur Phaeoacremonium aleophilum (10.0%), Phomopsis viticola (3.0%), Botryosphaeria obtusa (3.0%), B. rhodina (2.2%), B. parva (2.0%), Fusicoccum vitifusiforme (0.6%), B. australis, B. dothidea en ‘n onbeskryfde Diplodia sp. (0.2% elk), terwyl E. lata nie geïsoleer is nie. Hierdie patogene is elk geïsoleer vanuit ‘n verskeidenheid simptoomtipes, wat daarop dui dat siektediagnose nie alleenlik op simptomatologie gebaseer kan word nie. Pa. chlamydospora is geïsoleer vanuit al die gebiede, alhoewel die patogeen opmerklik meer voorgekom het in die winter-reënval area. Pm. aleophilum het hoofsaaklik voorgekom in Paarl, terwyl P. viticola slegs in hierdie area voorgekom het. Alhoewel B. obtusa nie voorgekom het in die De Doorns en Groblersdal areas nie, was dit die mees algemeen geïsoleerde Botryosphaeria sp. en het in Upington, Paarl en Trawal voorgekom. B. rhodina het slegs in Groblersdal voorgekom, B. parva in Paarl, Groblersdal en Trawal en B. australis het slegs in Paarl voorgekom. Die res van die isolate (33%) het bestaan uit steriele kulture, Exochalara, Cephalosporium, Wangiella, Scytalidium, en Penicillium spesies asook twee onbekende basidiomycete isolate, geïsoleer vanuit vyf monsters met geel eska-geassosieerde simptome vanuit die Paarl area. Hierdie resultate illustreer dus die feit dat wingerdstamsiektes deur ‘n kompleks van swampatogene veroorsaak word, wat belangrike implikasies het vir die bestuur en diagnose van hierdie siektes. Wondbeskerming teen infeksie van enige van hierdie stamsiekte patogene is die mees doeltreffende en koste-effektiewe manier om wingerdstamsiektes te voorkom. Vorige navorsing aangaande die effektiwiteit van chemiese wondbeskermingsmiddels het egter slegs gefokus op die beheer van Eutypa terugsterwing. In vitro swamdoder sensitiwiteitstoetse is gedoen vir Pa. chlamydospora, P. viticola en Eutypa lata, maar geen studies is al gedoen ten opsigte van die patogeniese Botryosphaeria spesies op wingerd in Suid-Afrika nie. Tien swamdoders is dus getoets vir inhibisie van in vitro miseliumgroei van die vier mees algemene en/of patogeniese Botryosphaeria spesies wat in Suid-Afrika voorkom, naamlik B. australis, B. obtusa, B. parva en B. rhodina. Iprodione, pyrimethanil, koper ammonium asetaat, kresoxim-metiel en boscalid was oneffektief by die hoogste konsentrasies getoets (5 μg/ml; 20 μg/ml vir koper ammonium asetaat). Benomyl, tebuconasool, prochloraz mangaan chloried en flusilasool was die mees effektiewe swamdoders met EC50 waardes tussen 0.36-0.55, 0.07-0.17, 0.07-1.15 en 0.04-0.36 μg/ml, onderskeidelik vir die verskillende spesies. Hierdie fungisiedes, behalwe prochloraz mangaan chloried, is geregistreer op druiwe in Suid-Afrika en is ook effektief gevind teenoor Pa. chlamydospora, P. viticola en E. lata. Resultate van biotoetse op 1-jaar-oue Chenin Blanc wingerd lote het getoon dat benomyl, tebuconasool en prochloraz mangaan chloried die effektiefste was om die lengte van letsels in snoeiwonde, geinokuleer met Botryosphaeria spesies na die aanwending van swamdoder behandelings, te verminder. Die bevindinge was egter onbeslis as gevolg van die lae en variërende her-isolerings data. Benomyl, tebuconasool, prochloraz mangaan chloried en flusilasool kan egter geïdentifiseer word as swamdoders wat verder geevalueer kan word as snoeiwond beskermingsmiddels teen Botryosphaeria spesies asook ander wingerd stamsiekte patogene in verdere biotoetse en wingerdproewe.

Thesis (MScAgric (Viticulture and Oenology))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: The table grape industry employ a wide range of viticultural management practices in order to produce the high quality grapes demanded by the export market. A common contributor to degrading the quality of table grapes is the occurrence of berry split, which not only has an unattractive visual effect, but also increases the berries’ susceptibility to infection by spoilage organisms. A number of environmental conditions such as rainfall and humidity, and/or agricultural practices, such as irrigation, and high density canopies, can lead to higher plant cell water content. This in turn, can increase the potential of berry split to occur. To date, the main method of berry split prevention has been the management of plant water status by; (i) regulating irrigation withdrawal times, and (ii) covering of canopies if rainfall is predicted prior to harvest. The aim of this study was to determine the effect that irrigation frequency, as induced by irrigation withdrawals; as well as boron (B) and calcium (Ca) treatments, applied as bunch directed sprays, have on pre- and post-harvest berry split. To this end, a newly released late ripening, white seedless cultivar, SoutherngrapeOne was chosen as a model cultivar as it has a high susceptibility to berry split. SoutherngrapeOne vines were subsequently subjected to a range of irrigation frequencies based on typical irrigation scheduling used in the table grape industry, which comprised of a low, medium and high frequency. The low frequency was duplicated in order to demonstrate the effect that a heavy irrigation, just before harvest may have on berry split. These treatments were further subdivided to investigate the effect that B and Ca may have on berry split. For the B treatment, four Solubor1 bunch directed sprays were applied from 8mm berry size to véraison. The Ca treatment consisted of Stopit R 2 and Caltrac R 3 bunch directed sprays applied over the same period. In addition, a combination of the B and Ca treatment were applied to investigate any possible interaction. To account for the effect of water as solvent in the B and Ca treatments, and the spraying effect, pure water as treatment was also evaluated. Control vines received no sprays. The applied irrigation treatments resulted in different plant water status conditions. Separate applications of B and Ca treatments resulted in a decrease of B and Ca content in the flesh respectively. The control and combination treatment, of B and Ca resulted in the same of B and Ca content in the flesh. Furthermore, none of the applied treatments resulted in an increase of either B or Ca content in the berry skin. It was found that the medium frequency irrigation resulted in the best irrigation strategy to prevent pre-harvest berry split. Surprisingly, all the subtreatments: B, Ca, and combination of B and Ca, resulted in an increased incidence of pre-harvest berry split when compared to the control group for the 2006/07 season. However, in the 2007/08 season only the B treatment resulted in an increase of pre-harvest berry split. Concerning post-cold-storage physiological disorders, Ca treatments appear to have reduced berry drop, but increased decay. In the 2006/07 season, the B treatment resulted in reduced post-cold-storage berry split, whereas Btreatment in the 2007/08 season had no effect. Both B and Ca should be considered as having the potential to increase the appearance of hairline cracking. Calcium treatment also led to an increase in decay which may have been as a result of the splitting it contributed to. Low frequency irrigation recieving irrigation before harvest was found to result in browner stems. Low irrigation frequencies decreased the cell size of the berry skin. The Ca treatment gave rise to thicker (weaker) cell walls, this morphological change may be responsible for the physiological disorders it caused. From these findings, it can be deduced that poorly managed irrigation, together with unnecessary application of B and/or Ca may result in an increase of berry split and other physiological disorders, with subsequent financial losses for the producer. / AFRIKAANSE OPSOMMING; Die tafeldruifindustrie maak gebruik van ’n wye reeks wingerdkundige praktyke ten einde die hoë gehalte druiwe te produseer wat die uitvoermark vereis. Korrelbars is ’n algemene verskynsel wat afbreek maak tot die gehalte van tafeldruiwe. Behalwe dat voorkoms van die druiwe benaadeel word, verhoog dit ook in vatbaarheid vir infeksie deur verrottingsveroorsakende swamme. Hoë reënval en humiditeit, sowel as wingerdkundige praktyke soos besproeiing en hoë lowerdigtheid, wat kan lei tot verhoogde waterstatus in plante, kan lei tot ’n toename in korrelbars. Daar word hoofsaaklik van twee metodes gebruik gemaak om korrelbars te beheer, naamlik die bestuur van plantwaterstatus deur; (i) beheer van besproeiingsontrekkingstye en (ii) bedekking van lowers indien reën voorspel word voor oestyd. Die doel van hierdie studie was om vas te stel wat die invloed van besproeiings frekwensies sowel as trosgerigte boor (B) en kalsium (Ca), spuitbehandelings, op voor- en na-oes korrelbars het. Die onlangs vrygestelde laat rypwordende, wit, pitlose kultivar, SoutherngrapeOne is gebruik, aangesien dit hoogs gevoelig is vir korrelbars. Stokke is aan verskillende besproeiings intervalle, soos tipies gebruiklik in die tafeldruifindustrie, blootgestel. Hierdie intervalle bestaan uit n’ lae, medium en hoë besproeiings frekwensie. Die lae besproeiings frekwensie is herhaal ten einde die invloed van besproeiing net voor oestyd op korrelbars te ondersoek. Die invloed van B- en Ca-behandeling op korrelbars is ook ondersoek. Vir die B-behandeling is vier Solubor1 trosgerigte spuite aangewend vanaf 8mm korrelgrootte tot deurslaan. Vir die Ca-behandeling is Stopit R 2 en Caltrac R 3 as trosgerigte spuite oor dieselfde tyd toegedien. Kombinasiebehandelings is ook aangewend om enige interaksie tussen B en Ca te ondersoek. Waterbehandelings is ook toegedien om die invloed van water as oplosmiddel van B- en Ca-behandelings sowel as die spuit-effek te ondersoek. Kontrole stokke is ook ingesluit en het geen spuitebehandeling ontvang nie. Die besproeiingsbehandelings het verskillende plantwater toestande tot gevolg gehad, B- en Ca-behandelings het gelei tot ’n afname in B- en Cainhoud in die vleis onderskeidelik. Die kombinasie en kontrole behandelings het eenderse hoeveelhede B en Ca in die vleis tot gevolg gehad. Geen van die aangewende behandelings gelei tot ’n toename in B- en Ca-inhoud in die dop nie. Die resultate toon dat medium besproeiings frekwensie die beste besproeiingsstrategie is om voor-oes korrelbars te voorkom. In vergelyking met die kontrole-behandeling in 2006/07, het B, Ca en die kombinasie van B en Ca, ’n toename in voor-oes korrelbars tot gevolg gehad. In die 2007/08 seisoen het slegs die B-toediening egter tot ’n toename in voor-oes korrelbars gelei. Kalsium behandelings het ’n afname in los-korrels, maar ’n verhoging in korrelbars tot gevolg gehad. In 2006/07, het B-toediening tot ’n afname in korrelbars na koelopberging gelei, maar in die 2007/08 seisoen het dit geen effek gehad nie. Beide B- en Ca-toediening het die potensiaal om haarlyn barste te veroorsaak. Kalsium toediening het bederf verhoog wat moontlik aan die hoër bars wat dit induseer toegeskryf kan word. Lae besproeiings frekwensie, het bruiner stingels veroorsaak, en ook gelei tot ’n afname van selgrootte in die dop. Die Ca-toediening het aanleiding gegee tot dikker selwande in die dop. Hierdie anatomiese veranderinge kan moontlik die rede wees vir die verhoging in fisiologise afwykings. Van hierdie bevindinge kan ons aflei dat swak bestuur van besproeiing, sowel as die onnodige aanwending van B en/of Ca, kan aanleiding gee tot ’n toename in korrelbars en ander fisiologiese afwykings, en dus finansiële verliese vir die produsent inhou.

Thesis (PhD)--Stellenbosch University, 2002 / ENGLISH ABSTRACT: Prototypes of a new polymer S02 gas-generating sheet for the control of Botrytis cinerea during the post-harvest storage of table grapes, were developed and manufactured for evaluation using a pilot scale production plant. Attention was paid to the appearance of the sheet, in order to make it technologically efficient as well as aesthetically acceptable to both industry and consumers. The storage quality of semi-commercial export consignments of various cultivars table grapes packed with the monolithic thin-film polymer S02 slow release sheet, was evaluated and compared to results obtained using the locally manufactured Uvasys S02 sheet. The following were investigated: the efficacy of the new polymer sheets in controlling storage decay, the stage at which S02 damage is manifested on table grapes, the level of S02 damage associated with different S02 concentrations, whether S02 damage is manifested more readily at a particular position on the bunch, and the possible effect of an increase in storage temperature, from an initial storage at -O.5°C to 10°C, on the levels of S02 bleaching. Results showed that the new polymer S02 sheet compared favourably with the existing, commercially available Uvasys S02 sheets. The exact S02 concentration required for effective decay control varied for different cultivars, as well as for the different types of grape packages. The S02 concentration incorporated within the sheet was shown to be lower for grapes packed in non-perforated bags, and slightly higher for those in perforated bags. Differences between cultivars occurred with regard to the level of control and the levels of S02 damage. Levels of S02 damage were also significantly affected by the storage period and temperature fluctuations. No significant differences in the levels of decay development and S02 damage were observed in relation to the orientation of the bunches in the carton. The extent of damage incurred to grape tissue by the absorption of S02 gas was determined by low-temperature scanning (LTSEM) and transmission electron microscopy (TEM) techniques. LTSEM and TEM micrographs of areas damaged by S02 gas revealed that exposure to S02 gas may lead to plasmolysis and the loss of cellular fluids. Although damage to the cell walls, cell wall structures and cell membranes, caused by S02 gas, was more prominent in the tissue layers nearer to the fruit surface, damage also occurred to a lesser extent in deeper tissue layers. S02 gas release-rate studies of polymer S02 sheets containing various concentrations Na2S205 revealed that levels of S02 gas emitted depended largely on the levels of Na2S205 incorporated into the sheets. Higher levels of S02 gas were released with the polymer sheets of higher concentrations Na2S205. The release curve for the commercial Uvasys S02 sheet was very different to that of the polymer sheets, with much higher levels of S02 gas emitted initially by the Uvasys S02 sheet compared to the polymer sheets, while the polymer sheets emitted low levels of S02 gas for longer periods compared to the Uvasys S02 sheet. The manufacturing process and the pilot scale production plant that was developed and constructed was successfully used to manufacture polymer S02 generating sheets that are technically sound and efficient, and aesthetically acceptable to industry. The efficacy of such sheets, regarding levels of decay control and S02 damage, was similar to that obtained with the presently available, commercially used Uvasys S02 sheet. / AFRIKAANSE OPSOMMING: 'n Nuwe polimeriese S02-gasvrystellingsvel vir die beheer van Botritis cinerea gedurende die na-oes opberging van tafeldruiwe is ontwikkel en vervaardig. 'n Nuwe loodsaanleg is spesiaal vir hierdie doel ontwerp en gebou. Aandag is geskenk aan die voorkoms van die velle aangesien dit belangrik is dat die nuwe velle beide tegnologies effektief en esteties aanvaarbaar moet wees vir die sagtevrugtebedryf en verbruikers. Die opbergingskwaliteit van semi-kommersiële uitvoerbesendings van verskeie kultivars tafeldruiwe, verpak met die nuwe monolitiese S02- gasvrystellingsvelle, is bepaal. Die volgende is ook bepaal: die effektiwiteit van die nuwe polimeriese velle, die stadium waarby S02-skade op die druiwe duidelik word, die vlak van S02-skade wat met verskillende konsentasies S02-gas geassosieer is, die moontlike invloed wat 'n toename in temperatuur (vanaf -0.5° tot 1DOC) op die verbleiking deur S02 sal hê, en of die S02-skade by voorkeur in 'n sekere posisie op die druiwe sal plaasvind. Die nuwe S02-vel het baie goed vergelyk met die kommersieël beskikbare Uvasys S02-vel. Die S02-konsentrasie benodig vir die effektiewe beheer van Botritis cinerea beskadiging het egter van kultivar tot kultivar verskil. Die keuse van die tipe verpakking, geperforeerd of ongeperforeerd, het ook 'n rol gespeel. Die konsentrasie S02-gas benodig vir effektiewe beheer was laer wanneer die druiwe in die nie-geperforeerde sakke verpak was. Vlakke van S02-skade is ook noemenswaardig beïnvloed deur die opbergingsperiode en variasies in temperatuur. Daar was geen duidelike verskil in die ontwikkeling van bederf en S02-skade ten opsigte van die posisie van die trosse in die karton nie. Die mate van S02-skade aan vrugweefsel is deur middel van laetemperatuurskandeerelektronmikroskopie (LTSEM) en transmissieelektronmikroskopie (TEM) bepaal. Daar is bevind dat die blootstelling aan S02 moontlik tot plasmolise en die uitlek van sellulêre vloeistof kon lei. Alhoewel S02-skade aan die selwande en membrane meer prominent in die weefsel naby die oppervlak van die vrug was, het skade ook in die onderliggende lae plaasgevind. Die vlakke van vrygestelde S02-gas het grootendeels afgehang van die konsentrasie natriummetabisulfiet in die velle. Die S02-vrystellingskurwe van die nuut ontwikkelde polimeriese S02-velle het baie verskil van dié van die Uvasys vel. Laasgenoemde lewer aanvanklik 'n hoë konsentrasie vrygestelde S02-gas vir 'n kort periode, gevolg deur baie lae S02 vlakke daarna, terwyl eersgenoemde 'n laer aanvanklike S02 vrystelling het, gevolg deur vergelykederwys hoër S02 konsentrasies daarna. Die ontwikkelde vervaardigingsproses en die loodsaanleg wat daaruit voortgevloei het is dus suksesvol aangewend om goeie polimeriese S02- vrystellingsvelle te vervaardig. Hierdie velle is tegnies effektief vir die beheer van Bofrifis cinerea gedurende die na-oes verpakking van tafeldruiwe en is esteties aanvaarbaar vir die Suid Afrikaanse sagtevrugtebedryf.