Thesis (MScAgric (Viticulture and Oenology))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: The table grape industry employ a wide range of viticultural management
practices in order to produce the high quality grapes demanded by the export
market. A common contributor to degrading the quality of table grapes is the
occurrence of berry split, which not only has an unattractive visual effect, but
also increases the berries’ susceptibility to infection by spoilage organisms.
A number of environmental conditions such as rainfall and humidity, and/or
agricultural practices, such as irrigation, and high density canopies, can lead
to higher plant cell water content. This in turn, can increase the potential
of berry split to occur. To date, the main method of berry split prevention
has been the management of plant water status by; (i) regulating irrigation
withdrawal times, and (ii) covering of canopies if rainfall is predicted prior to
harvest. The aim of this study was to determine the effect that irrigation frequency,
as induced by irrigation withdrawals; as well as boron (B) and calcium (Ca)
treatments, applied as bunch directed sprays, have on pre- and post-harvest
berry split. To this end, a newly released late ripening, white seedless cultivar,
SoutherngrapeOne was chosen as a model cultivar as it has a high susceptibility
to berry split. SoutherngrapeOne vines were subsequently subjected to a range
of irrigation frequencies based on typical irrigation scheduling used in the table
grape industry, which comprised of a low, medium and high frequency. The
low frequency was duplicated in order to demonstrate the effect that a heavy
irrigation, just before harvest may have on berry split. These treatments were
further subdivided to investigate the effect that B and Ca may have on berry
split. For the B treatment, four Solubor1 bunch directed sprays were applied
from 8mm berry size to véraison. The Ca treatment consisted of Stopit R
2 and
Caltrac R
3 bunch directed sprays applied over the same period. In addition,
a combination of the B and Ca treatment were applied to investigate any
possible interaction. To account for the effect of water as solvent in the B
and Ca treatments, and the spraying effect, pure water as treatment was also
evaluated. Control vines received no sprays.
The applied irrigation treatments resulted in different plant water status
conditions. Separate applications of B and Ca treatments resulted in a decrease
of B and Ca content in the flesh respectively. The control and combination
treatment, of B and Ca resulted in the same of B and Ca content in the flesh.
Furthermore, none of the applied treatments resulted in an increase of either
B or Ca content in the berry skin.
It was found that the medium frequency irrigation resulted in the best
irrigation strategy to prevent pre-harvest berry split. Surprisingly, all the subtreatments:
B, Ca, and combination of B and Ca, resulted in an increased
incidence of pre-harvest berry split when compared to the control group for
the 2006/07 season. However, in the 2007/08 season only the B treatment
resulted in an increase of pre-harvest berry split.
Concerning post-cold-storage physiological disorders, Ca treatments appear
to have reduced berry drop, but increased decay. In the 2006/07 season,
the B treatment resulted in reduced post-cold-storage berry split, whereas Btreatment in the 2007/08 season had no effect. Both B and Ca should be considered
as having the potential to increase the appearance of hairline cracking.
Calcium treatment also led to an increase in decay which may have been as
a result of the splitting it contributed to. Low frequency irrigation recieving
irrigation before harvest was found to result in browner stems.
Low irrigation frequencies decreased the cell size of the berry skin. The Ca
treatment gave rise to thicker (weaker) cell walls, this morphological change
may be responsible for the physiological disorders it caused.
From these findings, it can be deduced that poorly managed irrigation,
together with unnecessary application of B and/or Ca may result in an increase
of berry split and other physiological disorders, with subsequent financial losses
for the producer. / AFRIKAANSE OPSOMMING; Die tafeldruifindustrie maak gebruik van ’n wye reeks wingerdkundige praktyke
ten einde die hoë gehalte druiwe te produseer wat die uitvoermark vereis.
Korrelbars is ’n algemene verskynsel wat afbreek maak tot die gehalte van tafeldruiwe.
Behalwe dat voorkoms van die druiwe benaadeel word, verhoog dit
ook in vatbaarheid vir infeksie deur verrottingsveroorsakende swamme. Hoë
reënval en humiditeit, sowel as wingerdkundige praktyke soos besproeiing en
hoë lowerdigtheid, wat kan lei tot verhoogde waterstatus in plante, kan lei tot
’n toename in korrelbars.
Daar word hoofsaaklik van twee metodes gebruik gemaak om korrelbars te
beheer, naamlik die bestuur van plantwaterstatus deur; (i) beheer van besproeiingsontrekkingstye
en (ii) bedekking van lowers indien reën voorspel
word voor oestyd. Die doel van hierdie studie was om vas te stel wat die invloed van besproeiings
frekwensies sowel as trosgerigte boor (B) en kalsium (Ca), spuitbehandelings,
op voor- en na-oes korrelbars het. Die onlangs vrygestelde laat
rypwordende, wit, pitlose kultivar, SoutherngrapeOne is gebruik, aangesien dit
hoogs gevoelig is vir korrelbars.
Stokke is aan verskillende besproeiings intervalle, soos tipies gebruiklik
in die tafeldruifindustrie, blootgestel. Hierdie intervalle bestaan uit n’ lae,
medium en hoë besproeiings frekwensie. Die lae besproeiings frekwensie is
herhaal ten einde die invloed van besproeiing net voor oestyd op korrelbars
te ondersoek. Die invloed van B- en Ca-behandeling op korrelbars is ook ondersoek.
Vir die B-behandeling is vier Solubor1 trosgerigte spuite aangewend
vanaf 8mm korrelgrootte tot deurslaan. Vir die Ca-behandeling is Stopit R
2
en Caltrac R
3 as trosgerigte spuite oor dieselfde tyd toegedien. Kombinasiebehandelings
is ook aangewend om enige interaksie tussen B en Ca te ondersoek.
Waterbehandelings is ook toegedien om die invloed van water as oplosmiddel
van B- en Ca-behandelings sowel as die spuit-effek te ondersoek. Kontrole
stokke is ook ingesluit en het geen spuitebehandeling ontvang nie.
Die besproeiingsbehandelings het verskillende plantwater toestande tot
gevolg gehad, B- en Ca-behandelings het gelei tot ’n afname in B- en Cainhoud
in die vleis onderskeidelik. Die kombinasie en kontrole behandelings
het eenderse hoeveelhede B en Ca in die vleis tot gevolg gehad. Geen van die
aangewende behandelings gelei tot ’n toename in B- en Ca-inhoud in die dop
nie.
Die resultate toon dat medium besproeiings frekwensie die beste besproeiingsstrategie
is om voor-oes korrelbars te voorkom. In vergelyking met die
kontrole-behandeling in 2006/07, het B, Ca en die kombinasie van B en Ca, ’n
toename in voor-oes korrelbars tot gevolg gehad. In die 2007/08 seisoen het
slegs die B-toediening egter tot ’n toename in voor-oes korrelbars gelei.
Kalsium behandelings het ’n afname in los-korrels, maar ’n verhoging in
korrelbars tot gevolg gehad. In 2006/07, het B-toediening tot ’n afname in
korrelbars na koelopberging gelei, maar in die 2007/08 seisoen het dit geen
effek gehad nie. Beide B- en Ca-toediening het die potensiaal om haarlyn
barste te veroorsaak. Kalsium toediening het bederf verhoog wat moontlik aan die hoër bars wat dit induseer toegeskryf kan word.
Lae besproeiings frekwensie, het bruiner stingels veroorsaak, en ook gelei
tot ’n afname van selgrootte in die dop. Die Ca-toediening het aanleiding gegee
tot dikker selwande in die dop. Hierdie anatomiese veranderinge kan moontlik
die rede wees vir die verhoging in fisiologise afwykings.
Van hierdie bevindinge kan ons aflei dat swak bestuur van besproeiing,
sowel as die onnodige aanwending van B en/of Ca, kan aanleiding gee tot ’n
toename in korrelbars en ander fisiologiese afwykings, en dus finansiële verliese
vir die produsent inhou.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/4215 |
| Date | 03 1900 |
| Creators | Koekemoer, Abraham Leander |
| Contributors | Raath, P. J., Avenant, J. H., University of Stellenbosch. Faculty of Agrisciences. Dept. of Viticulture and Oenology. |
| Publisher | Stellenbosch : University of Stellenbosch |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | 92 p. : ill. |
| Rights | University of Stellenbosch |
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