Thesis (MSc)--Stellenbosch University, 2002. / ENGLISH ABSTRACT: The cultivation of table grapes in the warmer areas of South Africa, indeed worldwide, is
complicated by rest breaking problems in spring due to delayed budbreak. In order to
overcome these problems rest breaking agents, mainly hydrogen cyanamide, are applied.
However, instead of alleviating the problem, additional problems such as uneven
budbreak and reduced production are often induced. This study was initiated to further
understand the physiological processes occurring during budbreak and how the
application of hydrogen cyanamide influences these processes. The following aspects
were investigated in this study:
a. The effect of hydrogen cyanamide on tissue cytokinin (specifically zeatin
riboside) levels of Sultanina table grape vines after application at different times before
natural budbreak was studied over two seasons.
In 1997, hydrogen cyanamide was applied at three weeks before induced
budbreak and in 1998 at six weeks before induced budbreak. One year-old canes were
sampled weekly after hydrogen cyanamide application, divided into distal and proximal
sections, then further divided into buds, bark and wood tissues and the zeatin riboside
(ZR) levels determined. A relatively high amount of chilling coupled to late hydrogen
cyanamide application in 1997 led to a large effect on ZR release, but did not lead to
significant shifting of the budbreak pattern. Zeatin riboside peaks were observed in buds,
internode wood and bark of treated vines compared to control vines. The peaks were
higher in distal portions compared to proximal portions in all tissues. The relatively lower
chilling and earlier application of hydrogen cyanamide in 1998 had a larger effect on the
budbreak pattern while the bud ZR peak was shifted earlier. The distal portion bud ZR
. peak was again higher than the proximal portion bud ZR peak. In 1997, as sampling was
not initiated early enough, bud ZR peaks were only observed after budbreak, while in
1998 bud ZR peaks were observed before and after budbreak. The effect of these ZR
increases on the development of inflorescence primordia, subsequent bunch
development and ultimately production, are discussed.
b. Free xylem sap was sampled at cane and spur pruned lengths from unpruned
canes of Sultanina from budswell until after budbreak in 1999 and from three table
grape cultivars, i.e Sultanina, Alphonse Lavalleé and Sunred Seedless, in 2001 and ZR
levels determined. The ZR levels in the buds of these three table grape cultivars, pruned
to different cane lengths were also determined. One year old canes of these cultivars,
were each pruned to long canes (14 buds) and short spurs (2 buds). The ZR content in
buds of these canes at distal and proximal positions were determined weekly from
budswell until after budbreak in 1999. Xylary ZR peaks occurred before 50% budbreak. Spur xylary ZR levels of all
three cultivars followed a similar pattern, although at lower ZR levels than that of the
canes. This is similar to previous studies on xylary ZR levels of apple shoots. The high
levels of free ZR found in xylem sap at the distal portions of canes support the
hypothesis of a cumulative ZR build-up effect as cane length increases. Spur pruning
resulted in earlier budbreak and a higher final budbreak than cane pruning. The proximal
portions of shoots, whether spur pruned or the proximal portions of canes, showed
elevated ZR levels in all cultivars. This difference in ZR levels in bud tissue of different
portions of the cane would suggest a difference in ZR consumption or turnover.
The results of this study have important management implications for the cultivation of
vines in warmer areas in which hydrogen cyanamide is used to alleviate budbreak
problems. / AFRIKAANSE OPSOMMING: Die verbouing van tafeldruiwe in die warmer gebiede van Suid-Afrika, soos straks
wêreldwyd, word bemoeilik deur rusbreekprobleme in die lente weens vertraagde bot.
Rusbreekmiddels, meestal waterstofsiaanamied, word gevolglik toegedien om hierdie
probleme te probeer oorkom. In plaas van opheffing van die probleem, veroorsaak
hierdie toedienings somtyds addisionele probleme soos ongelyke bot en verlaagde
produksie. Hierdie studie is aangepak om die fisiologiese prosesse wat tydens bot
plaasvind, beter te verstaan, asook hoe die toediening van waterstofsiaanamied hierdie
prosesse beïnvloed. Die volgende is in hierdie studie ondersoek:
a. Die invloed van waterstofsiaanamied op lootweefsel sitokinien (naamlik zeatin
ribosied, ZR) vlakke van 'n Sultanina tafeldruif wingerd is oor twee seisoene ondersoek
na toediening op verskillende tye voor bot.
Waterstofsiaanamied is in 1997 drie weke en in 1998 ses weke voor
geïnduseerde bot toegedien. Een jaar oue lote is weekliks gemonster na
waterstofsiaanamied toediening, verdeel in apikale en basale gedeeltes en verder verdeel
in ogies, bas en houtweefsel en die ZR vlakke bepaal. Relatief hoër vlakke koue, gekoppel
met later watersiaanamied toediening het in 1997 tot 'n groot effek op ZR vlakke gelei,
maar het nie die botpatroon wesentlik verskuif nie. Zeatin ribosied pieke is waargeneem
in ogies, internode hout en bas van behandelde wingerd in vergelyking met kontrole
wingerd. Die pieke was hoër in apikale gedeeltes in vergelyking met basale gedeeltes in
alle weefsels. Die relatief laer koue en vroeër toediening van waterstofsiaanamied in 1998
het 'n groter effek op die botpatroon gehad, terwyl die ogie ZR piek vroeër geskuif is. Die
apikale gedeelte se ogie ZR piek was weereens hoër as die basale gedeelte se ogie ZR
piek. Monstering was nie vroeg genoeg begin in 1997 nie, aangesien ogie ZR pieke slegs
na bot waargeneem is, terwylogie ZR pieke in 1998 voor en na bot waargeneem is. Die
effek van hierdie verhoging in ZR vlakke op die ontwikkeling van blom primordia,
daaropvolgende tros ontwikkeling en uiteindelik produksie, is bespreek.
b. Vry xileemsap is gemonster van langdraer en kortdraer gedeeltes van
ongesnoeide lote van Sultanina vanaf ogieswel tot na bot in 1999 en vanaf drie tafeldruif
kultivars, naamlik Sultanina, Alphonse lavalleé en Sunred Seedless, in 2001 en die ZR
vlakke bepaal. Die ZR vlakke van ogies van hierdie drie kultivars, gesnoei tot verskillende
lootlengtes is ook bepaal. Eenjarige lote van hierdie kultivars is gesnoei tot langdraers
(14 ogies) en kortdraers (2 ogies). Die ZR vlakke in ogies geleë op apikale en basale
gedeeltes van hierdie lote is weekliks in 1999 bepaal vanaf ogieswel tot na bot
Xileemsap ZR pieke is waargeneem voor 50% bot. Kortdraer xileemsap ZR
vlakke het 'n soortgelyke patroon as die langdraers gevolg vir al drie kultivars, alhoewel teen laer ZR vlakke as die langdraers. Hierdie waarneming is soortgelyk aan vorige
studies op xileemsap ZR vlakke van appel lote. Die hoë ZR vlakke gevind in die xileemsap
van die apikale gedeeltes van lote ondersteun die hipotese van 'n kumulatiewe opbou van
ZR soos die lengte van die loot toeneem. Die snoei van lote as kortdraers het gelei tot
vroeër bot en 'n hoër finale bot persentasie as die snoei van langdraers. Die basale
gedeeltes van lote het verhoogde ZR vlakke in al drie kultivars getoon, onafhanklik van
die feit dat dit vanaf die kortdraer of die basale gedeelte van 'n langdraer was. Hierdie
verskil in ZR vlakke in ogie weefsel van verskillende gedeeltes van die loot impliseer 'n
verskil in ZR verbruik of omset.
The resultate van hierdie studie het belangrike bestuursimplikasies vir die verbouing van
wingerd in warmer gebiede, waar waterstofsiaanamied gebruik word om botprobleme te
oorkom.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/52617 |
| Date | 03 1900 |
| Creators | Lombard, Petrus Johannes |
| Contributors | Bellstedt, D. U., Cook, N. C., Stellenbosch University. Faculty of Science. Dept. of Biochemistry. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | Unknown |
| Type | Thesis |
| Format | 119 pages : illustrations |
| Rights | Stellenbosch University |
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