Thesis (MSc)--Stellenbosch University, 2000. / Full text to be digitised and attached to bibliographic record. / ENGLISH ABSTRACT: Enhancement of vegetative growth in young citrus plantings The establishment of citrus involves high input costs, with break-even usually only attained after six years, making early returns imperative for economic survival. Early production is inseparably associated with good growth of the trees in the non-bearing years. In cool and cold production regions, coupled with a high frequency of wind, the initial tree growth is unsatisfactory. Trials were conducted to evaluate the effect of foliar application of Progibb® (GA3), Promalin'" (G~+7 + BA), Kelpak® (seaweed extract containing auxins and cytokinins) and soil applications of Temik® (aldicarb) as a means to promote vegetative growth. GA3 and/or aldicarb significantly increased tree height, without increasing the stem diameter in comparison to the control trees on 'Eureka' lemon, but not on 'Lisbon' lemon. G~+7 + BA or Kelpak® treatments did not have an effect on tree growth or fresh weight distribution. In conclusion, growth stimulation by GA3 and/or aldicarb could lead to quicker filling of the allotted space, and consequently higher, earlier yields, but further trials are required to verify these results. Insufficient carbohydrate and nitrogen reserves are often implicated in poor establishment performance of nursery trees. The effect of tree size at planting and different topping heights on early growth in the field were evaluated; also the physical and chemical profile of tall nursery whip trees were quantified. Significant correlations were found between the initial stem diameter and final stem diameter and initial tree height and final tree height at the end of the first growing season. Stem diameter increase was significantly reduced in topped trees relative to untopped trees. Roots comprised approximately 22%, and the aboveground portion about 78% of total dry weight. Roots nearly always contained higher concentrations of carbohydrates and nitrogen reserves. However, the aboveground sections, comprising a higher proportion of total dry weight, contained more than two thirds of total carbohydrates and nitrogen reserves. Topping of nursery whip trees at 60 cm aboveground thus would result in a loss of 33 to 37% dry matter, 29 to 33% carbohydrates and 37 to 46% nitrogen. Therefore, planting large, untopped nursery trees enhance initial tree growth in the orchard. The use of well-branched nursery trees for orchard planting can shorten the time to commercial fruit production. Citrus nursery trees do not develop lateral shoots adequately in the nursery or in the field and therefore necessitate various branch induction techniques. Two trials on newly-planted (one or five months after planting) trees were conducted to evaluate various branch induction techniques, viz., girdling, Promalin® (G~+7 + BA) (at 1000 or 2000 mg/I) and/or leaf removal and notching either to individual buds or the whole trees. The first trial, on l-month-old trees did not yield significant results. In the second trial, notching and girdling significantly increased the number and total length of lateral branches, but notching was the most effective technique. As the first trial, on the very young trees, yielded no significant results, it seems that trees have to be well established before they will respond. In young, non-oearing trees a lot of energy is invested in the flowering process, which results in an inhibition of vegetative growth. Gibberellic acid (GA3) and heavy mineral oil (Bac-oil) treatments, either individually or in combination, applied during early winter were evaluated as a means to reduce flowering levels in young nonbearing citrus trees. GA3 and mineral oil either separately or in combination were sprayed from April to July to the whole tree. GA3 and mineral oil either individually or in combination applied late in May to late June markedly reduced flowering. GA3 application in mid April had a minimal effect on flowering levels. Peak responses to GA3 coincided with a significant reduction in bud sprouting. Although optimum application time proved to be around May to July, this time is likely to vary from year to year depending on the influence of the prevailing temperature and other climatic conditions. The winter application of GA3, specifically, and possibly in combination with mineral oil to inhibit flowering and early vegetative growth may be utilised commercially. However, response may vary dramatically from season to season. Effect of time of application and concentration of 2,4-dichlorophenoxypropionic acid (2,4-DP) and l-naphthaleneacetic acid (NAA) as potential fruit thinning agents to reduce fruit set soon after flowering and enhance vegetative growth were evaluated over a two year period. 2,4-DP at 150 and 300 mg/I and NAA at 200 and 400 mg/! were sprayed on 2- and 4-year-old 'Mihowase' Satsuma, as well as on 2-year-old 'Marisol', 'Nules' and 'Oroval' Clementine trees at two times (late October and early November). The higher concentration of 2,4-DP and NAA generally did not result in increased fruit abscission in the first year. However, in the case of 2,4-DP the higher concentration resulted in stronger thinning in the second year. 2,4-DP and NAA can be used as potential fruit thinning agents to reduce fruit set on young non-bearing trees. / AFRIKAANSE OPSOMMING: Verbetering van vegetatiewe groeie by jong sitrus-aanplantings Die vestiging van sitrus behels hoë insetkoste en die gelykbreekpunt word gewoonlik eers na ses jaar bereik. Vroë opbrengste is dus noodsaaklik vir ekonomiese oorlewing. In koel en koue produksie-areas, met baie wind, is die aanvanklike boomgroei onvoldoende. Studies is uitgevoer om die effek van blaarbespuitings van Progibb'" (GA3), Promalin® (G~+7 + BA), Kelpak (seewier-ekstrak wat ouksien en sitokiniene bevat) en grondtoedienings van Temik® (aldicarb), as metodes om vegetatiewe groei te verbeter te evalueer. GA3 en/of aldicarb het boornhoogte betekenisvol laat toeneem, sonder om stamdeursnit te bevoordeel op 'Eureka' suurlemoen, maar nie op 'Lisbon' suurlemoen nie. G~+7 + BA of Kelpak'" behandelings het geen effek op boomgroei of varsmassa-verspreiding gehad nie. Groeistimulasie deur GA3 en/of Aldicarb kan lei tot vinniger vul van spasie, en hoër en vroeër oeste, maar verdere studies is nodig om die resultate te bevestig. Onvoldoende koolhidraat- en stikstofreserwes word dikwels gekoppel aan swak vestigingsprestasie van kwekerybome. Die effek van boomgrootte by planttyd en verskillende tophoogtes op vroeë groei in die veld is geëvalueer; die fisiese en chemiese profiel van lang ongetopte kwekerybome is ook gekwantifiseer. Betekenisvolle korrelasies is gevind tussen die aanvanklike stamdeursnit en en finale stamdeursnit en tussen aanvanklike boomhoogte en finale boomhoogte aan die einde van die eerste groeiseisoen. Stamdeursnit-toenarne is betekenisvol verminder in getopte bome relatief tot ongetopte bome. Wortels het uit ongeveer 22% en die bogrondse porsie ongeveer 78% van die totale droë massa bestaan. Wortels het bykans altyd hoër konsentrasies koolhidrate- en stikstofreserwes bevat. Die bogrondse gedeeltes, wat ook 'n hoër proporsie van die totale droë massa bevat, het meer as twee derdes van die totale koolhidraat en stikstofreserwes. Die top van kwekerybome op 60 cm bo die grond sal lei tot 'n verlies van 33 tot 37% droë massa, 29 tot 33% koolhidrate en 37 tot 46% stikstof. Dus, die plant van groot, ongetopte kwekerybome sal die aanvanklike boomgroei in die boord verbeter. Die gebruik van goedvertakte kwekerybome by planttyd kan die tyd tot komrnersieële vrugteproduksie verkort. Sitrus-kwekerybome gee nie voldoende laterale vertakking in die kwekery of in die boord nie. Twee studies op pas-aangeplante bome (een en vyf maande na plant) is uitgevoer om verskillende tegnieke om laterale lootgroei te stimuleer te evalueer, nl. Promalin® (G~+7 + BA) (teen 1000 of 2000 mg/I) en/of blaarverwydering, en die maak van kerfies op individuele knoppe of op bome as geheel. In die eerste studie, op die een-maand-oue bome, is geen betekenisvolle resultate verkry nie. In die tweede studie het kerfies en ringelering die hoeveelheid en lengte van laterale takke betekenisvol vermeerder, maar kerfies was meer effektief. Die bome moet egter blykbaar goed gevestig wees voor dit reageer. In jong, nie-draende bome word baie energie gebruik in die blomproses en dit lei tot die inhibisie van vegetatiewe groei. Gibberelliensuur (GA3 ) en 'n swaar mineralolie (Bac-oil) wat individueel of in kombinasie toegedien is tydens die vroeë winter is geëvalueer as 'n tegniek om blomvlakke in jong nie-draende sitrusbome te verminder. GA3 en minerale olie individueel of in kombinasie, is gespuit vanaf April tot Julie op die bome as geheel. GA3 en minerale olie toegedien individueel of in kombinasie laat in Mei tot Junie het blomvlakke verminder. GA3 toegedien in middel April het 'n minimale effek gehad. Die beste reaksie op GA3 het saamgeval met 'n betekenisvolle vermindering in die bot van knoppe. Alhoewel die optimum tyd van toediening rondom Mei tot Julie is, mag hierdie tyd wissel van jaar tot jaar afhangende van die effek van heersende temperature en ander klimaatstoestande. Die wintertoediening van GA3, spesifiek en moontlik in kombinase met minerale olie om blomvlakke en vroeë vegetatiewe groei te verminder kan kommersieel gebruik word. Die reaksie op hierdie behandelings mag egter drasties wissel van seisoen tot seisoen. Die effek van die tyd van toediening en konsentrasie van 2,4- dichlorofenoksipropioonsuur (2,4-DP) en 1-naftaleenasynsuur (NAA) as potensiële vruguitdunagente om vrugset kort na blom totaal te verminder en om vegetatiewe groei te verbeter, is geëvalueer oor 'n twee-jaarperiode. 2,4-DP teen 150 en 300 mg/l en NAA teen 200 en 400 mg/l is gespuit op 2- en 4-jaaroue 'Mihowase' Satsuma, en ook op 2-jaaroue 'Marisoi', 'Nules' en 'Oroval' Clementines op twee tye (laat Oktober en vroeg November). Die hoër konsentrasies van 2,4-DP en NAA het oor die algemeen nie gelei tot 'n verhoging in vrugafsnoering in die eeste jaar nie. Met 2,4- DP het die hoër konsentrasie gelei tot strawwer uitdunning in die tweede jaar. 2,4-DP en NAA kan as potensiële vruguitdunagente op jong, nie-draende bome gebruik word.

Thesis (MScAgric)--University of Stellenbosch, 2000. / ENGLISH ABSTRACT: The understanding of pear branching and bearing habits is required to optimise management practices. The objective of this study was to quantify the branching and bearing habits of pear cultivars under South African conditions of sub-optimal winter chilling. Two-year-old branches of Pyrus communis L. were classified into groups according to the proleptic (from dormant buds) branching habit. In Winter 1998 upright and flat, two-year-old branches were randomly sampled from trees of seven pear cultivars, i.e., Forelle (on Quince A and BPI rootstocks), Abaté Fetel, Flamingo, Packham's Triumph, Golden Russet Bose, Rosemarie and Beurre D'Anjou (all on BPI rootstock). Laterals were classified according to length « lem, 1-5cm, 5-20cm and >20 cm) and position (distal to proximal quadrants on the two-year-old axis). The number of shoots per cm of quadrant length, per length class for each cultivar was subjected to a cluster analysis, then a canonical and a stepwise discriminant analysis. The cultivars were grouped into four groups from Group 1 (Flamingo) which resembles a spurred growth habit with strong apical control, to Group 4 (Packham's Triumph and Golden Russet Bose) which resembles a spreading growth habit and weak apical control. The bearing habits of the same pear cultivars were quantified. In Winter 1998 ten unpruned branches were tagged on trees of each of the seven cultivars. The description started with the development of the main fruiting branch, forming several leaves in the first year of growth (designated year Y), with meristems developing in the leafaxils. In the following season (year Y+1), these axillary meristems have five alternatives: to remain as a latent bud (L), to develop as a vegetative bud (V), to become a flower bud not setting fruit (F), to become a flower bud producing a fruit (P) or to abort and leave a scar (S). Each year the development of these axillary buds were observed and classified anew, giving rise to a sequence. Between 50% ('Forelle/QA') and 75% ('Rosemarie') of buds remained in the growing phase (comprising of V, F or P buds) during the years of monitoring. It was shown that the predominant bud state in the growing phase was V. Although flower formation was low for all cultivars throughout the trial period, 'Packham's Triumph' and 'Rosemarie' displayed a relatively high proportion ofF and P buds in year Y+1. The latter two cultivars also displayed the bourse-over-bourse bearing phenomenon (PP), producing flowers and fruit terminally on bourse shoots. Artificial extinction of reproductive buds was applied in Winter 1999 to individual branches of the pear cultivar Doyenne du Cornice. This pear variety bears on spurs and is prone to biennial bearing. The objective was to reduce the number of growing buds, thereby increasing the allocation of assimilates to remaining reproductive structures. Three thinning intensities, i.e. 0%, 33% and 66% removal of reproductive buds and two methods, i.e. removal of proximal reproductive buds and removal of reproductive buds situated distally on spurs (by means of cutting back) were utilised. Autonomy of fruiting structures was not enhanced, but results warrant the repetition of this trial using whole trees as experimental units. / AFRIKAANSE OPSOMMING: Dit is belangrik om die vertakkings- en drawyses van pere te verstaan, aangesien bestuurspraktyke hierdeur bepaal word. Die doel van hierdie studie was om die vertakkings- en drawyses van pere onder Suid-Afrikaanse toestande van sub-optimale winterkoue te kwantifiseer. Tweejaar-oue Pyrus communis L. takke is volgens hul proleptiese (vanuit dormante knoppe) vertakkingswyse in groepe geklassifiseer. Regop en plat takke van die peerkultivars Forelle (op Kweper A and BPI onderstamme), Abaté Fetel, Flamingo, Packham's Triumph, Golden Russet Bose, Rosemarie en Beurre D'Anjou (almalop BPI onderstam) is in die winter van 1998 gemonster. Jaarlote is volgens lengte « l cm, 1-5cm, 5-20cm and >20 cm) en posisie (distale tot proksimale kwadrante op die tweejaar-oue draer) geklassifiseer. Die getal lote per cm, per lengte klas per kwadrant vir elke kultivar is toe onderwerp aan 'n groep analise en daarna aan 'n kanoniese en 'n stapsgewyse diskriminant analise. Kultivars is in vier groepe gegroepeer vanaf Groep 1 (Flamingo) wat 'n spooragtige vertakkingswyse en sterk apikale kontrole toon, tot Groep 4 (Packham's Triumph en Golden Russet Bose) met 'n spreidende vertakkingswyse en swak apikale kontrole. Bogenoemde peerkultivars is ook gebruik vir die kwantifisering van drawyses. In die winter van 1998 is tien ongesnoeide takke per boom gemerk. Die beskrywing van die drawyses het begin met die ontwikkeling van die hoof tak van die dra-eenheid. In die eerste jaar van groei (genoem jaar Y) ontwikkel meristeme in die blaar oksels. In die daaropvolgende seisoen (jaar Y+1) is daar vyf ontwikkelings moontlikhede vir die oksellêre knoppe: om latent te bly (L), om vegetatief te ontwikkel (V), om te blom sonder die set van 'n vrug (F), om te blom en 'n vrug te set (P) of om te aborteer en 'n letsel te los (S). Die ontwikkeling van hierdie oksellêre knoppe is elke jaar gemonitor en opnuut geklassifiseer om sodoende 'n reeks te vorm. Gedurende die moniteringstydperk het tussen 50% ('ForelleIKweper A') en 75% ('Rosemarie') van die knoppe in die groeifase (G) (bevattende V, F ofP knoppe) gebly. Die proporsie knop tipes per jaar vir die onderskeie kultivars het getoon dat die oorheersende knop tipe in die G-fase V-knoppe is. Alhoewel blom inisiasie laag was gedurende die hele proeftydperk, het 'Packham's Triumph' en 'Rosemarie' relatiefhoë verhoudings F en P knoppe in jaar Y+1 getoon, wat gepaard gaan met dié kultivars se vermoë om vrugte op een jaar-oue lote te dra. Die beurs-oor-beurs verskynsel (PP) het ook by dié twee kultivars voorgekom. Reproduktiewe knoppe van die peerkultivar Doyenne du Comice is in die winter van 1999 verwyder (kunsmatige abortering) vanaf indivuduele takke. Hierdie peerkultivar dra op spore en is geneig tot alternatiewe drag. Die doel was om die hoeveelheid groeiposisies te verminder en sodoende die allokasie van reserwe assimilate na oorblywende reproduktiewe strukture te verhoog. Drie uitdun intensiteite (0%,33% en 66% van reproduktiewe knoppe verwyder) en twee metodes (verwydering van proksimale spoorknoppe en verwydering van distale spoorknoppe) is gebruik. Outonomiteit van reproduktiewe strukture was nie verhoog nie, maar resultate regverdig die herhaling van dié eksperiment. Daar word aanbeveel dat volledige bome dan as eksperimentele eenhede gebruik word.

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.

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.

Thesis (MSc)--Stellenbosch University, 2004. / Full text to be digitised and attached to bibliographic record. / ENGLISH ABSTRACT: The control of excessive vegetative growth is important in deciduous fruit orchards. Currently the plant growth regulator prohexadione-calcium (p-Ca) is used to control apple shoot growth in the Untited States of America and some European countries. The effect of P-Ca on the shoot and fruit growth of apples (Malus domestica B.), pears (Pyrus cummunis L.), plums (Prunus sa/icina L.) and nectarines (Prunus persica L.) was evaluated. Inhibition of shoot growth can effect fruit growth. Therefore I did a literature review on the fruit growth of pome- and stone fruit. Split pit, a physiological disorder associated with an increased fruit growth rate in stone fruit, was also investigated. During the course of the 2001 / 2002 season two trials were conducted in the Villiersdorp area of the Western Cape on 'Golden Delicious' and 'Granny Smith' apple trees. Single and multiple applications of P-Ca at different rates, with and without the surfactant Dash®, were applied. One of these trials was continued during the 2002 / 2003 season. In the 2001 / 2002 season, P-Ca reduced shoot growth in both trials on 'Golden Delicious'. The shoot growth of 'Granny Smith' was reduced in both trials where PCa was applied three or four times. There was an improvement in the fruit size of 'Golden Delicious' in both trials, but there was no improvement in the fruit size of 'Granny Smith'. In the 2002 / 2003 season, the single P-Ca application did not reduce shoot growth. Unfortunately 'Golden Delicious' was harvested before any data were obtained. Once again P-Ca had no effect on the fruit size of 'Granny Smith'. Dash® did not improve the effect ofP-Ca. In the 2002 / 2003 season we replicated one trial on five different pear cultivars in the Wolsely area of the Western Cape. Single and multiple applications of P-Ca at different rates were compared to a girdling treatment (2 weeks after full bloom). 'Early Bon Chretien', 'Rosemarie', 'Flamingo', 'Forelle' and 'Packham's Triumph' pear trees were used and Dash®was added to all 0f the treatments. P-Ca reduced shoot growth in all of the pear cultivars. Girdling reduced shoot growth only in 'Forelle'. P-Ca increased fruit set of 'Early Bon Chretien', 'Rosemarie' and 'Forelle', however, this was associated with a reduced fruit size of 'Early Bon Chretien' and 'Rosemarie'. Girdling did not increase fruit set, but increased fruit size of 'Flamingo' and 'Early Bon Chretien'. P-Ca reduced return bloom of 'Packham's Triumph' and 'Forelle', whereas girdling increased return bloom in all the cultivars except 'Packham's Triumph'. In the 2002 / 2003 season, trials were also conducted on 'Pioneer' and 'Songold' plums and 'May Glo' nectarine in the Wemmershoek and Stellenbosch area of the Western Cape. Single applications at different rates of P-Ca were applied. Dash® was added to all of the treatments. The higher rates of P-Ca reduced the shoot growth of 'Pioneer'. P-Ca only reduced shoot growth of 'Songold' initially and but did not reduce shoot growth of 'May Glo'. P-Ca had no influence on fruit size of 'Pioneer', 'Songold' or 'May Glo'. P-Ca did not aggravate the occurrence of split pit. In conclusion, P-Ca reduced shoot growth in apples and pears when applied at the appropriate rates. Although P-Ca reduced shoot growth of 'Pioneer' plum, more research needs to be done on stone fruit to optimise timing and rate of P-Ca applications. / AFRIKAANSE OPSOMMING: Die beheer van oormatige lootgroei is van kardinale belang in vrugtebome. Tans word die plantgroeireguleerder proheksadioon-kalsium (P-Ca) gebruik om die lootgroei van appels te beheer in die Verenigde State van Amerika en sekere lande in Europa. Die effek van P-Ca op lootgroei en vruggrootte is in proewe op appels (Malus domestica B.), pere (Pyrus cummunis L.), pruime (Prunus salicina L.) en nekatriens (Prunus persica L.) geëvalueer. Aangesien lootgroei inhibisie moontlik vruggroei kan vesnel, is 'n literatuurstudie oor die vruggroei van kern-en steenvrugte gedoen. Die ontwikkelling van gesplete pit by steenvrugte ('n fisiologiese defek geassosieer met versnelde vruggroei) is ook ondersoek. Gedurende die 2001 / 2002 seisoen is P-Ca in twee afsonderlike proewe in die Villiersdorp area van die Wes Kaap geëvalueer. Enkel en veelvuldige toedienings van verskeie konsentrasies P-Ca, met en sonder die benatter Dash", is op 'Golden Delicious' en 'Granny Smith' bome toegedien. Een proef is herhaal gedurende die 2002 / 2003 seisoen. In die 2001 /2002 seisoen het die P-Ca behandelings in beide proewe die lootgroei van 'Golden Delicious' verminder. Die lootgroei van 'Granny Smith' is in beide proewe verminder waar P-Ca 3 of 4 keer toegedien is. Die vruggrootte van 'Golden Delicious', maar nie 'Granny Smith' nie, is in beide proewe deur die P-Ca verbeter. In die 2002 / 2003 seisoen kon die enkeltoedienings van P-Ca nie die lootgroei verminder van 'Golden Delicious' of 'Granny Smith' nie. 'Golden Delicious' is geoes voor enige inligting oor die vruggrootte ingesamel kon word. Weereens het PCa geen invloed op die vruggrootte van 'Granny Smith' gehad nie. Dash® het nie die effek van P-Ca verbeter nie.In die 2002 / 2003 seisoen is proewe met P-Ca gedoen op 5 verskillende peer kultivars in die Wolsely area van die Wes Kaap. P-Ca is teen verskillende konsentrasies, met enkel en veelvuldige bespuitings toegedien en vergelyk met 'n ringelerings behandeling (2 weke na volblom). 'Early Bon Chretien', 'Rosemarie', 'Flamingo', 'Forelle' en 'Packham's Triumph' bome is gebruik en die benatter Dash® is by al die behandelings gevoeg P-Ca toedienings het lootgroei verminder in 'Early Bon Chretien', 'Rosemarie', 'Flamingo', 'Forelle' en 'Packham's Triumph'. Ringelering kon slegs die lootgroei van 'Forelle' verminder. P-Ca het die vrugset van 'Early Bon Chretien', 'Rosemarie'en 'Forelle' verhoog. Die toename in vrugset het gelei tot 'n afname in die vruggrootte van 'Early Bon Chretien' en 'Rosemarie'. Ringelering het die vruggrootte van 'Flamingo' en 'Early Bon Chretien' verbeter. P-Ca het 'n afname in die hoeveelheid reproduktiewe knoppe in die volgende seisoen, van 'Packham's Triumph' en 'Forelle' veroorsaak. Ringelering het 'n toename in die hoeveelheid vegetatiewe knoppe in die volgende seisoen gehad vir al die kultivars, behalwe 'Packham's Triumph'. Geduerende dieselfde seisoen is daar ook proewe gedoen op 'Pioneer' en 'Songold' pruime en 'May Glo' nektarienbome in onderskeidelik die Wemmershoek en Stellenbosch areas van die Wes Kaap. Bome is met enkel toedienings van verskillende konsentrasies P-Ca behandel en die benatter Dash® is by al die behandelings bygevoeg. Die hoër dosisse P-Ca het die lootgroei van 'Pioneer' verminder. P-Ca kon slegs die aanvanklike lootgroei op 'Songold' verminder en kon nie lootgroei van 'May Glo' beperk nie. P-Ca het geen invloed op die vruggrootte van 'Pioneer', 'Songold' of 'May Glo' gehad nie. P-Ca het nie die voorkoms van gesplete-pit vererger nie. Om saam te vat kan gesê word dat P-Ca lootgroei op appels en pere goed beperk teen die regte konsentrasies. Alhoewel P-Ca lootgroei suksesvol beheer het op 'Pioneer', moet daar meer werk gedoen word op steenvrugte.

Thesis (MScAgric)--University of Stellenbosch, 2002. / ENGLISH ABSTRACT: Excessive shoot growth of fruit trees may have various negative effects. These include a decrease in fruit set, fruit size, red colour and in return bloom. Cultural practices that are currently in use, such as the use of dwarfing rootstocks, girdling and pruning do not always give sufficient shoot growth control. The use of plant growth retardants, in combination with these cultural practices, offer additional possibilities. Trials were conducted to evaluate the effect of the new plant growth retardant prohexadione-calcium (P-Ca) on apple, pear and plum shoot growth. In addition, the effect of P-Ca on fruit set, fruit size, yield, fruit quality and return bloom were also evaluated. During the 1999/2000 season P-Ca was applied to full bearing twelfth leaf 'Golden Delicious' trees on M793 rootstock, twenty-sixth leaf 'Granny Smith' trees on seedling rootstock, ninth leaf 'Royal Gala' trees on M793 rootstock, seventh leaf 'Rosemarie' trees on seedling rootstock and eighth leaf 'Songold' trees on 'Marianna' rootstock in the Villiersdorp area in the Western Cape (33°59' S, 19°17' E; ca. 365 m a.s.l.; Mediterranean climate). P-Ca was applied at concentrations of 3 x 50, 4 x 50 and 3 x 67 mg.l' to the apple trees. The first application was at petal drop with no surfactant added with any of the treatments. P-Ca was applied at concentrations of2 x 62.5,125,250 and 2 x 125 mg.l" to the pear and plum trees. The first application was at petal drop and pit-hardening for the pear and plum trees respectively. Agral-90 was used as surfactant only with the first spray applied to the pear trees. During the 2000/2001 season the same 'Golden Delicious' and 'Royal Gala' trees were used as in the 1999/2000 season. Thirteenth leaf 'Granny Smith' trees on M793 rootstock in the Villiersdorp area were used. Sixth leaf 'Rosemarie' trees on BP3 rootstock, fifth leaf 'Golden Russet Bose' trees on BP3 rootstock, seventh leaf 'Forelle' trees on BP3 rootstock and 16th leaf 'Packham's Triumph' trees on seedling rootstock in the Wolseley area in the Western Cape were used. P-Ca was again applied at concentrations of 3 x 50,4 x 50 and 3 x 67 mg.l' to the apple trees. The first application in the 'Golden Delicious' and 'Granny Smith' trees was at full bloom and at petal drop in the 'Royal Gala' trees. The last application was at 45 days before harvest. No surfactant was added with any of the sprays. P-Ca was applied at concentrations of 50, 75, 150, 2 x 50,2 x 75 and 3 x 50 mg.l" to the pear trees with the first spray when 4 to 5 leaves were unfolded and the last one 45 days before harvest. Agral-90 was added as surfactant with all the pear sprays. The pear trial also included a girdling treatment. P-Ca effectively inhibited shoot growth of all three apple cultivars in both seasons. Regrowth occurred in both seasons in all the cultivars, therefore it is not clear which treatment(s) is optimal for reducing shoot growth. P-Ca increased fruit size in 'Royal Gala' in the 1999/2000 season and decreased yield expressed as kg fruit harvested 1 em trunk circumference in 'Golden Delicious' in the 2000/2001 season. This reduction in yield can be attributed to the low number of flower clusters in the spring of 2000 following P-Ca treatment in 1999. P-Ca decreased the number of developed seeds in 'Royal Gala' in both seasons and increased the number of seeds with aborted embrios in the 200012001 season. After four weeks of cold storage (± 5°C) and one week at room temperature (± 20°C), P-Ca had no effect on the occurrence of bitter pit in 'Golden Delicious'. The 'Granny Smith' trees were harvested before fruit analysis could be done in the 2000/2001 season. In pear, girdling was not effective in inhibiting shoot growth in any of the cultivars, but P-Ca proved to be an effective inhibitor of shoot growth of 'Rosemarie' and 'Golden Russet Bose', and to a lesser degree 'Packham's Triumph', but not 'Forelle'. Despite the re-growth that occurred ca. four weeks after harvest in 'Rosemarie' in the 2000/20001 season, it appears that a single high rate (250 and 150 mg.l' for the 1999/2000 and 2000/2001 seasons respectively) P-Ca application is more effective than a single low rate or multiple low rates in inhibiting shoot growth. In the 200012001 season P-Ca increased fruit set in 'Rosemarie' and 'Forelle'. In both seasons P-Ca reduced 'Rosemarie' fruit size while girdling increased 'Forelle' and 'Packham's Triumph' fruit size in 2000/2001. P-Ca increased 'Rosemarie' fruit firmness and 'Forelle' fruit colour in the 2000/2001 season and decreased the percentage of 'Packham's Triumph' fruit with cork spot. Girdling increased 'Packham's Triumph' fruit colour and TSS concentration while decreasing fruit firmness in 2000/2001. P-Ca reduced return bloom in 'Forelle' and 'Packham's Triumph' in 2001, while girdling increased 'Golden Russet Bose' and 'Forelle' return bloom. Due to poor flowering and thus low fruit number in 'Golden Russet Bose', fruit set in 2000 could not be determined and no fruit analysis could be done. In 'Songold' all four P-Ca treatments inhibited shoot growth, but the 2 x 125 mg.l' treatment were the most effective, both in terms of total shoot growth and in reduction of the re-growth that occurred ca. two weeks before the first commercial harvest date. P-Ca increased fruit firmness and decreased TSS concentration both at harvest and after four weeks of cold storage at dual temperature (10 days at -O.soC + 18 days at 7.S°C). In conclusion P-Ca is an effective inhibitor of shoot growth of the apples 'Golden Delicious', 'Granny Smith' and 'Royal Gala', the pears 'Rosemarie', 'Golden Russet Bose' and 'Packham's Triumph' and the plum 'Songold', but more work is needed to control re-growth. / AFRIKAANSE OPSOMMING: Oormatige lootgroei van vrugtebome kan verskeie negatiewe effekte tot gevolg he, insluitende 'n afname in vrugset, vruggrootte, rooi kleur en 'n verlaging in die daaropvolgende jaar se blom. Boordpraktyke soos die gebruik van dwergende onderstamme, ringelering en snoei, beheer nie altyd lootgroei doeltreffend nie. Die gebruik van groeireguleerders, in kombinasie met hierdie boordpraktyke, bied bykomende geleenthede. Proewe is uitgevoer om die effek van die nuwe groeireguleerder proheksadioon-kalsium (PCa) op appel, peer en pruim lootgroei te evalueer. Die effek van P-Ca op vrugset, vruggrootte, opbrengs, vrugkwalitiet en die daaropvolgende jaar se blom is ook geevalueer. Gedurende die 1999/2000 seisoen is P-Ca toegedien aan voldraende twaalfde blad 'Golden Delicious' bome op M793 onderstamme, ses-en-twintigste blad 'Granny Smith' bome op saailing onderstamme, negende blad 'Royal Gala' bome op M793 onderstamme, sewende blad 'Rosemarie' bome op saailing onderstamme en agste blad 'Songold' bome op 'Marianna' onderstamme in die Villiersdorp area in die Wes Kaap (33°25' S, 19°12' 0; ligging ong. 270 m.; Meditereense klimaat). P-Ca is aan die appelbome toegedien teen konsentrasies van 3 x 50, 4 x 50 en 3 x 67 mg.l' met die eerste toediening by blomblaarval. Geen benatter is by enige van die toedienings gevoeg nie. P-Ca is aan die peer- en pruimbome toegedien teen konsentrasies van 2 x 62.5, 125, 250 en 2 x 125 mg.l' met die eerste toediening by blomblaarval en pitverharding vir onderskeidelik die peer- en pruimbome. Agral-90 is as benatter gebruik slegs saam met die eerste toediening op die peerbome. Tydens die 2000/2001 seisoen is dieselfde 'Golden Delicious' en 'Royal Gala' bome gebruik as in die 1999/2000 seisoen. Derde blad 'Granny Smith' bome op M793 onderstamme in die Villiersdorp area is gebruik. Sesde blad 'Rosemarie' bome op BP3 onderstamme, vyfde blad 'Golden Russet Bose' bome op BPI onderstamme, sewende blad 'Forelle' bome op BP3 onderstamme en sestiende blad 'Packham's Triumph' bome op saailing onderstamme in die Wolseley area in die Wes Kaap is gebruik. P-Ca is weereens aan die appelbome toegedien teen konsentrasies van 3 x 50, 4 x 50 en 3 x 67 mg.l". Die eerste toediening aan die 'Golden Delicious' en 'Granny Smith' bome was by volblom en die eerste toediening aan die 'Royal Gala' bome by blomblaarval. Die laaste toediening is 45 dae voor oes gedoen. Geen benatter is met enige van die toedienings bygevoeg nie. P-Ca is aan die peerbome toegedien teen konsentrasies van 50, 75, 150,2 x 50, 2 x 75 en 3 x 50 mg.l' met die eerste toediening toe vier tot vyf blare ontvou was en die laaste een 45 dae voor oes. Agral-90 is as benatter gebruik met al die peer bespuitings. By die peer proef is ook 'n ringeleer behandeling ingesluit. In beide seisoene het P-Ca die lootgroei van al drie appel kultivars verminder. Hergroei het in beide seisoene in al drie kultivars plaasgevind. Dit is dus onduidelik watter behandeling(s) optimaal is vir lootgroei beheer. In die 1999/2000 seisoen het P-Ca 'Royal Gala' vruggrootte verbeter. In die 2000/2001 seisoen is 'Golden Delicious' opbrengs, uitgedruk as kg vrugte geoes / cm stamomtrek, verlaag. Hierdie verlaging in opbrengs kan toegeskryf word aan die lae blom aantal in die lente van 2000 wat gevolg het op die P-Ca behandeling in 1999. In beide seisoene het P-Ca die aantal ontwikkelde sade in 'Royal Gala' verminder terwyl die aantal sade met geaborteerde embrios verhoog is in die 2000/2001 seisoen. Na vier weke koelopberging (± 5°C) en een week by kamertemperatuur (± 20°C) het P-Ca geen effek op die voorkoms van bitterpit in 'Golden Delicious' gehad nie. Die 'Granny Smith' bome is in die 2000/2001 seisoen geoes voordat enige data ingesamel kon word. Ringelering het geen effek op lootgroei gehad in enige van die peer kultivars nie, maar P-Ca het lootgroei effektief beheer in 'Rosemarie' en 'Golden Russet Bose' en tot 'n mindere mate 'Packham's Triumph', maar het geen effek op 'Forelle' lootgroei gehad nie. Ten spyte van die hergroei wat voorgekom het in die 'Rosemarie' bome ongeveer vier weke na oes in die 2000/2001 seisoen, wil dit voorkom asof P-Ca toegedien teen 'n enkele hoe konsentrasie (250 en 150 mg.l' vir die 1999/2000 en 2000/2001 seisoene onderskeidelik) meer effektief was om lootgroei te beheer as 'n enkele lae konsentrasie of veelvuldige lae konsentrasies. P-Ca het vrugset in 'Rosemarie' en 'Forelle' verhoog in die 2000/2001 seisoen. In beide seisoene het P-Ca 'Rosemarie' vruggrootte verlaag terwyl ringelering 'Forelle' en 'Packham's Triumph' vruggrootte verbeter het in die 2000/2001 seisoen. P-Ca het 'Rosemarie' vrugfermheid en 'Forelle' vrugkleur verhoog in die 2000/2001 seisoen en die aantal 'Packham's Triumph' vrugte met kurkvlek verlaag. Ringelering het 'Packham's Triumph' vrugkleur en TSSkonsentrasie verhoog, maar vrugfermheid verlaag in die 2000/2001 seisoen. P-Ca het die aantal blomme in 'Forelle' en 'Packham's Triumph' verlaag in 2001, terwyl ringelering blom in 'Golden Russet Bosc' en 'Forelle' verhoog het. As gevolg van 'n lae blom- en dus vruggetal in 'Golden Russet Bosc' kon vrugset In 2000 nie bepaal word nie en geen vrugontledings kon gedoen word nie. Al vier P-Ca behandelings het lootgroei in 'Songold' beheer, maar die 2 x 12S mg.l' toediening was die effektiefste, beide in terme van totale lootgroei en in beheer van die hergroei wat ongeveer twee weke voor die eerste kommersieele oesdatum plaasgevind het. PCa het vrugfermheid verhoog en die TSS-konsentrasie verlaag, beide tydens oes en na vier weke koelopberging by dubbel temperatuur (10 dae by -O.soC + 18 dae by 7.S0C). Om saam te vat kan gese word dat P-Ca 'n effektiewe inhibeerder van lootgroei van die appels 'Golden Delicious', 'Granny Smith' en 'Royal Gala', die pere 'Rosemarie', 'Golden Russet Bosc' en 'Packham's Triumph' en die pruim 'Songold' is. Meer werk is egter nodig om die hergroei te beheer.