Production of the pollination constant astringent persimmon 'Triumph' under South African conditions

Ungerer, Samuel Frederik (2007-04)

Thesis (MScAgric)--University of Stellenbosch, 2007.

Thesis

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.

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