Thesis (MScAgric)--University of Stellenbosch, 2001. / ENGLISH ABSTRACT: Poor colour development in bi-coloured pears is a big concern for the South African
deciduous fruit industry, resulting in low Class 1 packouts with huge financial
implications. The objective of this study was, therefore, to evaluate manipulation
practices to improve colour development.
The effect of summer pruning on the colour development of 'Rosemarie' pear fruit
was studied over two seasons. Pruning consisted of removing the upright shoots of
the current season's growth on the lateral branches. The effect of the time of summer
pruning on Class 1 packout percentage and average fruit mass were determined. The
percentage blushed fruit (colour grading 1-10) of the trees pruned in November or
pruned repeatedly from November to just before harvest were significantly higher
than for unpruned control trees or trees pruned at other times. Fruit mass was not
affected by summer pruning. A second study was conducted on 'Rosemarie' and
'Forelle' pears and the treatments consisted of non-pinched and pinched, where the
bourse shoots were cut back at petal drop. There were no significant differences in
fruit colour, fruit size, flesh firmness and total soluble solids after pinching compared
to the control. In a third study on 'Rosemarie' and 'Forelle' trees, bourse shoots were
removed in combination with defoliation. Spur leaves were removed at different
times throughout the season from petal drop towards harvest. Both bourse shoots
(Rosemarie), or one bourse shoot (Forelle) per cluster was removed as control, one
treatment where no bourse shoots were removed served as a secondary control. Spur
leaf removal on 'Rosemarie' and 'Forelle' did not have any significant effect on fruit
set, fruit size or total soluble solids. In 'Rosemarie', there was also no significant
effect on fruit colour. In 'Forelle', colour improved significantly between
unmanipulated branches (control 1) and branches were one bourse shoot was removed
(control 2). However, all treatments compared to control 1, improved red colour,
indicated by a significant decrease in the hue angle values and an increase in Class 1
packout.
A fourth study was conducted on 'Flamingo', 'Forelle' and 'Rosemarie' pears. A
number of urea applications were made onto the fruit. Fruit nitrogen content
increased with urea sprays. Urea sprays did not affect red colour of 'Flamingo', 'Forelle' and 'Rosemarie' pears. Urea sprays had no effect on the anthocyanin
concentration (ug.g") of 'Rosemarie' and 'Flamingo'. However, there was a
quadratic relationship between number of urea sprays and anthocyanin concentration
of 'Forelle'. There were not significant differences in the chlorophyll a and b
concentrations of 'Flamingo' and 'Forelle'. Urea applications significantly increased
the chlorophyll a concentration of 'Rosemarie'. In contrast there was no significant
difference in the chlorophyll b concentration of 'Rosemarie'. The carotenoid
concentration of 'Flamingo' and 'Forelle' was not affected by urea applications. In
contrast the carotenoid concentration of 'Rosemarie' increased significantly after the
urea applications.
Overhead cooling was applied with a micro-irrigation system to 'Rosemarie' pears.
The water was applied with pulsed irrigation for a three-week period (24 December
1998 to 14 January 1999) before harvest. The system was activated when internal fruit
temperature reached 24°C (day) and 19°C (night), and irrigation continued until
internal fruit temperature reached 21°C (day) and 16°C (night). No significant
differences were found in colour, soluble solids; fruit size, fimmess or yields.
A study was conducted on 'Bon Rouge', 'Red d' Anjou' and 'Forelle' pears to assess
the effect of storage period for 6 and 8 weeks at -O.SoC and ripening at 21°C for 1
week on anthocyanins, carotenoids, chlorophyll a and chlorophyll b content. There
were no significant differences in the anthocyanin concentration in 'Bon Rouge' after
cold storage compared to fruit at harvest, whilst for 'Red d' Anjou' anthocyanin
concentration increased significantly after cold storage. Results with 'Forelle' were
inconsistent. During ripening anthocyanin of 'Red d' Anjou' did not change, whereas
the results for 'Bon Rouge' and 'Forelle' were inconsistent. However, cold storage
had no effect on the anthocyanin concentrations of 'Bon Rouge' and 'Forelle'. Cold
storage significantly decreased the carotenoid concentrations of 'Bon Rouge', but not
in 'Red d' Anjou' and 'Forelle'. The carotenoids of 'Bon Rouge', 'Red d' Anjou' and
'Forelle' decreased significantly more during ripening at 21°C. The chlorophyll
concentrations of 'Bon Rouge' decreased significantly during storage at -O.SoC,
compared to fruit at harvest, but not in 'Red d' Anjou' and 'Forelle'. During ripening
at 21°C chlorophyll a and chlorophyll b decreased significantly in 'Bon Rouge', 'Red
d' Anjou' and 'Forelle'. In conclusion it is clear from this study, that although light is important for initial
colour development, high December and January temperatures remain the biggest
problem in maintaining good red colour at harvest. Other factors, e.g. fertilisation are
secondary. / AFRIKAANSE OPSOMMING: Kleurverbetering van twee-kleur pere
Onvoldoende kleur ontwikkeling in twee-kleur pere is 'n groot probleem vir die Suid
Afrikaanse sagtevrugtebedryf aangesien dit lae Klas l-uitpakke tot gevolg het. Die
doel van hierdie studie was dus om manipulasie tegnieke te evalueer om sodoende
kleur ontwikkeling te verbeter.
Die effek van somersnoei op die kleur ontwikkeling van 'Rosemarie' pere is
ondersoek oor twee seisoene. Die snoei het bestaan uit die verwydering van regop
lote van die huidige seisoen se groei op laterale takke. Die effek van die tyd van
somersnoei op Klas I-uitpakpersentasie en gemiddelde vrugmassa is bepaal. Die
persentasie vrugte met 'n blos (kleur gradering 1-10) van die bome wat in November
of voortdurend vanaf November tot net voor oes gesomersnoei is, was betekenisvol
hoër as die onbehandelde bome of bome wat op ander tye gesnoei was. Vrugmassa
was nie beïnvloed deur somersnoei nie. 'n Tweede studie is gedoen op 'Rosemarie'
en 'Forelle' bome. Die behandelings was nie-getop of getop, waar die beurslote
teruggesny is na blomblaarval. Daar was geen betekenisvolle verskille in vrugkleur,
vruggrootte, vrugfermheid en totale oplosbare suikers tussen die getopte en
onbehandelde bome se vrugte nie. In 'n derde studie op 'Rosemarie' en 'Forelle' is
beurslote verwyder in kombinasie met die verwydering van spoorblare. Spoorblare is
verwyder op verskillende tye gedurende die seisoen vanaf blomblaarval tot oes. By
'Rosemarie' (beide beurslote per tros) en by 'Forelle' (een beursloot per tros) is
beurslote verwyder om te dien as die kontrole, een behandeling waar geen beurslote
verwyder was nie het gedien as die sekondêre kontrole. Spoorblaarverwydering by
'Rosemarie' en by 'Forelle' het geen betekenisvolle effek op vrugset, vruggrootte of
totale oplosbare suikers gehad nie. By 'Rosemarie' was daar ook geen betekenisvolle
effek op vrugkleur nie. By 'Forelle' is vrugkleur betekenisvol verhoog tussen
onbehandelde takke (kontrolel) en takke waar een beursloot verwyder was (kontrole
2). Alle behandelings het egter vrugkleur verhoog in vergelyking met kontrole 1. Dit
is waarneembaar in 'n betekenisvolle verlaging in die kleurskakering en 'n verhoging
in die Klas l-uitpakke. 'n Vierde studie is uitgevoer op 'Flamingo' en 'Forelle' en 'Rosemarie' pere. 'n
Aantal ureumtoedienings is gemaak op die vrugte. Die stikstofinhoud van die vrugte
is verhoog met ureumbespuitings. Ureum spuite het nie rooi vrugkleur van
'Flamingo', 'Forelle' of 'Rosemarie' pere beïnvloed nie. Ureumbespuiting het geen
effek op die antosianienkonsentrasie (ug.g") van 'Rosemarie' en 'Flamingo' gehad
nie. Daar was egter 'n kwadratiese verwantskap tussen die aantal ureumbespuitings
en die antosianienkonsentrasie van 'Forelle'. Daar was geen betekenisvolle verskille
in die chlorofiel a en b konsentrasies van 'Flamingo' en 'Forelle' nie.
Ureumtoedienings het die chlorofiel a konsentrasie van 'Rosemarie' betekenisvol
verhoog, daar was egter in teenstelling hiermee geen verskil in die chlorofiel b
konsentrasie van 'Rosemarie' nie. Die karotenoiedkonsentrasie van 'Flamingo' en
'Forelle' is nie beïnvloed deur die ureum toedienings nie. In teenstelling hiermee het
die karotenoiedkonsentrasie van 'Rosemarie' betekenisvol toegeneem na die ureum
toedienings.
Oorhoofse verkoeling is toegedien met 'n mikro-besproeiingsstelsel op 'Rosemarie'
pere. Die water is toegedien met puls besproeiing vir 'n periode van drie weke (24
Desember 1998 tot 14 Januarie 1999) voor oes. Die stelsel is geaktiveer wanneer die
interne vrugtemperatuur 24oe (dag) en 19°e (nag) bereik het, die besproeiing het
aangehou totdat die interne vrugtemperatuur 21°e (dag) en 16°e (nag) bereik het.
Daar was geen betekenisvolle verskil in kleur, totale oplosbare suikers, vruggrootte,
vrugfermheid of opbrengs nie.
'Bon Rouge' 'Red d' Anjou' en 'Forelle' pere is gebruik om die effek van
opbergingsperiodes van 6 en 8 weke by -O.5°e en rypwording by 21oe vir 1 week op
die antosianiene, karotonoied, chlorofiel a en chlorofiel b konsentrasies te bepaal.
Daar was geen betekenisvolle verskille in die antosienien konsentrasie van 'Bon
Rouge' na koue opberging nie, terwyl die konsentrasie antosianien by 'Red d' Anjou'
betekenisvol toegeneem het na koue opberging. Die resultate by 'Forelle' was nie
konstant me. Gedurende rypwording was daar geen verskille in die
antosianienkonsentrasie van 'Red d' Anjou' nie, die resultate by 'Bon Rouge' en
'Forelle' was nie konstant nie. Koue opberging het egter geen effek gehad op die
antosianienkonsentrasies van 'Bon Rouge'en 'Forelle' nie. Die karonotoied- konsentrasies van 'Bon Rouge', 'Red d' Anjou' en 'Forelle' het betekenisvol meer
afgeneem gedurend rypwording by 21°C. Die chlorofielkonsentrasies van 'Bon
'Rouge' het betekenisvol afgeneem gedurende opberging by -O.5°C teenoor die
vrugte by oes, maar nie by 'Red d' Anjou' en 'Forelle' nie. Gedurende rypwording
by 21°C het die chlorofiel a en chlorofiel b konsentrasies by 'Bon Rouge', Red 'd
Anjou' en 'Forelle' betekenisvol afgeneem.
Om op te som dit is duidelik uit hierdie studie dat alhoewel lig belangrik is vir vroeë
kleurontwikkeling, hoë temperature gedurende Desember en Januarie steeds die
grootste faktor is wat finale rooi vrugkleur by oes bepaal. Ander faktore soos
bemesting is van sekondêre belang.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/52166 |
| Date | 03 1900 |
| Creators | Reynolds, Johan Schalk |
| Contributors | Theron, K. I., Jacobs, G., Huysamer, M., Stellenbosch University. Faculty of AgriSciences. Dept. of Horticulture. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | Unknown |
| Type | Thesis |
| Format | 112 p. : ill. |
| Rights | Stellenbosch University |
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