Thesis (MScAgric)--Stellenbosch University, 2002. / ENGLISH ABSTRACT: Fruit size can be a problem in 'Clementine' mandarin and 'Valencia' orange in the Western Cape region of South Africa. Small fruit is not only unacceptable to the consumer but is also more difficult and expensive to harvest. Means of alleviating this problem is to manage the crop load. Hand thinning trials were conducted to evaluate the effect of timing and severity thereof in enhancing fruit size. The benefits of enhancing large fruit size was obtained by a heavy-thinning (60% fruitlet removed) treatment, but the actual benefits were offset by a reduction of total yield. Yield was reduced up to 30% when heavy thinning treatments were applied. No effect on early or late treatments were obtained since the trial was conducted rather late (4 to 6 weeks after the physiological fruit drop period) to obtain the desirable results. However, better packouts are expected with thinning treatments since blemished fruit are also removed. The effect of multiple 2,4-dichlorophenoxy propionic acid (dichlorprop) sprays were also evaluated on 'Nules Clemetine' mandarin. Comparing multiple sprays with a single spray, it was observed that more than one spray was no better in improving fruit size. The use of multiple dichlorprop sprays resulted in no additional yield reduction, while internal fruit quality was also not affected. The best results were obtained with dichlorprop at 50 mg. L-1 • The use of dichlorprop with different surfactants was evaluated in both 'Clementine' mandarin and 'Valencia' orange. The fruit size was increased from 50 mg. L-1 up to 100 mg. L-1 • Yield was usually not affected but, where reductions were experienced, yield of large fruit (>55 mm) was not significantly affected. In the 'Valencia' orange trials, during the first year, dichlorprop was sprayed relatively late (fruit diameter: 19 mm). No fruit size, yield and internal fruit quality effects were observed. The following year, when early and late sprays (fruit diameter at spray time = 8 and 12 mm, respectively) were evaluated, it was observed that late sprays had no effect on fruit size, whereas fruit size (48 fruit per carton) was significantly increased by early sprays. This implies that the dichlorprop effect on fruit size is during the early stages of fruit development, just after or during the late stage of the physiological fruit drop period. Yield was drastically reduced by up to 35%, which affected the actual kilograms of large fruit adversely in some treatments. Juice percentage was inconsistent and tended to be reduced by dichlorprop application. Dichlorprop tended to increase TSS slightly in year one and significantly so in year two, but did not affect the TSS:TA ratio. The use of Orchex mineral oils as surfactant at 150 mL. 100 L-1 was effective and seemingly allowed lower rates of dichlorprop to be used. Therefore, surfactants seemed to show potential in enhancing dichlorprop efficiency to reduce the application cost. The dichlorprop-sprayed fruit was used to measure carotenoid content of the rind during the later stage of fruit development. Observations indicate that dichlorprop-sprayed fruit at 50 mg. L-1 obtained better carotenoid content in both 'Clementines' mandarin and 'Valencia' orange. Also, fruit exposed to light had higher carotenoid levels as compared to fruit shaded with brown paper bags. However, dichlorprop-sprayed fruit at 100 mg. L-1 , even though exposed to light did not show significant differences with unsprayed in both shaded and exposed conditions. Therefore, no consistent effect of dichlorprop was established on total carotenoid content of the rind. / AFRIKAANSE OPSOMMING: Vruggrootte van 'Clementine' mandaryn en 'Valencia' lemoene kan 'n probleem wees in die Wes Kaap area van Suid Afrika. Klein vrugte is nie net onaanvaarbaar vir die verbruiker nie, maar is ook moeilik om te oes. Vrugdrag manipulasie is een manier om hierdie probleem te beheer. Hand uitdunningsproewe is uitgevoer om die effek van tyd en graad van uitdunning op vruggrootte te bepaal. Strawwe vruguitdunning (60% van vruggies verwyder) het groter vrugte tot gevolg gehad maar het gelei tot 'n verlaagde opbrengs. Opbrengs is tot soveel as 30% verlaag met die strawwe vruguitdunning. Vroeë en laat behandelings het egter geen effek gehad nie, aangesien die proewe te laat uitgevoer is (4 tot 6 weke na die fisiologiese vrugvalperiode) om die gewenste effek te verkry. Beter uitpak word verwag na uitdunning, aangesien vrugte met letsels ook verwyder word. Die effek van veelvuldige 2,4-dichlorofenoksie-propioonsuur (dichlorprop) spuite IS ook geëvalueer op 'Nules Clementine' mandaryn. Daar is geen verskil gevind tussen enkel en veelvuldige spuite in terme van vruggrootteverbetering nie. Die gebruik van veelvuldige dichlorprop spuite het nie tot 'n verlaging in opbrengs gelei nie, en interne vrugkwaliteit is ook nie beïnvloed me. Die beste resultate is verkry met die 50 mg. L-1 dichlorprop behandeling. Die gebruik van dichlorprop saam met verskillende benatters is op beide 'Clementine' mandaryn en 'Valencia' lemoene geëvalueer. Vruggrootte het toegeneem vanaf 50 mg. L-1 tot 100 mg. L-1 • Opbrengs was net in sekere gevalle verlaag en dan sonder 'n betekenisvolle verskil in groot-vrug produksie (>55 mm: Clementines). Tydens die eerste jaar van die 'Valencia' lemoen proef is die dichlorprop relatief laat gespuit (vrug deursneë: 19 mm). Daar was geen effek op vruggrootte, opbrengs en interne vrugkwaliteit nie. Tydens evaluasie van vroeë en laat bespuitings die volgende jaar is waargeneem dat laat bespuitings geen effek op vruggrootte gehad het nie, terwyl vruggrootte (48 vrugte per karton) betekenisvol verhoog is deur die vroeë bespuitings (Vruggrootte voor bespuiting = 8 en 12 mm, onderskeidelik). Dit impliseer dat dichlorprop se effek op vruggrootte gedurende die vroeë stadiums van vrugontwikkeling is, net na of gedurende die laat stadiums van die fisiologiese vrugvalperiode. Opbrengs is drasties verlaag deur dichlorprop, tot soveel as 35% wat die kilogram groot vrugte negatief beïnvloed het in sommige behandelings. Sappersentasie was nie konsekwent affekteer nie, maar is verlaag deur die dichlorprop bespuitings. Dichlorprop het die TSS effens verhoog in beide jare, maar het geen effek gehad op die TSS:TA verhouding nie. Die gebruik van Orchex minerale olie as benatter was effektief by 150 mL. 100 L-1 , en laat klaarblyklik die gebruik van dichlorprop by laer konsentrasies toe. Dus, kom dit voor dat benatters die potensiaal het om die effektiwiteit van dichlorprop te verbeter wat lei tot 'n verlaging in toedieningskoste. Die dichlorprop gespuite vrugte is gebruik om karotenoïed-inhoud van die skil te meet tydens die laat stadiums van vrugontwikkeling. Vrugte gespuit met dichlorprop teen 'n konsentrasie van 50 mg. L-1 het 'n beter karotenoïed-inhoud in beide 'Clementine' mandaryn en 'Valencia' lemoene tot gevolg gehad. Vrugte blootgestel aan lig het ook 'n hoër karatenoïedkonsentrasie gehad as vrugte wat met bruin papiersakke bedek was. Dichlorprop bespuite vrugte teen 100 mg. L-I, alhoewel blootgestel aan lig, het geen betekenisvolle verskil gehad in vergelyking met onbespuite vrugte nie. Dus is daar geen konsekwente effek van dichlorprop op karotenoïde inhoud van die skiI waargeneem nie.

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 (MScAgric)--Stellenbosch University, 2000. / ENGLISH ABSTRACT: The effect of foliar application oftriadimenol (a triazole), Promalin'", or scoring branches on fruit set, fruit size and fruit quality of 'Royal Gala' apples were evaluated. Four treatments were tested, viz., (a) an unsprayed control, (b) triadimenol sprayed on 6 March 1997 (one month after harvest) and then every two weeks for 8 weeks until leaf drop, as well as at mouse ear and full bloom, (c) as treatment b, plus Promalin® two weeks after full bloom, and (d) Promalin® two weeks after full bloom. Four scoring treatments were tested, viz., (a) a control, (b) scoring at full bloom, (c) scoring two weeks after full bloom, and (d) scoring four weeks after full bloom. Promalin® application two weeks after full bloom improved fruit size without any detrimental effects on fruit quality. This application was in addition to the standard commercial applications of Promalin'" as part of the chemical thinning program. The possible negative effect of the G~+7 on return bloom was however not determined. The scoring treatments were not severe enough to influence growth and development significantly and should be investigated again in the future. The influence of bearing position on apple flower and subsequent fruit quality was evaluated. At full bloom in the 1997/98 season, ten flower clusters from the following bearing positions were collected and evaluated: (a) dorsal spurs, (b) ventral spurs, (c) terminal on bourse shoot, (d) terminal on long shoot, and (e) lateral on long shoots. The same bearing positions were used, one week after full bloom, for the 1998/99 season. The flowering pattern was monitored for both seasons and just prior to harvest in both seasons the length and diameter of the fruit were measured as well as the length of the bourse shoot that had developed from the same bud. Fruit thinning by hand was done in 1997 by thinning to the largest fruit per cluster, but no thinning was done in the 1998 season. The results obtained in the morphological analysis of the flower cluster of 'Royal Gala' were not very consistent. In general, the dorsal spurs appeared to be the better quality flowers and the "king" flower is believed to be the best quality flower in the cluster as far as the receptacle dimensions are concerned. When fruit were harvested, no fruit on long shoots, either in the terminal or lateral positions, were found. Even though the percentage of these positions were low at bloom, this indicates a low set potential and possibly poor flower quality of these bearing positions in 'Royal Gala'. The size of the fruit at harvest in 1998/99, did not correlate well with the parameters measured at bloom. The correlation coefficients between bourse shoot length and fruit size were significant, but relatively small. We found a positive correlation between developed seed number and fruit dimensions. Thinning and heading pruning cuts affect fruit size and yield of 'Royal Gala' apple trees. During the 1997 winter trees were pruned as follows: (a) control with no further pruning, (b) thinning cuts of only entire secondary branches (branches that were thicker than half of the trunk diameter were removed at the point of attachment to the trunk), (c) thinning cuts of secondary branches and tertiary fruiting units (positioned on branches), (d) thinning of spurs only, without removal of branches or fruiting units, and (e) thinning cuts of branches and tertiary fruiting units combined with heading back of fruiting units into the spurs leaving four bud on the fruiting units. Treatments (b) through (e), were conducted at light or heavy pruning intensities, i.e., by leaving 300 or 150 reproductive buds/tree, respectively. Pruning was followed up by hand thinning of fruitlets to one fruit per cluster. All pruning treatments increased fruit size, primarily because of a indirect fruit thinning effect except the combined thinning and heading treatments where a direct effect resulted in the largest apples without having a negative effect on yield. In winter 1998 trees were pruned as follows: (a) control with no further pruning, (b) heavy thinning of secondary branches and fruiting units leaving 250 reproductive buds/tree, (c) light thinning of secondary branches and fruiting units leaving 400 reproductive buds/tree, (d) heavy thinning of secondary branches and fruiting units combined with heading back into the spurs of the remaining fruiting units leaving 250 reproductive buds/tree, and (e) light thinning of secondary branches and fruiting units combined with heading back into the spurs of the remaining fruiting units leaving 400 reproductive buds/tree. In 1998/99 season the advantage of pruning on fruit size were not observed. Lastly, the effect of artificial extinction (removal) of flower clusters on fruit size and quality of 'Royal Gala' apples were evaluated. Individual branches were pruned as follows: (a) control, (b) 25 % removal of fruiting spurs, (c) 50 % removal of fruiting spurs, (d) 75 % removal of fruiting spurs to test for any possible enhancements of fruit size. No subsequent hand thinning of fruitlets was done. Thinning by artificial extinction methods of the fruit buds did not influence fruit size, colour, seed set or seed development. No significant differences were found between fruit number, but with 50% and 75% bud removal fewer fruit were counted. In these data the absence of any significant fruit size improvement may be due to the lack of subsequent hand thinning of fruitlets. / AFRIKAANSE OPSOMMING: Die effek van blaarbespuiting van triadimenol en Promalin® asook ringelering op vrugset, vruggrootte en vrugkwaliteit is geëvalueer. Vier behandelings is toegepas nl: (a) onbehandelde kontrole, (b) triadimenol op 6 Maart 1997 en dan elke twee weke tot en met blaarval asook met "muis oor" en volblom, (c) soos behandeling b, plus Promalin® twee weke na volblom, en (d) Promalin® twee weke na volblom. Vier ringelering behandelings is ook toegepas nl: (a) geen ringelering (kontrole), (b) tydens volblom, (c) twee weke na volblom, en (d) vier weke na volblom. Promalin® bespuiting twee weke na volblom verbeter vruggrootte sonder enige nadelige effekte op vrugkwaliteit. Dit moet ingedagte gehou word dat hierdie behandeling van Promalin® was addisioneel toegevoeg tot die standard kommersiele gebruik van Promalin® wat deel vorm van die chemiese uitdun program. Die moontlike negatiewe effek van GA4+7 op blominisiasie is nie bepaal nie. Die ringelering behandelings was nie straf genoeg nie en dit het nie die groei en ontwikkeling betekenisvol beïnvloed nie en sal in die toekoms weer geëvalueer moet word. Verder is die invloed van draposisies op die appel blomkwaliteit en die daaropvolgende vrugkwaliteit geëvalueer. Met vol blom in die 1997/98 seisoen is tien blom trosse van die volgende draposisies versamel en geëvalueer: (a) dorsale spore, (b) ventrale spore, (c) terminaal op beurslote, (d) terminaal op langlote, en (e) lateraalop langlote. Dieselfde draposisies is versamel, een week na volblom, vir die 1998/99 seisoen. Die blompatroon is gemonitor gedurende beide seisoene. Net voor oes is die vruglengte en - deursnee gemeet as ook die lengte van die beurslote wat van dieselfde knop ontwikkel het as die vrugte. Vruguitdinning met die hand tot die grootste vrug per tros was gedoen in die 1997/98 seisoen, maar nie in die 1998/99 seisoen nie. Die resultate wat gekry is met die morfologiese analise van die blom trosse was nie baie konsekwent nie. In die algemeen vertoon die dorsale spore die beste kwaliteit blomme en die "koning" blomme het die grootste blombodems. Met die oes van die vrugte is geen vrugte op lang lote, hetsy in die terminale of laterale posisies gevind nie. Al was die persentasie van die posisies laag met volblom dui dit op lae setpotensiaal en moontlik ook op 'n lae blom kwaliteit van hierdie draposisies vir 'Royal Gala" appels. Die grootte van die vrugte van die 1998/99 oes korreleer nie goed met die parameters wat tydens blom gemeet is nie. Ongelukkig is die vrugte vir die 1998/99 seisoen nie gedurende die na-blom staduim uitgedun nie, wat daartoe bygedra het dat dit moeilik is om afleidings te maak. Die korrelasiekoeffisient tussen die beurslootlengte en vruggrootte was betekenisvol maar redelik klein. 'n Positiewe korrelasie tussen die aantal goed ontwikkelde sade en vrugdimensie is gevind. Die effek van uitdun en terugsnysnitte op vruggrootte eh opbrengs van 'Royal Gala' is ook geëvalueer. Gedurende die 1997 winter is die bome op die volgende manier gesnoei: (a) geen snoei (kontrole), (b) uitdunsnitte van hele sekondêre takke (takke wat dikker was as die helfde van die stam se deursnee by die punt van aanhegting aan die stam), (c) uitdunsnitte van sekondêre takke en tersiêre vrugdraende takke, (d) uitdun van spore alleen sonder om enige takke te verwyder, en (e) uitdunsnitte van sekondêre takke en tersiêre vrugdraende takke gekombineerd met terugsnysnitte van vrugdraende takke in die spoor sisteem in tot net vier spore per tak oorbly. Vir behandelings (b) tot (e) was die behandelings opgedeel in 'n ligte en 'n strawwe uitduning van knoppe deur onderskeidelik uit te dun tot 300 en 150 reproduktiewe knoppelboom. Die snoei was opgevolg deur handuitdunning tot een vrug per tros. Alle snoeibehandelings verbeter vruggrootte, primêr as gevolg van 'n indirekte vruguitdunnings, effek behalwe die behandeling met uitdunsnitte van sekondere takke en tersiêre vrugdraende takke gekombineerd met terugsnysnitte van vrugdraende takke. In hierdie behandeling is daar 'n direkte effek op vruggrootte sonder om 'n negatiewe effek op die oes opbrengs te he. In die winter van 1998 is die bome soos volg gesnoei: (a) geen snoei (kontrole), (b) strawwe uitdun snitte van hele sekondêre takke en vrugdraende takke tot op 250 reproduktiewe knoppe/boom, (c) ligteuitdun snitte van hele sekondêre takke en vrugdraende takke tot op 400 reproduktiewe knoppe/boom, (d) strawwe uitdunsnitte van sekondêre takke en tersiêre vrugdraende takke gekombineerd met terugsnysnitte van vrugdraende takke tot in die spoorsisteem tot op 250 reproduktiewe knoppelboom, en (e) ligte uitdunsnitte van sekondêre takke en tersiêre vrugdraende takke gekombineerd met terugsnysnitte van vrugdraende takke tot in die spoorsisteem tot op 400 reproduktiewe knoppelboom. Geen handuitdunning is gedurende die' seisoen gedoen nie, In die 1998/99 seisoen is geen voordeel van snoei op vruggrootte waargeneem nie. Snoei moet dus opgevolg word deur handuitdunning van vruggies. Laastens is daar na die effek van kunsmatige uitdun van blomtrosse op vruggrootte van 'Royal Gala' appels gekyk. Individuele takke is soos volg gesnoei: (a) kontrole, (b) 25 % verwydering van spore, (c) 50 % verwydering van spore, en (d) 75 % verwydering van spore. Geen opvolg handuitdunning is gedoen nie. Die uitdun tegniek het nie die vruggrootte, - kleur of die hoeveelheid en ontwikkeling van saad beïnvloed nie. Met die 50 % en 75 % verwydering is daar soos verwag minder vrugte geoes. Die rede dat geen vruggrootte verbetering gevind is nie kan moontlik daaraan toegeskryf word dat geen opvolg handuitdunning toegepas is nie.

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

Thesis (MScAgric)--Stellenbosch University, 1965. / ENGLISH ABSTRACT: no abstract available / AFRIKAANSE OPSOMMING: geen opsomming

Thesis (PhD(Agric) (Horticulture))--University of Stellenbosch, 2005. / Bitter pit fruit in commercial consignments of apples still poses an economic threat to exporters from South Africa. Bitter pit develops pre-harvest, but gets progressively worse during storage and is only traceable once the lesions appear after storage. Accurate, early indications of bitter pit incidence will allow for remedial pre-harvest measures in the field, e.g. Ca foliar applications, to reduce the potential losses. Similarly, the automatic detection of a bitter pit fruit during packing will reduce financial losses by identifying unacceptable fruit before shipping. Fluorescence imaging is a fast, non-destructive technique, able to evaluate numerous fruits individually. Results of pre-harvest imaging on apples to identify fruit susceptible to bitter pit showed that pitted fruit were correctly classified, but misclassification of non-pitted fruit with fluorescence imaging was still too high. NIR-spectroscopy point meter readings could distinguish visible bitter pit lesions from healthy tissue. Important wavelengths associated with visible bitter pit were identified. This technique could also identify immature apples, more prone to bitter pit development. It could however not distinguish between bitter pit and non-pitted fruit when applied randomly on the calyx end of apples at harvest. Pre-harvest foliar applications to increase fruit Ca content and reduce bitter pit incidence, is a standard practice world wide. External Ca uptake by fruit was monitored to determine the efficacy of applications during different stages of fruit development. Two periods of efficient uptake of external Ca were identified, viz., cell division and the last few weeks before harvest. Foliar Ca applications from 40 days after full bloom were more effective in increasing fruit Ca content and reducing bitter pit incidence than at 80 days after full bloom, which was recommended previously. Mineral analysis of fruit has been used with variable success to predict bitter pit prior to harvest. The possibility of increasing the accuracy of existing predictive models by using analysis of individual fruit rather than pooled samples, was investigated. By improving the normality of different mineral distributions and decreasing the overlap between pitted and non-pitted fruit classes, it was attempted to improve the reliability of predictions based on variable threshold values. The Ca distribution showed a variation between pitted and nonpitted classes, but still a significant overlap between classes reduced the accuracy of the predictive capacity of this distribution. Even though our results produced a correct classification of 85% for non-pitted fruit, which can be useful, this was still below the required tolerance, of less that 2%, expected on the market. The effect of pruning and fruit bearing position on two-year-old wood on dry mass and Ca allocation of fruit was determined. ‘Golden Delicious’ fruit set was the lowest at the basal bearing position compared to the other positions evaluated and was contrary to expectations. Fruit in a terminal bearing position was superior to the basal position regarding total dry weight and fruit size. Distal wood possibly inhibited growth and set on the basal position via auxin distribution. Ca allocation differed between seasons and cultivars and could either be influenced by bearing position or presence or absence of re-growth.

Thesis (PhD(Agric) (Horticulture))--Stellenbosch University, 2008. / It is a common practise in the Western Cape to use micro sprinklers as the standard irrigation system for apple trees. Over the past forty years much effort has been put into the optimisation of the tree canopy. Less attention has been given to root proliferation, and the question as to whether root stimulation and proliferation, through intensive water and nutrient management, can contribute towards improved tree efficiency and more efficient water use. This is addressed in this study. ‘Brookfield Gala’ apple trees were studied in the Genadendal area near Greyton, in the Western Cape Province, South Africa. The trees were planted in Dundee soil (well aerated sandy loam soil) during winter 2003. Both horticultural aspects (tree growth, shoot growth, fruit yield and quality, trunk circumference and root growth) and gas exchange were studied from 2004/5 until 2007/8 under three different water application strategies, namely micro sprinkler irrigation, daily drip and pulsing drip irrigation and using two different rootstocks: M793 and M7. Irrigation under micro sprinkler irrigation was applied once to three times weekly, daily drip irrigation once daily/twice daily, and pulsing drip irrigation one to six times daily. Water use for bearing apple trees was calculated using long-term evaporation data (for Villiersdorp and Caledon) and existing crop factors for apples. Annual nutrient requirements were adapted from literature and divided percentage-wise into the requirements for five different phenological stages. Soil sensors were used to keep plant available soil water between 100% and 50%. A computer software program was used to incorporate all the above mentioned information and calculate the exact amounts of water and nutrients, and the application times. In general, drip irrigation systems used ±26% less water than micro sprinkler irrigation system. Significantly higher fruit yields were obtained with trees under daily or pulsing drip irrigation than those under micro irrigation during 2005/6 and 2007/8. During 2006/7 the crop load was low due to unfavourable weather conditions during flowering, resulting in poor fruit set and no differences in yield. There was a significantly higher number of thin plus medium roots (3mm and less in diameter) in the 0─400mm rooting zone and total root mass at 0─800mm rooting zone under drip irrigation systems than under micro sprinkler irrigation. Brookfield Gala’ apple trees grown under daily drip irrigation and pulsing drip irrigation performed better compared to those grown under micro sprinkler irrigation with respect to CO2 assimilation rate (A), stomatal conductance (gs), water use efficiency (WUE) and leaf water potential. None of the three irrigation systems affected the biochemical efficiency of the leaf significantly, except on a few occasions during the pre-harvest period. This implied that the changes in leaf biochemical efficiency were as a result of both stomatal and non-stomatal effects (temperature and vapour pressure deficit). The removal of fruit at harvest had a great influence on leaf photosynthetic capacity under micro irrigation but less so under drip irrigation systems. Higher chlorophyll a and chlorophyll b concentrations were observed under drip irrigation systems than under micro sprinkler irrigation, implying efficient biochemical efficiency under these systems compared to micro sprinkler irrigation during the post-harvest period. Use of daily drip irrigation and pulsing drip irrigation delayed the process of leaf ageing. This study demonstrated the benefits of more intensive water and nutrient application for apple trees. Improved root proliferation, increased fruit yield and photosynthetic efficiency have been found under drip irrigation system than under micro sprinkler irrigation.

Dissertation (PhD(Agric))--University of Stellenbosch, 2006. / ENGLISH ABSTRACT: Advancement of the flowering time of Protea cv. Carnival by approximately three months, without compromising the product quality, was achieved by the application of 6- benzyladenine-containing plant growth regulators to three-flush shoots in autumn. This earlier flowering time coincides favourably with the prime European marketing period (November-January). The percentage three-flush shoots initiating an inflorescence following the brush application of the 6-benzyladenine (BA)-containing regulators, ABG- 3062 (active ingredient: BA 2% w/w) and Accel® (active ingredients: BA 1.8% w/w; gibberellins A4A7 0.18% w/w) on dormant terminal buds, increased with later application dates and flowering percentages as high as 90% was achieved. No inflorescences were initiated on flushes induced by Promalin® (active ingredients: BA 1.8% w/w; gibberellins A4A7 1.8% w/w). Phenological phase progression of green point, flush expansion and inflorescence development of 'Carnival' shoots as induced by BA was calculated to have base temperatures of 8°C, 6°C and 1°C respectively. The days required from application of the BA-containing growth regulator until green point stage increased progressively over the six consecutive treatment dates in autumn (14 March - 22 May 2003). In contrast, the days required to complete inflorescence development decreased with each successive treatment date. The days required between the respective stages were mostly negatively correlated with temperature, except for the phase 'green point to flush expansion', where the relationship was unclear. For three-flush shoots of eight-year old plants, between 13-57, 39-65 and 121-177 days were required to reach green point, to achieve full flush expansion following green point and to complete inflorescence after flush expansion respectively. BA application enhanced budbreak in most dormant shoots, irrespective of plant age, BA concentration, decreasing temperature over time or shoot characteristics. However, twoflush shoots treated in late May had low budbreak and hence low flowering percentages. Shoots varied considerably in their responsiveness to BA treatments. BA application (500mg·L-1) as MaxCelTM (active ingredients: BA 1.9% w/w) to terminal buds alone of mature three-flush shoots from less vigorous growing plants resulted in the highest flowering percentages. Applications were most effective when applied to the terminal bud in the dormant state or up to the ‘green point’ stage. Shoot characteristics such as flush length, leaf area, shoot dry mass, number and proximity of the leaves to the terminal bud were all positively correlated with the propensity of shoots to initiate inflorescence under BA induction. Terminal flush intercalation shoot diameter (>7mm) was identified as the most important variable influencing the likeliness of flowering and can effectively serve as a nondestructive estimation of a shoot's propensity to flower. The presence of developing inflorescences or possible floral inhibiting factors derived from the previous flowering season is suggested to be inhibitory to inflorescence initiation following BA application. Synchronisation of shoot growth by pruning plants in late winter appears to be an essential step to ensure high percentages inflorescence initiation with BA treatment the following autumn. The use of BA as a management tool to control flowering times in Protea for better market opportunities is shown to hold considerable commercial potential. / AFRIKAANSE OPSOMMING: Protea cv. Carnival se blomtyd is met ongeveer drie maande vervroeg sonder om produkkwaliteit prys te gee. Hierdie vervroegde blomtyd wat gunstig saam val met die optimale Europese bemarkingstyd van November-Januarie is bewerkstelling deur die herfstoediening van 6-bensieladenien-bevattende plantgroei-reguleerders op lote bestaande uit drie groeistuwings. Die persentasie lote met drie groeistuwings wat 'n bloeiwyse geïniseer het na 'n kwas-aanwending met die 6-bensieladenien (BA)-bevattende groeireguleerders, ABG-3062 (aktiewe bestandeel: BA 2% w/w) en Accel® (aktiewe bestandele: BA 1.8% w/w; gibberellins A4A7 0.18% w/w), het toegeneem met latere behandelingsdatums en blompersentasies so hoog as 90% is behaal. Geen bloeiwyses is geïnisieer op groeistuwings wat deur Promalin® (aktiewe bestandeel: BA 1.8% w/w; gibberellins A4A7 1.8% w/w) teweeggebring is nie. Basis temperature van 8°C, 6°C en 1°C respektiewelik is bereken vir fenologiese fasevordering vanaf groeireguleerder toediening tot by groenpunt, groeistuwing-voltooing en bloeiwyse-ontwikkeling van 'Carnival' lote soos geïnduseer deur BA. Die dae wat benodig was vanaf toediening van die BA-toediening totdat groenpunt stadium bereik is, het progressief toegeneem oor die ses opeenvolgende herfsbehandelingsdatums (14 Maart-22 Mei 2003). In teenstelling met bostaande, het die vereiste aantal dae om bloeiwyseontwikkeling te voltooi afgeneem met elke opeenvolgende behandelingsdatum. Die aantal dae wat benodig was vir die onderskeie fases was meestal negatief gekorreleer met temperatuur, behalwe vir die fase 'groenpunt tot groeistuwing-voltooing', waar die verhouding onduidelik was. Vir lote van agt-jaar-oue plante met drie groeistuwings was tussen 13-57, 39-65 en 121-177 dae respektiewelik benodig om groenpunt te bereik, volledige groeistuwingverlenging te bewerkstellig en om bloeiwyse-ontwikkeling wat volg na groeistuwing verlenging, te voltooi. BA-toediening het knoprusbreking bevorder in die meeste dormante lote, ongeag plant ouderdom, BA konsentrasie, afname in temperatuur met tyd of loot eienskappe. Lote met twee groeistuwings wat laat in die herfs behandel is, het egter lae rusbreking en dus gevolglik ook lae blompersentasies getoon. Lote varieer aansienlik in hul reaksie op BA behandeling. BA toediening (500mg·L-1) as MaxCelTM (active ingredients: BA 1.9% w/w) op die terminale knop van afgeharde lote met drie groeistuwings en afkomstig van minder groeikragtige plante het tot die hoogste blompersentasies gelei. Die effektiwiteit van die behandeling was die hoogste met toedienings aan dormante terminale knoppe tot en met groenpuntstadium. Loot eienskappe soos groeistuwinglengte, blaaroppervlakte, loot droë massa, asook die aantal en nabyheid van die blare relatief tot die terminal knop was almal positief gekorreleerd met die vermoë van die loot om 'n blom te inisisieer in reaksie op BA induksie. Terminale groeiverstuwing interkalasie-lootdikte (>7mm) is geïdentifiseer as die belangrikste veranderlike wat die vermoë om te kan blom kan beïnvloed en kan gebruik word as 'n nie-destruktiewe voorspeller vir blom-inisiasie. Die teenwoordigheid van ontwikkelende bloeiwyses of potensiële blom-inhiberende faktore aanwesig in die loot na die vorige blomperiode, word moontlik beskou om inhiberend te wees vir BA-geïnduseerde blom-inisiasie. Sinchronisering van lootgroei deur die snoei van plante in laat-winter blyk krities te wees om 'n hoë blompersentasie met BA behandeling te verseker in die daaropvolgende herfs. Die aanwending van BA as 'n bestuurstegniek om die blomtyd van Protea te posisioneer vir beter bemarkingsgeleenthede toon aansienlike kommersiële potensiaal.

Thesis (MScAgric)--Stellenbosch University, 2011. / ENGLISH ABSTRACT: Commercial production of the southern highbush blueberries (SHB) ‘Jewel’, ‘Emerald’, ‘Star’, ‘Snowchaser’ and ‘Bluecrisp’ started recently in the Western Cape. In South Africa, no research has been conducted on pruning and pollination of SHB, and various questions regarding these practices have arisen. Six experiments were conducted to evaluate the self-compatibility and the effect of cross-pollination on berry characteristics of ‘Star’, ‘Emerald’, ‘Jewel’, ‘Bluecrisp’ and ‘Snowchaser’. The effect of cross-pollination on fruit set, berry weight, berry diameter and fruit development period is cultivar dependant. ‘Bluecrisp’ appears self-incompatible and ‘Misty’ or ‘Emerald’ can be recommended as cross-pollinators. ‘Snowchaser’ seems self-compatible and solid block plantings can be recommended. ‘Misty’ and ‘Emerald’ would be recommended as cross-pollinators for ‘Star’ and ‘Jewel’ respectively, even though these cultivars will set an adequate crop when self-pollinated. Although ‘Emerald’ seem self-compatible, the fruit set tends to vary greatly and cross-pollination with ‘Jewel’, ‘Misty’ and ‘Bluecrisp’ is recommended to obtain early maturing berries of the required size. Another season’s data is required before final conclusions can be drawn. In order to establish sustainable summer pruning strategies for South African growing conditions that will maximise yield and berry quality for SHB, two pruning trials were conducted. In the first trial, the severity of pruning of ‘Star’, ‘Emerald’ and ‘Jewel’ was evaluated. We established that summer pruning is a compromise between total yield and desired berry size. All the pruning treatments reduced total vegetative growth and shoot number, but increased individual shoot length. Summer pruning increased berry weight and diameter by reducing total yield, but also by developing better quality bearing wood. Vigorous laterals stimulated by pruning seize growth later thereby delaying reproductive bud initiation and harvest. An increase in the severity of pruning increased the level to which the plants responded. No pruning and ‘light pruning’ gave the highest yields, but one more season’s data will clarify whether successive light pruning is sustainable. “Standard pruning” resulted in a well-balanced plant with an intermediate yield and berry size. Heading of one-year-shoots as part of the pruning strategy is not recommended for any of the cultivars. “Severe pruning” will only be recommended for young, newly established plantings where vegetative growth is the main objective. A second trial was conducted to study the effect of time of summer pruning. At Teeland, delaying pruning resulted in a decrease in total new growth and shoot number thereby reducing yield. This was probably due to progressively more buds that became endodormant. For all three cultivars, pruning as soon as possible after harvest would therefore be recommended. At Lushof, the effect of time of summer pruning was not significant. This could be due to the fact that plants were younger and more vigorous or because the area is warmer and growth continued for longer. One more season’s data is needed before any final conclusions are drawn. / AFRIKAANSE OPSOMMING: Kommersiële verbouing van die “southern highbush” bloubessies (SHB) ‘Jewel’, ‘Emerald’, ‘Star’, ‘Snowchaser’ en ‘Bluecrisp’ is ’n nuwe ontwikkeling in die Wes-Kaap. In Suid-Afrika is nog geen navorsing oor die snoei en bestuiwing van SHB onderneem nie, en verskeie vrae het oor hierdie praktyke ontstaan. Ses eksperimente is gedoen om die self-verenigbaarheid, sowel as die effek van kruisbestuiwing op bessie-eienskappe van ‘Star’, ‘Emerald’, ‘Jewel’, ‘Bluecrisp’ en ‘Snowchaser’ te evalueer. Die effek van kruisbestuiwing op vrugset, bessiegewig, bessiedeursnee en vrugontwikkelingsperiode is kultivar spesifiek. ‘Bluecrisp’ blyk self-onverenigbaar te wees en kruisbestuiwing met ‘Misty’ of ‘Emerald’ word aanbeveel. ‘Snowchaser’ blyk self-verenigbaar te wees en suiwer blok aanplantings kan dus aanbeveel word. ‘Misty’ en ‘Emerald’ word onderskeidelik as kruisbestuiwers vir ‘Star’ en ‘Jewel’ aanbeveel, alhoewel beide kultivars ‘n goeie oes sonder kruisbestuiwing kan lewer. Vir ‘Emerald sal kruisbestuiwing met ‘Jewel’, ‘Misty’ of ‘Bluecrisp’ aanbeveel word, indien vroeë, groot bessies belangrik is. ’n Tweede seisoen se data word benodig om bogenoemde te bevestig voor finale aanbevelings gemaak kan word. Twee snoeiproewe is uitgevoer om volhoubare somersnoei-strategieë te ontwikkel wat die opbrengs en kwaliteit van bessies onder Suid-Afrikaanse groeitoestande sal maksimeer. In die eerste snoeiproef is die intensiteit van snoeisnitte vir ‘Star’, ‘Emerald’ en ‘Jewel’ ondersoek. Daar is vasgestel dat totale opbrengs en bessiegrootte teen mekaar opgeweeg moet word wanneer strafheid van snoei ge-evalueer word. Somersnoei verminder totale vegetatiewe groei en aantal nuwe lote, maar vermeerder lootlengte en bessiegrootte. Somersnoei het ‘n toename in bessiegrootte tot gevolg deur dat die totale opbrengs verminder, maar ook deur die kwaliteit van draende lote te verbeter. Meer groeikragtige lote gestimuleer deur somersnoei, staak verlengingsgroei later in die seisoen wat dan lei tot later bloknopinisiasie en oes. Geen snoei, sowel as “ligte snoei” het gelei tot die grootste opbrengs na die afloop van een seisoen, maar nog ‘n seisoen se data word benodig om vas te stel of dit volhoubaar is. “Standaard snoei’” lei tot ‘n goed gebalanseerde plant met ‘n gemiddelde opbrengs en bessiegrootte. “Harde snoei” sal slegs aanbeveel word vir nuwe aanplantings waar vegetatiewe groei die hoof prioriteit is. Om die tydsbereking van somersnoei aan te spreek, is ‘n tweede snoeiproef uitgevoer. Op Teeland, het ‘n uitstel van somersnoei gelei tot ‘n afname in vegetatiewe groei en aantal lote en dit het dan gelei tot ‘n afname in opbrengs. Hierdie was moontlik die gevolg van meer knoppe wat mettertyd in endodormansie ingegaan het. Op Lushof het die tydsberekening van somersnoei geen betekenisvolle effek gehad nie. Dit kan moontlik toegeskryf word aan die jonger, groeikragtige plante, of aan die langer groeiseisoen weens die warmer klimaat in die area. Nog ‘n seisoen se data word egter benodig voor enige finale gevolgtrekkings gemaak kan word.

Thesis (MScAgric (Horticulture))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: The size of the navel-end opening is an important parameter for external fruit quality in navel oranges [Citrus sinensis (L.) Osbeck]. The application of 2,4-dichlorophenoxyacetic acid (2,4-D) to increase the percentage of closed navel-ends and reduce the size of the navel-end opening was conducted on six different navel orange cultivars. Treatments were applied at full bloom (FB), 100% petal drop (PD), as well as 2 weeks (2 WAPD) and 4 weeks after 100% petal drop (4 WAPD), at 15 mg·L-1 to 45 mg·L-1, to determine the most effective timing and concentration. The application of 2,4-D at FB consistently decreased the average navel-end size (all fruit) and increased the percentage of closed navel-ends in all the cultivars, with later applications at PD, 2 WAPD and 4 WAPD being generally ineffective, regardless of the concentration applied. There were no major negative side effects on internal and external fruit quality, except for the reduction in juice content (%), especially with the later treatments. Therefore, 15 mg·L-1 2,4-D at FB can be applied to increase the percentage of closed navel-ends and possibly increase export packouts. Navel oranges have a small secondary fruit located inside the primary fruit at the stylar-end and an opening at the stylar-end called the navel-end opening or the stylar-end aperture. Fruit growth and development was studied in three navel orange cultivars by measuring the primary fruit diameter, the secondary fruit diameter and the navel-end opening fortnightly, using both destructive and non-destructive sampling methods. The relationships between the primary fruit size, the secondary fruit size and the navel-end opening size were studied using correlation analysis. In addition, the effect of 2,4-D on fruit morphology, when applied as a treatment to reduce the size of the navel-end opening, was also evaluated on the same cultivars. The primary fruit, the secondary fruit and the navel-end opening followed a similar developmental pattern, although the navel-end opening developed later, about six weeks after FB. The primary fruit size was not related to the size of the secondary fruit or the navel-end opening. Similarly, the size of the navel-end opening was not related to the size of the secondary fruit. No negative effects were noted on the primary fruit morphology when 2,4-D was applied. Fruit splitting is a major physiological disorder of ‘Marisol’ Clementine mandarin (Citrus reticulata) fruit. The effect of application of 2,4-D on fruit splitting and fruit quality was evaluated on ‘Marisol’ Clementine mandarin trees grafted on Troyer citrange rootstock. Treatments included an untreated control, 2,4-D applied at 15 mg·L-1 or 25 mg·L-1 at FB and 15 mg·L-1 or 25 mg·L-1 at PD. The application of 2,4-D reduced fruit splitting in ‘Marisol’ Clementine fruit. Internal fruit quality was not affected by the treatments, however, the fruit developed a coarse rind due to enlarged oil glands and the styles stayed attached on the fruit until harvest. Therefore, although 2,4-D reduced fruit splitting, it cannot be recommended at the timings and concentrations evaluated. / AFRIKAANSE OPSOMMING: Die grootte van die nawel-ent opening is ‘n belangrike parameter vir eksterne vrugkwaliteit van nawel lemoene [Citrus sinensis (L.) Osbeck]. Die toediening van 2,4-dichlorofenoksie asynsuur (2,4-D) om die persentasie geslote nawel-ente te vermeerder en die grootte van die nawel-ent opening te verklein is uitgevoer op ses verskillende nawel lemoen kultivars. Behandelings is toegedien by volblom (FB), 100% blomblaarval (PD), asook 2 weke (2WAPD) en 4 weke na 100% blomblaarval (4 WAPD), teen 15 mg·L-1 tot 45 mg·L-1, om die mees effektiewe tyd van toediening en konsentrasie te bepaal. Die toediening van 2,4-D by FB het herhaaldelik die gemiddelde nawel-ent grootte (alle vrugte) verminder en die persentasie geslote nawel-ente vermeerder in al die kultivars, terwyl die later toediening by PD, 2 WAPD en 4 WAPD oor die algemeen nie effektief was nie, ongeag die konsentrasie toegedien. Daar was geen noemenswaardige negatiewe effekte op interne en eksterne vrugkwaliteit nie, behalwe vir ‘n verlaging in die sapinhoud (%) van vrugte, veral by die later behandelings. Dus kan 15 mg·L-1 2,4-D by FB toegedien word om die persentasie geslote nawel-ente te vermeerder en moontlik ook die uitvoerpersentasie te verhoog. Nawel lemoene het ‘n klein sekondêre vrug binne die primêre vrug aan die styl-ent en ‘n opening by die styl-ent wat die nawel-ent opening of die styl-ent opening genoem word. Die vruggroei en ontwikkeling van drie nawel kultivars is bestudeer deur die primêre en sekondêre vrugdeursnit en die nawel-ent opening elke twee weke te meet, deur gebruik te maak van destruktiewe en niedestruktiewe monsterneming. Die effek van 2,4-D op vrugmorfologie, toegedien as ‘n behandeling om die nawel-ent grootte te verklein, is ook ge-evalueer op dieselfde kultivars. Die primêre vrug, die sekondêre vrug en die nawel-ent opening het dieselfde ontwikkelingspatroon gevolg, alhoewel die nawel-ent opening later ontwikkel het. Daar was geen sterk verwantskap tussen die primêre vruggrootte en die sekondêre vruggrootte of die grootte van die nawel-ent opening nie. Daar was ook nie ‘n vewantskap tussen die grootte van die nawel-ent opening en die sekondêre vruggrootte nie. Geen negatiewe effekte op vrugmorfologie as gevolg van die 2,4-D toediening is waargeneem nie. Vrugsplit is ‘n belangrike fisiologiese abnormaliteit van ‘Marisol’ Clementine (Citrus reticulata) vrugte. Die effek van 2,4-D op vrugsplit en vrugkwaliteit is ge-evalueer op ‘Marisol’ Clementine mandaryn bome op Troyer citrange onderstamme. Die behandelings het ‘n onbehandelde kontrole, 2,4-D toegedien teen 15 mg·L-1 of 25 mg·L-1 by FB en 15 mg·L-1 of 25 mg·L-1 by PD ingesluit. Die toediening van 2,4-D het vrugsplit verminder. Interne vrugkwaliteit was nie geaffekteeer deur die behandelings nie, maar die vrugte het ‘n growwe skil ontwikkel as gevolg van vergrote oliekliere en die style het aangeheg gebly aan die vrugte tot oestyd. Dus, alhoewel 2,4-D vrugsplit verminder het, kan dit nie aanbeveel word teen die tyd van toediening en konsentrasie soos ge-evalueer in hierdie studie nie.