Thesis (MscAgric (Horticulture))--University of Stellenbosch, 2006. / Rind colour is one of the main cosmetic preferences consumers use when purchasing citrus (Citrus spp.) fruit. To enhance the cosmetic quality of citrus fruit, attempts were made to stimulate preharvest chlorophyll degradation and carotenoid biosynthesis to obtain a deeper, more uniform, orange rind colour in early-maturing citrus cultivars. As part of a larger study to stimulate rind colour enhancement, an initial study was conducted on ‘Eureka’ lemon [C. limon (L.) Burm. f.] nursery trees to determine the concentration of various gibberellin biosynthesis inhibitors required to obtain a biological response in citrus trees, as measured by vegetative growth. Thereafter, different concentrations of prohexadione-calcium (ProCa; Regalis®) were applied at various stages of fruit development on early-maturing citrus cultivars to establish the concentration and timing of ProCa required to improve rind colour by enhancing chlorophyll degradation and carotenoid biosynthesis. In addition, a search to enhance rind colour development of early-maturing citrus cultivars was conducted by screening various nutritional, hormonal and possible physiological stress-inducer products and some combination treatments thereof. Multiple applications of gibberellin biosynthesis inhibitors on ‘Eureka’ lemon nursery trees significantly reduced internode length and hence vegetative growth. Regalis® applied at 4 to 8 g·L-1 and Sunny® (uniconazole) applied at 10 to 20 mL·L-1 had the greatest effect in reducing internode length, and were therefore identified as potential candidates for further field studies to test their effect on rind colour enhancement of citrus fruit. The late, double applications (6 plus 3 weeks before anticipated harvest) of ProCa applied at 400 mg·L-1 consistently improved rind colour of all Citrus spp. tested. However, these effects were more pronounced after harvest, as ethylene degreening and cold-storage stimulated additional chlorophyll degradation, unmasking the carotenoids, resulting in overall better coloured fruit. In most instances in this study, ProCa stimulated chlorophyll degradation allowing the underlying carotenoids to be expressed. Therefore, the improvement of rind colour of citrus fruit following the application of a gibberellin biosynthesis inhibitor (400 mg·L-1 ProCa applied 6 plus 3 weeks before harvest) supports the hypothesis that there may be a relationship between vegetative vigour and rind colour development of citrus fruit. Preharvest applications of boric acid, Thiovit® (elemental sulphur), ammonium thiosulphate (ATS) and half the recommended rate of Ethrel® (48% ethephon) in combination with Thiovit® and ATS stimulated chlorophyll degradation in both orange- and yellow-rinded fruit, and ColourUp® (neutralised calcium carbonate) and Figaron® (ethyclozate) stimulated chlorophyll degradation only in orange-rinded fruit. Boric acid and the Thiovit®-ATSEthrel ® combination treatment stimulated carotenoid biosynthesis in orange-rinded fruit, thereby improving the carotenoid to chlorophyll ratio. The screening of chemical products which stimulate chlorophyll degradation in combination with chemical products which stimulate carotenoid biosynthesis warrants further evaluation. Worldwide, research on rind colour improvement has received attention for several decades, particularly during the 1980s. Yet, rind colour still remains a problem at the beginning of certain seasons. In the present study, the approach to improving rind colour was to manipulate rind pigments through the reduction of vegetative vigour, which was hypothesised to be an antagonist of chloro-chromoplast transformation. To this end, the preharvest application of prohexadione-calcium stimulated chlorophyll degradation and carotenoid biosynthesis in citrus fruit rinds. Furthermore, preharvest applications of various chemical products provides a novel approach to stimulate chlorophyll degradation and carotenoid biosynthesis. Together, the results of this study provide potential commercial treatments that will result in deeper, more uniform orange rind colour, thereby meeting consumer needs.

Thesis (MscAgric (Horticulture))--University of Stellenbosch, 2006. / Fruit quality, and especially eating quality, of nectarines has become very important to markets and consumers in recent years. Pre- and post harvest factors that influence the eating quality of nectarines were studied to optimise fruit quality at harvest and to maintain this quality during export. This will ensure good returns for a producer and will maximise his profit. The influence of the variables canopy position, initial fruit size and bearing position was studied to determine the variation in fruit quality within a nectarine tree. ‘Red Jewel’ and ‘Ruby Diamond’ fruit from the upper part of the tree canopy had significantly higher total soluble solids (TSS). Fruit position on the shoot does not seem to play a significant role in fruit quality for ‘Red Jewel’ nectarines, which will allow producers to leave more than one fruit per bearer if necessary. Fruit thinning is an important means to improve fruit size and quality in ‘Red Jewel’, but poor thinning can cause extreme variability in size and quality. Fruit that were small at thinning remained significantly smaller, weighed less, had lower sugars and higher acids at harvest. If it is possible to reduce the variation in size at thinning, fruit will be much more homogenous at harvest. The effect of pre-conditioning (PC) prior to storage and controlled atmosphere (CA) storage was evaluated on ‘Red Jewel’ and ‘Spring Bright’ nectarines. Free juice percentage was determined at the end of a simulated export protocol. The severity of woolliness differed between the two seasons for both nectarine cultivars. PC, to a firmness of 6 kg, followed by regular atmosphere (RA) storage increased percentage free juice significantly in ‘Spring Bright’ and ‘Red Jewel’ nectarines. However, a PC protocol for each cultivar and each producer must be determined beforehand to ensure fruit quality. CA storage is another technique that can be used to prevent the development of chilling injury (CI) symptoms. Both ‘Spring Bright’ and ‘Red Jewel’ showed an increase in percentage free juice with the use of CA storage during both seasons.The eating quality of nectarines depends on the composition of the individual sugars and organic acids and the ratio between them. Sucrose, fructose, glucose and sorbitol were found to be the major sugars in all evaluated nectarine cultivars. Sucrose was the dominant sugar in all cultivars at optimum maturity. The three main organic acids in nectarine cultivars were malic, citric and quinic acid, with malic acid being dominant at optimum maturity. Small amounts of shikimic, fumaric and succinic acid were also observed. It was evident that cultivars differ in the composition of sugar and organic acids at optimum maturity, especially the standard acid cultivars and the new low-acid cultivars. Individual sugars and organic acids in cultivars also differ in how they react during storage.

Thesis (MscAgric (Horticulture))--University of Stellenbosch, 2006. / Protea, Leucadendron and Leucospermum belong to the Proteaceae family. These three genera form an important part of the floriculture industry in South Africa and are commonly used as fresh cut flowers or dried flowers for both the local and international market. The distribution of macro and micro - nutrients was investigated in Protea ‘Cardinal’ using rooted cuttings grown from October 2001 to March 2002. The plants were divided into 1st flush leaf and stem, 2nd flush leaf and stem, basal leaf and basal stem, roots and the flower bud. These tissues were analysed to determine N, P, K, Ca, Mg, Fe, S, Na, B and Mn concentration. Results indicated that N decreased over time in all tissues and accumulated more in leaves than in stems. P in leaves and stems increased with time, while K increased in leaf tissues and remained stable in stem tissue. Ca did not change in young leaves but was high in old leaves. Mg in leaves increased but in basal stem, 1st flush stem and roots Mg decreased over time. Fe in leaves and roots increased with time and not a less significant change occurred in stems. In most tissues, B and Na decreased with time. S increased in leaves and decreased in stems with time. Mn was relatively stable in most tissues except in basal leaves where it increased. Nutrient concentration in tissues, especially in leaves, showed no distinct pattern in the distribution of nutrients. Eleven cultivars from the three genera, namely Protea, Leucadendron and Leucospermum, were used to develop deficiency symptoms of macro - nutrients by using different nutrient compositions. The plants were grown in 20cm pots from December 2002 to September 2003. The eleven cultivars were chosen because of their high market value. Visual symptoms were recorded in two stages with a five - month interval for each stage. The first stage was recorded from December 2002 to April 2003 and the second stage was recorded from May 2003 to September 2003. Observed symptoms indicated significant differences between the control and treatments in which specific nutrients were withheld. Some cultivars exhibited some symptoms that are commonly noticed under field conditions, e.g. in the N deficiency treatment the upper leaves of Protea ‘Sylvia’ were reddish and the lower leaves were chlorotic especially at the later stage. Protea ‘Red Rex’ in the P deficiency treatment had random red tints around the leaf including the petiole, these symptoms are also commonly noticed in Protea ‘Red ‘Rex’ in field conditions. Leucadendron ‘Rosette’ also showed some uncommon symptoms of accumulating “sugar” on leaf tips in Ca deficiency treatment that was not observed in any other cultivar. In some cultivars the symptoms were systematic e.g. Leucadendron ‘Chameleon’ while in other cultivars the deficiency affected a certain leaf age e.g. Leucospermum ‘High Gold’ in the Ca deficiency treatment. The buds in 'High Gold' died prematurely in the Ca deficiency treatment. Protea ‘Cardinal’ was used to determine the optimal N and P source and concentrations for optimal growth. Protea ‘Cardinal’ was grown in a temperaturecontrolled glasshouse for seven months using silica sand as growth medium. Different levels and sources of N and P were applied. The N was applied in a complete nutrient solution as NH4 +, NO3 -, NH4 +: NO3 - (1: 1, 1: 4 and 4: 1 ratios) and Urea, at different concentration levels: 5 mM, 1 mM and 0.1 mM. P was applied at 1 mM, 0.1 mM and 0.01 mM. The plants were fertigated manually with 1L nutrient solution on every second day of the week. P at 0.01 mM and 0.1 mM resulted in optimal plant growth. The 1 mM P resulted in marginal leaf scorching or dryness. When N was applied at 5 mM plant growth was more optimal than when N was applied at 1 mM and 0.1 mM. More dry weight was accumulated at 5 mM than at 1 mM or 0.1 mM N. The dry weight of leaves, stem and roots tissues at 5 mM were higher in the NO3 - treatment.

Thesis (MScAgric)--University of Stellenbosch, 2000. / ENGLISH ABSTRACT: The quality of wine is influenced by numerous factors. These factors include the quality of the grapes, winemaking techniques and quality control throughout the winemaking process. It is thus very important that any process leading to the lowering of the quality of the wine be prevented. Evidence in the wine industry shows that bacterial spoilage is still very much a common problem in many wineries. The spoilage of wine by bacteria can lead to amongst other problems, elevated volatile acidity levels, of which only a certain concentration limit in wine is permitted. Usually more than 90% of the volatile acidity of wine consists of acetic acid. Different yeast strains, heterofermentative lactic acid bacteria and acetic acid bacteria (which can all be spoilage microorganisms) can produce acetic acid in high concentrations. It is thus important to be able to prevent the formation of this acid by controling the unwanted growth of these spoilage microorganisms. Acetic acid and other medium chain fatty acids, octanoic- and decanoic acid, can also lead to stuck or sluggish fermentations. A stuck or sluggish fermentation can also lead to wine spoilage, due to sugar remaining in the fermentation which can be utilized by spoilage microorganisms. Acetic- and other fatty acids enter the yeast cell by passive diffussion and releases its proton in the cytoplasm, thereby acidifying the cytoplasm and inhibiting some enzymes. These acids can also work synergistically with ethanol and its inhibitory effect is also dependent on the temperature. Yeast strains can also differ in their resistance to acetic and other medium chain fatty acids and these acids can also influence the growth of lactic acid bacteria. How acetic acid bacteria influence the winemaking process and the used measures to keep these bacteria from spoiling wine have been the subject of very little attention in the past. This was due to the belief that the anaerobic conditions prevailing in wine and the use of sulfur dioxide are enough to control these bacteria, since acetic acid bacteria were always described as being strictly aerobic microorganisms. Recently, some evidence showed that acetic acid bacteria can survive and even overcome the limits that the winemaking process places on its growth. These bacteria are also known to inhibit the yeasts growth and fermentation ability due to the production of acetic acid and other factors. A research programme on the origin of volatile acidity in South African wines had been initiated at the Department of Viticulture and Enology and at the Institute for Wine Biotechnology at the University of Stellenbosch after increases in volatile acidity in different South African wines had been reported. This spurred us to investigate the occurrence of acetic acid bacteria in South African red wine fermentations, which forms part of this study, and to identify the dominant acetic acid bacterial strains. The sulfur dioxide resistance of five representative strains were also determined, as well as the effect of metabolites which were produced by these bacteria on yeast growth and fermentation ability. Our results indicate that acetic acid bacteria can occur in high concentrations in the fresh must and during alcoholic fermentation. In the 1998 harvesting season acetic acid bacteria occurred at 106-107 cfu per ml in the fresh must. In 1999 these numbers were 104-105 cfu/ml. Acetic acid bacteria numbers decreased in 1998 to 102-103 cfulml during fermentation. The survival of these bacteria in 1999 correlated with the pH of the must, as well as sulfur dioxide dosages in the must. In must with a low pH and higher sulfur dioxide the number of acetic acid bacterial numbers decreased more drastically than in the high pH, low sulfur dioxide musts. This was also true for acetic acid bacterial counts during cold soaking of musts, with the number of acetic acid bacteria increasing during the cold soaking period in musts with a high pH. In musts with a low pH and higher S02 dosages acetic acid bacterial counts did not, however, increase during cold soaking. Gluconobacter oxydans dominated in the fresh must with Acetobacter liquefaciens and especially Acetobacter pasteurianus dominating during the fermentation. Different biochemical and physiological tests revealed that 52% of the 115 isolates tested belong to A. pasteurianus. The high occurrence of A. liquefaciens with A. pasteurianus during fermentation showed that the dominant acetic acid bacterial species in South Africa differed from reports from other wine producing countries. The sulfur dioxide resistance of the acetic acid bacteria tested also differed in white grape juice, with a molecular sulfur dioxide concentration of 0.64 mg/I being necessary to eliminate all the acetic acid bacterial strains tested. The A. hansenii strain was found to be the most resistant to sulfur dioxide and G. oxydans the least resistant. The latter strain was eliminated by only 0.05 mg/I molecular sulfur dioxide, while A. hansenii was only eliminated by 0.64 mg/I molecular sulfur dioxide. The A. pasteurianus, A. liquefaciens and A. aceti strains tested displayed varying degrees of resistance to sulfur dioxide. The volatile acidity produced by these bacteria profoundly influenced the growth and fermentation ability of yeast, which led to slow/stuck fermentation. The A. hansenii and A. pasteurianus strains produced the most volatile acidity in grape juice, with up to 4.02 g/I for A. hansenii within 4 days, which led to a stuck alcoholic fermentation. This was, however, prevented by inhibiting or eliminating the acetic acid bacteria with sufficient sulfur dioxide additions prior to yeast inoculation. Compounds produced by acetic acid bacteria can also influence wine quality. Certain organic acids were produced and metabolized by acetic acid bacteria, as well as acetoin. We could not, however, detect any other fatty acids that are inhibitory to yeast (produced by these bacteria). This study clearly showed that acetic acid bacteria could occur during fermentation and that certain winemaking techniques, like the maintenance of a low pH in the must and sulfur dioxide additions can influence the growth and survival of acetic acid bacteria. Acetic acid bacteria also influence both the winemaking process by inhibiting yeast as well as the quality of the wine by producing acetic acid and/or other compounds. This study also shed some light on the occurrence of acetic acid bacterial species in the South African context and could be important in assisting the winemaker, as well as the scientific reseacher, in finding ways to inhibit acetic acid bacteria in the ongoing battle against these spoilage microorganisms of wine. / AFRIKAANSE OPSOMMING: Wynkwaliteit word deur verskillende faktore beinvloed. Dit sluit die druifkwaliteit, wynmaak tegnieke en kwaliteitsbeheer deur die wynmaakproses in. Enige prosesse en faktore wat tot die verlaging in wynkwaliteit kan lei moet dus ten alle koste voorkom word. Die bederf van wyn deur bakterieë kan en is 'n algemene probleem in enige kelder. Bakteriese bederf kan, onder andere, lei tot verhoogte vlugtige suurheid, waarvan 'n sekere konsentrasie limiet in wyn toegelaat word. Asynsuur maak gewoonlik 90% van die vlugtige suurheid uit. Asynsuur kan deur verskillende gisrasse, heterofermantatiewe melksuurbakterieë en asynsuurbakterieë (wat almal wyn kan bederf) gevorm word. Die vorming van asynsuur in wyn kan dus voorkom word deur die ongewenste groei van dié organismes te voorkom. Asynsuur en ander medium ketting vetsure, soos oktanoë- en dekanoësuur, kan ook tot slepende of gestaakte gistings lei. Suiker wat in die wyn agterbly wat In slepende/gestaakte fermentasie ondergaan kan deur bederf bakterieë gebruik word om die wyn te bederf. Ongedissosieerde asynsuur en ander vetsure dring die gissel binne deur passiewe diffussie en stel 'n proton vry in die sitoplasma wat sitoplasma versuur en sekere ensieme inhibeer. Hierdie sure werk ook sinergisties met etanol en hul inhiberede effek is ook temperatuur afhanklik. Gisrasse verskil in hul weerstandbiedendheid teen asynsuur- en ander mediumketting vetsure en dié vetsure kan ook melksuurbakterieë se groei beïnvloed. Hoe asynsuurbakterieë wyn bederf en die aksies wat geneem kan word om dit te verhoed is in die verlede nie baie ondrsoek nie. Dit is hoofsaaklik daaraan toe te skryf dat geglo is dat die anaerobiese kondisies in wyn en die gebruik van swaweidioksied die groei van asynsuurbakterieë, wat altyd beskryf is as streng aerobe mikroorganismes, kan beheer. Daar is onlangs aangetoon dat asynsuurbakterieë kan oorleef in wyn en selfs die ongunstige kondisies daarin kan oorkom. Hierdie bakterieë is ook in staat om gisgroei en fermentasie vermoë te inhibeer deur die produksie van asynsuur en ander faktore. In Navorsingsprogram om die oorsprong van verhoogde vlugtige suurheid in Suid-Afrikaanse wyne te bepaal is deur die Departement Wingerd- en Wynkunde en die Instituut vir Wynbiotegnologie van die Universiteit van Stellenbosch geinisieer. Dit het ons aangemoedig om die voorkoms van asynsuurbakterieë in Suid-Afrikaanse rooiwyngistings, wat deel vorm van hierdie ondersoek, en ook die dominante asynsuurbakterie rasse te identifiseer. Die swaweidioksied bestandheid van vyf verteenwoordegende rasse en die effek wat metaboliete wat deur dié bakterieë geproduseer is op gisgroei en gisitingsvermoë is bepaal. Ons resultate bewys dat asynsuurbakterieë teen hoë getalle in vars mos en gedurende alkoholiese gisting kan voorkom. Asynsuurbakterieë het gedurende die 1998 seisoen teen 106-107 kve/ml en in 1999 teen 104-105 kve/ml in die vars mos voorgekom. Gedurende fermentasie het hierdie getalle in die 1998 seisoen gedaal na 102-103 kve/ml. Die oorlewing van hierdie bakterieë het gedurende die 1999 seisoen gekorrelleer met die pH en swaweidioksied konsentrasies van die mos. In die lae pH, hoë swaweidioksied moste het asynsuurbakterie getalle vinniger en meer dramaties gedaal as in die hoë pH, lae swaweidioksied moste. Asynsuurbakterie getalle het dieselfde tendens getoon in moste gedurende dopkontak by lae temperature. In moste met 'n hoë pH het asynsuurbakterie getalle toegeneem gedurende koue dopkontak, terwyl dit nie gebeur het nie in moste met 'n lae pH en hoë swaweidioksied konsentrasies. In die vars mos het Gluconobacter oxydans en gedurende die fermentasie Acetobacter liquefaciens en veral Acetobacter pasteurianus oorheers. Verskillende biochemiese en fisiologiese toetse het bepaal dat 52% van die 115 isolate A. pasteurianus is. Die hoë voorkoms van A. liquefaciens saam met A. pasteurianus gedurende gisting bewys dat die voorkoms en dominansie van asynsuurbakterieë in Suid- Afrika verskil van ander wynproduserende lande. Die swaweidioksied weerstandbiedendheid van die asynsuurbakterieë wat getoets het, het ook verskil, met 0.64 mg/I molekulêre swaweIdioksied nodig om hul almal te elimineer in wit druiwesap. Die A. hansenii en G. oxydans rasse was die mees weerstandbiedend en sensitiefste onderskeidelik ten opsigte van swaweidioksied. Slegs 0.05 mg/I molekulêre swaweidioksied was voldoende om G. oxydans te elimineer, terwyl A. hansenii deur 0.64 mg/I molekulêre swaweidioksied geëlimineer is. Die A. pasteurianus, A. liquefaciens en A. aceti rasse het verskillende swaweidioksied weerstandbiedendheid getoon. Die vlugtige suurheid wat deur dié bakterieë geproduseer is het die groei en gistingvermoë van gis drasties beinvloed, wat tot slepende/gestaakte fermentasies gelei het. Die A. hansenii en A. pasteurianus rasse het die meeste vlugtige suurheid geproduseer, met tot 4.02 g/I geproduseer deur A. hansenii na vier dae se groei, wat tot 'n gestaakte fermentasie gelei het. Dit is egter voorkom deur die asynsuurbakterieë te elimineer deur genoegsame swaweidioksied toevoegings tot die mos voor gisinokulasie te doen. Verbindings wat deur asynsuurbakterieë geproduseer word kan ook wynkwaliteit beinvloed. Sekere anorganiese sure is deur hierdie bakterieë geproduseer, terwyl ander gemetaboliseer is. Asetoïen is geproduseer deur die getoetse asynsuurbakterieë. Ons kon egter nie ander vetsure wat gis inhibeer opspoor nie. (Geproduseer deur die bakterieë). Hierdie studie bewys dat asynsuurbakterieë gedurende alkoholiese fermentasie kan voorkom en dat sekere wynmaaktegnieke, soos die verkryging van moste met 'n lae pH en genoegsame swaweidioksied toevoegings die groei en oorlewing van asynsuurbakterieë kan beivloed. Asynsuurbakterieë kan ook beide die wynmaakproses, deur giste te inhibeer, en die wynkwaliteit beivloed deur die produksie van asynsuur en/of ander verbindings. Hierdie studie het ook kennis oor die voorkoms van asynsuurbakterieë in Suid-Afrikaanse moste verbeter en kan ook as 'n nuttige hulpmiddel dien vir die wynmaker en navorser in die stryd om hierdie bederf organismes van wyn te elimineer.

Thesis (MScAgric)--University of Stellenbosch, 2001. / ENGLISH ABSTRACT: The aim of this study was to determine the effect of a grass herbicide, a broadleaf herbicide with some grass control capabilities, method of tillage (tine and no-tillage) at planting of wheat as well as different medic cultivars on the regeneration, dry matter (OM) production and quality of a medic pasture. The trial was conducted at Langgewens experimental farm in the Swartland wheat producing area. Nine medic cultivars of three different species were evaluated after being sprayed with either haloxyfop-R-methyl (HAL) ester or imazamox (IMI) and subjected to either a tine tillage or a no tillage treatment at planting of wheat. Soil samples were taken during January 2000 to determine the size of the medic and weed seedbank as well as the degree of dormancy in the medic seeds, while OM samples were taken throughout the growing season to determine the OM production of the different medic cultivars and weed species. OM samples taken during October 1998 on the same pasture, were used to determine the crude protein (CP) and neutral detergent fibre (NOF) content of the pasture. The samples were subjected to in vitro digestion and the digestibility of pasture CP (OCP), NOF(ONOF) and DM (DOM)were determined. Results showed that seedling establishment differed between cultivars used, herbicide treatments applied as well as the crop stage in the rotation. The cultivars produced more seedlings where IMI was applied compared to HAL as well as where the area consisted of two year pasture compared to one year pasture (1998) and one year wheat (1999). After a year of pasture and a year of wheat, cultivars Sephi and Paraggio produced the most seedlings, while Caliph and Orion produced the least. Caliph however, showed a very high degree of seed dormancy while Orion's low seedling establishment was due to its sensitivity to the IMI herbicide used. Little difference was found between the nine cultivars early in the season (July - August) with regard to cumulative OM production, except for Orion, whose growth was severely damaged by the IMI treatment. At the end of the growing season (October), the cultivar Caliph's cumulative OM production (2010.1 kg/ha) was significantly higher than all the other cultivars, except for Parabinga (1053. 4 kg/ha). Oifferent pasture samples, of which the botanical composition was known, was analysed for CP, NOF, OOM, OCP and ONOF. There was no significant difference in pasture composition during 1998 but variation in the pasture composition did however cause the IMI treatment, compared to the HAL treatment, to have a lower ONOFand OOMcontent. A modelling procedure was used to predict the pasture quality parameters (CP, NOF, OOM,OCP and ONOF) from the pasture composition (medic hay, medic pods, grassy and broadleaf weeds). This prediction of CP, NOF, OOM, ONOF and OCP from the pasture components had a relative low accuracy (49 -74.1 %) and a further refinement of this model for possible use on farms in order to improve grazing management and animal production is advised. In conclusion it could be said that broadleaf weed control caused a definite increase in medic seed and OMproduction, but Orion should not be used with an IMI herbicide. All the cultivars, except for Orion, produced enough seedlings up to the second year to ensure sustainability of the medic pasture. All the cultivars, except for Orion, produced a sufficient amount of OM early in the growing season. Caliph however, produced by far the most OM later in the growing season. A reduction of broadleaf weeds and medic pods will increase the digestibility of NOFand OMand therefore increase the quality of the pasture. Pods however are an important part of summer forage and the aim should therefore rather be to reduce the number of broadleaf weeds in the pasture. / AFRIKAANSE OPSOMMING: Die doel van hierdie studie was om die effek van 'n gras en breëblaar onkruiddoder (wat sekere grasse beheer), metode van bewerking tydens die saai van koring asook nege verskillende medic kultivars op die regenerasie, droë materiaal produksie en kwaliteit van medic weidings te bepaal. Die proef is gedoen op Langgewens proefplaas wat geleë is in die Swartland koring produserende gebied. Nege medic kultivars is geëvalueer nadat die weiding met of haloxyfop-R-metiel ester (HAL) of imazamox (IMI) onkruiddoders gespuit is en onderwerp is aan of 'n vlak tand of geen bewerking tydens die saai van koring. Grondmonsters is geneem in Januarie 2000 om die grootte van die medic en onkruid saadbank asook om die graad van dormansie in die verskillende medic kultivars se sade te bepaal. Droë materiaal monsters is gedurende die 2000 groeiseisoen geneem om die droë materiaal produksie van die verskillende medic kultivars asook onkruid spesies te bepaal. Droë materiaal monsters is gedurende Oktober 1998 geneem en gebruik om die ruproteïn (CP) en neutraaloplosbare vesel (NDF) inhoud van die weiding te bepaal. Die monsters is in vitro verteer en die verteerbaarheid van CP (OCP), NDF (ONOF) en droë materiaal (DOM) is bepaal. Resultate wys dat saailing vestiging verskil tussen die verskillende kultivars wat gebruik is, verskillende onkruiddoder behandelings asook die stadium van die weidings/koring. Die kultivars het meer geproduseer waar die weiding met IMI behandel is in vergelyking met waar HAL toegedien is, asook waar koring nog nie gesaai is nie. Na 'n jaar van weiding en 'n jaar van koring, het die kultivars Sephi en Paraggio die meeste saailinge, en Caliph en Orion die minste saailinge gehad. Caliph het egter 'n hoë graad van dormansie in sy saad getoon, terwyl die swak vestiging van Orion die gevolg is van die kultivar se hoë sensitiwiteit teenoor IMI. Min verskil is gevind tussen die nege kultivars, vroeg in die groei seisoen (Julie - Augustus), wat kumulatiewe droë materiaal produksie betref, behalwe vir Orion wat erg beskadig is deur die IMI behandeling. Aan die einde van die groeiseisoen (Oktober 2000) was die kumulatiewe droë materiaal produksie van die kultivar Caliph (2010.1 kg/ha) betekenisvol hoër as al die ander kultivars behalwe vir Parabinga (1053.4 kg/ha). Weidingsmonsters, waarvan die botaniese samestelling bekend was, is ontleed vir CP, NDF, DDM, DCP en DNDF. Daar is geen betekenisvolle verskille gevind in die botaniese samestelling van die weidingmonsters geneem in 1998 nie,maar die variasie in botaniese samestelling het veroorsaak dat IMI in vergelyking met HAL 'n laer DNDF and DDM inhoud het. 'n Model is opgestel wat die weidingskomponente (medic hooi, medic peule, gras en breëblaar onkruide) gebruik om die kwaliteits parameters (CP, NDF, DDM, DCP en DNDF) van die weiding te skat. Hierdie skatting van CP, NDF, DDM, DCP en DNDF deur van die weidingskomponente gebruik te maak het 'n relatiewe lae akuraatheid gehad (49 -74.1 %) en verdere verfyning van hierdie model vir moontlike gebruik op plase, ten einde weidings bestuur en diere produksie te verbeter, word voorgestel. Die gevolgtrekking kan gemaak word dat breëblaar onkruidbeheer 'n definitiewe verbetering in die medic saailing en droë materiaal produksie van die medies te weeg gebring het, maar die kultivar Orion behoort nie saam met 'n IMI gebruik te word nie. AI die getoetste kultivars, behalwe Orion, het voldoende saad oorlewing vertoon tot en met die tweede jaar van die rotasie om lewensvatbaarheid van die sisteem te verseker en alle kultivars, behalwe Orion, het voldoende droë materiaal produseer vroeg in die groeiseisoen. Caliph het egter laat in die groeiseisoen by verre die meeste droë materiaal geproduseer. 'n Vermindering in die hoeveelheid breëblaar onkruide en peule in die weiding sal tot 'n verhoging in die verteerbaarheid van NDF en DM lei en dus 'n verhoging in die kwaliteit van die weiding tot gevolg hê. Peule is egter 'n belangrike bron van voedsel aan weidende diere gedurende droë somermaande en die verbetering van weidings moet eerder gedoen word deur te poog om breëblaar onkruide te beheer.

Thesis (PhD)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: The use of cowdung as an organic fertilizer in Asian and African agriculture is an ancient practice. This explains its renewed interest, partly due to the financial inability of most farmers to purchase agrochemicals but also the ever increasing need to adopt greener technologies that do not adversely affect soil health, water quality, biodiversity and promote sustained or even increased food production. In this context, many innovative farmers have developed their own novel technologies based on the use of local resources. One such innovation is Sanjeevak (a mix of cow dung, cow urine, water and a handful of sugar); which showed very promising boosting effect on crop productivity. However, very little scientific work has so far been conducted to evaluate its effect as an organic product for soil amendments. The present study was subdivided into three main objectives. (i) To assess the fertilizing value, human health and ecological risk profiles of Sanjeevak; (ii) To screen Sanjeevak for phytohormones content using Salkowski colorimetric method and liquid chromatography – mass spectrometry (LC-MS) (iii) To evaluate Sanjeevak application at various rates on growth parameters and yield of various crops cultivated in glasshouse and field conditions. Sanjeevak was assessed for its micro and macro nutrients contents. The analysis showed the presence of micronutrients such as Mg, Na, Ca and Zn at variable concentrations and phosphorus (P) (0.007%) and potassium (K) (0.063%). However, Sanjeevak content in total nitrogen (TN) (0.11%), and total organic carbon (TOC) (0.71%) was very low; suggesting that it may be a viable source of nutrients only if applied at higher and consistent rates or alternatively by improving its formulation. Also, Sanjeevak was analysed for its microbiological characteristics and level of heavy metals content in comparison to the strictest legislations that regulate the use and application of wastewater sludge to agricultural land in South Africa. The findings showed that heavy metals, which averaged from 0.03±0.01 for Arsenic (As) to 4.74±0.92 mg/kg for Zinc (Zn) and feacal coliform was estimated at 1.2×102 CFU/g dry matter measured were considerably below the threshold (for Arsenic between 40 to 75 mg/kg dry weight; for Zinc between 2800 to 7500 mg/kg dry weight) and faecal coliform bacteria between 1000 to 1×107 CFU/g dry weight for application as a source of soil amendments. Studies investigating the detection and concentration of phytohormones in Sanjeevak were carried out. In using the Salkowski colorimetric method to detect and quantify auxins from Sanjeevak and its composites (cow urine and dung), the results showed the presence of indole-3-acetic acid (IAA) at variable concentrations ranging from 20.38±2.1 ppm in cow urine, 20.1±6.6 ppm in cow dung, Sanjeevak 17.90±1.1 ppm to up to 138.31±12.6 ppm when LTRP was added to Sanjeevak bacterial cultures and by varying parameters such as incubaton time and temperature. Screening of the above mentioned samples for IAA using LC-MS analysis validated earlier findings. Further analysis of these results strongly emphasized the influence of bacteria in Sanjeevak in producing IAA. Trials were carried out both in the glasshouse and the field. In the greenhouse, different Sanjeevak application rates consistently confirmed its root promoting effect on crops such as tomato, cucumber and grapevine and increased wheat yield independent of the nutrients it contains. Marginal increases were recorded between treatments under field conditions; for example compost and compost + Sanjeevak 20.35 and 20.61 t/ha; and 2.46 and 2.60 t/ha compared to the control 11.67 t/ha and 1.29 t/ha respectively for tomato and maize. However, statistical analysis of the results obtained, revealed that there was no difference between treatments (control, compost, Sanjeevak and compost + Sanjeevak) for the same crop tested due to the high coefficient of variation of the data. Therefore, the use of Sanjeevak as an organic source of soil amendments may be considered as a cheaper alternative to effective microorganisms (EM) technology made up of local and natural resources. As observed in the study, it may be best used in combination with a reliable source of plant nutrients. / RESUMEE: L'utilisation des excréments de vaches comme engrais organique dans l'agriculture asiatique et africaine est une pratique très ancienne. Ceci explique son intérêt renouvelé, en partie due à aux restrictions monétaires de la plupart des agriculteurs d'acheter des produits agrochimiques, mais aussi la nécessité croissante d'adopter des technologies vertes qui ne nuissent pas à la qualité des sols, des eaux, la biodiversité et qui permettent d’améliorer la production agricole. C’est dans ce contexte que de nombreux paysans ont développé des techniques nouvelles dépendant des ressources naturelles et locales. L’utilisation de Sanjeevak (un mélange d’excréments de vaches, d’urine de vaches, l'eau et du sucre), a démontré sa capacité à accroître la productivité des plantes vivrières. Cependant, très peu de travaux scientifiques ont jusqu'à présent été menée pour étudier ce produit organique. La présente étude a été subdivisée en trois objectifs principaux. (i) Evaluation de la valeur fertilisante, et les profils de risques écologiques et sanitaires de Sanjeevak, (ii) Etudes de détection des phytohormones et leurs concentrations en utilisant une méthode colorimétrique adaptée de celle de Salkowski et la chromatographie liquide - spectrométrie de masse (LC-MS) (iii) Etude des effets de l’utilisation de Sanjeevak a différents taux d’applications sur la croissance et le développement des plants. Sanjeevak a été évaluée pour son contenu en micro et macro nutriments. L'analyse a montré la présence d'oligo-éléments tels que Mg, Na, Ca et Zn à des concentrations variables. De plus, son contenu en éléments majors tels que le phosphore (P) (0.007%), le potassium (K) (0.063%), l’azote (N) (0.11%), et carbone (C) (0.71%) est très faible; suggérant qu'il pourrait être une source viable de nutriments que si elle est appliquée à des taux plus élevés et répétés ou alternativement en améliorant sa formulation. En outre, Sanjeevak a été analysé pour ses caractéristiques microbiologiques et sa concentration en métaux lourds en comparaison a la législation qui réglemente l'utilisation et l'application de déchets liquide d’origines domestiques sur les terres agricoles en Afrique du Sud. Les résultats ont révélé que des métaux lourds et le niveau de coliformes fécaux mesuré était inférieur aux seuils d'application en tant que source d'amendements de sols agricoles. Les études portant sur la détection et la concentration d’hormones végétales ont été effectuées. En utilisant la méthode colorimétrique de Salkowski pour détecter et quantifier les auxines de Sanjeevak, les urines et les excréments de vaches; les résultats ont révélé la présence d'acide indole-3-acétique (AIA) à des concentrations variables dans les urines, les excréments et Sanjeevak. Une autre analyse des échantillons mentionnés ci-dessus pour les AIA en utilisant LC-MS a validé les résultats obtenus au préalable. L’étude détaillée de ces résultats confirme l'influence des micro-organismes dans la production des hormones végétales. Concernant les expériences sous serre, les différents taux d'application de Sanjeevak ont confirmé son effet stimulant à la croissance accélérée des racines des plantes telles que la tomate et les raisins et augmenté le rendement du blé indépendamment des nutriments qu'il contient. L'analyse statistique des résultats obtenus dans des conditions de terrain, a révélé qu'il n'y avait pas de différence entre les traitements (contrôle, compost, compost + Sanjeevak et Sanjeevak) pour la même plantes testées. Par conséquent, l'utilisation de Sanjeevak comme un produit organique qui améliore la qualité des sols et le rendement des cultures vivrières; peu être considéré comme un inoculum contenant des microorganismes constitué de ressources locales et naturelles. Comme l'a observé dans l'étude, il pourrait être mieux utilisé en combinaison avec une source fiable de nutriments végétaux. / AFRIKAANSE OPSOMMING: Die gebruik van beesmis as 'n organiese kunsmis in Asië en Afrika is' n eeu-oue landbou praktyk. Dit verklaar die hernude belangstelling, deels vanweë die finansiële onvermoë van meeste boere om landbouchemikalieë aan te koop, maar ook as gevolg van die toenemende behoefte vir groener tegnologie wat nie nadelig is vir grond gesondheid, waterkwaliteit, biodiversiteit en wat volhoubaarheid of selfs verhoogde voedselproduksie bevorder. In hierdie konteks het baie vindingryke boere hul eie nuwe tegnologie, gebaseer op die gebruik van plaaslik verkrygde hulpbronne, ontwikkel. `n Voorbeeld hiervan is Sanjeevak ('n mengsel van beesmis, beesurine, water en die handvol melasse), wat belowende bevorderende effekte op gewas produktiwiteit en grond mikroflora getoon het. Tot dusver was daar egter baie min wetenskaplike werk gedoen om die effek daarvan as 'n organiese produkte vir grond wysigings te evalueer. Hierdie studie was verdeel in vier belangrike doelwitte. (i) Om die bemestingswaarde, menslike gesondheid en ekologiese risiko-profiele van Sanjeevak te evalueer; (ii) Om Sanjeevak vir fitohormone inhoud en vlakke met behulp van 'n kolorimetriese metode afgelei van dié van Salkowski en vloeistofchromatografie – massaspektrometrie (LC-MS) te besigtig; (iii) Glashuis en veld waarneming reaksies met betrekking tot groei parameters en opbrengs van verskeie gewasse na die toediening van Sanjeevak by verskillende tempos; (iv) Laastens, om die effek van die Sanjeevak voorbehandeling op saad ontkieming en voortplanting te toets in vergelyking met die metodes en tegnieke wat gereeld gebruik word. Sanjeevak is geassesseer vir die mikro-en makro voedingstowwe inhoud. Die analise het die teenwoordigheid van mikrovoedingstowwe soos Mg, Na, Ca en Zn by wisselende konsentrasies, asook fosfor (P) (0.007%) en kalium (K) (0.063%), getoon. Sanjeevak inhoud van totale stikstof (TN) (0.11%), en die totale organiese koolstof (TOC) (0.71%) was egter baie laag, wat daarop dui dat dit slegs 'n lewensvatbare bron van voedingstowwe is indien dit by hoër en konsekwente tempos toegedien word of alternatiewelik wanneer formulering daarvan verbeter word. Sanjeevak was ook ontleed vir die mikrobiologiese eienskappe en die vlakke van swaar metale in vergelyking met die streng wetgewing wat die gebruik en toediening van afvalwater slyk op landbougrond in Suid-Afrika reguleer. Die bevindinge het getoon dat swaar metale en fekalieë kolivorm vlakke hier gemeet, aan die drumpel vereistes voldoen vir die toediening as ‘n grondverbeteringsmiddel. Studies wat die opsporing en die konsentrasie van fitohormone in Sanjeevak ondersoek is uitgevoer. In die gebruik van die Salkowski kolorimetrise metode om die ouksiene op te spoor en te kwantifiseer uit Sanjeevak en sy mengsel (beesurine en mis), het die resultate die teenwoordigheid van indol-3-asynsuur (IAA) by wisselende konsentrasies wat wissel van 20 tot 140 ppm in beesurine, beesmis en Sanjeevak getoon. Evaluering van die bogenoemde monsters vir IAA met behulp van LC-MSanalise bevestig vroeër bevindings. Verdere ontleding van hierdie resultate beklemtoon sterk die invloed van Sanjeevak mikrobiota in fitohormone produksie. Proewe is uitgevoer in die glashuis en die veld. In die glashuis eksperimente, is het die verskeie toedieningstempo van Sanjeevak herhalend die wortelbevorderende effekte bevestig op gewasse soos tamaties, komkommer en wingerdstok en dit het opbrengs van koring verhoog, onafhanklik van die voedingstowwe wat dit bevat. Statistiese analise van die resultate verkry onder veldtoestande, het getoon dat daar geen verskil tussen die behandelings (kontrole, kompos, Sanjeevak en kompos + Sanjeevak) was nie, gegee dat dieselfde gewas getoets was. Ten slotte, laboratorium-eksperimente op Sanjeevak as voor-behandeling om die beworteling te verbeter van die wingerdstok (Ramsey) onderstok steggies, het baie belowende resultate getoon in vergelyking met naftaleen asynsuur (NAA) voorbehandeling en die kontrole. Dit beklemtoon die feit dat Sanjeevak 'n alternatief kan wees en wat verdere studie verdien, hoofsaaklik as gevolg van sy lae-koste en omgewingsvriendelike prosedures. Die gebruik van Sanjeevak as 'n organiese grondverbeteringsmiddel vir gewasproduksie en voortplanting kan beskou word as' n goedkoper alternatief tot effektiewe mikro-organisme (EM) tegnologie wat uit plaaslike en natuurlike hulpbronne saamgestel is. Soos waargeneem in die studie, kan dit die beste gebruik word in kombinasie met 'n betroubare bron van plantvoedingstowwe. Dus, moet die gebruik daarvan vir die produksie van gewasse en voortplanting aangemoedig word.

Thesis (PhD(Agric))--Stellenbosch University, 2012 / ENGLISH ABSTRACT: Field spectroscopy was used to study leaf composition and selected factors (including canopy growth manipulation and water status changes) that may impact on it in a Vitis vinifera cv. Shiraz vineyard, showing considerable variability in vigour. Temporal and spatial variability in leaf composition were incorporated into measurements by analysing leaves in different shoot positions and at different developmental stages during three different growing seasons. Irrigation and canopy manipulation treatments were also imposed in order to provide new insights into assessing the grapevine leaf and possibly also the canopy growth and ageing dynamics as well as pigment content, as a basis of executing a generally non-destructive measurement approach. Despite large climatic differences between the seasons, canopy size seemed of crucial importance in determining grapevine water relations in the grapevines from the different canopy manipulation treatments. Drastic compensation effects in terms of secondary shoot growth also followed the canopy reduction treatment. Despite this, canopy microclimate was apparently improved, considering the results from light measurements as well as the ripening dynamics in the reduced canopies. Reduced canopies also seemed to display a different canopy composition, in favour of secondary growth. This could have impacted positively on water use efficiency as well as ripening, due to higher photosynthetic efficiency of these leaves during the ripening stages. The reduced canopy treatments offered the possibility of attaining technological ripeness at an earlier stage and at comparatively lower potential alcohol levels. This study illustrated the relevance of considering the vegetative development of the grapevine, along with leaf ageing in the canopy, when conducting calibrated non-destructive measurements of leaf pigments, structure and water content. The relevance of using multivariate techniques in leaf spectroscopy was shown. This can be applied and simplified to aid in non-destructive leaf pigment, structure and water content estimation in future studies. Even with the general variation encountered in this vineyard, predictions of the major pigments in grapevine leaves were within acceptable error margins. Further work is required to improve the modelling of xanthophylls, which may require non-linear multivariate techniques. Logistical shoot growth modelling was used in leaf age estimation and classification, which made it possible to simplify statistical analysis of the leaf parameters mentioned. Practical application of the modelled and predicted parameters was shown for a specific period in season two by comparing the reaction of different treatments to developing water deficits. The results indicated that several parameters, with special mention of the carotenoid:chlorophyll ratio and chlorophyll a:b ratio, can be monitored on young and old leaves in the canopy in order to monitor developing water deficit stress. The modelled parameters, however, did not seem to be sensitive enough to allow specific prediction of predawn leaf water potential values. Specific leaf mass, equivalent water thickness, total specific leaf mass as well as leaf chronological age were successfully predicted from leaf spectral absorbance data, and this may be useful in future work on quantifying leaf adaptation to the micro-environment within the canopy. / AFRIKAANSE OPSOMMING: Veldspektroskopie is gebruik om blaarsamestelling en spesifieke faktore (insluitend lowergroei manipulasie en waterstatus veranderinge) wat ‘n impak kan hê in ‘n Vitis vinifera cv. Shiraz wingerd, met beduidende variasie in groeikrag, te ondersoek. Ruimtelike, asook tydsgebonde, variasie in blaarsamestelling is geïnkorporeer in die metings deur blare van verskillende lootposisies en vir verskillende ontwikkelingstadia gedurende drie verskillende groeiseisoene te meet. Besproeiings- en lowermanipulasie behandelings is ook uitgevoer om die dinamiek van blaar- en lowergroei, veroudering, asook pigmentinhoud te bestudeer binne die konteks van die uitvoering van ‘n nie-destruktiewe meetstrategie. Ondanks groot klimaatsverskille tussen die seisoene, blyk lowergrootteverskille belangrik te wees in die bepaling van wingerdstok-waterverhoudings in die verskillende lowermanipulasie behandelings. Drastiese kompensasiereaksies ten opsigte van sylootgroei is waargeneem in reaksie op die gereduseerde lowerbehandeling. Indien die resultate van ligmetings en druifrypwording in die gereduseerde lowerbehandeling in ag geneem word, is lowermikroklimaat egter steeds verbeter. Hierdie behandeling het oënskynlik ook veranderde lowersamestelling gehad, tot voordeel van sylootgroei. Dit kon moontlik ‘n positiewe invloed gehad het op waterverbruikseffektiwiteit asook druifrypwording, as gevolg van moontlike hoër fotosintetiese effektiwiteit van die blare gedurende die rypwordingstadia. Die gereduseerde lowerbehandeling het die moontlikheid gebied om tegnologiese rypheid by ‘n vroeër datum te bereik, met moontlike laer alkoholvlakke in die wyn. Hierdie studie het die belangrikheid beklemtoon om die vegetatiewe ontwikkeling van die wingerdstok in ag te neem wanneer gekalibreerde nie-destruktiewe metings van blaarpigmente, blaarstruktuur asook waterinhoud onderneem word. Die belang van multi-variant meettegnieke in blaarspektroskopie is aangetoon. Dit kan verder vereenvoudig word ter ondersteuning van niedestruktiewe meting van blaarpigment, -struktuur en -waterinhoudsbepaling in toekomstige studies. Selfs met die variasie wat in die wingerd voorgekom het, was die voorspellings van die vlakke van die belangrikste pigmente wat in wingerdblare aangetref word binne aanvaanbare foutgrense. Opvolgwerk is nodig om die modellering van xanthofil te verbeter, aangesien dit moontlik nielineêre multi-variant analise mag benodig. Logistiese groeimodellering is gebruik om blaarouderdom te bepaal en te klassifiseer, wat dit moontlik gemaak het om statistiese analise te vereenvoudig vir die genoemde blaarparameters. Die praktiese toepassing van die gemodelleerde en voorspelde parameters is aangetoon vir ‘n spesifieke gedeelte in seisoen twee, deur die reaksie van verskillende behandelings op toenemende watertekorte te bestudeer. Resultate het aangetoon dat verskeie parameters, met spesifieke klem op die karotenoïed:chlorofil verhouding, asook die chlorofil a:b verhouding, gemoniteer kan word op jong en ouer blare in die lower ten einde ontwikkelende waterstrestoestande te identifiseer. Die gemodelleerde parameters was egter klaarblyklik nie sensitief genoeg vir akkurate voorspelling van voorsonsopkoms-waterpotensiaalvlakke nie. Spesifieke blaarmassa, ekwivalente waterdikte, totale spesifieke blaarmassa, sowel as blaarouderdom kon suksesvol voorspel word deur gebruik te maak van absorpsieblaarspektroskopie, wat nuttig kan wees in toekomstige studies wat handel oor die kwantifisering van blaaraanpassing by die mikro-omgewing binne ‘n wingerdlower.

Thesis (PhD(Agric))--Stellenbosch University, 2012. / ENGLISH ABSTRACT: A lack of defects is required for successful table grape marketing, which pre-suppose optimal vine performance, berry development and post-harvest quality. The supply of mineral nutrients affects vine development, physiology and berry quality. Despite a vast amount of research conducted over decades, there remain many unresolved issues regarding table grape vine nutrition to ensure optimal table grape quality and shelve-life. Unjustified fertilisation practices often include excessive applications of nitrogen (N), potassium (K) and calcium (Ca). A four-year field trial was therefore conducted on a sandy soil in the Paarl district of South Africa, using grafted on Ramsey, and trained to a gable trellis system. Nitrogen, potassium and calcium were applied, singular or in combination, at rates up to 300% the calculated annual nutritional requirement. The effect of these excessive applications on table grape performance under typical South African cultivation conditions was investigated for Vitis vinifera L. cv. Prime Seedless, a very early seedless table cultivar that is produced with minimum berry diameter of 18mm, with special reference to 1) vegetative growth, 2) expression of grapevine nutrient availability through foliar analyses, 3) berry nutrient accumulation patterns of this early cultivar, 4) manipulation of berry nutrient content through soil and bunch directed applications and 5) the effect of berry nutrient content on its quality. No definite vegetative growth responses (expressed as shoot length, leaf surface area and shoot mass) and leaf chlorophyll content differences were obtained for all the treatments. These results were obtained in a vineyard on a sandy soil where excessive N fertilisation caused a reduction of soil pH to detrimentally low levels and where the excessive N, K and Ca applications reduced mutual concentrations and that of Mg, in the soil. A lack of stimulation in vegetative growth may therefore be ascribed to the combined negative effect of these excessive applications on soil pH and vine nutrition. Although the N content of petioles was higher for treatments where N was applied, consistent significant increases in petiole N with N fertilisation were not observed. Petiole N concentration showed a decreasing trend throughout the season. Petiole K concentrations were significantly increased by the K fertilisation at all phenological stages. None of the K fertilisation treatments, however, succeeded to raise petiole K concentrations above the accepted maximum norms and petiole K concentration at a specific sampling stage varied significantly between the four seasons. A general decrease in petiole K concentration was found for all seasons. Calcium fertilisation did not increase soil Ca content, resulting in a lack of differences in petiole Ca concentrations between treatments. An increase in petiole Ca concentration towards harvest was obtained. Correlations between petiole nutrient concentration and berry mineral content at harvest were poor. The only way of knowing the mineral content of berries would seem to be by measuring it directly instead of deducing it from the results of leaf or petiole analyses. The dynamics of berry growth impacted on berry nutrient concentration. Early rapid berry growth, predominantly due to cell division and cell growth, was associated with the most rapid decreases in N, P and Ca concentration. Due to mobility of K and Mg in the plant, that exceeds other nutrients, the decrease in concentration of these two mineral elements was not as pronounced as that of the others. Nutrient accumulation was most rapid during the pre-véraison period, but only Ca showed a definite termination during the early ripening period. The continued inflow of N, P, K and Mg, albeit at slower rates immediately after véraison, should be taken into consideration when fertilisation is applied. As a table grape, total accumulation of each nutrient in Prime Seedless berries also far exceeded that of other cultivars studied thus far. A particular difference is that the berry flesh:skin ratio is much higher than that of previously studied cultivars, leading to higher levels of nutrient accumulation in the flesh. Slightly larger berry size was obtained for N applications and is ascribed to slight increases in early vegetative growth, allowing a better response to GA3 treatments. The use of GA3 for berry enlargement is also considered the reason why K fertilisation, resulting in increased berry K levels, did not affect berry size, as is often found for wine grapes. Higher available NO3 - in the soil on account of excessive N applications resulted in higher levels of berry N, despite sub-optimal soil pH regimes that were created by these treatments. Berry K concentration and content were increased by K fertilisation. Rapid vine K uptake and translocation to the berries seem to negate the reduced vine nutritional status as observed in petioles for situations of over-fertilisation with N. Berry Ca levels were not increased by Ca fertilisation or by bunch applied Ca. The rapid rates of berry growth, together with low rates of berry Ca uptake and Ca uptake that terminates at the onset of ripening, are assumed to be the main reasons for this result. Low levels of decay as well as a lack of consistently increased decay were obtained for N containing treatments. Nitrogen levels in the berries above which their susceptibility to fungal infection is increased, should be established. Information on specific N compounds that may lead to more susceptibility is required. Potentially increased berry browning on account of high rates of K fertilisation needs to be further investigated; indications that this may occur were observed. Neither soil applied Ca nor bunch applied Ca improved berry quality, although Ca treatments seemed to reduce decay during the only season that significant differences were obtained. The negative effect of excessive fertilisation on soil chemistry of sandy soils has again been highlighted by this study. This annuls the fertilisation, leading to inefficient fertilisation and a lack of the desired responses. As indicator of vine nutrient availability, petiole analysis, was proven unreliable and should be evaluated in parallel with soil analyses, taking seasonal variation into consideration. The danger of being only guided by published norms for leaf nutrient concentrations when establishing fertilisation practices has again been highlighted by this study. This research indicated that for a very early cultivar like Prime Seedless, nutrient accumulation dynamics can already start to change during the pre-véraison period in some seasons. This is due to different edaphic and climatic conditions as well as berry size, which leads to much higher flesh:skin ratios. Future research on table grapes would need to develop an understanding of the various factors and dynamics that determine berry nutrient concentration and accumulation of early ripening, large berry sized, seedless table grape cultivars. / AFRIKAANSE OPSOMMING: Suksesvolle bemarking van tafeldruiwe is ten nouste afhanklik van die beskikbaarheid van druiwe sonder defekte, wat ‘n direkte verband met optimale wingerdprestasie, korrelontwikkeling en na-oes kwaliteit inhou. Voorsiening van minerale voedingstowwe beïnvloed die stok se groei, fisiologie en korrelgehalte. Ten spyte van ‘n oorweldigende hoeveelheid navorsing wat oor dekades reeds gedoen is, is daar steeds onopgeloste kwessies aangaande bemesting van tafeldruiwe vir optimale druifgehalte en houvermoë. Die gevolg is onoordeelkundige bemestingspraktyke wat o.a. aanleiding gee tot oorbemesting met stikstof (N), kalium (K) en kalsium (Ca). ‘n Vier-jaar-lange veldproef is gevolglik op ‘n sandgrond in die Paarl distrik (Suid-Afrika) onderneem deur gebruik te maak van Vitis vinifera L. cv. Prime Seedless geënt op Ramsey en op ‘n dubbel-gewel prieelstelsel opgelei is. Stikstof, K en Ca is alleen, of in kombinasie, toegedien teen hoeveelhede gelykstaande aan 300% van die wingerd se jaarlikse behoefte. Die effek van hierdie oormatige toedienings op tafeldruif prestasie onder Suid-Afrikaanse verbouingstoestande is ondersoek, met spesiale verwysing na 1) vegetatiewe groei, 2) uitdrukking van voedingstofbeskikbaarheid deur blaarontledings, 3) die voedingstof akkumulasie patrone van korrels van hierdie vroeë kultivar, 4) manipulasie van korrel voedingstofinhoud deur grond en trosgerigte toedienings en 5) die effek van korrel voedingstofinhoud op kwaliteit. Die doel van die proef was om bemestinspraktyke van Prime Seedless, ‘n baie vroeë pitlose tafeldruifkultivar met ‘n minimum korrelgrootte van 18 mm, te verfyn. Deur die akkumulasie patrone van die druiwe uit te klaar is daar ook ondersoek ingestel of oestyd en na-oes gehalte deur oormatige toediening van voedingstowwe affekteer word. Geen duidelike verskille betreffende vegetatiewe groeireaksies (uitgedruk as lootlengte, blaaroppervlaktes en lootmassas) asook verskille in blaar chlorofilinhoud is vir die behandelings verkry nie. Hierdie resultate is verkry in ‘n wingerd op ‘n sandgrond, waar oormatige N-bemesting aanleiding gegee het tot grond pH verlagings tot die peil van nadelige vlakke. Verder het die oormatige N, K en Ca toedienings wederkerige verlagings in konsentrasies, asook op dié van Mg, in die grond teweeggebring. Die tekort aan vegetatiewe groeiresponse op die behandelings kon dus toegeskryf word aan ‘n gekombineerde effek van die oormatige toedienings op grond pH en voedingstofbalanse. Hoewel die N-inhoud van bladstele hoër was vir behandelings wat N toediening ingesluit het, was daar nie konstante toenames in die vlakke verkry nie. Bladskyf N-konsentrasie het afgeneem deur die loop van die groeiseisoen. Vir alle fenologiese stadiums was bladskyf Kkonsentrasies betekenisvol verhoog deur K-bemesting. Nie een van die Kbemestingsbehandelings het egter daarin geslaag om bladskyf K inhoud vir enige monstertyd bo die algemeen aanvaarde maksimum norms te lig nie. Verder het bladskyf K inhoud by ‘n spesifieke fenologiese stadium ook betekenisvol tussen seisoene verskil. Die K-inhoud van bladskywe het afgeneem met verloop van die seisoen. Kalsiumbemesting het nie die grond se Ca inhoud deurgans verhoog nie, wat dus die tekort aan verskille in Ca konsentrasies tussen die behandelings verklaar. ‘n Toename in Ca konsentrasie en korrel Ca inhoud is vanaf set tot oes waargeneem. Swak korrelasies tussen bladskywe se voedingstofinhoude en korrels se voedingstofinhoude is verkry. Die enigste manier waarop korrels se voedingstofinhoude dus afgelei kan word, blyk te wees deur direkte bepaling daarvan. Voedingstofinhoude van korrels is deur groeipatrone daarvan beïnvloed. Vroeë korrelgroei, hoofsaaklik a.g.v. seldeling en selgroei, het met die vinnigste afnametempo van N, P en Ca gepaard gegaan. As gevolg van die hoër beweeglikheid van K en Mg in die plant in vergelyking met ander voedingstowwe, was die afname in konsentrasie van hierdie twee elemente nie so groot soos vir die ander nie. Voedingstofakkumulasie was die vinnigste in die periode voor deurslaan. Slegs Ca het ‘n beeïndiging van opname aan die einde van hierdie periode getoon. Die voortgesette opname van N, P, K en Mg, alhoewel stadiger kort na deurslaan, moet in ag geneem word wanneer bemesting toegedien word. Vir hierdie kultivar het die totale opname van elke bemestingstof dié van die ander kultivars wat tot hede bestudeer is, ver oorskry. ‘n Spesifieke verskil is ‘n baie hoër vleis:dop verhouding as wat vir ander kultivars verkry is. Dit gee aanleiding tot baie hoër vlakke van voedingstofakkumulasie in die vleis. Effens groter korrelgroottes is verkry waar N toedienings gemaak is. Dit word toegeskryf aan klein toenames in vroeë vegetatiewe groei, wat dus beter reaksie op GA3 behandelings tot gevolg gehad het. Die gebruik van GA3 vir korrelvergroting word ook beskou as die rede waarom K-bemesting, wat tot hoër vlakke van K in die korrels aanleiding gegee het, nie korrelgrootte, soos by wyndruiwe, bevorder het nie. Hoër NO3 - in die grond (water), na aanleiding van N toedienings, het aanleiding gegee tot hoer vlakke van N in die korrels. Dit het plaasgevind ten spyte van sub-optimale grond pH wat deur die oormatige N toedienings veroorsaak is. Korrel K konsentrasie en -inhoud is deur K-bemesting verhoog. Vinnige opname en translokasie van K na die korrels het ook geblyk die rede te wees waarom die verlaagde voedingstatus van die stokke a.g.v. oorbemesting met N nie die korrels se K inhoud geaffekteer het nie. Die vinnige groeitempo van die korrels, tesame met lae vlakke van Ca opname, asook korrels se Ca opname wat tydens rypwording ophou, word as die redes vir die tekorte aan behandelingseffekte beskou. Lae vlakke van bederf, asook ‘n tekort aan betroubare tendense dat bederf deur Nbemesting verhoog word, is verkry. Daar moet vasgestel word of daar N vlakke in die korrels is waarbo hul vatbaarheid vir swaminfeksies verhoog word, en of daar spesifieke N verbindings is wat die korrels meer vatbaar maak vir bederf. Indikasies dat K-bemesting interne verbruiningsvlakke verhoog het, regverdig verdere ondersoek. Korrelkwaliteit is nie deur grond- of trosgerigte toedienings bevoordeel nie. Die negatiewe effek van oormatige bemesting op die chemiese samestelling van sandgronde is weer deur hierdie navorsing uitgelig. Dit lei tot oneffektiewe bemesting en ‘n tekort aan die verlangde effekte. Blaarontledings blyk onbetroubaar te wees as aanduiding van voedingstof beskikbaarheid. Dit moet evalueer word saam met grondontledings en ook seisoenale variasie in ag neem. Die gevaar om slegs deur gepubliseerde norme gelei te word wanneer bemestingspraktyke bepaal word, is weer deur hierdie navorsing uitgelig. Voorst is daar in hierdie navorsing gevind dat voedingstof akkumulasiepatrone van ‘n baie vroeë kultivar soos Prime Seedless alreeds voor deurslaan begin verander a.g.v. omgewingstoestande en korrelgroei wat tot ‘n veel hoër vleis:dop verhouding aanleiding gee. Toekomstige navorsing op tafeldruiwe behoort die faktore en dinamika wat voedingstofkonsentrasie en -akkumulasie in korrels van vroeë, groot korrel, pitlose tafeldruifkultivars beïnvloed verder te ondersoek.

Thesis (PhD(Agric))--Stellenbosch University, 2012. / ENGLISH ABSTRACT: Grapevines are one of the most important and diverse crops in the world, but tend to be susceptible for numerous pests and diseases. The dagger nematode, Xiphinema index (X. index) is a well-known soil-borne pest of grapevine and vector of grapevine fanleaf virus. Several Vitis species showed resistance to this pest. Breeding efforts have been underway for several decades to create resistant rootstocks. However, conventional breeding efforts are time consuming due to grapevines being a perennial crop, its heterozygosity, as well as its long growth cycle. Breeding new grapevine varieties are also expensive and work intensive. The development of marker-assisted selection introduced a way to overcome some of the abovementioned problems. The aim of this study was to broaden the genetic evaluation and breeding efforts for improved X. index resistance in grapevine rootstocks. In 2007 several crosses were made in the University of California, Davis vineyards. The background for all these crosses consisted of V. arizonica. These V. arizonica plants are part of a collection obtained by H.P. Olmo during the 1960’s. In recent studies it was established that X. index resistance is controlled by a single dominant gene. The 0701 (R8916-07 (Wichita Refuge x b40-14) x R8916-32), 0704 (161-49C x b40-14) and 0705 (161-49C x R8916-22) populations were created to confirm the homozygous nature of b40-14, a V. arizonica accession. In addition, several V. arizonica species were screened to confirm their resistance or susceptibility towards X. index feeding. The 0705 population was also used to create a genetic map for X. index resistance. In this study a new and improved screening method was developed to inoculate vines under greenhouse conditions. This screening method proved to be quicker and less damaging on the nematodes than traditional systems. Control varieties were used and O39-16, a commercial rootstock showed no damage, even with high nematode pressure, whereas V. rupestris Saint George had severe root damage and decline after eight weeks of exposure. A range of V. arizonica accessions was tested for their resistance to X. index feeding. Of the 18 genotypes tested, half showed resistance and the rest were susceptible. It is possible that these genotypes are not pure V. arizonica genotypes. Genotypes with V. arizonica in the background were also tested. Wichita Refuge was used as a susceptible female parent and the progeny were expected to be heterozygous resistant. Some of the progeny allowed low levels of feeding damage, which may have been the result of the more effective inoculation method described above. The 0701 population confirmed the hypothesized model of 3:1 (Resistance (R):Susceptible (S)) segregation although 13 of the genotypes showed significantly higher gall numbers than the susceptible female parent. The possibility of transgressive segregation exists, but needs to be confirmed. All progeny from the 0704 population should be heterozygous resistant, but a 1:1 (R:S) segregation pattern was observed. The 0705 population was created as a mapping population to study X. index resistance. This population was also tested in the greenhouse for its X. index resistance and was expected to segregate 1:1 (R:S). The X2 analysis did not fully support this model. A genetic map covering all 19 linkage groups, and positioning 175 polymorphic SSR markers was created for the 164 progeny in the 0705 population. MapQTL analysis revealed a major QTL on linkage group 9 and two minor QTL’s on groups 13 and 19. The major QTL placed between markers VMC1c10 and CTG1032918 with a LOD score of 33.4 explaining 70.5% of the phenotypic variance for X. index. This QTL is the second major QTL discovered for X. index resistance. With the discovery of a second major QTL, the two types of resistance can be pyramided. Work is underway to saturate the area around the major QTL on linkage group 9 and to move towards physical mapping of X. index resistance. The b40-14 V. arizonica accession is also known for its resistance to Pierce’s disease and the possibility of simultaneous expression of two types of resistance is created. The 0705 population can also be used to evaluate phenotypical characteristics in the field to determine if useful rootstocks can be selected. Taken together, the results obtained in this study provide improved methods and highly characterized plant populations to support the efforts in obtaining improved X. index resistance in grapevine rootstocks. / AFRIKAANSE OPSOMMING: Wingerde is van die belangrikste en mees diverse gewasse op aarde, maar hulle neig om vir ‘n verskeidenheid plae en siektes vatbaar te wees. Die dolk-aalwurm, Xiphinema index (X. index), is ‘n bekende grondgedraagde plaag van wingerd en ‘n vektor vir wingerd- netelblaarvirus. Verskeie Vitis-spesies toon weerstand teen hierdie plaag. Daar word reeds vir dekades pogings aangewend om weerstandbiedende onderstokke te kweek. Konvensionele kweekpogings is egter tydrowend omdat wingerd ‘n meerjarige gewas is, op grond van die heterosigositeit van die gewas, sowel as die lang groeisiklus. Dit is ook duur en arbeidsintensief om nuwe wingerdvariëteite te kweek. Die ontwikkeling van merkerondersteunde seleksie het dus ‘n metode verskaf om sommige van bogenoemde probleme te oorkom. Die doelwit van hierdie studie was om die genetiese evaluerings- en kweekpogings vir verbeterde X. index-weerstand in wingerd-onderstokke te verbreed. In 2007 is verskeie kruisings in die wingerde by die Universiteit van Kalifornië, Davis gemaak. Die agtergrond vir al hierdie kruisings het bestaan uit V. arizonica. Hierdie V. arizonica-plante vorm deel van ‘n versameling wat in die 1960’s deur H.P. Olmo verkry is. In onlangse studies is daar bepaal dat X. index-weerstand deur ‘n enkele dominante geen beheer word. Die 0701 (R8916-07 (Wichita Refuge x b40-14) x R8916-32), 0704 (161-49C x b40-14) en 0705 (161-49C x R8916-22) bevolkings is geskep om die homosigotiese geaardheid van b40-14, ’n V. arizonicaafstammeling, te bevestig. Daarbenewens is verskeie V. arizonica-spesies gesif om hulle weerstand teen of vatbaarheid vir X. index voeding te bevestig. Die 0705 bevolking is ook gebruik om ‘n genetiese kaart vir X. indexweerstand te skep. In hierdie studie is ‘n nuwe en verbeterde siftingsmetode ontwikkel om wingerdstokke onder glashuistoestande te inokuleer. Daar is gewys dat hierdie siftingsmetode vinniger en minder skadelik vir die aalwurms as tradisionele metodes is. Beheervariëteite is gebruik en O39-16, ‘n kommersiële onderstok, het geen skade getoon nie, selfs met hoë aalwurmdruk, terwyl V. rupestris Saint George ernstige wortelskade en agteruitgang na agt weke se blootstelling getoon het. ‘n Verskeidenheid V. arizonica-afstammelinge is vir hulle weerstand teen X. index-voeding getoets. Van die 18 genotipes wat getoets is, het die helfte weerstand getoon en die res was vatbaar. Dit is moontlik dat hierdie genotipes nie suiwer V. arizonica-genotipes was nie. Genotipes met V. arizonica in hulle agtergrond is ook getoets. Wichita Refuge is as ‘n vatbare vroulike ouer gebruik en die verwagting was dat die nageslag heterosigoties weerstandbiedend sou wees. Sommige van die nageslag het lae vlakke van voedingskade toegelaat, wat moontlik die gevolg was van die meer doeltreffende inokulasiemetode wat hierbo beskryf word. Die 0701 bevolking het die veronderstelde model van 3:1 (Weerstandbiedend (W):Vatbaar (V)) segregasie bevestig, hoewel 13 van die genotipe noemenswaardig hoër galgetalle as die vatbare vroulike ouer getoon het. Die moontlikheid van transgressiewe segregasie bestaan, maar dit moet nog bevestig word. Alle nageslag van die 0704 bevolking behoort heterosigoties weerstandbiedend te wees, maar ‘n 1:1 (W:V) segregasiepatroon is waargeneem. Die 0705 bevolking is as ‘n karteringsbevolking geskep om X. index-weerstand te bestudeer. Hierdie bevolking is ook in die glashuis vir sy X. index-weerstand getoets en daar is verwag dat dit 1:1 (W:V) sou segregeer. Die X2 analise het nie hierdie model ten volle ondersteun nie. ‘n Genetiese padkaart wat al 19 skakelingsgroepe en die posisies van 175 polimorfiese SSR merkers toon, is vir die 164 afstammelinge in die 0705 bevolking geskep. MapQTL analise het ‘n groot kwantitatiewe eienskap lokus (QTL) op skakelingsgroep 9 en twee kleiner QTL’e op groepe 13 en 19 onthul. Die groot QTL is tussen merkers VMC1c10 en CTG1032918 met ‘n LOD telling van 33.4 geplaas en het 70.5% van die fenotipiese variansie van X. index verklaar. Hierdie QTL is die tweede groot QTL wat vir X. index-weerstand ontdek is. Met die ontdekking van ‘n tweede groot QTL, kan die twee soorte weerstand gepiramideer word. Werk word reeds onderneem om die area rondom die groot QTL op skakelingsgroep 9 te versadig en om na die fisiese kartering van X. index-weerstand te beweeg. Die b40-14 V. arizonica-afstammeling is ook bekend vir sy weerstand teen Pierce se siekte en die moontlikheid word geskep vir die gelyktydige uitdrukking van twee soorte weerstand. Die 0705 bevolking kan ook gebruik word om die fenotipiese kenmerke in die veld te evalueer om te bepaal of bruikbare onderstokke geselekteer kan word. In kombinasie behoort die resultate wat in hierdie studie verkry is, verbeterde metodes en hoogs gekarakteriseerde plantbevolkings te lewer wat die pogings sal ondersteun om verbeterde X. index-weerstand in wingerdonderstokke te verkry.

Thesis (MScAgric (Agronomy)--University of Stellenbosch, 2007. / The Cape Floristic Region is a highly distinctive phytogeographical unit which is recognized as a floral Kingdom on its own. Buchu (Agathosma betulina) plants fall under this important Kingdom. Buchu is one of the traditional medicinal plants originating in the Western Cape province of South Africa and the essential oil derived from the leaves is exported in large volumes. Due to high demand, under supply, restrictions of wild harvesting and high prices for Buchu essential oil, growers have started to introduce and commercialize this species as a crop. This commercialization of Buchu necessitated agronomic research to optimize production techniques. The objective of this study was to determine the optimum pH range for the cultivation of high yielding Buchu with acceptable essential oil quality under controlled conditions and compare this with the conditions in the natural habitat. Plant, soil and climatic data were gathered from eleven sites in the natural habitat of Buchu (A. betulina) in the Cederberg Mountains. At all sites most rainfall occurred from May to September, while high temperatures were recorded in summer. Soil analyses indicated low levels of nutrients and low soil pH, ranging from 3.7 to 5.3 at all the sites studied. Low levels of nutrients were also obtained from foliar analysis collected from plants at each of the different sites. Chemical analyses of the essential oil indicated that the plants were from a high quality diosphenol chemotype. In the greenhouse experiment, five different pH levels (pH 33.99, 4-4.99, 5-5.99, 6-6.99 and 7-7.99) were evaluated to determine the effect on growth, yield and quality of A. betulina. Complete nutrient solutions were used to irrigate the plants grown in pots filled with a sand and coco peat mixture. Although the plants subjected to the pH treatment of 4-4.99 tended to have the highest growth rate and yield, this did not differ significantly (P=0.05) from plants subjected to pH values between 3 and 6.99. In contrast, the pH 7-7.99 treatment lead to reduced growth and lower vegetative yields. Levels of nutrients obtained from the leaf mineral analysis differed significantly with different pH treatments. High pH levels resulted in high nitrogen, phosphorus, sodium, manganese and boron contents, but lower contents of copper. Nitrogen, phosphorus, calcium and zinc were higher than those recorded for plants from their natural habitat, but still within the norm reported for most plants. Levels of manganese, sodium, magnesium and copper were found to be more or less similar to the values obtained in plants from the natural habitat. No significant differences were found in essential oil quality in response to the pH treatments. However, high pulegone levels (10.8 to 13.2 %) were obtained from all the treatments in the greenhouse experiment. The high levels of this essential oil constituent could have a negative effect on the marketability of the oil and this aspect may need some attention in future studies.