Thesis (MScAgric)--University of Stellenbosch, 2007. / ENGLISH ABSTRACT: Persimmon production is new to the Western Cape region of South Africa and is well suited to its Mediterranean climate. Export market opportunities for out-of-season fruit in traditional Northern Hemisphere markets have led to the planting of almost 700 ha of the astringent cultivar ‘Triumph’ since 1998. Production of other cultivars is negligible compared to ‘Triumph’. There is a need to study the vegetative and reproductive phenology of ‘Triumph’ in order to improve production under local conditions. In order to determine the physical characteristics of good bearing units, the effect of length and orientation of one-year-old shoots on bud break, vegetative growth, flowering, fruiting and fruit quality was evaluated. Further trials were conducted to determine the duration of the flowering period, flower distribution on one-year-old shoots and the timing of flower initiation. Shoots between 30-60 cm, the longest length studied, produced the most new vegetative growth, had the most flowers, and set the most fruit. Fruit also ripened faster on 30-60 cm shoots compared to shorter shoots. Shoots with more flowers were thicker than shoots of equal length, but with fewer flowers. Poor fruit set is one of the most important problems in persimmon cultivation. Experiments were conducted to determine the efficacy of gibberellic acid (GA3) and scoring or girdling during full bloom (FB) to increase fruit set and yield. Different GA3 concentrations (20 mg·L-1 and 40 mg·L-1) were evaluated. GA3 applications and scoring/girdling were applied at 30% FB or 30 and 70% FB. While GA3 treatments were ineffective, scoring increased fruit set and yields in young orchards (< 5-year-old) up to three times. In general, GA3 sprays decreased fruit size although it did not increase the number of fruit per tree. In more mature orchards (> 5 years old), scoring or girdling in combination with GA3 applications at 30 and 70% FB increased yield by an average of 16 tons (45%) compared to GA3 treatment on its own (35 tons). This increase in yield did not affect fruit size. Girdling and scoring were equally effective in increasing yield. When it comes to GA3 applications to improve fruit set in mature orchards, producers must bear in mind that 30% full bloom occurs already 2 to 4 days after the first flowers are open. Based on these data, guidelines to manage fruit set can be developed for the South African persimmon industry. However, these guidelines will also need to entail pruning and thinning strategies to prevent alternate bearing that may result from the high yields. ‘Triumph’ preferentially initiates flowers laterally in terminal quadrants of one-year-old shoots. This has to be taken into consideration with the development of pruning strategies. When timing thinning treatments, producers should keep in mind that flower initiation starts shortly after shoot elongation has ended and soon after fruit set. The short harvesting period of ‘Triumph’ puts pressure on producers and packing facilities, and shortens the marketing window of fruit. The final objective of this study was to advance or delay harvesting by using scoring or plant growth regulators. The effect of these treatments on fruit quality at harvest and after storage for 3 months at -0.5 °C and shelf life of 5 to 7 days at 15 °C were evaluated over two seasons. n-Propyl dihydrojasmonate (PDJ), aminoethoxyvinylglycine (AVG) and scoring generally did not affect fruit ripening and storability. 2-Cloroethyl phosphonic acid (ethephon) applied at 24 mg·L-1 4 weeks before the first of two harvest dates (WBFH) advanced ripening. Gibberellic acid (GA3) application at 50 mg·L-1 2 WBFH and 1-methylcyclopropene (MCP) applied immediately after harvest, delayed fruit ripening and reduced fruit softening during storage and shelf life. Future research should evaluate combined treatments of ethephon with MCP or GA3 to advance harvesting without negatively effecting storability of fruit. / AFRIKAANSE OPSOMMING: Verbouing van persimmon is ‘n nuut tot die Wes-Kaap streek van Suid-Afrika met sy geskikte Mediterreense klimaat. Uitvoergeleenthede vir buite-seisoen vrugte na tradisionele Noordelike Halfrond markte het sedert 1998 gelei tot die aanplant van bykans 700 ha van die vrank cultivar, ‘Triumph’. Ander cultivars word ook verbou, maar die hoeveelhede is weglaatbaar in vergelyking met ‘Triumph’. Daar bestaan ‘n behoefte om die vegetatiewe en reproduktiewe fenologie van ‘Triumph’ te bestudeer ten einde produksie onder plaaslike toestande te verbeter. Die effek van lengte en oriëntasie van een-jaar-oue lote op knopbreek, vegetatiewe groei, blomtyd, vrugset en vrugkwaliteit is geëvalueer ten einde die fisieke eienskappe van goeie dra-eenhede te bepaal. Verdere proewe is uitgevoer om die duur van die blomperiode, die verspreiding van blomme op een-jaar-oue lote en die periode van blominisiasie te bepaal. Lote tussen 30–60 cm, die langste lengte wat bestudeer is, produseer die meeste nuwe vegetatiewe groei, het die meeste blomme en set die meeste vrugte. Vrugte op 30–60 cm lange lote het ook vinniger ryp geword in vergelyking met vrugte op korter lote. Lote met baie blomme was dikker as lote van dieselfde lengte, maar met minder blomme. Swak vrugset is een van die belangrikste probleme wat persimmon produksie kniehalter. Eksperimente is uitgevoer om te bepaal of toediening van gibberelliensuur (GA3) en insnyding (scoring) of ringelering gedurende volblom (VB) effektief is om vrugset en produksie te verhoog. Verskillende GA3 konsentrasies (20 mg·L-1 en 40 mg·L-1) is geëvalueer. GA3 toegediening en insnyding/ringelering is uitgevoer by 30% VB of by 30% en 70% VB. Terwyl GA3 ondoeltreffend was in jong boorde (< 5-jaar-oud), het insnyding vrugset en produksie tot drie keer verhoog. GA3 het vruggrootte oor die algemeen verminder sonder dat daar ‘n toename in die aantal vrugte per boom was. In meer volwasse boorde (>5-jaar-oud) het insnyding/ringelering in kombinasie met GA3 toediening by 30 en 70% VB, produksie met gemiddeld 16 ton (45%) verhoog in vergelyking met net GA3-behandeling (35 ton). Hierdie verhoging in produksie het geen effek op vruggrootte gehad nie. Ringelering en insnyding was ewe effektief in die verhoging van produksie. Met die toediening van GA3 in volwasse boorde moet produsente in gedagte hou dat 30% VB bereik kan word binne 2 tot 4 dae nadat die eerste blomme oopgegaan het. Bogenoemde data stel ons in staat om riglyne vir die bestuur van vrugset te ontwikkel vir die Suid-Afrikaanse persimmon bedryf. Ten einde die ontstaan van alternerende drag as gevolg van hoë vrugladings te vermy, sal snoei- en uitdunstrategieë egter in ag geneem moet word met die saamstel van hierdie riglyne. ‘Triumph’ inisieer blomme hoofsaaklik lateraal in die terminale kwadrante van een-jaar-oue lote. Dit moet in aanmerking geneem word met die ontwikkeling van snoeistrategieë. Met die tydsberekening van uitdunbehandelings, moet produsente in gedagte hou dat blominisiasie in aanvang neem kort na lootgroeistaking en vrugset plaasgevind het. Die kort oesperiode van ‘Triumph’ plaas produsente en verpakkingsaanlegte onder druk, en verkort die bemarkingsvenster van vrugte. Die laaste doelwit van hierdie studie was om oes te vervroeg of uit te stel deur gebruik te maak van insnyding of plantgroeireguleerders. Die effek van hierdie behandelings op vrugkwaliteit met oes, na opberging vir 3 maande by -0.5 oC en raklewe van 5 tot 7 dae by 15 oC is geëvalueer oor twee seisoene. Npropieldihidrojasmonaat (PDJ), amino-etoksievinielglisien (AVG) en insnyding het oor die algemeen geen effek op die rypwording en opbergingsvermoë van vrugte gehad nie. Toediening van 2-chloro-etielfosfiensuur (ethephon) teen 24 mg·L-1, 4 weke voor die eerste van twee oeste het rypwording versnel. Toediening van gibberelliensuur (GA3) teen 50 mg·L-1 2 weke voor die eerste oes en 1-metielsiklopropeen (MCP) onmiddelik na oes, het rypwording vertraag en het die sagword van vrugte gedurende opberging en raklewe verminder. Ten einde oesdatums te vervroeg sonder om die opbergingsvermoë van vrugte te benadeel, behoort die kombinasie van ethephon met MCP of GA3 geëvalueer te word.

Thesis (MScAgric (Horticulture))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: Persimmon production is new to South Africa with about 700 ha planted to the dioecious, parthenocarpic Triumph cultivar since 1998. Little local expertise is available to assist growers in achieving high yields of high quality fruit and previous research has shown that recipes that are followed in Israel, from where ‘Triumph’ was introduced to South Africa, do not necessarily have any beneficial effect in South Africa. ‘Triumph’ orchards in South Africa are often late in reaching full production. Persimmon trees are generally vigorous and prone to excessive fruit drop, partly due to excessive vegetative growth, especially when young and grown on the very vigorous Diospyros lotus seedling rootstock. The first objective of this study was to evaluate the use of growth retardants and various severities of girdling to increase flower formation, fruit set and yield in vigorous, young ‘Triumph’ orchards. Scoring and girdling improved fruit set and yield in two such orchards and are recommended as tools to improve yield in ‘Triumph’ in South Africa. Strapping, prohexadione-Ca (P-Ca) and paclobutrazol (PBZ) did not increase yield whereas 5 mm bark removal was too severe a treatment and decreased fruit quality in the current season and yield in the following season. None of the treatments had an effect on flower formation or decreased vegetative growth. PBZ, especially as foliar spray, appears to advance fruit maturity. P-Ca at 125 mg L-1 and 250 mg L-1 induced phytotoxicity symptoms and decreased yields in both orchards. However, further research is required before P-Ca and PBZ are completely discarded as treatments to manage vigor in ‘Triumph’ persimmon in South Africa. In contrast to the negative effect of excessive vigor on fruit production, the profitability of orchards is dependent on the rapid growth of trees after planting in order to fill the allotted canopy volume and achieve full production as quickly as possible. Hence, the second objective of this study was to determine optimum levels of irrigation and fertilizer application rates to attain early, high yields in newly planted ‘Triumph’. Fertigation was applied at three levels, viz. ½X, 1X and 2X with 1X being the commercial standard application rate. Irrigation was also applied at these levels without addition of fertilizer. In addition, fertilizer was applied at 0X, ½X and 1X at 1X irrigation level. Tree size increased with an increase in water application rate. Yield also increased linearly with an increase in water application rate due to a linear increase in fruit size. Fertigation and ½X water as well as an increase in fertilizer application rate at 1X irrigation substantially delayed fruit ripening. Hence, careful management of fertilizer and water application rate could be used to extend the harvesting period and, therefore, the marketing window of South African ‘Triumph’. We recommend that the trial be continued for a further few seasons so that the effect of water and fertilizer application rates on fruit quality and storability can be assessed. Fruit set may also be affected as trees reach their mature size with a concomitant increase in shading. / AFRIKAANSE OPSOMMING: Persimmonverbouing is ‘n nuwe bedryf in Suid-Afrika met ongeveer 700 ha van die tweeslagtige, partenokarpiese Triumph cultivar wat sedert 1998 aangeplant is. Min plaaslike kundigheid is beskikbaar om produsente van raad te bedien oor hoe om te werk te gaan om hoë opbrengste van hoë kwaliteit te verkry. Vorige navorsing het getoon dat resepte wat ‘Triumph’ van Israel na Suid-Afrika gevolg het, nie noodwendig suksesvol hier toegepas kan word nie. ‘Triumph’ boorde in Suid-Afrika neig om lank te neem alvorens hul hul maksimum produksievermoë bereik. Persimmons is oor die algemeen baie groeikragtig en geneig tot hoë vrugval, deels as gevolg van hul geil groei, en veral terwyl hulle jonk is en op die uiters groeikragtige Diospyros lotus saailingonderstam geënt is. Die eerste doelwit van hierdie studie was om die invloed van groei inhibeerders en verskillende grade van strafheid van ringelering op blomvorming, vrugset en oesopbrengs in jonk, sterk-groeiende ‘Triumph’ boorde te evalueer. Insnyding en ringelering met ‘n handsaag het vrugset en oeslading in twee groeikragtige boorde verbeter en word aanbeveel as geskikte ingrepe om die oeslading van ‘Triumph’ te verhoog. Draad-ringelering, en aanwending van prohexadione-Ca (P-Ca) en paclobutrazol (PBZ) het nie die opbrengs verhoog nie terwyl die verwydering van `n 5 mm strook bas té aggresief was en die vrugkwaliteit in die seisoen van toediening en opbrengs in die daaropvolgende seisoen verlaag het. Geen van die behandelings het blomvorming geaffekteer of vegetatiewe groei verminder nie. Dit wil voorkom asof PBZ, veral as blaartoediening, vrugrypwording kan versnel. Blare het tekens van fitotoksisiteit getoon na aanwending van P-Ca teen 125 mg L-1 en 250 mg L-1. P-Ca het ook die opbrengs in beide boorde aansienlik verlaag. Verdere navorsing is egter nodig alvorens P-Ca en PBZ sondermeer verwerp word as behandelings om die groei van ‘Triumph’ te beheer. Die winsgewendheid van boorde is afhanklik daarvan dat bome aanvanklik vinnig groei ten einde die toegekende boomryvolume so spoedig moontlik te vul en sodoende so vinnig as moontlik hul vol produksievermoë bereik. Bogenoemde is natuurlik teenstrydig met die negatiewe effek van uitermatige geil vegetatiewe groei op vrugproduksie. Die tweede doelwit van hierdie studie was dus om die optimale vlakke van besproeiing en bemesting te bepaal wat die vroeë aanvang van hoë opbrengste in nuwe ‘Triumph’ boorde sal verseker. Vloeibare bemesting is in kombinasie met besproeiing teen drie vlakke toegedien nl. ½X, 1X en 2X met 1X die kommersiële standaard vlak van toediening. Besproeiing is ook teen hierdie vlakke toegedien sonder dat kunsmis bygevoeg is. Addisioneel hiertoe is bemesting ook toegedien teen ½X, 1X en 2X teen 1X besproeiing. Boomgrootte het toegeneem met `n toename in die vlak van besproeiing. `n Lineêre toename in vruggrootte met ‘n toename in die vlak van besproeiing het ‘n oorsaaklike lineêre toename in opbrengs tot gevolg gehad. Bemesting in kombinasie met besproeiing, ½X besproeiing sonder bemesting, asook `n toename in die bemestingsvlak by 1X besproeiing het vrugrypwording substansieel vertraag. Die omsigtige bestuur van bemesting- en besproeiingsvlakke kan moontlik gebruik word om die oesperiode, en dus die bemarkingsvenster, vir Suid-Afrikaanse ‘Triumph’ te verleng. Ons beveel aan dat die proef vir ‘n vêrdere aantal seisoene voortgesit word sodat die effek van bemesting- en besproeiingsvlakke op vrugkwaliteit en -houvermoë bepaal kan word. Verhoogde oorskaduwing soos wat bome van sekere behandelings hul toegekende spasie bereik en oorskry, kan ook in die toekoms ‘n invloed op vrugset uitoefen.