Thesis (MScAgric)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: ‘Triumph’ persimmon production in South Africa is export driven and the profitability
of the industry is largely dependent on consumer demand and supermarket shelf
space in the European market. In order to realise high returns, it is important to
advance harvest maturity to attain early fruit that arrives on the market prior to
European summer fruits. In addition, market feedback suggests that fruit picked
during the second half of the harvesting period stores poorly and rapidly softens
during shelf life. It is important to establish whether this is the case.
The effect of paclobutrazol (PBZ) application rate on fruit maturity and keeping
quality, return bloom and vegetative growth was investigated over two seasons.
Advanced harvest maturity was attained at a compromise of reduced fruit storage
quality and stunted growth with the severity of the compromise increasing with
increasing PBZ application rate. To advance harvest maturity while maintaining
acceptable keeping quality, PBZ application at 0.75 ml per plant is recommended
although effects on harvest maturity will not persist into the subsequent season as
found at higher application rates.
Prohexadione-calcium (P-Ca) as an alternative for PBZ in advancing harvest
maturity was evaluated over two seasons. A positive response to three foliar
applications of P-Ca at 200 mg·L-1 was noticed in the first season. In the second
season, a single application of P-Ca at 300 mg·L-1 two weeks before harvest
significantly advanced harvest maturity. Due to the rapid metabolism of P-Ca in the
plant, it is unlikely that growth in the subsequent season will be affected. Based on
these results, the persimmon industry will undertake commercial trials in the 2012
season to further assess the efficacy of P-Ca application in advancing harvest
maturity.
The effect of various rest breaking agents (RBAs) on bud break, flowering, fruit
maturity and quality as well as vegetative growth was assessed for one season.
RBAs did not increase or advance bud break and flowering. Consequently, yield and harvest maturity were unaffected by the treatments. The ineffectiveness of the RBAs
could be due to the low application rates used or the fulfilment of the chilling
requirement prior to treatment application.
An experiment was carried out to determine whether storability and shelf-life differ
between “early” and “late” production areas in South Africa as well as between
orchards within these areas. The data indicated that fruit colour is a good maturity
parameter and indicator of fruit storability. However, “late” fruit were about 1 kg softer
than “early” fruit at the same colour chart value. We therefore recommend that fruit
from late regions are harvested at colour chart values of 5 and 6 (yellow-green)
instead of 3 and 4. Fruit from “late” orchards as well as GA3-treated fruit with a colour
chart value of 3 and less should be culled due to the high propensity (>20%) of these
fruit to become soft during storage and shelf life. A delay in 1-MCP treatment and
interruption of the cold chain considerably increased fruit softening during storage
and shelf-life. Further research is required to verify this result. / AFRIKAANSE OPSOMMING: ‘Triumph’ persimmon produksie in Suid-Afrika is uitvoergedrewe en die
winsgewendheid van die bedryf is grootliks afhanklik van verbruikervraag en
supermark spasie in die Europese mark. Ten einde hoë pryse te realiseer, is dit
belangrik om ʼn vroeë oes te verkry sodat vrugte voor die Europese somervrugte op
die mark beland. Mark terugvoer dui verder daarop dat vrugte wat tydens die tweede
helfte van die oesperiode gepluk word, swakker opberg en vinnig sag word
gedurende op die rak. Dit is belangrik om vas te stel of hierdie waarneming juis is.
Die effek van paklobutrazol (PBZ) toedieningshoeveelheid op vrugrypwording en -
houvermoë, opvolgblom en vegetatiewe groei is oor twee seisoene ondersoek.
Oesrypheid is vervroeg, maar tot nadeel van vrughouvermoë en vegetatiewe groei.
Die omvang van die negatiewe effekte van PBZ het toegeneem met ʼn toename in
toedieningshoeveelheid. Ten einde oesrypheid te vervroeg terwyl aanvaarbare
houvermoë behou word, word toediening van PBZ teen 0.75 ml per plant aanbeveel
alhoewel die effek op oesrypheid anders as die geval met hoër
toedieningshoeveelhede nie in die opeenvolgende seisoen sal voortduur nie.
Proheksadioon-kalsium (P-Ca) as alternatief tot PBZ om oesrypheid te vervroeg is
oor twee seisoene gee-valueer. ʼn Positiewe effek op vrugrypwording is in die eerste
seisoen verkry met drie blaartoedienings van P-Ca teen 200 mg·L-1. In die tweede
seisoen is oesrypheid betekenisvol vervroeg deur ʼn enkel toediening van 300 mg·L-1
P-Ca ʼn maand voor oes. Vanweë hierdie resultate gaan die persimmonbedryf in die
2012 seisoen kommersiële proewe onderneem om die effektiwiteit van P-Ca om oes
te vervroeg, verder te ondersoek.
Die effek van verskeie rusbrekende middels (RBAs) op bot, blom, vrugrypheid,
vrugkwaliteit en vegetatiewe groei is vir een seisoen ondersoek. RBAs het bot en
blom vervroeg of vermeerder nie en het daarom ook geen effek op produksie en
oesrypheid gehad nie. Die oneffektiwiteit van die RBAs kan moontlik toegeskryf word aan die lae toedieningsvlakke wat gebruik is of aan die kouebehoefte wat bevredig is
voor toediening van RBAs.
ʼn Eksperiment is gedoen om vas te stel of die opberging- en houvermoë van vrugte
verskil tussen “vroeë” en “laat” produksieareas in Suid-Afrika en ook tussen boorde
in hierdie areas. Die data dui daarop dat vrugkleur ʼn goeie rypheidsparameter en
indikator van opbergingsvermoë is. Vrugte van laat areas was egter omtrent 1 kg
sagter as vrugte van vroeë areas van dieselfde kleur. Ons beveel gevolglik aan dat
vrugte van laat areas by ʼn kleurkaartwaarde van 5 tot 6 (geelgroen) geoes word
eerder as by 3 tot 4. Vrugte van laat boorde sowel as vrugte wat met GA3 behandel
is met ʼn kleurkaartwaarde van 3 en laer moet afgradeer word weens die hoë
geneigdheid (>20%) van hierdie vrugte om sag te word tydens opberging en op die
rak. Uitstel van 1-MCP behandeling en die onderbreking van die koueketting
veroorsaak ʼn aansienlike toename in sagte vrugte tydens opberging en op die rak.
Verdere navorsing word benodig om hierdie resultaat te verifieer.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/20110 |
| Date | 03 1900 |
| Creators | Bill, Malick |
| Contributors | Steyn, W. J., Theron, K. I., Ungerer, S. F., 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 | 119 p. : ill. |
| Rights | Stellenbosch University |
Page generated in 0.0028 seconds