Thesis (MScAgric (Horticulture))--University of Stellenbosch, 2011. / Includes bibliography. / ENGLISH ABSTRACT: Climatic differences between production areas or seasons directly affect the rate of fruit maturation and the eating quality following storage and ripening. South African ‘Forelle’ pears are harvested at an optimum firmness of 6.4 kg and have mandatory cold storage duration of 12 weeks at -0.5°C to ensure even ripening. The firmness variable alone, however, is not a good indicator of ripening potential. Hence, various maturity variables (ethylene production, ground colour, firmness, total soluble solids (TSS) titratable acidity (TA), and starch breakdown) and their rates of change were evaluated to identify consistent maturity indices that can be reliably used in a prediction model to determine optimum harvest maturity (Chapter 2). This was then related to the ripening potential (Chapter 3) and eating quality (Chapter 4), defined by optimum ‘edible firmness’ (3.5 kg), presence or absence of astringency or mealiness. Fruit were harvested from three main producing areas: Warm Bokkeveld (WBV), Elgin and Koue Bokkeveld (KBV). Harvesting was done biweekly on five harvest dates over three successive seasons (2007-2009). At harvest, 20 of 240 fruit per block were used to determine maturity using all the mentioned parameters in order to understand their changes and behaviour pre-harvest. The remaining 220 fruit were stored at -0.5°C for three storage durations followed by ripening at 15°C. At harvest, the 2007 season’s fruit were more advanced in ground colour and were significantly softer (6.7 kg) than the 2008 (7.0 kg) and 2009 (7.1 kg) seasons. Firmness, ground colour, TSS and TA, all displayed a linear relationship with days after full bloom. For the firmness and ground colour, more than 90% and 73%, respectively, was explained by the variation in the linear model, while for the TSS and TA less than 70% could be accounted for by the model. Fruit harvested before commercial harvest (pre-optimum) in 2007 and 2009 failed to ripen to an ‘edible firmness’ when stored for eight weeks at -0.5oC plus 11 days at 15oC. In 2008, eight weeks storage was sufficient to induce ripening changes in pre-optimum harvested fruit. The development of ripening potential in the 2008 earlier harvested fruit, corresponded with a higher rate of change (3.15 µL.kg-1.h-1.day-1) in ethylene production at 15oC compared to the 2007 (1.98 µL.kg-1.h-1.day-1) and 2009 (1.87 µL.kg-1.h-1.day-1) seasons. The 2007 season fruit experienced maximum incidence of astringency (36.7%) on the first harvested fruit. In all three seasons, fruit harvested at commercial harvest time and later (optimum and post-optimum), required an eight week storage period to induce ripening. However, the eight weeks storage period developed highest mealiness. More than 40% of the last harvested fruit were mealy after eight weeks at -0.5°C plus seven days at 15°C. Mealiness significantly reduced with prolonged storage at -0.5°C. Fruit from the WBV and Elgin, warmer areas than the KBV, were more prone to mealiness. In conclusion, firmness was the most consistent variable at harvest and could be used in conjunction with ground colour to determine ‘Forelle’ harvest maturity. Furthermore, the study does not support shortening the current mandatory 12 weeks period at -0.5°C due to the higher incidence of astringency and mealiness. / AFRIKAANSE OPSOMMING: Klimaats verskille tussen produksie areas of seisoene affekteer die tempo van vrugrypwording en eetkwaliteit na opberging en rypwording direk. Suid-Afrikaanse ‘Forelle’ word ge-oes by ‘n optimum fermheid van 6.4 kg en het ‘n verpligte opbergingstydperk van 12 weke by -0.5°C om egalige rypwording te verseker. Die veranderlike ‘fermheid’ is egter nie ‘n goeie aanduiding van die rypheidspotensiaal op sy eie nie. Dus is verskeie rypheidsparameters (etileen produksie, agtergrond kleur, fermheid, total oplosbare vaste stowwe (TOVS), titreerbare suur (TS) en stysel afbraak) en die tempo van verandering ge-evalueer om konstante rypheidsverwysings te identifiseer wat met vertroue in ‘n voorspellingsmodel gebruik kan word om optimum oes rypheid te kan bepaal (Hoofstuk 2). Dit is dan in verband gebring met die rypwordingspotensiaal (Hoofstuk 3) en eetgehalte (Hoofstuk 4), wat gedefiniëer is deur “eetbare fermheid” (3.5 kg), frankheid en melerigheid. Vrugte is ge-oes uit drie, hoof verbouingsareas: Warm Bokkeveld (WBV), Elgin en Koue Bokkeveld (KBV). By oes is 20 van die 240 vrugte per blok gebruik om die vrug rypheid te bepaal, deur al die bogenoemde parameters te gebruik, om die verandering en reaksie voor oes te begryp. Die oorblywende 220 vrugte is opgeberg by -0.5°C vir drie opbergingstye, gevolg deur rypmaking by 15°C. By oes was die vrugte van die 2007 seisoen verder gevorderd in agtergrond kleur en betekenisvol sagter (6.7 kg) as die van 2008 (7 kg) en 2009 (7.1 kg). Fermheid, agtergrond kleur, TOVS en TS het almal ‘n lineêre verband getoon met dae na volblom. In geval van fermheid en agtergrond kleur, is meer as onderskeidelik 90% en 73% verklaar deur die variasie in die lineêre model, terwyl in geval van die TOVS en TS, minder as 70% deur die model verklaar kon word. Vrugte wat voor die kommersiële oes (pre-optimum) ge-oes is in 2007 en 2009, het nie daarin geslaag om ryp te word tot by ‘eetbare fermheid’ na ag weke by -0.5°C en 11 dae by 15°C nie. Daarteenoor kon vrugte wat pre-optimum ge-oes is in 2008, wel geïnduseer word om ryp te word met ag weke opbeging. Die ontwikkeling van die rypwordingspotensiaal van vrugte wat vroeër ge-oes is, stem ooreen met die hoër tempo van verandering (3.15 µL.kg-1.h-1.dag-1) in etileen produksie by 15°C in vergelyking met seisoene 2007 (1.98 µL.kg-1.h-1.dag-1) en 2009(1.87 µL.kg-1.h-1.dag-1). Die 2007 seisoen vrugte het die maksimum voorkoms van frankheid (36.7%) getoon vir vrugte van die eerste oes datum. In al drie seisoene waar vrugte wat by kommersiële oes of later (optimum en post optimum) ge-oes is, was ‘n ag weke periode van opgeberging voldoende om rypwording te inisiëer, alhoewel die ag weke opberging ook gelei tot die hoogste voorkoms van melerigheid. Meer as 40% van die laat ge-oeste vrugte was melering na ag weke opberging by -0.5°C en sewe dae by 15°C. Melerigheid is betekenisvol verlaag met ‘n verlengde opbergingsperiode by -0.5°C. Vrugte vanaf die WBV en Elgin, warmer areas as die KBV, was meer onderhewig aan melerigheid. Opsommend was fermheid die reëlmatigste veranderlike by oes en kan tesame met agtergrondkleur, gebruik word om vrugrypheid van ‘Forelle’ te bepaal. Verder het die studie nie ‘n verkorting van die huidige, verpligte 12 week opberingsperiode by -0.5°C gesteun nie, weens die hoë voorkoms van frankheid en melerigheid.

ENGLISH ABSTRACT: The export of Japanese plums from South Africa is challenging, since most cultivars are prone to develop chilling injury (CI) when stored at low temperatures. This injury manifests as gel breakdown or internal browning in the mesocarp tissue of the fruit on removal from low storage temperature conditions, i.e. in the consumer’s fruit basket, who subsequently does not buy plums again. Loss of cell membrane integrity and oxidative stress are, respectively, the primary and secondary physiological responses to CI. The main aim of this study was to investigate changes in cell membrane composition and levels of antioxidants in plums throughout fruit development and maturation, during forced air cooling (FAC) and storage under different temperature regimes. ‘Sapphire’ (a chilling susceptible cultivar) accumulated high levels of glutathione and polyunsaturated fatty acids (PUFAs) during fruit development. Therefore, the cultivar is protected against lipid peroxidation while developing on the tree, but the high levels of PUFAs, which are easily oxidised, may cause this cultivar to be chilling susceptible when stored at low temperatures. It is suggested that the high levels of monounsaturated fatty acids (MUFAs), which are not easily oxidised, and ascorbic acid that accumulated in ‘Angeleno’ (a chilling resistant cultivar) during fruit development, render this cultivar CI resistant during long-term cold-storage. When stored at -0.5 °C, CI development increased at a higher rate, ethylene evolution rates were higher and water soluble antioxidant activity (HAA), ascorbic acid and glutathione levels, and the MUFA:PUFA ratio were lower in H2 (more mature) ‘Sapphire’ plums than H1 fruit (less mature). Therefore, concurrent with H2 fruit having lower levels of antioxidants to quench free radicals caused by chilling stress, their cell membranes were more vulnerable to oxidation due to their phospholipid fatty acid composition. H2 fruit also had higher levels of saturated fatty acids, and hence less fluid cell membranes than H1 fruit when stored at -0.5 °C. An intermittent warming (IW) regime delayed symptom appearance and reduced CI severity in plums significantly compared to storage at -0.5 °C. Fruit stored under the IW regime had a more optimal phospholipid fatty acid composition and lower membrane sterol levels under shelf-life conditions to keep the membranes fluid. It also had higher levels of HAA and lipid soluble antioxidant activity, ascorbic acid and glutathione, which rendered fruit better protected against oxidation. Elevated storage temperatures (2.5 °C to 7.5 °C) caused higher levels of lipid peroxidation or low ascorbic acid levels and poor fruit quality compared to the IW regime in ‘Sapphire’ plums. ‘Laetitia’ plums stored at 5 °C and 7.5 °C had significantly less CI than under the IW regime, but softened quicker due to higher ethylene evolution rates. ‘Sapphire’ tolerated both long and short FAC durations, but a slower initial FAC rate prevented CI manifestation and caused a higher HAA after cold-storage in this fruit. ‘Laetitia’ cooled with a slower initial FAC rate and for a longer duration resulted in the best fruit quality and had higher HAA, total phenolic, phospholipid and saturated phospholipid fatty acid concentrations during storage. / AFRIKAANSE OPSOMMING: Die uitvoer van Japanese pruime vanaf Suid-Afrika hou talle uitdagings in, want die meeste van die kultivars ontwikkel koueskade wanneer hulle by lae temperature opgeberg word. Koueskade manifesteer as gelverval of interne verbruining in die mesokarpweefsel van die vrugte wanneer die vrugte verwyder word uit die lae opbergingstemperatuuromstandighede, m.a.w. in die verbruiker se vrugtemandjie, wat nie weer pruime koop nie. Verlies aan selmembraanintegriteit en oksidatiewe druk is, respektiewelik, die primêre and sekondêre fisiologiese reaksies op koueskade. Die hoofdoel van hierdie studie was om die veranderinge in selmembraansamestelling en antioksidantkonsentrasie in pruime te ondersoek tydens vrugontwikkeling en volwassewording, tydens geforseerde lugverkoeling (GLV) en tydens opberging onder verskillende temperatuurregimes. ‘Sapphire’ (‘n koueskade sensitiewe kultivar) het hoër konsentrasies van glutatioon en polionversadigde vetsure (POV) tydens vrugontwikkeling geakkumuleer. Dié kultivar is dus voldoende beskerm teen lipiedperoksidasie tydens vrugontwikkeling aan die boom, maar die hoë konsentrasies van POVs, wat maklik oksideer, mag veroorsaak dat hierdie kultivar meer koueskadesensitief is wanneer dit by lae temperature opgeberg word. Die hoë konsentrasies van mono-onversadigde vetsure (MOV), wat nie maklik oksideer nie, en askorbiensuur wat in ‘Angeleno’ (‘n koueskade weerstandbiedende kultivar) geakkumuleer het tydens vrugontwikkeling, verleen moontlik weerstandbiedendheid teen koueskade aan hierdie kultivar tydens langtermyn koelkopbering. Tydens opberging by -0.5 °C het koueskade ontwikkeling vinniger toegeneem, was etileenvrystellingstempos hoër en die wateroplosbare antioksidantaktiwiteit (HAA), askorbiensuuren glutatioonkonsentrasies en die MOV:POV verhouding laer in H2 (meer volwasse) ‘Sapphire’ pruime as in die H1 vrugte (minder volwasse). Dus, tesame met die laer antioksidantkonsentrasies in die H2 vrugte om die vry radikale veroorsaak deur koelopbering te verminder, was hul selmembrane ook meer vatbaar vir oksidasie a.g.v. die vetsuursamestellling van hul membraanfosfolipiede. Die H2 vrugte het ook ‘n hoër konsentrasie van versadigde vetsure, en dus minder vloeibare membrane as die H1 vrugte gehad tydens opberging by -0.5 °C. Die dubbeltemperatuurregime (DT) het simptoomontwikkeling vertraag en koueskade-intensiteit betekenisvol verminder in vergelyking met pruime wat by -0.5 °C opgeberg is. Vrugte wat met die DT regime opgeberg is, het ‘n meer optimale fosfolipiedvetsuursamestelling en laer konsentrasie van membraansterole tydens gesimuleerde raklewe gehad wat meer vloeibare membrane verseker het. Hierdie behandeling het ook hoër HAA en lipiedoplosbare antioksidantaktiwiteit (LAA), askorbiensuur- en glutatioonkonsentrasies gehad wat die vrugte beskerm het teen oksidatiewe druk. Verhoogde opbergingstemperature het hoër vlakke van lipiedperoksidasie of lae askorbiensuurkonsentrasies asook swak vrugkwaliteit in ‘Sapphire’ pruime veroorsaak in vergelyking met die DT regime. ‘Laetitia’ pruime wat by 5 °C en 7.5 °C opgeberg is, het betekenisvol minder koueskade gehad in vergelyking met die DT regime, maar het vinniger sag geword a.g.v. hoër etileenvrystellingstempos. ‘Sapphire’ kon lang en kort GLV tye weerstaan, maar ‘n stadiger inisiële GLV spoed het die manifestasie van koueskade voorkom en het ‘n hoër HAA in die vrugte tot gevolg gehad na koelopberging. ‘Laetitia’ wat met ‘n stadiger inisiële GLV spoed en oor ‘n langer tyd verkoel is, het die beste vrugkwaliteit, en hoër HAA, totale fenool-, fosfolipied- en versadigde fosfolipiedvetsuurkonsentrasies as die ander behandelings tydens koelopberging gehad

Thesis (MScAgric)--University of Stellenbosch, 2004. / ENGLISH ABSTRACT: Rind colour is one of the most important external quality characteristics of citrus fruit and plays an important role in purchasing decisions by consumers. Consumers perceive brightlycoloured fruit to be sweet and mature, whereas citrus with a green rind is perceived to be sour and immature. However, there is a poor correlation between rind colour and internal quality, contradicting what is generally assumed by the fruit-buying public. In general, a bright orange rind colour improves consumer acceptance. Thus, it is important to ensure that the rind of citrus fruit is well-coloured on arrival at the market. Various pre-harvest cultural practices and postharvest techniques can be applied to improve rind colour. Degreening with ethylene gas is the most commonly used postharvest technology to improve rind colour, but has various negative side-effects. Degreened fruit are more prone to decay, have rinds which appear dull and flaccid, have been reported to develop off-flavours and have a shorter shelf-life period. Therefore, it is necessary to find alternatives to ethylene degreening and to extend shelf-life of citrus fruit. Under normal orchard conditions, rind colour development is associated with low night temperatures, usually experienced during autumn or following the passing of a cold front. To simulate cold front conditions, a hydrocooler and cold room were used to rapidly drop fruit temperature to 4 ºC for 6 hours, and then fruit were incubated at 20 to 22 ºC for 72 hours. This “cold shock” treatment of ‘Nules Clementine’ mandarin improved rind colour to a level similar to that of degreened fruit in the 2002 season due to a decrease in chlorophyll content and increase in carotenoid content. However, this result could not be repeated. Storage temperature is one of the most important postharvest factors affecting rind colour. Citrus fruit shipped to export markets requiring low temperatures (-0.6 ºC) for pest disinfestations purposes have been reported to arrive with poor rind colour. Shipping under low temperatures results in poor rind colour of fruit on arrival in the market. To comply with the USA’s phytosanitary requirement for imported citrus, fruit is held at -0.6 ºC for a minimum of 22 days. The effect of shipping at various temperatures (-0.6 ºC or 4.5 ºC), durations and the influence of initial rind colour, “orange” or “yellow”, on fruit colour upon arrival in the market was evaluated. Fruit shipped at a higher temperature (4.5 ºC) had a marginally better rind colour than fruit shipped at -0.6 ºC. The perceived loss of rind colour following shipping at sub-zero temperatures is probably due to carotenoid degradation. Therefore, initial rind colour plays a critical role in final product quality. Depending on market destination and shipping temperature, pale-coloured fruit should not be packed for markets sensitive to rind colour. Holding temperature after shipping can be effectively used to improve the rind colour of fruit arriving in the market with undesirable rind colour. An intermediate holding temperature of between 11 and 15 ºC resulted in the greatest improvement in rind colour after 2 weeks. A high holding temperature (20 ºC) caused colour degradation, whereas a low holding temperature (4.5 ºC) resulted in the maintenance of rind colour. By selecting the correct holding temperature, even after shipping at sub-zero temperatures, final colour can be improved. / AFRIKAANSE OPSOMMING: Tyd-temperatuur interaksie op na-oes skilkleur ontwikkeling by sitrus Skilkleur is een van die belangrikste eksterne kwaliteitseienskappe van die sitrusvrug en spëel ʼn belangrikke rol in wat verbruikers koop. Verbruikers verwag dat heldergekleurde vrugte soet en ryp sal wees, terwyl sitrus met ʼn groen skil geassosieer word met onrypheid en ʼn suur smaak. In teenstelling hiermee is daar egter ʼn swak korrelasie tussen skilkleur en interne kwaliteit. Aangesien ʼn heldergekleurde oranje skil verbruikersaanvaarding verbeter, is dit dus belangrik om te verseker dat die sitrusvrug ʼn goeie skilkleur het teen die tyd wat dit die mark bereik. Verskeie voor-oes bestuurspraktyke en na-oes tegnieke kan toegepas word om die skilkleur te verbeter. Ontgroening met etileen gas is die tegnologie wat mees algemeen gebruik word om skilkleur na oes te verbeter, maar dit het egter verskeie newe effekte tot gevolg. Ontgroende vrugte is meer vatbaar vir bederf en verwelkde skille met ʼn dowwe voorkoms. Afsmaake kan voorkom en ʼn verkorte rakleeftyd is al gerapporteer. Dit is dus noodsaaklik om ʼn alternatief vir etileen ontgroening te ontwikkel en die rakleeftyd van sitrusvrugte te verleng. Onder normale boordomstandighede word skilkleur ontwikkeling geassosieer met lae nag temperature wat gewoonlik in die herfs of na ʼn kouefront ondervind word. Om soortgelyke omstandighede na te boots, was ʼn “hydrocooler” en koelkamers gebruik om die temperatuur vinnig te laat daal tot by 4 °C en dit vir 6 uur daar te hou. Die vrugte was dan by 20 tot 22 °C geinkubeer vir 72 uur. Hierdie “koueskok” behandeling van ‘Nules Clementine’ mandaryn het skilkleur verbeter tot ʼn vlak vergelykbaar met ontgroende vrugte in die 2002 seisoen wat ontstaan het weens ʼn verlaging in chlorofil en ʼn toename in die karotinoïed inhoud van die skil. Opbergingstemperatuur is een van die belangrikste na-oes faktore wat skilkleur beinvloed. Sitrusvrugte wat verskeep word na uitvoermarkte wat lae temperature (-0.6 °C) vir disinfestasie vereis arriveer soms by die mark met ʼn swak skilkleur. Om die fitosanitêre vereistes vir die invoer van sitrus deur die VSA na tekom, was vrugte vir ʼn minimum van 22 dae by -0.6 °C gehou. Die effek van verskeping by verskeie temperature (-0.6 °C of 4.5 °C), tydperke en die invloed van aanvanklike skilkleur, “oranje” of “geel” was geevalueer by aankoms in die mark. Vrugte wat by hoër temperature (4.5 °C) verskeep was het ʼn effens beter skilkleur as vrugte by -0.6 °C getoon. Die verlies in skilkleur wat waargeneem word na verskeping onder vriespunt kan moontlik toegeskryf word aan karotenoiëd afbraak. Daarom speel aanvanklike skilkleur ʼn kritieke rol in finale produk kwaliteit. Die finale mark bestemming en verskepingstemperatuur sal bepaal of swakgekleurde vrugte verpak kan word. Opbergingstemperatuur na verskeping kan effektief gebruik word om die skilkleur van vrugte wat swak gekleur was met aankoms by die mark te verbeter. Matige temperature tussen 11 en 15 °C het na 2 weke die beste verbetering in skilkleur gelewer. Hoër temperature (20 °C) het skilkleur nadelig beinvloed, terwyl lae temperature skilkleur behou het. Deur die korrekte temperatuur te kies, selfs na verskeping by temperature onder vriespunt, kan uiteindelike skilkleur steeds verbeter word.

Thesis (MscAgric (Horticulture))--University of Stellenbosch, 2008. / ‘Brookfield Gala’ apple trees were planted out in July 2003 in a Dundee soil form, consisting of well-aerated sandy loam soil. During the first 12 months trees received young tree solutions high in nitrogen. The nutrient solution of the 2nd leaf trees was based on a yield estimation of 10 ton. ha-1 plus 30%. Nutrient solutions for the 3rd leaf trees were based on 25 ton. ha-1 yield estimations and adapted upwards. Seasonal uptake and distributions were determined for macro and micro elements, using twoand three-year-old apple trees during the seasons 2004/2005 and 2005/2006. In the bearing apple trees the macro nutrient accumulated rapidly from late winter to late autumn. Prior to leaf drop most of the N, P, S, Mg and a small portion of K were redistributed back into the permanent parts of the tree. On the other hand, all Ca in the leaves was lost through leaf drop. Apple fruit contains comparatively large quantities (±60.2%) of K, which are removed during harvest. Guidelines for minimum and maximum nutritional requirements based on the amount necessary to produce 1 kg fruit were determined. For the 3rd leaf trees the minimum macro nutrient requirements (g. kg-1 yield) of N, P, K, Ca, Mg and S were ±1.7, ±0.3, ±2.3, ±0.5, ±0.2 and ±0.2, respectively. The maximum nutrient requirements (g. kg-1 yield) for N, P, K, Ca, Mg and S were ±2.6, ±0.4, ±3.3, ±1.9, ±0.4 and ±0.2, respectively. For the 3rd leaf trees the minimum micro nutrient requirements (mg. kg-1 yield) of Na, Mn, Fe, Cu, Zn, B and Mo were ±75.1, ±1.3, ±28.7, ±0.9, ±3.0, ±5.7 and ±0.3, respectively. The maximum nutrient requirements (mg. kg-1 yield) of Na, Mn, Fe, Cu, Zn, B and Mo were ±102.9, ±7.8, ±32.6, ±1.1, ±6.5, ±7.6 and ±0.3, respectively. Labelled N uptake and distribution for two- and three-year-old apple trees were also determined during the same seasons. The labelled N uptake and distribution results indicated that there was a low labelled N uptake in the initial growth stages, suggesting the importance of internal N reserves for plant development at the beginning of the season. In the active growing period more than 60% of the labelled N was found in the new growth. Uptake efficiency improved as the trees grew older. The effect of different nutrient levels on tree growth, yield and fruit quality was assessed: lower (80%) than the standard (100%) and three higher (120%, 140% and 160%). Results indicated that different nutrient levels had no effect on yield, blush or TSS during the 18 months of application over two bearing seasons. The application of biological products (humic acid, and compost plus compost extract) over a period of 18 months had a significant influence on the TSS, malic acid and citric acid concentrations. A tendency towards an increase in total fine root number and length occured with the addition of biological ameliorant.

Thesis (MScAgric (Horticulture))--Stellenbosch University, 2008. / Sweet cherries (Prunus avium L.) have a high chilling requirement and grow best in areas receiving >1 100 Utah chill units during winter. The main production areas in South Africa, and particularly the eastern Free State, frequently receive insufficient winter chilling and late spring frosts leading to problems of poor budburst, flowering, floral abnormalities and poor fruit set. Research was conducted on the cultivar ‘Bing’ to determine the main factors causing its low fruit set. Various trials were conducted to optimize the timing of rest breaking agents, identify suitable cross pollinizers that flower synchronously with ‘Bing’, and evaluate the influence of temperature and pollen-pistil interactions on fertilization and fruit set. Pollen biology studies using 2- to 3-year-old ‘Bing’ sweet cherry trees were conducted near Clarens, eastern Free State, during the 2005 and 2006 seasons to determine the most suitable cross pollinizer/s for ‘Bing’ and to assess the influence of temperature and pollen-pistil interactions on pollen tube growth and ovule longevity. Significant differences in pollen germination (‘rates’ deleted) occurred between pollinizers, although differences were noted in pollen performance on the stigma and style (in vivo) compared to the artificial media (in vitro), indicating a lack of correlation between in vitro germination and in vivo pollen-pistil interactions. Pollen tube growth, following cross pollination, was influenced by pollinizer genotype, temperature, and the number of pollen grains deposited on the stigma. The highest pollen tube growth rates in ‘Bing’ styles were recorded for the pollinizers ‘Black Tartarian’ (2006), ‘Lapins’ and ‘Rainier’ sweet cherry cultivars at temperatures of approximately 21°C. Temperature had the most significant influence on ovule longevity with the lower orchard temperatures extending ovule viability compared to the higher laboratory temperatures, although pollen tube growth rates were also reduced, thus shortening the effective pollination period. Cross pollination was also shown to extend ovule viability. The results indicate that ‘Black Tartarian’, ‘Lapins’ and ‘Rainier’ were the most suitable pollinizers for ‘Bing’. Hand-pollination with pollen from these donors resulted in a several-fold increase in seed set over naturally-pollinated control flowers. It appears that the principle factors causing poor fruit set in ‘Bing’ sweet cherry are premature abortion of the ovule before fertilization and inadequate transfer of sufficient viable pollen under orchard conditions. Rest breaking trials were conducted on 4-year-old ‘Bing’ sweet cherry trees on ‘Gisela® 5’ rootstock near Clarens (28°28’S; 28°19’E, 1860m) and Reitz (28°0’S; 28°28’E; 1717m) in the eastern Free State, South Africa, during the 2005 and 2006 seasons respectively. In 2005 five treatments were evaluated; viz. 1% and 2% Dormex® (hydrogen cyanamide, HCN); 1% Dormex® + 3% mineral oil; and 3% Lift® (thidiazuron and mineral oil) sprayed at three dates (29 July 2005, 5 August 2005 and 12 August 2005) preceding expected the “green-tip” stage of flower development, plus an unsprayed control. In 2006 four treatments were evaluated; viz. 1% Dormex®; 1% Dormex® + 3% mineral oil; 3% Lift® applied on three dates (26 July 2006, 7 August 2006 and 12 August 2006) and an unsprayed control. No interaction was observed between time of application and type of rest breaking agent (RBA). RBAs were effective at improving budburst and yield during both seasons with the time of application of RBAs having the most significant influence on budburst and production efficiency in ‘Bing’ sweet cherry trees. RBAs were most effective at improving vegetative budburst when applied 9 to 16 days before the (‘actual’ deleted) “green-tip” stage of flower development. Floral budburst and yield were increased by 1% Dormex® + 3% mineral oil and 3% Lift®, but results varied between seasons indicating that time of RBA application should be based on chilling accumulation and bud development stage and not based on calendar date. This current research suggests that ‘Bing’ sweet cherry is poorly suited climatically to the current production areas of the eastern Free State and short-term research needs to identify methods of improving chilling and fruit set by means of evaporative cooling and fruit set-enhancing plant growth regulators. Longer term work requires the identification of new, lower chill cultivars with improved climatic adaptation to South African conditions.

Thesis (MScAgric)--Stellenbosch University, 2008. / ENGLISH ABSTRACT: Stone fruit is susceptible to chilling injury and intermittent warming has been shown to alleviate chilling injury during cold storage. A dual temperature storage regime was developed in South Africa for plums based on the principles of intermittent warming. The regime consists of an initial period at -0.5°C, a variable duration warming period at 7.5°C, followed by -0.5°C. Refrigerated integral containers were designed to maintain product temperature and not to reduce product temperature, per se. Considering that dual temperature shipment requires significant refrigeration and effective distribution of cool air to remove sensible- and respiratory heat, the capacity of integral containers to ship plums successfully at dual temperature is questioned. The objectives of this study were, firstly, to analyse pulp temperature data and possibly identify different temperature zones within containers shipping plums at dual temperature. Secondly, to understand the underlying processes differentiating the temperature zones and thirdly, to determine the effect of container performance on fruit quality. Three processes were identified as important characteristics of pulp temperature data sets recorded during dual temperature shipping, namely cooling down, heating up and over heating in the container. The order of importance differed according to the cultivar shipped and the container’s performance. Three temperature zones were identified in dual temperature containers, where the average pulp temperature, time to heat up and time to cool down for each temperature zone increased along the length, across the width from the left to the right and up the container system. The variable temperature conditions were possibly due to a variation in delivery air temperature, poor airflow and the effect of increased respiration and, therefore, production of vital heat by the fruit. The cooling down process was identified as the most important process discriminating the temperature zones. With the exception of ‘Fortune’, variable temperature conditions found within integral containers shipping plums at dual temperature had a significant influence on the fruit firmness post-shipment, where deterioration levels increased from the front to the door end of the container due to an increase in pulp temperature. However, it was also shown that fruit firmness prior to shipment could have a determining effect on differences found. It could not be proven that variable temperature conditions resulted in significantly higher levels of internal defects within the integral container. Temperature zones could not be identified within refrigerated integral containers shipping plums at single temperature, suggesting that the containers are able to maintain the temperature well throughout the container area. A constant 2°C storage temperature could possibly replace the commercial dual temperature regime in the case of ‘Pioneer’ plums due to improved fruit firmness, similar colour development to the control and less sensible heat produced in the container resulting in a more stable container environment. However, unacceptably high levels of shrivel and internal browning were found. / AFRIKAANSE OPSOMMING: Steenvrugte is vatbaar vir koueskade en dit is bewys dat periodieke verwarming gedurende koelopberging koueskade kan verlig. Die dubbeltemperatuur opbergingsregime is in Suid- Afrika ontwikkel vir pruime en is gebaseer op die beginsels van periodieke verwarming. Die regime bestaan uit ‘n inisiële periode by -0.5°C, ‘n variërende periode by 7.5°C, gevolg deur -0.5°C. Verkoelde integrale houers is ontwerp om produktemperature te handhaaf en nie soseer om produktemperatuur te verlaag nie. Die kapasiteit van integrale houers om pruime suksesvol teen dubbeltemperatuur te verskeep word dus bevraagteken, in ag geneem dat dubbeltemperatuurverskeping betekenisvolle verkoeling en effektiewe verspreiding van koue lug vereis om die waarneembare- en respiratoriese hitte te verwyder. Die doelwitte van die studie was eerstens om die pulptemperatuurdata te analiseer en moontlik verskillende temperatuursones binne houers wat pruime teen dubbeltemperatuur verskeep te identifiseer. Tweedens, om die onderliggende prosesse wat die temperatuursones van mekaar onderskei te verstaan, en derdens om die effek van die houer se werkverrigting op vrugkwaliteit te bepaal. Drie prosesse is geïdentifiseer as belangrike eienskappe van pulptemperatuur datastelle aangeteken gedurende dubbeltemperatuurverskeping, naamlik afkoeling, opwarming en oorverhitting wat binne die houer plaasvind. Die volgorde van belangrikheid het gevarieer afhangende van die kultivar verskeep en die houer se werkverrigting. Drie temperatuursones is geïdentifiseer binne integrale houers wat pruime teen dubbeltemperatuur verskeep, waar die gemiddelde pulptemperatuur, die opwarmingstyd en die afkoelingstyd vir elke temperatuursone in die lengte, oor die wydte van links na regs en van onder na bo in die houersisteem toegeneem het. Die variërende temperatuur toestande kan moontlik toegeskryf word aan ‘n variasie in leweringstemperatuur, swak lugvloei en die effek van toenemende respirasie, en dus die produksie van hitte vrygestel deur die vrugte. Die afkoelingsproses is geïdentifiseer as die belangrikste proses wat die temperatuursones van mekaar onderskei. Behalwe in die geval van ‘Fortune, het variërende temperatuurtoestande in integrale houers wat pruime teen dubbeltemperatuur verskeep ‘n betekenisvolle invloed op die vrugfermheid na verskeping gehad, waar vrugveroudering toegeneem het van voor in die houer na die deur van die houer as gevolg van ‘n toename in pulptemperatuur. Daar is egter bewys dat die vrugfermheid voor verskeping ook ‘n bepalende effek kon hê op die fermheidsverskille. Dit kon nie bewys word dat die variërende temperatuurtoestande betekenisvol hoër vlakke van interne defekte binne die integrale houer veroorsaak het nie. Temperatuursones kon nie geïdentifiseer word binne verkoelde integrale houers wat pruime teen enkeltemperatuur verskeep het nie, wat dus impliseer dat die houers daartoe instaat is om temperatuur goed te onderhou binne die houer. ‘n Konstante 2°C opbergingstemperatuur kan moontlik die kommersiële dubbeltemperatuurregime vervang in die geval van ‘Pioneer’ pruime as gevolg van verbeterde vrugfermheid, soortgelyke kleurontwikkeling as die dubbeltemperatuurregime en minder hitte geproduseer binne die houer deur die pruime, wat ‘n meer stabiele houeromgewing veroorsaak. Onaanvaarbare hoë vlakke van verrimpeling en interne verbruining is egter gevind.

Thesis (MScAgric)--University of Stellenbosch, 2005. / ENGLISH ABSTRACT: Quality of certain Leucospermum and Leucadendron cultivars after approximately 21 days shipping has been reported to be substandard due to ‘drying out’ of leaves and, in the case of Leucadendrons, involucral leaves. The nature of the symptoms of this ‘drying out’ and the conditions under which they form, viz. long exposures to low temperatures, has led us to hypothesize that these are symptoms of chilling injury (CI). Chilling injury, as far as we are aware, has not been documented on Leucospermums or Leucadendrons. Typical CI symptomology is discussed and shown for Leucospermum ‘Gold Dust’, ‘High Gold’ and ‘Succession’ and for Leucadendron ‘Chameleon’, ‘Laurel Yellow’ and ‘Safari Sunset’. The nature of CI symptoms for Leucospermums and Leucadendrons was generally membranous breakdown that manifested in some cases as a ‘water soaked’ appearance which, at a more advanced stage, was generally visible as ‘dried out’ patches on the leaves. In the case of the Leucadendrons CI was also visible on the immature involucral leaves which are more sensitive to chilling conditions than mature leaves. Dark discoloration of especially immature involucral leaves is also a symptom of CI. As water uptake of shoots with chilling injury is hindered the styles of the Leucospermums wilt. As can be expected, the lower the temperature below the threshold temperature and the longer the exposure the more severe the symptoms. CI was recorded on cut flower shoots of Leucospermum ‘Gold Dust’, ‘High Gold’, ‘Rigoletto’, ‘Succession’ and ‘Vlam’ after 21 and 24 days storage at 1ºC. After 24 days storage the chilling injury was more severe than after 21 days storage in most cases. Each cultivar was pulsed with 5 ml per stem of a 2% (w/v) sugar solution of either lactulose, sucrose, glucose, fructose or mannose before storage. After storage, CI was recorded on day 0, 3, 7 and 10 of the vase phase. Of the cultivars tested ‘Vlam’ and especially ‘Rigoletto’ were more prone to chilling injury development. ‘High Gold’ and ‘Vlam’ shoots were pulsed with 0 (control), 1.5, 3 or 4% (w/v) solutions of either mannose or fructose. The best control of CI for both cultivars was achieved with 1.5% (w/v) solution. Lower concentrations of mannose and fructose were tested on ‘High Gold’ shoots, with a 1% (w/v) solution giving the best control for both. At high concentrations signs of toxicity became evident directly after pulsing. ‘High Gold’ shoots were pulsed with 1% (w/v) solutions of mannose and fructose and sugar analyses were performed on shoots at different stages of storage and after 10 days in the vase. A slight increase in mannose and fructose was detectable in the stems of the shoots directly after pulsing but not in the leaves or the inflorescences. This is due to the low concentrations being used. The levels of all the carbohydrates decreased during the 21 days storage and more so during the vase phase of the flowering shoots. The fact that such low concentrations were effective in controlling chilling injury suggests that the sugars may have an effect other than on the osmotic potential. Cut ‘flower’ shoots of Leucadendron ‘Chameleon’, ‘Laurel Yellow’ and ‘Safari Sunset’ were stored for 14, 21 and 28 days, at 1º, 3º and 5ºC and CI development recorded during the subsequent 10 day vase phase. ‘Laurel Yellow’ and ‘Safari Sunset’ showed signs of chilling injury on the leaves after 28 days storage at 3ºC or lower and ‘Safari Sunset’ stored for 21 days developed chilling injury during the vase phase. Immature involucral leaves were more sensitive to chilling injury than leaves. CI increased with longer exposure times and lower storage temperatures for all three cultivars evaluated. ‘Chameleon’ was the most chilling tolerant of the cultivars up to 21 days. At 5ºC chilling injury was low irrespective of cold storage duration but longer exposures to 1º and 3ºC resulted in increased chilling injury development during the vase phase. All three cultivars were pulsed with 5 ml per stem of a 1% (w/v) solution of lactulose, sucrose, glucose, fructose or mannose and stored for 14, 21 and 28 days at 1ºC. The sugars reduced chilling injury on the leaves for ‘Safari Sunset’ when stored for 28 days and, to a lesser extent, in ‘Chameleon’. The sugars failed to reduce chilling injury of the involucral leaves of ‘Chameleon’ and ‘Laurel Yellow’ whereas there was some control especially after 28 days for ‘Safari Sunset’. In some cases the sugar pulse exacerbated chilling injury. Chilling injury generally increased rapidly after storage during the first three days in the vase and then at a lower rate for the next seven days. Leucadendron ‘Chameleon’, ‘Laurel Yellow’ and ‘Safari Sunset’ ‘cut flower’ shoots were pulsed with a 1% (w/v) glucose solution. Expressed on a dry weight basis, an increase in glucose concentration was not detected. The reduction in chilling injury of leaves by a sugar pulse is speculated, as for the Leucospermums, to be as a result of their presence in the apoplast and not the symplast and that their presence there protects the membranes against chilling conditions in some way. / AFRIKAANSE OPSOMMING: Die kwaliteit van sekere Leucospermum en Leucadendron kultivars na ongeveer 21 dae verskeping is waargeneem as substandaard as gevolg van die uitdroog van blare en, in die geval van Leucadendrons, die ‘involucral’ blare. Die aard van die simptome van hierdie uitdroging en die toestande waaronder dit plaasvind nl. lang periodes van blootstelling aan lae temperature, het ons tot die hipotese gebring dat hierdie simptome van koueskade is. Sover as wat ons bewus is, is koueskade nog nie gedokumenteer op Leucospermums of Leucadendrons nie. Tipiese koueskade simptomologie word bespreek en gewys vir Leucospermum ‘Gold Dust’, ‘High Gold’ en ‘Succession’ en vir Leucadendron ‘Chameleon’, ‘Laurel Yellow’ en ‘Safari Sunset’. Die koueskade simptome vir Leucospermums en Leucadendrons was oor die algemeen membraan afbraak wat ‘n water deurdrenkte voorkoms tot gevolg gehad het wat in ‘n meer gevorderde stadium sigbaar was as uitgedroogde kolle op die blare. In die geval van Leucadendrons was koueskade ook sigbaar op die onvolwasse ‘involucral’ blare wat meer sensitief is vir koue toestande as volwasse blare. Donker verkleuring van veral onvolwasse ‘involucral’ blare is ook ‘n simptoom van koueskade. Aangesien wateropname van stele met koueskade verhinder word, verwelk die ‘styles’ van die Leucospermums. Soos verwag kan word hoe laer die temperature onder die drempel temperatuur en hoe langer die blootstelling, hoe meer ernstig die simptome. Koueskade is aangeteken op gesnyde blomstele van Leucospermum ‘Gold Dust’, ‘High Gold’, ‘Rigoletto’, ‘Succession’ en ‘Vlam’ na 21 en 24 dae opberging by 1°C. Na 24 dae opberging was die koueskade meer ernstig as na 21 dae opberging in meeste gevalle. Elke kultivar het 5ml per steel van ‘n 2% (g/v) suiker oplossing van laktolose, sucrose, glucose, fruktose of mannose voor opberging opgeneem. Na opberging is koueskade aangeteken op dag 0, 3, 7 en 10. Van die kultivars wat getoets is, was ‘Vlam’ en veral ‘Rigoletto’ meer geneig tot koueskade ontwikkeling. ‘High Gold’ en ‘Vlam’ stele is geplaas in oplossings van 0 (kontrole), 1.5, 3 of 4 % (g/v) oplossings van mannose of fruktose. Die beste beheer van koueskade vir beide kultivars is deur die 1.5 (g/v) oplossing behaal. Laer konsentrasies van mannose en fruktose is getoets op ‘High Gold’ stele met ‘n 1% (g/v) mannose oplossing wat die beste beheer gegee het. Met hoë konsentrasies het tekens van toksisiteit sigbaar geword direk na opneem van die oplossing. ‘High Gold’ stele is geplaas in 1% (g/v) oplossings van mannose of fruktose en suiker analises is uitgevoer op stele by verskillende stadiums van opberging en na 10 dae in die vaas. ‘n Effense toename in mannose en fruktose is waargeneem in die stele van die blomme direk na opname van die oplossing, maar nie in die blare of die blomme nie. Dit is as gevolg van die lae konsentrasies wat gebruik is. Die vlakke van al die koolhidrate het afgeneem gedurende die 21 dae opberging en nog meer so gedurende die vaas periode van die blommende stele. Die feit dat sulke lae konsentrasies effektief is in die beheer van koueskade dui daarop dat die suikers ‘n effek het anders as op die osmotiese potensiaal. Snyblomme van Leucadendron ‘Chameleon’, ‘Laurel Yellow’ en ‘Safari Sunset’ is opgeberg vir 14, 21 en 28 dae, by 1º, 3º en 5°C en koueskade ontwikkeling is aangeteken gedurende die opvolgende 10 dae vaas periode. ‘Laurel Yellow’ en ‘Safari Sunset’ het tekens gewys van koueskade op die blare na 28 dae opberging by 3°C of laer en ‘Safari Sunset’ opgeberg vir 21 dae het koueskade ontwikkel gedurende die vaas periode. Onvolwasse ‘involucral’ blare was meer sensitief vir koueskade as die blare. Koueskade het toegeneem met langer blootstellingstye en laer opbergins temperature vir al drie kultivars geëvalueer. ‘Chameleon’ was die mees koueverdraagsaam van die drie kultivars tot op 21 dae. By 5°C was laag ongeag van die koue opberging tydperk, maar langer blootstellings aan 1º en 3°C het gelei tot toename in koueskade ontwikkeling gedurende die vaas periode. Al drie kultivars is voorsien met 5ml per steel van ‘n 1% (g/v) oplossing van lactulose, sucrose, glucose, fruktose of mannose en opgeberg vir 14, 21 en 28 dae by 1°C. Die suikers het koueskade verminder op die blare van ‘Safari Sunset’ wanneer opgeberg vir 28 dae en, tot ‘n mindere mate, in ‘Chameleon’. Die suikers het egter nie koueskade verminder van die ‘involucral’ blare van ‘Chameleon’ en ‘Laurel Yellow’ nie, waar daar egter wel in ‘n mate beheer was veral na 28 dae vir ‘Safari Sunset’. In sommige gevalle het die voorsiening van suiker die koueskade vererger. Koueskade het oor die algemeen vinnig toegeneem na opberging gedurende die eerste drie dae in die vaas en dan teen ‘n laer tempo vir die volgende sewe dae. Leucadendron ‘Chameleon’, ‘Laurel Yellow’ en ‘Safari Sunset’ snyblom stele is voorsien van ‘n 1% (g/v) glukose oplossing. Uitgedruk op ‘n droëmassa basis is ‘n toename in glukose konsentrasie nie waargeneem nie. Die afname in koueskade van blare deur die voorsiening van ‘n suiker oplossing is gespekuleer vir die Leucospermums, om ‘n resultaat te wees van hulle teenwoordigheid in die apoplas en nie die simplas nie, en dat die teenwoordigheid daar die membrane op ‘n manier beskerm teen koue toestande.

Thesis (MscAgric (Horticulture))--University of Stellenbosch, 2008. / Commercial production of sweet cherries has recently increased in South Africa, with more than 400 ha planted by 2006. Cherry, a high chilling fruit variety, is however not suited for the mild winter climate of South Africa. This was recognizable through common observed symptoms of delayed foliation and poor fruit set. In addition, cherry is exposed to long and hot summers in the postharvest period. The objective of this study was to evaluate cherry cultural practices that can manipulate (reduce) the trees chilling requirement under South African conditions. Cultural practices where aimed at increasing reserves (nitrogen, cytokinin and carbohydrates) in the tree. In addition, bud dormancy progression of cherry buds was quantified to determine the bud dormancy progression pattern under mild winter conditions. This was achieved through sampling of cherry shoots from different cherry production areas which was then forced in the growth cabinets. A model was developed to identify possible factors and groupings that can explain the cherry bud dormancy pattern. A model, comprising two joined straight lines, was fitted in order to characterize bud dormancy behaviour for sweet cherry cultivars under mild winter conditions. All cherry cultivars followed the expected pattern of entrance and exit from dormancy. Factor analysis showed that factors related to the entrance into dormancy primarily characterize bud dormancy behaviour. Bud dormancy patterns were also a function of environmental conditions within a year as shown by cluster analysis. In addition, buds entered dormancy in mid-summer and remained dormant until chilling accumulation commenced. Bud dormancy release was generally extended over a three to five-month period for all cultivars. Prior to spring budburst exit of both lateral and terminal buds occurred rapidly. Data indicate that there is no ecodormant phase for cherry under the prevalent climatic conditions in South Africa. Further experimentation was aimed at increasing reserves within the trees through cultural practices. In the nitrogen trials, fertilization in the postharvest period had no significant effect on field budburst or bud dormancy progression in one-year-old shoots. Time of flowering was advanced in N treatments during 2007 only. Yield was not significantly increased. Therefore, in this trial, N fertilization in the postharvest period did not significantly reduce the chilling requirement of mature sweet cherry trees under mild winter conditions. Application of particle films (Surround® and Raynox®) or ethylene inhibitors (Retain®) in the summer did not reduce the heat stress the trees experienced. Treatments had no significant effect on carbon assimilation, stomatal conductance, leaf surface temperature, fluorescence, bud dormancy, budburst, flowering and fruit set. Cytokinins sprays (benzyladenine) in autumn did not affect bud dormancy progression, spring budburst or flowering. Hydrogen cyanamide application in spring significantly advanced budburst, time to full bloom and increased yield. Promalin® and Retain®, however, had no significant effect on budburst, flowering or yield. It is therefore evident that cherry, due to its unexpected bud dormancy behaviour and its inability to be significantly influenced by several cultural practices, adapts poorly to South African climatic conditions through not reducing its chilling requirement significantly.

Thesis (MscAgric (Horticulture))--University of Stellenbosch, 2009. / ENGLISH ABSTRACT: Experiments were conducted to increase the percentage class one ‘Granny Smith’ and ‘Cripps’ Pink’ apples. ‘Granny Smith’ is the most widely grown apple cultivar in South Africa, but its profitability is compromised by the high incidence of sunburn, red blush and poor green colour development. ‘Cripps’ Pink’ is a very lucrative cultivar and producers are striving to maximise the production of fruit that qualify for export. Fruit technologists and growers are debating whether it is best to maximise class one fruit in ‘Cripps’ Pink’ by increasing total yield or by increasing fruit quality. The relationship between ‘Granny Smith’ canopy position and external fruit quality was investigated. Light exposure, peel temperature, green colour development, sunburn and red blush development was followed for individual fruit from the outer, intermediate and inner canopy. Dark green fruit were exposed to moderate to high light levels (25-50% full sun) during the first half of fruit development, similar to fruit that eventually developed sunburn and red blush. The difference came in during the latter half of fruit development when dark green fruit became shaded (3% full sun). Pale green fruit contained less chlorophyll due to consistent low light levels (2% full sun). Fruit at partially shaded canopy positions had a lower occurrence of sunburn and red blush than outside fruit and better green colour development than fruit from the heavily shaded inner canopy. Based on these data, pruning strategies and mulching were evaluated to alter canopy vigour and the light environment in such a way that green colour development is promoted and the occurrence of sunburn and red blush is reduced. In an older, vigorous orchard with a dense canopy, pruning was done to increase light distribution for green colour development and to induce more growth on the side of the trees that are prone to sunburn and red blush. Pruning improved green colour development without affecting sunburn or red blush. In a younger, non-vigorous orchard, pruning and mulching were used to invigorate the canopy to increase shading of fruit and thereby decrease sunburn and red blush. However, these treatments were not effective. Further research should focus on the use of shade nets, accompanied by rigorous pruning, to reduce sunburn and red blush while not decreasing green colour. Five different crop loads were established in an exceptionally high yielding (averaging over 100 ton·ha1) ‘Cripps’ Pink’ orchard by first the thinning of clusters, then the removal of small fruit and, finally, the selective removal of fruit from the shaded inner canopy. Treatments had no effect on iv fruit quality in the first season. The most severe thinning treatment increased the percentage class one fruit in the second season by increasing the number of fruit with adequate red blush. However, seen cumulatively, the higher crop loads yielded more class one fruit per hectare than the lower crop loads, without affecting reproductive and vegetative development or fruit storability. Producers should strive for the highest crop loads allowed by the fruit size limitations in cultivars that are not prone to alternate bearing / AFRIKAANSE OPSOMMING: Eksperimente is uitgevoer om die persentasie uitvoerkwaliteit ‘Granny Smith’ en ‘Cripps Pink’ appels te verhoog. ‘Granny Smith’ maak die grootste deel uit van appel aanplantings in Suid Afrika, maar die winsgewendheid daarvan word beperk deur `n hoë voorkoms van sonbrand, rooi blos en swak groen kleurontwikkeling. ‘Cripps’ Pink’ is `n baie winsgewende kultivar en produsente streef daarna om die persentasie uitvoerkwaliteit vrugte te maksimaliseer. Vrugte tegnoloë en produsente debatteer oor die wenslikheid daarvan om uitvoerkwaliteit vrugte te maksimeer deur totale produksie te verhoog of deur vrugkwaliteit te verbeter. Die verband tussen ‘Granny Smith’ draposisie in die blaredak en eksterne vrugkwaliteit is ondersoek. Ligvlakke, skiltemperatuur, groen kleurontwikkeling, sonbrand en rooi blos ontwikkeling is deur die loop van die seisoen gevolg vir individuele vrugte aan die buitekant, binnekant en intermediêre posisies binne die blaredak. Daar is gevind dat die donkerste groen vrugte, nes vrugte wat uiteindelik sonbrand en rooi blos ontwikkel het, blootgestel was aan matige tot hoë ligvlakke (25-50% vol son) gedurende die eerste helfte van vrugontwikkeling. Donker groen vrugte is egter oorskadu (3% vol son) tydens die tweede helfte van vrugontwikkeling. Vanweë konstante lae beligting (2% vol son) het binne vrugte min chlorofiel geakkumuleer en daarom is hierdie vrugte lig van kleur. Vrugte in gedeeltelike skadu ontwikkel min sonbrand en rooi blos in vergelyking met buite vrugte en toon beter groen kleurontwikkeling as vrugte in diep skadu binne die boom. Gegrond op bogenoemde resultate is die gebruik van snoei strategieë en deklae om die groeikrag en die ligomgewing van die boom te modifiseer, ten einde groen kleur ontwikkeling te bevorder en sonbrand en rooi blos te verminder, geëvalueer. In ‘n ouer, groeikragtige boord met ‘n digte blaredak is snoei gebruik om ligverspreiding te verbeter vir groen ontwikkeling en om meer groei te stimuleer aan die buitekant van die boom wat meer geneig is tot sonbrand en rooiblos. Groen kleur is wel verbeter, maar sonbrand en rooi blos is nie geaffekteer nie. In `n jonger, minder groeikragtige boord is ‘n deklaag aangebring en eenjarige lote getop, sodoende groei te stimuleer om sonbrand en rooi blos te verminder deur oorskaduwing van vrugte. Hierdie behandelings was egter nie effektief nie. Toekomstige navorsing moet fokus op die gebruik van skadunette tesame met ‘n nougesette snoei strategie om sonbrand en rooi blos te verminder sonder om groen kleur te verswak. Vyf verskillende vrugladings is geskep in `n uitermatig produktiewe (gemiddeld meer as 100 ton·ha-1) ‘Cripps’ Pink’ boord deur eers vrugtrosse uit te dun, gevolg deur die verwydering van klein vrugte en, laastens, die selektiewe verwydering van vrugte in die diep skaduwee van die binneste blaredak. Vrugkwaliteit is nie in die eerste seisoen nie deur oeslading geaffekteer nie. Die strafste uitdunbehandeling het wel die persentasie uitvoerbare vrugte in die tweede seisoen verhoog deur die aantal vrugte met voldoende rooi blos te vermeerder. Kumulatief gesien, het die hoër oesladings egter meer klas een vrugte per hektaar opgelewer sonder om die reproduktiewe en vegetatiewe ontwikkeling of die stoorvermoë van vrugte te affekteer. Produsente moet strewe na die hoogste oesladings wat toegelaat word deur vruggrootte beperkings in kultivars wat nie geneig is tot alternerende drag nie

Thesis (MscAgric (Horticulture))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: Commercial fig production with popular European cultivars, Bourjasotte Noire, Col de Damme Noire and Noire de Caromb, is new to the Western Cape. Little research on fig production has been conducted in South Africa and producers are struggling to implement effective commercial practices. In order to establish practices that will maximise yield of quality fruit, the most productive one-year-old shoot lengths were identified in a phenological study. All shoot length categories evaluated in ‘Bourjasotte Noire’ (10 – 15 cm, 25 – 40 cm, 50 – 65 cm, 75+ cm) yielded fruit and will probably yield well the following season. In ‘Col de Damme Noire’, shoots longer than 60 cm seem to be suited to reproduction, yet they might produce a poor yield the following season. Shoots 10 – 20 cm long in ‘Noire de Caromb’ are productive relative to their length, while shoots 30 – 50 cm and 60 – 80 cm long are also fairly productive. Shoots longer than 100 cm produced suitable shoot lengths for yield the following season. Two experiments were conducted on ‘Bourjasotte Noire’ and ‘Col de Damme Noire’ to establish the type (Experiment 1, different intensity heading cuts) and timing (Experiment 2) of pruning cuts required to stimulate the growth of shoots of the same length as the shoots selected to be optimal for yield in the phenology study, and to reduce the expression of distal branching. In ‘Bourjasotte Noire’, removing one third of the total length of one-year-old shoots on 21 July by heading stimulated the development of more growth and longer current season shoots compared to other treatments, while reducing yield slightly. Heading back to three nodes in ‘Col de Damme Noire’ stimulated the growth of current season shoots of the optimal length established in the phenology study, while heading cuts on 30 June produced the longest average current season shoot length in ‘Col de Damme Noire’. To further address the effects of distal branching (acrotony), an experiment was conducted to establish whether rest breaking agents (RBA’s) in combination with tip-pruning can increase tree complexity by improving bud break, and whether increased complexity would increase yield in all three cultivars. A second experiment was conducted to evaluate the effects of timing RBA applications on bud break and harvest scheduling. Lift® increased the number of buds breaking in ‘Bourjasotte Noire’, while in ‘Noire de Caromb’ Dormex® and oil increased bud break. Tip-pruning increased the average shoot length in ‘Bourjasotte Noire’ and ‘Col de Damme Noire’, while causing a reduction in the amount of new growth in ‘Noire de Caromb’. Lift® applied 3 August and Dormex® applied 30 June shortened the number of days to 50% bud break in ‘Bourjasotte Noire’ and ‘Col de Damme Noire’. Both Lift® and Dormex® applied on 30 June decreased the number of days to 50% bud break and 50% harvest of the breba crop in ‘Noire de Caromb’. These treatments increased the number of fruit in both the breba and main crop of ‘Noire de Caromb’, but reduced fruit size. In conclusion, different approaches with regards to pruning needs to be followed for each cultivar to establish or maintain the optimal shoots for reproduction, while RBA’s can be used to force earlier, increased- bud break and harvest of breba fruit. / AFRIKAANSE OPSOMMING: Kommersiele verbouing van drie Europese vykultivars, Bourjasotte Noire, Col de Damme Noire en Noire de Caromb is nuut tot die Wes-Kaap. Baie min navorsing oor die verbouing van vye is al in Suid-Afrika gedoen, met die gevolg dat produsente sukkel om effektiewe kommersiële verbouingspraktyke te implementeer. ‘n Fenologiese studie van die drie kultivars is uitgevoer om vas te stel wat die mees produktiewe een-jaar-oue lootlengte is, met die doel om die opbrengs van kwaliteit vrugte te maksimeer. Al vier kategorieë wat ge-evalueer is in ‘Bourjasotte Noire’ (10 – 15 cm, 25 – 40 cm, 50 – 65 cm, 75+ cm) is gevind om geskik te wees vir huidige en volgende seisoen opbrengs. Lote langer as 60 cm is geskik vir opbrengs in ‘Col de Damme Noire’ in die huidige seisoen, maar mag in die volgende seisoen swak presteer a.g.v. die gebrekkige lengte van nuwe lote wat daarop ontwikkel. In ‘Noire de Caromb’ is gevind dat lote 10 – 20 cm lank baie produktief is relatief tot hul lengte en dat lote 20 – 50 cm en 60 – 80 cm lank ook relatief produktief is. Lote langer as 100 cm was minder produktief, maar het nuwe lote gelewer wat geskik is vir opbrengs die volgende seisoen. Twee snoei eskperimente is uitgevoer op ‘Bourjasotte Noire’ en ‘Col de Damme Noire’ om vas te stel wat die mees geskikte tipe snoeisnit (Eksperiment 1, verskillende dieptes van topsnitte) en tydstip om te snoei (Eksperiment 2) is met die doel om lote te produseer soortgelyk in lengte aan die wat in die fenologie studie uitgewys is as die produktiefste, en om moontlik die voorkoms van “kaalnekke” te verminder. In ‘Bourjasotte Noire’ is gevind dat die wegsnoei van ‘n derde van die loot op 21 Julie aanleiding gee tot meer groei, langer een-jaar-oue lote en ‘n effense afname in opbrengs. Geskikte lote langer as 60 cm kan in ‘Col de Damme Noire’ verkry word deur lote te top sodat net drie nodes oorbly. Die uitvoer van topsnitte op 30 Junie het langer gemiddelde lootlengtes tot gevolg gehad. Om die probleem van “kaalnekke” (apikale dominansie) verder aan te spreek, is ‘n eksperiment uitgevoer om vas te stel of rusbreekmiddels gekombineerd met tip-snoei gebruik kan word om kompleksiteit te vermeerder deur knopbreek te verhoog, en indien wel, of dit sal aanleiding gee tot verhoogde opbrengs in al drie kultivars. ‘n Tweede eksperiment met verskillende toedieningstye van rusbreekmiddels is uitgevoer om vas te stel of oeste geskeduleer kan word. Lift® het knopbreek verhoog in ‘Bourjasotte Noire’, terwyl Dormex® en olie knopbreek verhoog het in ‘Noire de Caromb’. Tip-snoei het die gemiddelde lootlengtes verhoog in ‘Bourjasotte Noire’ en ‘Col de Damme Noire’, terwyl dit groei verminder het in ‘Noire de Caromb’. Lift® toediening op 3 Augustus en Dormex® toediening op 30 Junie het die aanvang van 50% knopbreek vervroeg in ‘Boujasotte Noire’ en ‘Col de Damme Noire’. Beide Lift® en Dormex® toediening op 30 Junie het die bereiking van 50% knopbreek- en 50% oes vervroeg in ‘Noire de Caromb’. Hierdie behandeling het ook die aantal vrugte van die breba- en hoofoes vermeerder, maar vruggrootte verminder. Verskillende snoeibenaderings behoort dus gevolg te word om vir elke kultivar die regte lootlengtes te genereer of te onderhou, terwyl rusbreekmiddels gebruik kan word om knopbreek te vervroeg en verhoog, en om die breba oes te vervroeg.