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Postharvest berry split and abscission in 'Thompson Seedless' and 'Waltham Cross' table grapesBurger, D. A. (Dirk Albert) 12 1900 (has links)
Thesis (MScAgric) -- University of Stellenbosch, 2000. / ENGLISH ABSTRACT: Postharvest berry split and abscission are prevailing physiological disorders that negatively
impact on the quality of table grapes exported from South Africa. Inferior grape quality due to
these disorders results in a considerable decline in consumer confidence in the branded
product, which leads to a drop in demand, and consequently, lower prices. Since information
concerning postharvest factors influencing postharvest berry split and abscission is limited, the
search for reliable methods to adequately control these problems remains elusive. In an
attempt to obtain the required information, the influence of harvest temperature, harvest
maturity, perforated liners, field heat removal prior to packing, delay periods before and after
packing, storage duration and the elevation of storage temperature on the development of berry
split and abscission in 'Thompson Seedless' (Vitis vinifera Linnaeus) table grapes was
investigated. Changes in abscission related factors during berry development, and the influence
of pre-and postharvest ethylene inhibitors on the development of berry abscission in 'Waltham
Cross' table grapes, was also studied.
Berry split was aggravated by packing 'Thompson Seedless' grapes at high pulp temperatures
of approximately 30°C, especially if the grapes were packed in non-perforated bags. The
incidence of berry split could be reduced by between 80 and 90% by packing grapes in
perforated instead of non-perforated liners. Perforated bags also reduced levels of S02
damage. However, due to significantly more moisture loss from grapes in perforated bags,
compared to non-perforated bags, the risk of higher fruit and stem desiccation and softer berries
existed. Optimum size and density of perforations needs to be determined to reduce berry split
without excessive loss of moisture from the grapes, and S02gas from the air space surrounding
the product. The influence of harvest temperature and liner type on berry abscission was not
conclusive. Advanced maturity increased grape resistance to berry split. However, grapes
harvested too mature were prone to stem desiccation and the development of Botrytis decay.
The occurrence of berry abscission also appeared to increase with advanced harvest maturity.
Consequently, to ensure optimal post-storage quality, 'Thompson Seedless' grapes should be
harvested as soon as horticultural maturity has been reached, which appears to be at
approximately 18°Brix.
Field heat removal for 1.5 hours at 19°C prior to packing had no beneficial or adverse effect on
berry split and abscission. Delay periods prior to packing aggravated berry abscission, but did
not influence berry split significantly. Grapes delayed for 12 hours showed a significant increase
in berry abscission and Botrytis decay, compared to grapes delayed for only 3 or 8 hours. Considering that the absence of fungal decay is the most important quality prerequisite in table
grapes, it is of vital importance to pack grapes with as short a delay period as possible. Grapes
packed in non-perforated liners and delayed for different durations after packing, before the
onset of forced-air cooling (FAC), showed significant differences regarding the incidence of
berry split. Grapes delayed for 18 hours had significantly higher levels of berry split directly after
the delay period, compared to grapes delayed for 6 or 12 hours. No significant difference in
berry abscission occurred between grapes delayed for different periods. To minimise the
amount of berry split, FAC should be applied as rapidly as possible after the packing of grapes
in non-perforated liners.
Two storage related factors significantly influenced the incidence of berry split in 'Thompson
Seedless' grapes during cold storage significantly, viz. the duration of storage at -O.soC,and the
increase in temperature after low temperature storage. Berry split increased almost linearly with
prolonged storage at -O.soC. An elevation of storage temperature from -O.soC to 10°C any time
during the cold storage period, further aggravated the split problem. Consequently, the
reduction of berry split in 'Thompson Seedless' table grapes during cold storage requires (a) the
shortest possible cold storage period, and (b) good temperature management throughout
distribution, from initiation of cooling until the final point of sale.
The grape berry abscission potential, as quantitatively indexed by the measurement of the fruit
removal force (FRF), showed significant changes during berry development of 'Waltham Cross'
table grapes, from 27 to 111 days after full bloom (OAFB). This showed that at certain stages of
fruit growth, 'Waltham Cross' grapes are more prone to berry abscission. At 27 OAFB, when the
berries had an average diameter of 6.6mm, the grape bunches showed a significantly higher
potential for berry abscission, compared to grapes sampled at a later stage. 'Waltham Cross'
has inherently straggly bunches with bare shoulders. Therefore, any abscission during berry
development will aggravate the problem. Consequently, it is of vital importance that any
adverse factors such as moisture stress be avoided, especially during the period when
'Waltham Cross' grapes appear to be very susceptible to berry abscission. Of all parameters
measured, moisture loss showed the best correlation with abscission. Grapes harvested with
total soluble solids (TSS) of 12.3°Brix, 83 OAFB, had a significantly higher abscission potential
than grapes harvested more mature. Therefore, by harvesting 'Waltham Cross' grapes at
optimum maturity, at a TSS of approximately 16.4°Brix, berry abscission can be reduced to a
great extent. It was evident that at veraison, the metabolism of grape berries changes
drastically, and additional to the rapid increase in sugars and the rapid decrease in acidity, a
decrease in FRF occurs. Preharvest sprays of ReTain™ (a derivative of aminoethoxyvinylglycine), which inhibits ethylene
synthesis, showed no promise as a means to reduce postharvest berry abscission. A
postharvest treatment with EthylBloc® (1-methylcyclopropene), which inhibits ethylene action,
only reduced berry abscission during one season. / AFRIKAANSE OPSOMMING: Die fisiologiese defekte korrelbars en los korrels wat algemeen voorkom tydens opberging van
sekere tafeldruif-kultivars, het 'n negatiewe invloed op tafeldruiwe wat uitgevoer word vanaf
Suid-Afrika. Minderwaardige kwaliteit as gevolg van hierdie defekte het 'n aansienlike afname
in verbruikers-vertroue tot gevolg wat aanleiding gee tot 'n ooreenkomstige afname in aanvraag
en prys van die produk. Inligting rakende na-oes faktore wat die voorkoms van korrelbars en los
korrels beïnvloed is beperk, en geen gewaarborgde metode bestaan om hierdie twee defekte
volkome te beheer nie. In 'n poging om dié gewenste inligting te bekom, is ondersoek ingestel
na die effek van oes-temperatuur, oes-rypheid, geperforeerde sakke, veldhitte verwydering voor
verpakking, vertragingsperiodes voor en na verpakking, tydsduur van opberging, en die
verhoging van die opbergingstemperatuur, op die voorkoms van korrelbars en los korrels by
'Thompson Seedless' (Vitis vinifera Linnaeus) druiwe. Daar is ook ondersoek ingestel na
veranderings in afsnoering verwante faktore tydens korrel-ontwikkeling, en die invloed van vooren
na-oes toedienings van etileen inhibeerders op die ontwikkeling van los korrels by 'Waltham
Cross'tafeldruiwe.
Korrelbars is vererger deur 'Thompson Seedless' met hoë pulptemperature van ongeveer
29.5°C te verpak, veral indien dit in 'n riie-geperforeerde sak verpak is. Die voorkoms van
korrelbars kon tussen 80 en 90% verminder word deur 'Thompson Seedless' druiwe in
geperforeerde sakke te verpak, in plaas van nie-geperforeerde sakke. Geperforeerde sakke het
ook S02 skade op die druiwe verminder. Tog, as gevolg van betekenisvol meer vogverlies
vanaf druiwe in geperforeerde sakke as vanaf druiwe in nie-geperforeerde sakke, bestaan die
risiko van meer stingel-uitdroging en minder ferm korrels indien druiwe in geperforeerde sakke
verpak word. Optimale grootte en digtheid van perforasies moet bepaal word om korrelbars te
verminder, maar sonder oormatige vogverlies vanaf die druiwe en oormatige verlies aan S02.
Die invloed van oes-temperatuur en sak-tipe op los korrels was nie oortuigend nie. Gevorderde
oes-rypheid het die druif se weerstand teen korrelbars verhoog. Daarteenoor was druiwe wat té
ryp geoes is, meer gevoelig vir stingel-uitdroging en Botrytis bederf. Dit wilook voorkom of die
voorkoms van los korrels toeneem met gevorderde rypheid. Dus, om optimum kwaliteit na
opberging te verseker, moet 'Thompson Seedless' geoes word sodra hortologiese rypheid
bereik word, wat blyk om by 'n totale opgeloste vaste stof-inhoud (TOVS) van ongeveer 18°Brix
te wees.
Veldhitte verwydering voor verpakking, vir 1.5 uur by 19°C, het geen effek gehad op die
voorkoms van korrelbars en los korrels nie. 'n Vertragingsperiode voor verpakking het die los korrel-probleem vererger, alhoewel dit geen betekenisvolle invloed op die voorkoms van
korrelbars gehad het nie. Druiwe wat vir 12 uur voor verpakking vertraag is, het betekenisvol
meer los korrels en Botrytis bederf getoon, in vergelyking met druiwe wat slegs 'n
vertragingsperiode van 3 of 8 uur ondergaan het. Aangesien die afwesigheid van bederf die
belangrikste kwaliteits-vereiste vir tafeldruiwe is, is dit van kardinale belang om druiwe so gou as
moontlik na oes te verpak. Druiwe, verpak in nie-geperforeerde sakke, wat vir verskillende
periodes vertraag is voor geforseerde-lug verkoeling, het betekenisvolle verskille getoon
betreffende die voorkoms van korrelbars. Druiwe vertraag vir 18 ure voor verkoeling, het
betekenisvol meer korrelbars getoon, soos gemeet onmiddellik na die vertragingsperiode, in
vergelyking met druiwe wat slegs vir 6 of 12 ure vertraag was. Geen betekenisvolle verskille in
los korrels het voorgekom tussen druiwe wat verskillende vertragingsperiodes ondergaan het
nie. Om korrelbars te verminder, moet geforseerde-lug verkoeling so gou as moontlik na
verpakking van druiwe in nie-geperforeerde sakke toegepas word.
Twee opbergings-verwante faktore beïnvloed die voorkoms van korrelbars by 'Thompson
Seedless' druiwe tydens koelopberging, naamlik die tydsduur van opberging by -O.soC,asook 'n
styging in temperatuur vanaf -O.soC tot 1DoC. Korrelbars het feitlik liniêr toegeneem met
verlengde opberging by -O.soC. 'n Styging in temperatuur vanaf -O.SoCtot 1DoCop enige tydstip
gedurende die koelopbergingsperiode, het korrelbars verder vererger. Dus, om korrelbars by
'Thompson Seedless' tydens opberging tot die minimum te beperk, moet die tydsduur van
opberging so kort as moontlik wees, en moet die koue ketting regdeur die distribusie-proses
gehandhaaf word, vanaf inisiëring van verkoeling tot en met die uiteindelike verkoop van die
produk.
Die afsnoerings-potensiaal van druiwe, soos kwantitatief geïndekseer is deur meting van die
vrug-verwyderings-vermoë (VVV), het betekenisvol verander gedurende korrel-ontwikkeling van
'Waltham Cross' tafeldruiwe, vanaf 27 tot 111 dae na volblom (DNVB). Dit het getoon dat
'Waltham Cross' druiwe by sekere stadiums van vrug-groei meer gevoelig is vir korrel
afsnoering. By 27 DNVB, wanneer die korrels 'n gemiddelde deursnee van 6.6mm gehad het,
het die druiwe 'n betekenisvolle hoër potensiaal vir afsnoering getoon, in vergelyking met druiwe
wat op 'n latere stadium getoets is. 'Waltham Cross' is inherent geneig tot yl trosse met kaal
skouers, gevolglik sal enige afsnoering tydens korrel-ontwikkeling die probleem vererger. Dus
is dit van kardinale belang dat enige nadelige faktor, soos byvoorbeeld vogstres, vermy moet
word, veral gedurende periodes wanneer dit wil voorkom of 'Waltham Cross' baie vatbaar is vir
korrel afsnoering. Van al die parameters wat gemeet is, het vogverlies die beste korrelasie met
korrel afsnoering getoon. Druiwe wat 83 DNVB, by 'n TOVS van 12.3°Brix geoes is, het 'n betekenisvol hoër potensiaal vir korrel afsnoering getoon, in vergelyking met druiwe wat ryper
geoes is. Dus, deur 'Waltham Cross' druiwe by optimum rypheid te oes, by 'n TOVS van
ongeveer 16.4°Brix, kan korrelbars in 'n groot mate verminder word. Tydens verelson, wanneer
die metabolisme van die druiwe drasties verander, was daar gepaardgaande met die drastiese
toename in TOVS en die drastiese afname in totale titreerbare sure (TSS), ook 'n afname in
Voor-oes bespuitings met ReTain™, wat etileen sintese inhibeer, het geen potensiaal getoon
om los korrels by 'Waltham Cross' te verminder nie. 'n Na-oes behandeling met EthyIBloc®,
wat etileen werking inhibeer, het slegs korrel afsnoering in een van die seisoene effens
verminder.
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The effect of atmospheric and soil conditions on the grapevine water statusLaker, Mareli S. (Mareli Susan) 12 1900 (has links)
Thesis (MScAgric)--University of Stellenbosch, 2004. / ENGLISH ABSTRACT: Due to the extraordinary drought resistance of the grapevine, viticulture without
irrigation in the winter rainfall coastal areas of South Africa is a feasible and
commonly used practice. Wine quality is largely determined by the quality of the
grapes from which it is made. Grapevine physiology is affected both directly and
indirectly by water stress, which may vary according to soil type and prevailing
atmospheric conditions. The water status of the grapevine can affect grape
composition profoundly, either directly or indirectly, in either a positive or negative
way, depending on the degree as well as the duration of water stress. There are
three important factors involved in the development of water stress, namely the
transpiration rate, the rate of water movement from the soil to the roots, and the
relationship of soil water potential to leaf water potential. All three these factors are
affected by atmospheric and/or soil conditions.
In warm winelands such as South Africa (Western Cape), with a mediterranean
climate which is characterised by a hot, dry summer period, the most important
characteristic of soil is its ability to supply sufficient water to the grapevine during the
entire growing season. Leaf water potential (Ψl) has gained wide acceptance as a
fundamental measure of grapevine water status, and has been widely applied in
viticultural research. Shortly before dawn, Ψl approaches equilibrium with soil water
potential and reaches a maximum daily value.
The study formed an integral part of a comprehensive, multi-disciplinary research
project (ARC Infruitec-Nietvoorbij Project No. WW13/01) on the effect of soil and
climate on wine quality, which commenced in 1993 and will be completed in 2004.
This study was conducted during the 2002/03 growing season in two Sauvignon
blanc vineyards situated at Helshoogte and Papegaaiberg, both in the Stellenbosch
district, approximately nine kilometres apart. Two experiment plots, representing
contrasting soil types in terms of soil water regime, were selected in each vineyard.
At Helshoogte the two soils represented the Tukulu and Hutton forms, and the soils
at Papegaaiberg were of the Avalon and Tukulu forms.
The aim of this study was to determine the effect of atmospheric conditions and
soil water status on the level of water stress in the grapevines for each soil at each
locality, as well as the effect of grapevine water stress on yield and wine quality. This
was done by determining and comparing the soil water status, soil water holding
capacity of the soils and the evapotranspiration of the grapevines on the two different
soils, at each of the two localities differing in mesoclimate and topography. The
atmospheric conditions at the two localities during the 2002/03 season were also
determined and compared to the long-term average atmospheric conditions, and the
level of water stress of grapevines on each soil at each locality was measured. During the 2002/03 growing season, atmospheric conditions were relatively warm
and dry in comparison to the long-term averages of previous seasons. These
conditions accentuated the effects of certain soil properties that may not come
forward during wetter, normal seasons.
The usually wet Tukulu soil at Helshoogte was drier than expected during the
2002/03 season compared to the Hutton soil. Due to more vigorous growth on the
Tukulu soil, grapevines extracted more soil water early in the season, leading to a
low soil water matric potential and more water stress in the grapevines. Due to the
higher vigour, resulting in more canopy shading, and more water stress, the dominant
aroma in wines from the Tukulu soil was fresh vegetative. The Hutton soil maintained
consistency with regards to both yield and wine quality compared to previous
seasons. On the other hand the Tukulu soil supported a higher yield, but with lower
than normal wine quality.
The Avalon soil at Papegaaiberg maintained the highest soil water potential
towards the end of the season, probably due to capillary supplementation from the
sub-soil. Grapevines on the Tukulu soil at Papegaaiberg experienced much higher
water stress than ones on the other three soils, especially during the later part of the
season. This could be ascribed to a combination of factors, the most important being
the severe soil compaction at a shallow depth, seriously limiting rooting depth and
root distribution, which is detrimental to grapevine performance.
Both the soil water status and atmospheric conditions played important roles in
determining the amount of water stress that the grapevines experienced at different
stages. The air temperature and vapour pressure deficit throughout the season were
consistently lower at Helshoogte, the cooler terroir, compared to Papegaaiberg, the
warmer terroir. At flowering, Ψl was lower for grapevines at Helshoogte than at
Papegaaiberg, showing that diurnal grapevine water status was primarily controlled
by soil water content. The difference in grapevine water status between the two
terroirs gradually diminished until it was reversed during the post harvest period when
Ψl in grapevines at Papegaaiberg tended to be lower compared to those at
Helshoogte. The relatively low pre-dawn Ψl at Helshoogte indicated that the
grapevines were subjected to excessive water stress resulting from the low soil water
content. However, grapevines at Helshoogte did not suffer material water stress (i.e.
Ψl < -1.20 MPa) during the warmest part of the day, suggesting that partial stomatal
closure prevented the development of excessive water stress in the grapevines.
This suggests that low pre-dawn Ψl values do not necessarily imply that
grapevines will experience more water stress over the warmer part of the day, or visa
versa. This does not rule out the possibility that side-effects of partial stomatal closure, such as reduced photosynthesis, can have negative effects on grapevine
functioning in general. These results also suggest that measurement of diurnal Ψl
cycles at various phenological stages is required to understand and quantify terroir
effects on grapevine water status. / AFRIKAANSE OPSOMMING: Danksy die droogteweerstand van die wingerdstok is die verbouing van wingerde
sonder besproeiing ‘n praktiese en algemene verskynsel in die winterreënval-areas
van Suid-Afrika. Wynkwaliteit word grootliks bepaal deur die kwaliteit van die druiwe
waarvan dit gemaak word. Wingerdfisiologie word direk en indirek beïnvloed deur
waterstres, wat kan varieer volgens die grondtipe en die heersende atmosferiese
toestande. Die waterstatus van die wingerdstok beïnvloed druifsamestelling, direk of
indirek, en positief of negatief, afhangend van die graad en tydsduur van die
waterstres. Daar is drie belangrike faktore betrokke by die ontwikkeling van
waterstres, naamlik die transpirasietempo, die tempo van waterbeweging vanaf die
grond na die wortels, en die verhouding tussen die grondwatermatrikspotensiaal tot
blaarwaterpotensiaal. Al drie die faktore word beïnvloed deur die atmosferiese en/of
grondtoestande.
In warm wynboulande soos Suid-Afrika (Weskaap), met ‘n meditereense klimaat
wat gekarakteriseer word deur ‘n warm, droë somerperiode, is die belangrikste
eienskap van grond die vermoë om voldoende water aan die wingerdstok te verskaf
gedurende die hele seisoen. Blaarwaterpotensiaal (Ψl) het wye aanvaarding bekom
as die fundamentele meting van wingerstokwaterstatus, en word wyd toegepas in
wingerdkundige navorsing. Kort voor sonsopkoms, nader Ψl ‘n ewewig met die
grondwatermatrikspotensiaal en bereik ‘n maksimum daaglikse waarde.
Die studie vorm ‘n integrale deel van ‘n omvattende, multi-dissiplinêre
navorsingsprojek (ARC Infruitec-Nietvoorbij Projek No. WW13/01) op die effek van
grond en klimaat op wynkwaliteit, wat in 1993 in aanvang geneem het en in 2004
afgehandel sal word. Hierdie studie is uitgevoer gedurende die 2002/03 seisoen in
twee Sauvignon blanc wingerde geleë by Helshoogte en Papegaaiberg, beide in die
Stellenbosch distrik, ongeveer nege kilometer van mekaar. Twee eksperimentele
persele, elkeen verteenwoordigend van kontrasterende grondtipes in terme van
grondwaterregime, is geselekteer in elke wingerd. By Helshoogte word die twee
gronde verteenwoordig deur die Tukulu en Hutton grondvorms, en die gronde by
Papegaaiberg is van die Avalon en Tukulu vorms.
Die doel van die studie was om die effek van atmosferiese toestande en
grondwaterstatus op die wingerdstok se waterstatus vir elke grond by die twee
lokaliteite te bepaal, sowel as die effek van die wingerdstok se waterstatus op die
opbrengs en wynkwaliteit. Dit is gedoen deur die grondwaterstatus, die
grondwaterhouvermoë, sowel as die evapotranspirasie van die wingerdstokke op die
twee verskillende gronde by elk van die twee lokaliteite, wat verskil in mesoklimaat
en topografie, te bepaal en vergelyk. Die atmosferiese toestande by die twee
lokaliteite gedurende die 2002/03 seisoen is ook bepaal en vergelyk met die langtermyn gemiddelde atmosferiese toestande. Die vlakke van waterstres in
wingerdstokke op elke grond by elke lokaliteit is ook gemeet.
Gedurende die 2002/03 groeiseisoen, was die atmosferiese toestande relatief
warm en droog in vergelyking met die langtermyn gemiddeldes van vorige seisoene.
Hierdie kondisies aksentueer die effek van sekere grondeienskappe wat nie
noodwendig na vore kom gedurende normale, natter seisoene nie.
Die gewoonlike nat Tukulu grond by Helshoogte was droër as verwag gedurende
2002/03 in vergelyking met die Hutton grond. As gevolg van sterker groekrag op die
Tukulu grond, het wingerdstokke meer grondwater onttrek vroeg in die seisoen, wat
gelei het tot ‘n lae grondwatermatrikspotensiaal en meer waterstres in die
wingerdstokke. Die sterker groeikrag het meer beskaduwing van die lower asook
meer waterstres veroorsaak, wat gelei het daartoe dat die dominante aroma in wyne
vanaf druiwe op die Tukulu grond vars vegetatief was. Die Hutton grond het
bestendig gebly in terme van opbrengs en wynkwaliteit in vergelyking met vorige
seisoene. Daarteenoor het die Tukulu grond ‘n hoër opbrengs gelewer, maar met laer
as gewoonlike wynkwaliteit.
Die Avalon grond by Papegaaiberg het die hoogste grondwatermatrikspotensiaal
behou tot die einde van die seisoen, heelwaarskynlik a.g.v. kapillêre aanvulling
vanuit die ondergrond. Wingerdstokke op die Tukulu grond by Papegaaiberg het
heelwat meer waterstres ondervind as op die ander drie gronde, veral later in die
seisoen. Dit kan toegeskryf word aan ‘n kombinasie van faktore, die belangrikse
daarvan die erge grondkompaksie vlak in die grond, wat worteldiepte en
-verspreiding ernstig beperk het, wat op sy beurt nadelig is vir wingerdprestasie.
Beide die grondwaterstatus en atmosferiese toestande het ‘n belangrike rol
gespeel in die bepaling van die hoeveelheid waterstres wat die wingerdstok op
verskillende stadiums ondervind het. Die lugtemperatuur en waterdampdruktekort
was regdeur die seisoen laer by Helshoogte, die koeler terroir, as by Papegaaiberg,
die warmer terroir. Gedurende blom was die Ψl laer vir wingerdstokke by Helshoogte
as by Papegaaiberg, wat daarop wys dat daaglikse wingerdstok waterstatus
hoofsaaklik deur die grondwaterinhoud bepaal was. Die verskil in wingerdstok
waterstatus tussen die twee terroirs het geleidelik verminder totdat dit omgekeer was
gedurende die na-oes periode toe Ψl in wingerdstokke by Papegaaiberg geneig het
om laer te wees in vergelyking met die by Helshoogte. Die relatiewe lae voorsonop Ψl
by Helshoogte het daarop gedui dat die wingerdstokke aan oormatige waterstres
onderwerp was. Die wingerdstokke by Helshoogte het egter nie materiële waterstres
(i.e. Ψl < -1.20 MPa) gedurende die warmste gedeelte van die dag ondervind nie, wat
aandui dat gedeeltelike huidmondjiesluiting plaasgevind het om die ontwikkeling van
oormatige waterstres te verhoed.Dit dui aan dat lae voorsonop Ψl waardes nie noodwendig impliseer dat
wingerdstokke meer waterstres gedurende die warmste gedeelte van die dag sal
ondervind nie, of visa versa. Dit sluit nie die moontlikheid uit dat negatiewe neweeffekte
van gedeeltelike huidmondjiesluiting, soos ‘n vermindering in fotosintese, ‘n
negatiewe effek kan hê op die wingerdstok se funksionering in die algemeen nie.
Hierdie resultate stel voor dat die meting van daaglikse Ψl siklusse gedurende
verskeie fenologiese stadia benodig word om die effek van terroir op die wingerdstok
se waterstatus te verstaan en te kwantifiseer.
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Interaction of water deficit, canopy modification and ripening : effect on the phenolic and colour composition of Shiraz grapes & subsequent wineVan Noordwyk, Marelize 12 1900 (has links)
Thesis (MScAgric)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: Phenolic compounds are important quality indicators of a red wine, as they can contribute to the
colour of a young red wine, colour stability during ageing as well as astringency, bitterness,
body and overall mouthfeel properties. Wine composition is commonly influenced by
winemaking and viticultural practices.
In South Africa it often happens that vines are excessively vigorous, resulting in canopies
that are too dense, which in turn could have a negative effect on the quantity and quality of the
grapes produced. Viticultural practices such as judicious canopy management and irrigation are
designed to control vine vigour and yield, thus improving fruit ripening and colour development.
Artificial shading and water deficit have been reported to have an influence on the sensory
properties of red wine as well as on the flavonoid composition. These effects are dependent on
a number of factors, however, including the season, cultivar, light intensity, and the extent and
timing of water deficit.
There is limited research on the possible interactive effects of grapevine water deficits and
canopy manipulation on grape and wine flavonoid composition in Shiraz, as well as the
relationships between berry and wine composition. We thus investigated the effect of canopy
reduction in combination with water deficit on the phenolic and colour composition of Shiraz
grapes at different levels of ripeness, and in their corresponding wines after alcoholic and
malolactic fermentation as well as after six months’ ageing. This study found that it is possible to
improve the phenolic composition of grapes and wine by shoot removal, and some of the
tendencies in the wines were also observed after the ageing period. If the shoot removal is not
performed at a very early stage, sunburn damage can occur and this will result in berries with a
lower mass and volume at harvest due to excessive exposure without the berry having adapted
to the imposed conditions.
Harvesting at different ripeness levels also affected the chemical and phenolic composition
of the grapes and resulting wines. The water deficit effect on most phenolic parameters
measured in the grapes and wine was not as prominent as that of the canopy manipulation
treatment.
This study improved our understanding of how an improvement in the canopy microclimate
of Shiraz could be reflected in the phenolic composition of wines, along with a potentially
important effect of harvesting date. On this basis it may be possible to attain a specific wine
style. Harvesting at a ripe stage, for example, could result in the production of wines with higher
colour density and astringency, while unripe grapes could result in wines with higher levels of
perceivable fresh berry attributes. In particular, canopy reduction could increase the astringency
and body of wines made from grapes subjected to water deficit. / AFRIKAANSE OPSOMMING: Fenoliese verbindings is belangrike kwaliteitsparameters van rooiwyn, aangesien dit kan bydra
tot die kleur van ‘n rooiwyn, kleurstabiliteit tydens veroudering sowel as frankheid, bitterigheid
en mondgevoel. ‘n Wyn se fenoliese samestelling word algemeen bepaal deur wynmaak- en
wingerdkundige praktyke.
In Suid-Afrika gebeur dit gereeld dat wingerde uitermatig groeikragtig is, wat lei tot te digte
lower wat sodoende ‘n negatiewe effek op kwantiteit en kwaliteit van die druiwe wat
geproduseer word, het. Wingerdkundige praktyke soos oordeelkundige lowerbestuur en
besproeiing is ontwerp om wingerdstokke se groeikrag en opbrengs te beheer, en sodoende
vrugrypwording en kleurontwikkeling te verbeter.
Kunsmatige beskaduwing en waterstres is gerapporteer om ‘n invloed te hê op die
sensoriese eienskappe van rooiwyn sowel as op die flavonoïedsamestelling. Hierdie effekte is
egter afhanklik van ‘n verskeidenheid faktore, insluitende die seisoen, kultivar, ligintensiteit en
die mate en tyd van waterstres toegepas.
Daar is beperkte navorsing op die moontlike interaktiewe effekte van waterstres en
lowermanipulasie op die druif en wyn flavonoïedsamestelling in Shiraz, sowel as die
verhoudings tussen druif en wyn samestelling. Ons het dus die effekte van lowerbestuur in
kombinasie met waterstres op die fenoliese en kleursamestelling van Shiraz druiwe by
verskillende rypheidsvlakke ondersoek, asook in hul ooreenstemmende wyne na alkoholieseen
appelmelksuurfermentasie sowel as na ses maande veroudering. Hierdie studie het gevind
dat dit moontlik is om die fenoliese samestelling van druiwe en wyn deur lootverwydering te
verbeter, en sommige van die tendense is ook waargeneem in die wyn na die
verouderingsperiode. Indien lootverwydering nie toegepas word by ‘n baie vroeë stadium nie,
kan sonbrand voorkom en dit kan lei tot korrels met ‘n laer massa en volume by oes as gevolg
van oormatige blootstelling sonder dat die korrel aangepas het by die spesifieke kondisies.
Oes by verskillende rypheidsvlakke affekteer ook die chemiese en fenoliese samestelling
van die druiwe en ooreenstemmende wyne. Die waterstreseffek op meeste van die fenoliese
parameters gemeet in druiwe en wyn was nie so prominent soos dié van die lowermanipulasie
behandeling nie.
Hierdie studie het ons begrip verbeter van hoe ‘n verbetering van die lower mikroklimaat
van Shiraz gereflekteer kan word op die fenoliese samestelling van die wyn, saam met ‘n
potensiële belangrike effek van oesdatum. Op grond van hierdie basis is dit dus moontlik om ‘n
spesifieke wynstyl te verkry. Oes by ‘n ryp stadium, byvoorbeeld, kan die produksie van wyn
met ‘n hoër kleurdigtheid en frankheid tot gevolg hê, terwyl onryp druiwe wyne met hoër vlakke
van waarneembare vars bessiekenmerke tot gevolg kan hê. Verlaging van lowerdigtheid kan
veral die frankheid en mondgevoel van wyne gemaak van druiwe blootgestel aan waterstres,
verbeter.
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Isolation of grapevine promoters with special emphasis on the vacuolar pyrophosphataseVenter, Mauritz 04 1900 (has links)
Dissertation (PhD)--University of Stellenbosch, 2004. / ENGLISH ABSTRACT: Understanding the complex nature of grapevine molecular biology is of great importance for
viticulturists. Progress in the elucidation of key events on a genetic level could provide further
insight into the underlying cues responsible for the precise control of physiological and
metabolic changes during a specific condition such as fruit development. The use and analysis
of molecular ‘tools’, such as promoters controlling the site and level of gene activity, could
assist in the understanding of grapevine biology and serve as a platform for the future design
and development of recombinant DNA protocols and strategies for Vitis vinifera L.
A high-throughput gene expression system, cDNA-AFLPs, was successfully used to analyse
large-scale transcriptional activity during berry ripening. Candidate cDNA fragments were
selected on the basis of desired expression patterns and/or known gene function for subsequent
promoter isolation. From three candidate cDNAs selected, the promoter of a gene encoding
vacuolar pyrophosphatase (V-PPase) was isolated for computational and comparative analyses.
Promoter activity was evaluated on a transient level using the green fluorescent protein (GFP)
reporter gene. Comparative integration has allowed for putative correlation of cis-elements,
acting as receptors within promoter regions, to regulate V-PPase gene expression in response to
development, environmental stress and tissue-specificity.
In this study, integration of genetic data have advanced the understanding and transcriptional
role of a key enzyme (V-PPase) during grape ripening. Although never a replacement for
experimental verification, this integrative strategy of combining gene expression profiles with
bioinformatics and regulatory data will greatly assist in further elucidation of various other key
components and regulatory cues associated with grapevine molecular biology. This study has
allowed us to use molecular tools that could assist in gaining further insight into genetic
complexities and could serve as a platform for a more refined genetic manipulation strategy in
Vitis vinifera L. / AFRIKAANSE OPSOMMING: Begrip van die komplekse aard van wingerd molekulêre biologie is van groot belang vir wingerdkundiges. Vooruitgang in die begrip van belangrike gebeurtenisse op ń genetiese vlak behoort verdere insig in die onderliggende instruksies vir die noukeurige beheer van fisiologiese en metaboliese veranderinge tydens ń spesifieke kondisie soos vrug rypwording te bevorder. Die gebruik en analise van molekulêre ‘instrumente’ soos promoters, wat die posisie en vlak van geen aktiwiteit beheer, kan bydra tot n beter begrip van wingerd biologie en sodoende dien as ń platform vir die toekomstige ontwerp en ontwikkeling van rekombinante DNS (deoksiribonukleiensuur) protokolle en strategieë vir Vitis vinifera L. ń Hoë-kapasiteit geen uitdrukkings sisteem, nl. kDNS-AFLPs (komplementêre deoksiribonukleiensuur- geamplifiseerde fragment lengte polimorfisme), is suksesvol gebruik vir die analise van grootskaalse transkripsionele aktiwiteit tydens druif rypwording. Kandidaat kDNS fragmente is geselekteer, gebaseer op verlangde uitdrukkings-patrone en/of bekende geen funksie vir daaropvolgende promoter isolering. Van drie geselekteerde kandidaat kDNS fragmente, is die promoter van ń geen wat vakuolêre pirofosfatase (V-PPase) kodeer geïsoleer vir rekenaar- en vergelykende analise. Promoter aktiwiteit is op ń nie-stabiele vlak deur die gebruik van ń groen-fluoresserende proteien (GFP) verklikker geen geëvalueer. Vergelykende integrering het dit moontlik gemaak om veronderstelde korrelasies van cis-elemente, wat as reseptore binne ń promoter area dien, en die regulering van V-PPase geen uitdrukking, in reaksie tot ontwikkeling, omgewings stres en weefsel-spesifisiteit, te maak. Tydens hierdie studie, het die integrering van genetiese data gehelp om die transkripsionele rol van ń belangrike ensiem (V-PPase) tydens druif rypwording beter te verstaan. Alhoewel dit nooit ń plaasvervanger vir eksperimentele bewyse sal wees nie, kan hierdie gëintegreerde strategie, wat die kombinasie van geen-uitdrukkingsprofiele met bioinformatika en regulatoriese data behels, grootliks bydra om verskeie ander belangrike komponente en regulatorieseaanwysings geassosieërd met wingerd molekulêre biologie te ontrafel. Hierdie studie het verdere insig in genetiese kompleksiteite verleen, en kan nou dien as ń platform vir ń meer presiese genetiese manipulering strategie in Vitis vinifera L.
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Hardiness studies of some French American hybrid grapesGhosheh, Najati Saleh. January 1956 (has links)
Call number: LD2668 .T4 1956 G46 / Master of Science
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WingerdoorentingstudiesOrffer, C. J. (Christian Johannes) 12 1900 (has links)
Thesis (MScAgric)--Stellenbosch University, 1954. / No Abstract Available
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Phosphorus fractions, movement and fertilizer requirements of grapes grown on White House soil.Janat, Mohamad Mussaddak. January 1989 (has links)
A two-year fertilizer study on a mature vineyard of Vita vinifera, C. V. Cabernet Sauvignon and Sauvignon blanc, has been conducted on White House sandy loam (fine, mixed, thermic Ustollic Haplargid), at Page Ranch, International Agricultural Center. Furthermore, eleven different varieties grown at Page Ranch and treated with different levels of nitrogen fertilizer were tested for total P content in plant tissue and NO₃-N. Moreover, in another site with similar soil, a Cabernet Sauvignon grown at the Vina Sonoita Vineyard was treated with both soil and foliar applications of P fertilizer, and was tested for total P content in plant tissue. Soil phosphorus (P) fractions of the White House soil were determined in order to evaluate the various forms of soil P and determine the most important form which contributes most to the availability index. The objectives of this study were to study the various inorganic P forms of White House soil, compare two methods of extracting available P (Olsen and Bray P.), and examine the relationships between soil pH, extractable Al, Fe, Mn, and Zn with the availability index of soil P. Furthermore, the effect of P rates and placement on the P status of plant tissue, grape yield, wine quality and petiole-P to blade-P ratio had been investigated. Three different placements of surface, 25 and 50 cm depth at rates of 88 g of P and 80 g of N per vine, were in RCB design in 1987. In 1988, three P rates of 0, 88, and 176 g of P and 207.5 g N per vine, and the two mentioned varieties CS and SB were arranged in RCB design with factorial type. The results showed that placements did not have a significant effect of P status in plant tissue and grape yield. Yet grapes showed a significant response to P fertilizer in terms of increasing P content in plant tissues and grape yield. Petiole P to Blade P ratios were calculated for the CS, and SB grown at Page Ranch, as well as for CS grown at Sonoita vineyard. This ratio is a good indicator for diagnosis of P status in a given vineyard. Nitrogen stress had its clear and profound effect on P content of grape petioles.
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Effects of vine architecture on water use, microclimate, fruit composition, and yield of Vitis vinifera L. 'Petite Sirah' grapevines.Morsi, Taher Hussein. January 1991 (has links)
Effects of trellising on water use, absorption of photosynthetically active radiation (PAR, 400 to 700 nm wavelength) by foliage and potentially by fruit, fruit composition, and yield were studied in 1988 under semi-arid conditions on field-grown Vitis vinifera L. 'Petite Sirah' grapevines in a mature vineyard. The positioning of shoots on trellises resulted in canopies that were (1) positioned vertically (vertical canopy), (2) positioned in a "V" pattern with sides inclined 60° from horizontal (inclined canopy), and (3) inclined toward the vineyard floor (standard canopy). Seasonal water use values determined from neutron scattering data were 393 ± 61, 554 ± 73, and 455 ± 57 mm for the standard, vertical and inclined canopies, respectively. On average, about 50% of seasonal water consumption occurred between fruit set and filling stages for each type of canopy. Average crop factors (ratio of actual to reference crop evapotranspiration) of 0.383, 0.540 and 0.444 were for the period bud burst to harvest for standard, vertical and inclined canopy systems, respectively. The diurnal water use patterns of the three trellising canopies were very similar when measured by either the heat pulse technique or by porometer. The average daily heat pulse velocity (HPV) for selected vertical, inclined and standard canopies for 6 days were 8.77, 7.58 and 6.85 cm h⁻¹, respectively. The HPV technique indicated that the average daily water use of the whole plant was 0.227, 0.192 and 0.137 kg/m² leaf area/d for standard, vertical and inclined canopies, respectively. The daily average transpiration rates as measured by the HPV technique were 32, 31, and 25% higher than the average transpiration rates estimated from porometer data for standard, vertical and inclined canopies, respectively. Stomatal conductances of the vertical and inclined canopies were 20 and 40%, respectively, below that of standard canopy. PAR absorption by foliage during mid-day was highest in the standard trellis, and lowest in the inclined trellis. PAR potentially available for absorption by fruits was lowest in the standard trellis, and highest in the inclined trellis. In both inclined and vertical canopies, the average sunfleck values were 26%, but was only 2% in the standard canopy. Analysis of fruit composition at harvest revealed that total dissolved solids (°Brix) was significantly higher in the inclined trellis than for the vertical trellis or the standard trellis. The inclined trellis resulted in the highest alcohol content of wine. Per vine yields did not differ significantly among the three trellis systems. Overall, the standard trellis was optimum because grapevines consumed less water and produced a shading which protected the fruit from direct solar radiation.
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BUDBREAK AND FRUITFULNESS OF DESERT GRAPES (VITIS VINIFERA L.) (DEFOLIATION, PRUNING, HORMONES).DUARTE, MIGUEL ANGEL. January 1983 (has links)
Dinitro-ortho-cresol (500, 1000, and 2000 ppm) and dormant oil (2.5, 5.0, and 10%) were applied to Thompson Seedless and Perlette grapevines alone and in combination to enhance budbreak and fruitfulness. Applications were made immediately after pruning. Use of these materials during the winter, immediately after pruning, had no effect on either fruitfulness or budbreak in Perlette or Thompson Seedless. Thompson Seedless cuttings collected in August were exposed to six temperatures (7, 13, 18, 24, 29 and 35 C) for five time periods (2, 4, 6, 8 and 12 weeks). After temperature treatment the cuttings were planted in the greenhouse at 24 (+OR-) 1 C. Cuttings exposed to 24, 29 and 35 C broke sooner than those exposed to 7, 13, 18 C at all time periods. The percentage of the bud openings of cuttings at 29 C for a period of 2 and 4 weeks was 95% and 100% respectively. The optimum temperature for budburst was 29 C. Gibberellic acid, Thiourea, dinitro-ortho-sec-butyl-phenol (DINOSEB), potassium nitrate and Endothal were used at two concentrations alone and in combination, to break rest of Thompson Seedless buds. Thiourea at 2% and DINOSEB at 1000 ppm alone were the only treatments which gave a higher percentage of bud opening after 20 forcing days at 25 (+OR-) 1 C temperature. Similar results were obtained from cuttings taken in both winter and summer. Three times after harvest, Perlette and Thompson Seedless were defoliated using the senesce enhancer Endothal. Defoliation times (4, 8, and 12 weeks) after harvest were used. In half of the treatments, regrowth was controlled with Endothal. Gibberellic acid (1000 ppm) Thiourea (2%) and DINOSEB (2000 ppm) were applied at the time of defoliation. The four- and twelve-week defoliation periods with new vine growth controlled for improving budbreak and fruitfulness were best. Growth regulators did not improve the defoliation treatments. The best treatments hastened budbreak by 10 days, more than doubled vine fruitfulness, and increased sugar content in berries resulting in a 10-day earlier harvest than in the control. Results were similar in both Thompson Seedless and Perlette. Thompson Seedless and Cardinal vines grown under Arizona desert conditions were defoliated 4 weeks after harvest with 2000 ppm Endothal. Two weeks later they were pruned and treated with 1000 ppm gibberellic acid, 2% Thiourea, and 1000 ppm DINOSEB. Cardinal and Thompson Seedless vines produced a second commercial crop in December of the same year. Thiourea (2%) and 1000 ppm DINOSEB did not have a significant effect; however, 1000 ppm Gibberellic acid reduced the number of clusters per vine.
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Nutritional Status of Wine Grap Cultivars Grown in Southern ArizonaKilby, Michael W. 09 1900 (has links)
Ten winegrape vineyards consisting of different cultivars were leaf petiole sampled at bloomtime. Petioles were analyzed and results composited for the survey. There were indications that boron, iron, nitrogen and phosphorus were nutrients where potential problems (deficiencies) were likely to occur. This survey supplied information for the basis of developing a monitoring program on an annual basis.
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