Thesis (MScAgric)--Stellenbosch University, 2002. / ENGLISH ABSTRACT: Internal breakdown (internal browning - IB and gel breakdown - GB), over maturity and immaturity are the main factors adversely affecting the quality of exported South African plums. Maturity problems occur when plums are strip harvested, i.e., all the fruit in a block or orchard are harvested once, when the majority of the fruit are at optimum maturity. This results in both ovennature and immature fruit being harvested and contributes to a high percentage of fruit being rejected for export. In general, internal browning occurs when plums are exported under a single 10\,,, temperature regime and gel breakdown occurs when plums are exported under a dual temperature regime. However, GB can also occur at harvest in fruit that are very ripe and may occur at single low temperatures, where it would be masked by lB. While it is known that some cultivars, like 'Angeleno', can withstand a single temperature regime, others cannot. To the best of our knowledge, the reason for this difference is not understood. Many factors affect the quality of plums, including light incidence in the canopy, mineral nutrition and harvest maturity. Plums that were grown on high density training systems such as 'a V- or spindle system yielded consistently high quality fruit with low incidences of gel breakdown. This was in contrast to earlier findings where low-density training systems produced high levels of GB, especially in the lower part of the tree canopy. Branches that were shaded with 80% shade netting yielded fruit with high levels of GB, indicating that the main effect of improved canopy structure on quality was improved light management. A postharvest boron application on 'Songold' plums prior to storage had no effect on the incidence of intemal breakdown in the fruit, but did damage the cuticle, resulting in severe shrivel. However, internal conductivity and firmness measurements indicated that there was some effect of the boron on cell membranes. A more thorough investigation of pre- and postharvest application of boron is recommended in order to determine whether there could be a positive effect of boron in improving fruit quality in plums. Four cultivars of plums ('Pioneer', 'Sapphire', "Songold ' and 'Angeleno') were harvested throughout, and extending beyond, the commercial harvesting period. In all cultivars, the drop in firmness between harvests was not as great as expected and the later harvested fruit were of a similar, if not superior, quality as compared to the earlier harvested fruit. Later harvested plums tended to have higher TSS and better colour development. Contrary to what was expected, later harvested fruit did not have more internal disorders than earlier harvested fruit. This indicates the importance of harvesting at optimum maturity. 'Angeleno' plums had no internal disorders, even after five weeks of cold storage at a single low temperature. 'Pioneer' and 'Sapphire' plums were classified as climacteric and 'Songold' and 'Angeleno' were classified as suppressed climacteric based on ethylene production. The climacteric plums respired and produced ethylene at a higher rate than the suppressed climacteric plums. Climacteric plums ripened faster during shelf life than suppressed climacteric plums. Furthermore, while climacteric plums did not need a cold storage period prior to ripening, suppressed climacteric plums needed a cold storage period in order to ripen normally. The longer the cold storage period prior to transfer to higher temperatures, the faster the plums ripened and the higher the ethylene production at the higher temperature. The suppressed climacteric genotype could possibly be incorporated into plum breeding programs in order to extend the storage period and shelflife of new plum cultivars. The long storage times required to ship plums from South Africa to the export markets has necessitated research on postharvest physiology and quality of this fruit. The use of the climacteric and suppressed climacteric system to classify fruit is expected to assist in understanding the different physiological responses of the cultivars and assist in developing handling protocols. Preharvest factors, particularly light and nutrition, also playa role in postharvest quality. / AFRIKAANSE OPSOMMING: Interne verval (interne verbruining en gelverval), oorrypheid en onryp vrugte, is die hoof faktore wat die uitvoer van Suid Afrikaanse pruime negatief beïnvloed. Rypheidsprobleme ontstaan wanneer pruime gestroop-oes word, met ander woorde, al die vrugte in 'n blok of boord word geoes wanneer die meerderheid vrugte optimum rypheid bereik het. As gevolg hiervan word 'n groot persentasie vrugte vir uitvoer afgekeur, omdat hulle te ryp of nie ryp genoeg is nie. Oor die algemeen vind interne verbruining plaas wanneer vrugte onder 'n enkel lae temperatuur uitgevoer word en gelvervel vind plaas wanneer vrugte onder 'n dubbele temperatuur regime vervoer word. Gel verval kan egter in baie ryp vrugte by oes voorkom en mag by enkel lae temperature voorkom .waar dit deur interne verbruining gemaskeer sal word. Kultivars soos 'Angeleno' kan onder enkel lae temperatuur uitgevoer word sonder interne probleme, terwyl ander pruimkultivars me so uitgevoer kan word nie. So ver ons weet, word die rede hiervoor nie goed verstaan nie. Daar is baie faktore wat die kwaliteit van pruime beïnvloed, onder meer lighuishouding, minerale voeding en die rypheid waarby die pruime geoes word. Pruime wat in hoë-digtheid sisteme soos 'n V- of "spindle" groei het goeie kwaliteit vrugte met 'n lae persentasie gelverval gelewer. Dit is in teenstelling met vroeër bevindinge, waar vrugte van lae digtheid boorde hoë persentasies geverval gelewer het, veral in die onderste gedeeltes van die boom. Takke wat met 80% skadunet bedek is het hoër persentasies gelverval as die kontrole gelewer, wat aandui dat die hoof effek van die verbeterde boom struktuur op kwaliteit, verbeterde lighuishouding was. 'n Na-oes aanwending van boor op 'Songold' pruime het geen effek op die voorkoms van gelverval gehad nie, maar het die kutikula beskadig en tot hoë persentasies verrimpeling gelei. Fermheid en inteme weerstand lesings het egter getoon dat daar wel 'n effek van die boor op die selmembrane en selwande was. 'n Meer omvattende ondersoek van voor- en na-oes aanwending van boor word aanbeveel om vas te stelof daar wel 'n positiewe effek van boor in die verbetering van pruim kwaliteit is. Vier pruim kultivars, ('Pioneer', 'Sapphire', 'Songold' en 'Angeleno'), is gedurende, sowel as later as die kommersiële oesperiode geoes. In al die kultivars was die afname in fermheid kleiner as wat verwag is, en vrugte wat later geoes is het dieselfde, en soms beter, kwaliteit as die vrugte wat vroeër geoes is gehad. Pruime wat later geoes is het beter kleur en gewoonlik hoër suikers gehad. In teenstelling met wat verwag is, het pruime wat later geoes is nie meer interne verval gehad as die pruime wat vroeër geoes is nie. Dit dui die belangrikheid van optimale oesrypheid aan. 'Angeleno' het geen interne verval gehad nie, selfs na vyfweke opberging by -0.5°C. 'Pioneer' en 'Sapphire' pruirne is as klimakteries en 'Songold' en 'Angeleno' as onderdrukte klimakteries geklassifiseer, gebaseer op etileen produksie. Die klimakteriese pruime het teen 'n hoër tempo gerespireer en etileen geproduseer as die onderdrukte klimakteriese pruime. Gedurende raklewe het klimakteriese vrugte vinniger as onderdrukte klimakteriese vrugte ryp geword. Verder, terwyl klimakteriese pruime nie opbgerging by 'n lae temperatuur nodig gehad het nie, het onderdrukte klimakteriese vrugte welopberging by 'n lae temperatuur nodig gehad om normaal ryp te word. Hoe langer die koel opbergingsperiode was, hoe vinniger het die pruime ryp geword by raklewe en hoe hoër was hulle etileen produksie. Die onderdrukte klimakteriese genotipe kan moontlik in teelprogramme geïnkorporeer word om kultivars met verlengde opbergings- en raklewe te teel. Die lang vervoer tye wat benodig word om Suid Afrikaanse pruime by die uitvoer markte te kry het dit nodig gemaak om navorsing oor die na-oes fisiologie en kwaliteit van pruime te doen. Die klassifisering van pruime as klimakteries of onderdrukte klimakteries kan ons in staat stelom die verskillende fisiologiese reaksies van die kultivars te verstaan en om hanterings prosedures te ontwikkel. Voor-oes faktore, veral lighuishouding en mineraalvoecling speelook 'n rol in na-oes kwaliteit van pruime.

Thesis (MScAgric)--University of Stellenbosch, 2002. / ENGLISH ABSTRACT: In order to study the dormancy of apple buds in conditions of inadequate chilling a number of trails were done during 2000 and 2001. Year-old, unbranched shoots of 'Royal Gala', 'Braeburn', 'Cripps' Pink' and 'Granny Smith' apple were harvested randomly from bearing commercial orchards in the Koue Bokkeveld [33°S, 945m, ca.1300 Utah model chili units (CU)) and Elgin (34 "S, 305m, ca.750CU) regions of the Western Cape, South Africa, respectively. Shoots were chilled at 5-rC. Two replicate bundles were removed from the cold room, prepared and forced at 25°C with continuous illumination until budburst had occurred on at least 25% of the shoots per bundle. The change in the rate of budburst over time was calculated for each orchard and to this response; either a linear or a quadratic function was fitted. Poorly correlated variables were selected that best describe these functions. Using these variables, the orchards were separated into cluster groupings that represented a dormancy pattern. The first split separated the lower chilling requirement cultivars from the higher cultivars. The second and third split separated the orchards according to area differences. The clusters representing the warmer area orchards initially entered deeper into dormancy before exiting. The clusters for the colder area immediately had an increased budburst rate. This data confirm that the chilling requirement includes a period of dormancy induction. An important genotype and environment interaction, other than cold unit accumulation, was observed that could be responsible for terminating bud dormancy. Terminal apple buds from 'Royal Gala' Braeburn', 'Cripps' Pink' and 'Granny Smith' apples were cut from orchards in the Koue Bokkeveld and Elgin regions of the Western Cape, South Africa. Buds were harvested every two weeks during the dormant period. The buds were cut in half and leaf scales removed before the water potential were measured. Fresh and dry weights of the buds were also determined. The data presented confirms the changes in availability of free water in dormant buds and that it could be measured in this way. A definite influence of temperature was illustrated. The water potential from buds in a cold production area (Koue Bokkeveld) behaved more "normally" - water is in a bound form during most of the winter and change to an available form later in winter - whereas buds from a warmer production area did not change much in water potential or content. In the trial, two-year-old proleptic-branched shoots, ca. 500mm long, were selected from a 'Royal Gala' orchard in the Koue Bokkeveld region in the Western Cape, South Africa. During the dormancy period of 2000, shoots received two cold treatments; chilling in a cold room at 5-7°C and the natural chilling received in the field. In 2001, the trail was repeated, but only with the field chilling. The shoots received five dormant pruning treatments: control (not pruned), pruning back to the fourth lateral (heading) before or after chilling; and removal of the 2nd and 3rd laterals (thinning) before or after chilling. After pruning and chilling treatments, the shoots were removed from the orchard or cold room every two weeks and forced in a growth chamber. The rate of bud burst (1/days to 50% bud burst) was calculated for the terminal buds of the lateral shoots. Laterals were categorisation according to position: the terminal extension shoot, the 4th lateral, and all other laterals were pooled. Removing distal tissue by pruning (heading more than thinning) promoted bud burst on laterals. Pruning before chilling was more effective than after chilling. The correlative phenomena that inhibit bud burst on proximal shoots within two-yearold branches were manipulated by pruning. The branching response of one-year-old unbranched shoots, 0.5m long, from 'Royal Gala' and 'Cripps' Pink' apple and 'Rosemary' pear were studied after physical manipulation treatments. Shoots for treatment a to d were re-orientated from either a horizontal or vertical position or left in the original position as control, treatment e to h involved the same re-orientation of shoots and were headed. The amount of growth (in mm) from each node was recorded as well as the position from the terminal bud. The 'Cripps' Pink' had a definite shift in the acrotonic branching pattern (for headed and unheaded), towards a more basitonic response. The reduced effect on 'Royal Gala' and 'Rosemary' suggest a difference in genotype response to the treatments as well as time of treatment. / AFRIKAANSE OPSOMMING: Ter wille van die navorsing oor die invloed van gebrekige koue op dormansie van apple knoppe en die gepaardgaande probleme is 'n reeks proewe gedoen gedurende 2000 en 2001. Jaar oue onvertakte lote van 'Royal Gala', 'Braeburn' , 'Cripps' Pink' en 'Granny Smith' appels is ewekansig geoes vanaf komersieële boorde in die Koue Bokkeveld [33°S, 945m, ca.1300 Utah koue eenhede (CU)] en Elgin (34°S, 305m, ca.750CU) omgewings van die Wes Kaap , Suid Afrika. Die lote is daarna verkoel gehou by 5- 7°C. Lote is elke twee weke vanuit die koue kamer geneem en geforseer met 25°C en deurlopend belig. Die aantal knoppe wat groenpunt bereik het is genoteer totdat 25% van die lote begin bot. Die verandering oor tyd vir elke boord is bereken en 'n liniëre of kwadratiese funksie is daarop gepas. Swak gekorreleerde waardes is gekies wat die funksies die beste beskryf. D.m.v hierdie die waardes is die boorde in groepe ingedeel wat 'n dormansie patroon verteenwoordig. Na die eerste vedeeling is die hoë en lae koue behoefte kultivars geskei. In opvolgende verdelings is die boorde verder in die twee areas geskei met elk 'n spesifieke dormansie patroon. Die groepe wat die warmer area se boorde bevat het aanvanklik dieper in dormansie in beweeg voor dit 'n styging in groei potensiaal getoon het. Die groepe vanaf die kouer produksie area het onmiddelik 'n verhooging in bot tempo getoon. Die data bevestig dat 'n koue behoefte 'n periode van dormansie induksie insluit. 'n Belangrike kultivaromgewing- interaksie, ten spyte van koue eenhede akkumulasie, is waargeneem wat verantwoordlik kan wees vir beëindiging van dormansie. Om die verandering van water status in dormante appel knoppe te bestudeer, was die volgende proef uitgevoer. Terminale apple knoppe van dieselfde vier kultivars en vanaf die selfde twee areas in die Wes Kaap as bogenoemde, is elke tweede week gedurende die winter 2001 gesny vanaf komersieële boorde. Daarna is die knoppe middel deur gesny en die skudblare verwyder voor die vars massa gemeet en daarna die waterpotensiaal bepaal is. Die data het bevestig dat daar veranderings in beskikbaarheid van vry water in dormante knoppe gedurende dormansie plaasvind. 'n Definitiewe invloed van temperatuur op waterpotensiaal is geïllustreer. Die waterpotensiaal van knoppe in die kouer produksie area toon 'n meer normale respons (gedurende die winter is die water in 'n gebonde vorm, wat later in die winter na vry water verander). Daar teenoor is daar in die knoppe van die warm produksie area nie veel verandering in waterpotensiaal of water massa getoon nie. Gedurende die winter van 2000 is twee jaar oue proleptiese vertakte 'Royal Gala' lote, ongeveer 500mm lank, gekies vanaf 'n boord in die Koue Bokkeveld. Die lote is verdeel en het twee koue behandelings ontvang. Koue kamer by 5-T'C en natuurlike koue in die boord. In 2001 is net die natuurlike koue behandeling herhaal. Daar is vyf dormante snoei behandeling op die lote gedoen; kontrole (geen), snoei terug tot die vierde lateraal voor en na die koue; verwydering van die 2de en 3de laterale voor en na koue. Na koue en snoei is die lote verwyder en in die groeikamer geforseer by 25°C en met konstante illuminasie. Die tempo waarteen die laterale gebot het is bereken (1\dae to 50% groen punt) waarna die laterale in klasse gedeel is; terminale knop, die vierde lateraal en die res van die laterale saam. Verwydering van distale weefsel d.m.V. snoei verhoog die tempo waarteen laterale knoppe groenpunt bereik. Snoei voor die koue behandeling was meer effektief as daarna. Die korrelatiewe fenomeen wat bot inhibeer van proksimale lote kan gemanipuleer word in die twee jaar apple loot. Die vertakkings gedrag van een jaar oue onvertakte 'Royal Gala', 'Cripps' Pink' apple en 'Rosemary' peer lote, 0.5m lank, is ondersoek na fisiese manipulasies gedoen is gedurende mid winter 2000. Vir die eerste vier behandelings (a,b,c,d) is die lote in 'n horisontale of vertikale possisie gelos as kontrole, of horisontale of vertikale gebuig en daar gehou d.m.v. binddraad. Behandelings e tot h het dieselfde behels maar die lote is ook nog in die helfte deur gesny (getop). Die hoeveelheid groei in mm vir elke node is aangeteken asook die posisie vanaf die terminale knop. Die 'Cripps' Pink' het 'n definitiewe veskuiwing vanaf 'n akrotoniese na 'n basitoniese vertakkingspatroon getoon. Die reaksies op die manipulasies of die gebrek daaraan ('Royal Gala' en 'Rosemary' ) kan 'n aanduiding wees dat genotipes verskillend reageer op die behandelings asook op die tyd wat dit gedoen was.

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

Thesis (MScAgric)--Stellenbosch University, 1969. / ENGLISH ABSTRACT: no abstract available / AFRIKAANSE OPSOMMING: geen opsomming

Thesis (MScAgric)--Stellenbosch University, 1962. / ENGLISH ABSTRACT: no abstract available / AFRIKAANSE OPSOMMING: geen opsomming

Thesis (MScAgr)--Stellenbosch University, 1962. / ENGLISH ABSTRACT: no abstract available / AFRIKAANSE OPSOMMING: geen opsomming

Thesis (MScAgric)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: We aimed to determine how canopy microclimate influences fruit quality and consumer preference in apples. Our postulate was that consumer preference would be higher for the taste, but not necessarily for the appearance of outer canopy fruit. Outer canopy fruit, exposed to higher irradiance and temperatures, accumulated more phenolics and ascorbic acid, and had higher antioxidant capacities in their peel compared to inner canopy fruit. Phenolic levels and antioxidant capacity were also higher in the flesh of outer canopy fruit while ascorbic acid was higher in the flesh of outer canopy ‘Granny Smith’. From a marketing perspective, outer canopy fruit can be seen as possessing greater potential health benefits. Outer canopy fruit were higher in dry matter content (DMC), sugars and TSS, but lower in TA in the first season of the study. The sweeter and less sour taste of outer canopy fruit was preferred in all three cultivars over two years of study. Sunburnt fruit were higher in DMC, TSS:TA ratio, lower in TA and were perceived to be the sweetest, least sour and lowest in apple flavour and textural attributes. The effect of canopy position on apple flavour and textural attributes was inconsistent. The redder outer canopy ‘Starking’ fruit were preferred by consumers because this cultivar is marketed with full red colour. The appearance of blushed, outer canopy ‘Granny Smith’ and ‘Golden Delicious’, and sunburnt ‘Golden Delicious’ were not preferred by consumers. Consumers are not familiar with such fruit. Blushed ‘Granny Smith’ is downgraded and sometimes sold at a lower price while sunburnt apples are processed or dumped depending on sunburn severity. The consistency of these results was investigated in one season for ‘Golden Delicious’ from five locations. The consumer taste preference differential for inner and outer canopy fruit diminished as canopy size decreased. This indicates that there generally would be no benefit in harvesting and marketing outer and inner canopy ‘Golden Delicious’ separately. We investigated the effect of familiarity on consumer preference by utilising an “experienced” consumer group of farm labourers from Ceres who are familiar with all fruit on a tree compared to an “inexperienced” consumer group of Stellenbosch consumers who are only exposed to fruit on the commercial market and eat apples less frequently. Both groups preferred the taste and appearance of outer canopy ‘Starking’. The taste of sunburnt fruit was preferred by a substantial segment of both consumer groups, but the appearance was preferred by only some Ceres consumers. A small segment of Ceres consumers preferred the taste and appearance of the blushed outer canopy ‘Granny Smith’ and ‘Golden Delicious’ while some Stellenbosch consumers preferred the taste of outer canopy ‘Golden Delicious’, but not ‘Granny Smith’. Therefore, Ceres consumers who are more familiar with the taste attributes of sunburnt and blushed fruit of green cultivars have a higher preference for the appearance of these fruit. Based on our results, fruit marketers may be able to develop niche markets for outer canopy and sunburnt ‘Golden Delicious’ fruit. / AFRIKAANSE OPSOMMING: Ons het ondersoek hoe vrugkwaliteit en verbruikersvoorkeur in appels deur die blarekoepel mikroklimaat beïnvloed word. Ons vermoede was dat verbruikersvoorkeur hoër sou wees vir die smaak, maar nie noodwendig vir die voorkoms van vrugte aan die buitekant van die boom (buitevrugte) nie. Buitevrugte was blootgestel aan hoër ligstraling en temperature en hul skil het meer fenole en askorbiensuur geakkumuleer asook hoër antioksidantkapasiteit gehad vergeleke met binnevrugte. Fenole en die antioksidantkapasiteit was ook hoër in die vleis van buitevrugte terwyl askorbiensuur hoër was in die vleis van ‘Granny Smith’ buitevrugte. Vanuit bemarkingsperspektief kan buitevrugte gesien word as vrugte met hoër potensiële gesondheidsvoordele. Buitevrugte was hoër in droë materiaal inhoud (DMC), suikers en TSS, maar laer in TA, laasgenoemde slegs in die eerste seisoen van die studie. Verbruikers het die soeter en minder suur smaak van buitevrugte verkies in beide jare van die studie. Vrugte met sonbrand was hoër in DMC, TSS:TA verhouding, laer in TA en was die soetste, minste suur en laagste in appelgeur en tekstuureienskappe. Die effek van blaredakposisie op appelgeur en tekstuureienskappe was variërend. Verbruikers het die rooier buitevrugte van ‘Starking’ verkies. Ons reken dit is omdat hierdie kultivar as ‘n volrooiappel bemark word. Verbruikers het minder van die voorkoms van rooiblos ‘Granny Smith’ en ‘Golden Delicious’ asook van ‘Golden Delicious’ met sonbrand gehou. Verbruikers is nie vertroud met sulke vrugte nie. Rooiblos ‘Granny Smith’ appels word afgradeer en word soms teen laer pryse verkoop terwyl sonbrand appels geprosesseer of uitgeskot word afhangend van die graad van sonbrand. Die konsekwentheid van ons resultate is ondersoek met ‘Golden Delicious’ van vyf lokaliteite. Die smaakvoorkeur differensiaal tussen binne- en buitevrugte het afgeneem met afname in boomgrootte. Oor die algemeen sou daar dus geen voordeel wees om ‘Golden Delicious’ binne- en buitevrugte apart te oes en te bemark nie. Ons het die effek van vertroudheid op verbruikervoorkeur ondersoek deur gebruik te maak van “ervare” verbruikergroep bestaande uit plaasarbeiders in Ceres en “onervare” verbruikersgroep van Stellenbosch. Die Ceres verbruikers is vertroud met al die appels op die boom vergeleke met die Stellenbosch verbruikers wat net blootstelling het aan vrugte op die kommersiële mark en ook minder gereeld appels eet. Beide verbruikersgroepe het die voorkoms en smaak van ‘Starking’ buitevrugte verkies. Substansiële segment van beide verbruikersgroepe het die smaak van sonbrand vrugte verkies, maar die voorkoms van hierdie vrugte is slegs deur sommige Ceres verbruikers verkies. Klein segment Ceres verbruikers het die smaak en voorkoms van ‘Granny Smith’ en ‘Golden Delicious’ buitevrugte verkies terwyl sommige Stellenbosch verbruikers die smaak van ‘Golden Delicious’, maar nie ‘Granny Smith’ buitevrugte verkies het nie. Ceres verbruikers is meer vertroud met die smaakeienskappe van sonbrand en blosvrugte van groen kultivars en het gevolglik hoër voorkeur vir die voorkoms van hierdie vrugte. Gebaseer op ons resultate kan bemarkers moontlik nismark vir gebloste en sonbrand ‘Golden Delicious’ vrugte ontwikkel.

Thesis (MScAgric)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: Maintaining constant high yields in „Abate Fetel‟ and „Forelle‟ orchards in South Africa is challenging. Improving productivity in these orchards could be achieved by increasing fruit set and fruit size. Fruit size is an important marketing and quality parameter and has a significant effect on the economic value of fruit. Various protocols to improve fruit set are used by South African producers but these are not well researched. We therefore evaluated different combinations of plant growth regulators including gibberellic acid (GA3), gibberellins 4+7 (GA4+7), GA4+7 combined with 6-benzyladenine (6-BA), aminoethoxyvinylglycine (AVG) and prohexadione-calcium (P-Ca) in combination with trunk girdling during flowering on „Forelle‟ and „Abate Fetel‟ to determine the best fruit set strategy. All applied growth regulators improved fruit set relative to an untreated control over two consecutive seasons, but GA3 and P-Ca reduced return bloom and AVG resulted in smaller fruit size relative to the other treatments. The application of synthetic cytokinins are believed to enhance fruit size by stimulating and extending the cell division period in fruit when applied at the correct stage of fruit growth. In addition, combination of P-Ca with GA4+7 was used successfully on Japanese pear (Pyrus pyrifolia Nakai) and „Bing‟ sweet cherry to improve fruit size. This combination of GA4+7 and P-Ca was evaluated and combined with 6-BA treatments on European pear (Pyrus communis L.) cultivars, Forelle and Abate Fetel, to see if a similar effect on fruit size could be achieved under South African growing conditions. On both „Forelle‟ and „Abate Fetel‟ the combination of GA4+7 and P-Ca increased fruit size, but was more pronounced in „Abate Fetel‟. Growth regulators N-phenyl-N‟ -1,2,3-thiadiazol-5-ylurea (TDZ), N (2-chloro-4-pyridyl)-N‟ -phenylurea (CPPU), 6-BA and 2,4-dichlorophenoxyacetic acid (2,4-D) successfully increased fruit size in pear cultivars Coscia and Spadona in Israel. These growth regulators were applied to „Forelle‟ and „Abate Fetel‟ to determine if a similar effect could be achieved. None of the synthetic cytokinins applied had a significant effect on increasing fruit size in these two cultivars over two consecutive seasons although 6-BA increased return bloom and 2,4-D application resulted in increased fruit set. The stage when the cell division period in „Forelle‟ and „Abate Fetel‟ ends was also determined as 34 and 45 days after full bloom respectively, which can be used in the future to better plan the timing of fruit size enhancement treatments. Based on results from various fruit set and fruit size improvement trials, it can be recommended to use GA4+7 or AVG to increase fruit set on „Forelle‟ and „Abate Fetel‟, depending on the fruit set history of the orchard. Results from fruit size improvement trials were variable, and emphasises the fact that a balance between yield and fruit size must be determined for an orchard to achieve good fruit size and maximum return. / AFRIKAANSE OPSOMMING: Die handhawing van konstante, hoë opbrengste in „Abate Fetel‟ en „Forelle‟ boorde in Suid-Afrika is 'n uitdaging. Produktiwiteit in hierdie boorde kan verhoog word deur vrugset en vruggrootte te verbeter. Vruggrootte is 'n belangrike bemarkings- en kwaliteitsparameter en het 'n betekenisvolle effek op die ekonomiese waarde van vrugte. 'n Verskeidenheid protokolle om vrugset te verbeter word deur Suid-Afrikaanse produsente gevolg, maar hierdie protokolle is nog nie goed nagevors nie. Verskillende kombinasies van plantgroeireguleerders insluitend gibberelliensuur (GA3), gibberellien 4+7 (GA4+7), GA4+7 in kombinasie met 6-bensieladenien (6-BA), aminoetoksievinielglisien (AVG) en prohexadioon-kalsium (P-Ca) in kombinasie met stamringelering is aan „Forelle‟ en „Abate Fetel‟ bome gedurende blomtyd toegedien om die beste vrugsetstrategie te bepaal. Alle plantgroeireguleerdes wat toegedien is het vrugset verbeter relatief tot 'n onbehandelde kontrole oor twee opeenvolgende seisoene, maar GA3 en P-Ca het die aantal blomme in die daaropvolgende seisoen verlaag en AVG het kleiner vruggrootte gelewer relatief tot alle ander behandelings. Dit is wel bekend dat die toediening van sintetiese sitokiniene vruggrootte verbeter deur die stimulering en bevordering van seldeling in vrugte wanneer dit in die regte groeifase toegedien word. Die kombinasie van P-Ca en GA4+7 was suksesvol om vruggrootte te verbeter toe dit aan Japanese pere (Pyrus pyrifolia Nakai) en „Bing‟ kersies toegedien is. Hierdie kombinasie van GA4+7 en P-Ca is geëvalueer en gekombineer met 6-BA-behandelings op die Europese peer (Pyrus communis L.) kultivars, Forelle en Abate Fetel, om te bepaal of dieselfde effek op vruggrootte bereik kan word onder Suid-Afrikaanse groei kondisies. Op beide „Forelle‟ en „Abate Fetel‟ het die kombinasies van GA4+7 en P-Ca vruggrootte verbeter, maar dit was meer opmerklik in die geval van „Abate Fetel‟. Die groeireguleerders N-feniel-N‟ -1,2,3-thiadiazol-5-ylurea (TDZ), N (2-chloro-4-piridiel)-N‟ -fenielurea (CPPU), 6-BA en 2,4- dichloorfenoksieasynsuur (2,4-D) het vruggrootte verbeter in „Coscia‟ en „Spadona‟ pere in Israel. Hierdie plantgroeireguleerders is toegedien aan „Forelle‟ en „Abate Fetel‟ om vas te stel of dieselfde effek verkry kon word. Nie enige van die sintetiese sitokiniene wat toegedien is het 'n betekenisvolle effek op die verbetering van vruggrootte in hierdie twee kultivars oor twee opeenvolgende seisoene getoon nie, alhoewel 6-BA die verbetering van blom in die daaropvolgende seisoen tot gevolg gehad en 2,4-D vrugset verbeter het. Die stadium waar seldeling in „Forelle‟ en „Abate Fetel‟ eindig is vasgestel as 34 en 45 dae na volblom, onderskeidelik, wat in die toekoms gebruik kan word om die beplanning en tydsberekening van vruggrootte behandelings te verbeter. Na verskeie vrugset en vruggroote verbeterings proewe, kan aanbeveel word dat GA4+7 of AVG gebruik kan word om vrugset in „Forelle‟ en „Abate Fetel‟ te verbeter, afhangende van die vrugset geskiedenis van die boord. Resultate van vruggrootte verbeterings proewe het gevarieër en beklemtoon net weer die feit dat 'n balans tussen opbrengs en vruggrootte bepaal moet word om optimale vruggrootte te handhaaf en so hoë winste te verseker. / SAAPPA

Thesis (PhD(Agric) (Horticulture))--University of Stellenbosch, 2009. / ENGLISH ABSTRACT: Branch architecture is the position and length of lateral shoots along a main axis, and is dependant on competitions (dominance) among meristems and lateral shoots. In areas with inadequate winter chilling, branch architecture is altered, the dynamics of which are poorly understood. The aim of this work was to better understand the dynamics underlying plant architecture. In the first part of the study, the dynamics of apple branch architecture were characterized for two cultivars, Golden Delicious and Granny Smith, in areas with differing degrees of inadequate winter chilling (a warm area and a cool area). In an additional study, progeny of a mapped ‘Telamon’ (columnar habit) and ‘Braeburn’ (normal habit) population were used to quantify branch architecture in an effort to develop quantitative trait loci (QTLs) for branching habit. Although branch architecture could be quantified, it was difficult to relate these to known qualitative branching habits, as the columnar gene is dominant and limited the number of progeny that were not columnar. With the exception of organogenesis in the season preceding growth, acrotonic tendencies (number of growing laterals, lateral length, fruit set) were not related to temporal (primigenic) dominance of the distally located buds or flowers within an axis. In the warm area, both relative time of budburst and flowering among buds within an axis did depict a loss of acrotony (positional dominance of the distally located buds and shoots within an axis). The first buds to burst and flower in the warm area had the greatest ability to grow out and set fruit, respectively, regardless of position within the shoot, implicating a role for primigenic dominance when chill unit accumulation was inadequate. Overall, temporal (primigenic) dominance in the warm area, and positional dominance (acrotony) in the cool area dictated lateral outgrowth and development. / AFRIKAANSE OPSOMMING: Takargitektuur verwys na die posisie en lengte van laterale lote soos dit oor die hoofas versprei voorkom. Dit is afhanklik van kompetisie (dominansie) tussen meristeme en laterale lote. In areas met onvoldoende winterkoue word takargitektuur verander, maar die dinamika van hierdie veranderinge word nog nie goed verstaan nie. Die doel van hierdie navorsing was om die onderliggende dinamika wat plantargitektuur beïnvloed beter te verstaan. In die eerste deel van die studie is die dinamika van appeltakargitektuur van twee cultivars Golden Delicious en Granny Smith, in twee areas met verskillende mate van onvoldoende winterkoue bestudeer (’n warm en ’n koel area). In ’n verdere studie is die nageslag van ‘n ‘Telemon’ (kolomgroeiwyse) en ‘Braeburn’ (normale groeiwyse) kruising gebruik om takargitektuur te kwantifiseer. Dit is gedoen in ’n poging om kwantitatiewe eienskapslokusse vir vertakking te ontwikkel. Alhoewel takargitektuur kwantifiseer kon word, was dit moeilik om dit in verhouding te bring met kwalitatiewe vertakkingspatrone daar die kolomgroeiwyse-geen dominant is en die aantal indiwidue in die nageslag wat nie ’n kolomgroeiwyse gehad het nie beperk was. Met die uitsondering van organogenese in die seisoen wat groei voorafgaan, is akrotoniese neigings (aantal laterale lote, laterale lootlengte, vrugset) nie beïnvloed deur tydelike (primigeniese) dominansie van distale knoppe of blomme binne ’n as nie. In die warm area het beide relatief tot knopbreek en blomtyd binne ’n assestelsel die verlies aan akrotonie beskryf (posisionele dominansie van distale knoppe en lote in assestelsel). Die eerste knoppe wat bot en blom in die warm area het die beste vermoë om te groei en vrugte te set, onafhanklik van hul posisie. Dit impliseer die rol van primigeniese dominansie wanneer ’n gebrek aan winterkoue ervaar word. Algemeen gesien was dit tydelike (primigeniese) dominansie in warm areas en posisionele dominansie (akrotonie) in die koeler area wat lateraal bot en ontwikkeling bepaal het.

Stellenbosch University. Faculty of AgriSciences. Dept. of Horticulture. / Thesis (PhD (Agric))--Stellenbosch University, 2006. / ENGLISH ABSTRACT: Market preferences for larger fruit have forced producers to adopt cultural practices that will ensure bigger fruit even if this comes at the expense of reduced total yields. In order to obtain acceptable fruit size there must be an adequate supply of photosynthetic carbon products especially during the cell division stage of fruit growth. Competition between fruits and between fruit and vegetative growth, as well as adverse climatic conditions, may limit the carbon supply to the fruits at this critical period and thus limit the final fruit size. Growers are showing renewed interest in the use of girdling or scoring in combination with the usual fruit thinning program to achieve growth control and increase fruit size. A new and milder chemical growth retardant, prohexadione-calcium (ProCa), is now also available for vegetative growth control of apple trees. [n this study, the effects of, and potential interaction between scoring, ProCa and fruit thinning were investigated, with respect to shoot and fruit growth, yield and photosynthetic capacity, in 'Royal Gala" 'Fuji' and 'Cripps' Pink' apple trees. ProCa decreased final extension shoot length in all three cultivars. Extension shoots were generally more sensitive than bourse shoots to scoring and ProCa. ProCa seems to be a more effective way of controlling shoot growth than scoring, with 'Fuji' and 'Cripps' Pink' being more sensitive than 'Royal Gala' to the application of ProCa. Scoring led to increased fruit growth rates during the first 40 days after full bloom (DAFB), and culminated in better fruit size at harvest. Scoring improved the total soluble solids concentration (TSS) of 'Fuji' and 'Cripps' Pink' compared to control and ProCa treatments. ProCa inhibited shoot growth effectively, but no evidence was found for improved carbon allocation to fruits and reproductive buds. Yield efficiencies of scored trees were significantly improved in all cultivars during the second season, due to better reproductive bud development after the first year of scoring. On 'Royal Gala' and 'Cripps' Pink', the efficiency of scoring to stimulate reproductive bud development on old and new spurs declined after 4 weeks after full bloom (WAFB). In 'Fuji', scoring later than I WAFB led to a decreasing positive response on old and new spurs. In contrast, reproductive bud development on long shoots increased with later scoring (6 and 8 W AFB) on all cultivars. It seems that the most beneficial time of scoring is 2-4 W AFB, as early as possible during the cell division stage offruit growth, but not before natural drop has occurred. The combination of early-season scoring and application of ProCa seems to hold potential for increasing carbon allocation to the fruit and improving fruit size and quality attributes. Scoring early in the season reduced photosynthetic capacity, and this reduction in carbon availability led to earlier cessation of shoot growth as well as shorter shoots. Later in the season, reduced fruit numbers led to a decrease in photosynthesis. The optimum temperature range for photosynthesis was found to adjust according to seasonal temperature variations. The harvest-induced reduction in sink strength changed stomatal sensitivity to higher temperature. Due to a reduced demand for carbohydrates by the plant, the maximum rate of photosynthesis (Amax) was reduced post-harvest. Following this reduction in sink strength and Am .. , stomata became more sensitive to high leaf temperatures, thus restricting water loss. Pre-harvest there was a strong demand for carbohydrates, therefore stomata were kept open at higher temperatures to ensure a high rate of C02 incorporation, but at a cost with regard to water use efficiency. The sharp increase in dark respiration (Rd) in leaves and fruit with an increase in temperature would mean that significant carbohydrate shortages could occur in trees during source limited periods early in the season, especially under warm weather conditions commonly experienced in the Western Cape region. / AFRIKAANSE OPSOMMING: Die effek van omgewings- en interne faktore op koolstofproduksie en -allokasie in appelbome (Malus domestlca Borkh.). Mark voorkeur vir groter vrugte forseer produsente om tegnieke te gebruik wat groter vrugte sal verseker selfs al beteken dit verlaagde totale opbrengste. Om aanvaarbare vruggrootte te bereik moet daar voldoende voorsiening van fotosinteties geproduseerde koolstofprodukte aan die vrug wees, veral gedurende die selverdelingstadium van vruggroei. Kompetisie tussen vrugte, en tussen vrugte en vegetatiewe groei sal die voorsiening van koolstof gedurende die kritieke stadium aan die vrug beperk en so vruggroote benadeel. Daar is dus hernude belangstelling in die gebruik van ringelering in kombinasie met die gewone vrug uitdunprogramme om groei te beheer en vruggrootte te verbeter. 'n Nuwe, sagter chemiese groeireguleerder, proheksadioon-kalsium (ProCa) is ook nou beskikbaar vir groeibeheer op appelbome. In hierdie studie is die effekte van, en moontlike interaksie tussen ringelering, ProCa en vruguitdunning ondersoek ten opsigte van loot- en vruggroei en opbrengs, sowel as die effekte op gaswisseling op 'Royal Gala', 'Fuji' en 'Cripps' Pink' appelbome. ProCa veroorsaak korter lote in aJ drie kultivars. Verlengingslote is meer sensitief as beurslote vir ringelering en ProCa. ProCa is effektiewer as ringelering om lootgroei te beheer, en 'Fuji' en 'Cripps' Pink' is sensitiewer as 'Royal Gala'. Ringelering lei tot verbeterde vruggroeitempos gedurende die eerste 40 dae na volblom en verbeterde vruggrootte by oes. Ringelering verbeter die totale oplosbare vastestotkonsentrasie (TOVS) van 'Fuji' en 'Cripps' Pink' in vergelyking met kontrole- en ProCa-behandelings, onderskeideHk. ProCa inhibeer lootgroei effektief, maar geen bewyse van verbeterde koolstomllokasie na vrugte en reproduktiewe knoppe is gevind nie. Opbrengseffektiwiteit van geringeleerde borne verhoog gedurende die tweede seisoen van ringelering weens beter reproduktiewe knopontwikkeling. Ringelering later as 4 weke na volblom (WNVB) is minder effektief om reproduktiewe knopontwikkeling op ou en nuwe spore in 'Royal Gala' en 'Cripps' Pink' te stimuleer. Die positiewe effek van ringelering op reproduktiewe knoppe op 'Fuji' verminder sodra dit later as I WNVB gedoen word. Op langlote het 'n laat ringelering (6 en 8 WNVB) die beste effek op reproduktiewe knopontwikkeling. Die mees voordelige tyd om te ringeIeer was 2-4 WNVB, so vroeg as moontlik gedurende die selverdelingstadium van vruggroei, maar nie voor natuurlike vrugval voltooi is nie. Die kombinasie van vroei! ringelering en die toediening van ProCa het potensiaal om koolstofallokasie na die vrug te verbeter, met die gepaardgaande verbetering in vruggrootte en -kwaliteit. RingeJering vroeg in die seisoen inhibeer fotosintese en hierdie verlaging in koolstof beskikbaarheid het tot gevolg dat lootgroei vroei!r gestaak word. Later in die seisoen veroorsaak verlaagde vruggetalle 'n afname in fotosintese. Die optimum temperatuur vir fotosintese verander na gelang van heersende lugtemperature. Die oes-geinduseerde verlaging in sinksterkte verander stomatale sensitiwiteit vir hoo temperature. Weens 'n verJaagde aanvraag vir koolhidrate deur die plant word fotosintese verlaag na-oes. Weens die verlaging is stomata sensitiewer vir hoer temperature en beperk dus waterverlies. V oor oes is daar 'n hoo aanvraag na koolhidrate dus word stomata oop gehou selfs by hoe temperature ten koste van watergebruiksdoeltreffendheid. Die skerp styging in donker respirasie in blare en vrugte met 'n verhoging in temperature sal beteken dat koolhidraat-tekorte kan ontstaan in bome gedurende die bron-beperkte periodes vroeg in die seisoen, veral onder warm toestande 500S wat algemeen ervaar word in die Wes Kaap.