The evaluation of production alternatives in agriculture requires a close examination of their economic and environmental impacts. This study was conducted to identify the crops with the highest profit potential given terminal market prices over the last five years, evaluate the feasibility of adopting new crop alternatives, given historical price information and limited production resources, and determine the potential environmental impacts of adopting new cropping strategies in Accomack and Northampton Counties on the Eastern Shore of Virginia. A database of daily terminal price information was created to identify the market windows for specific commodities, their respective high, median and low prices, and their price variability over the last five years. A linear programming model was used to determine optimal farming operations for those farmers that grow only wheat and soybean versus farmers who are willing and able to include vegetables in their crop mix. PLANETOR, an environmental impact computer program, was used to estimate the potential soil erosion, pesticide leaching and runoff, nitrogen leaching, and phosphorous runoff for different scenarios. The model shows that some of the new vegetable commodities could substantially increase the net returns of the farming operations in question. Romaine and Boston Lettuce were consistently selected as the most profitable alternatives while the region's traditional crops offered little competition. Wheat and soybean production showed acceptable levels of soil erosion, as defined by the T-values for the region, and low potential for nitrogen leaching. They did, however, exhibit a higher potential for water contamination, through leaching, or runoff, of high toxicity chemicals. Although lettuce production had higher than recommended soil losses, a well-diversified crop mix offsets its negative impacts at the farm level. Lettuce also uses low toxicity chemicals, decreasing potential health hazard from their leaching or runoff. The introduction of the new vegetable commodities is recommended on the basis of the high profits that they offer, as well as the more positive pesticide leaching and runoff potential. Their final adoption, however, should take place only after establishing a well defined marketing strategy and resolving potential marketing problems. No crop exists that could offer both high profits and have no impact on the environment. Kenaf was thought to be one, but it was soon eliminated on both grounds. This study showed, however, that the new vegetable crops considered may offer better net returns, while they do not necessarily translate into environmental disasters. / Master of Science

New hybrid Echinacea cultivars, based on crosses of Echinacea purpurea (L.) Moench with several other Echinacea species, have generated interest and excitement in the marketplace due to novel flower colors and forms. However, these cultivars vary significantly in their growth habits and requirements from the species. We examined factors in the production of Echinacea hybrid cultivars to provide guidance to growers. Foliar sprays 600 mg·L⁻¹ benzyladenine (BA) increased numbers of branches between 19% and 83% in Echinacea cultivars while 400 mg·L⁻¹ dikegulac sodium or 500 mg·L⁻¹ ethephon did not improve branching. Of several height control PGRs applied to E. ‘Marmalade,’ only plants treated with two applications of 5000 mg·L⁻¹ daminozide were shorter (24%) compared to untreated controls although flowering was also reduced by 70%. Echinacea ‘Harvest Moon’ plants were shorter in response to all of the PGRs applied, with the best results seen in plants treated with foliar sprays of uniconazole (one application of 30 mg·L⁻¹ or two applications of 15 mg·L⁻¹ ), two applications of 5000 mg·L⁻¹ daminozide, or 4 mg·L⁻¹ paclobutrazol applied once as a drench. Supplying N at 150 mg·L -1 during the growing season provided Echinacea cultivars adequate nutrition and maximized numbers of branches and flowers and shoot dry weight. In overwintering, fertilization treatments that resulted in low substrate electrical conductivity going into dormancy, 5.0 kg·m controlled release fertilizer 15N-3.9P-10K or 150 mg·L⁻¹ N using 15N-2.2P-12.5K applied using constant liquid feed, resulted in the highest survival rates of Echinacea cultivars. As a monitoring tool, SPAD measurements were not successful in predicting tissue N levels in Echinacea hybrids. Twenty-one hybrid cultivars acquired as stage 3 tissue culture plantlets were grown under one of three photoperiods (10-hour, 16-hour, or 24-hour) for 10 weeks before being transplanted to larger containers and grown under natural daylength until flowering. Providing Echinacea hybrid cultivars with a 16-hour photoperiod during liner production resulted in plants which flowered soonest without negative effects on growth. The need for height control PGRs varied by cultivar; however, overall height control PGRs controlled flower stalk height and increased market rating. / Ph. D. / New hybrid <i>Echinacea</i> cultivars, based on crosses of <i>Echinacea purpurea</i> (L.) Moench with several other <i>Echinacea</i> species, have generated interest and excitement in the marketplace due to novel flower colors and forms. However, these cultivars vary significantly in their growth habits and requirements from the species. We examined factors in the production of <i>Echinacea</i> hybrid cultivars to provide guidance to growers. Foliar sprays 600 mg·L-1 benzyladenine (BA) increased numbers of branches between 19% and 83% in <i>Echinacea</i> cultivars while 400 mg·L-1 dikegulac sodium or 500 mg·L-1 ethephon did not improve branching. Of several height control PGRs applied to E. ‘Marmalade,’ only plants treated with two applications of 5000 mg·L-1 daminozide were shorter (24%) compared to untreated controls although flowering was also reduced by 70%. <i>Echinacea</i> ‘Harvest Moon’ plants were shorter in response to all of the PGRs applied, with the best results seen in plants treated with foliar sprays of uniconazole (one application of 30 mg·L-1 or two applications of 15 mg·L-1 ), two applications of 5000 mg·L-1 daminozide, or 4 mg·L-1 paclobutrazol applied once as a drench. Supplying N at 150 mg·L -1 during the growing season provided <i>Echinacea</i> cultivars adequate nutrition and maximized numbers of branches and flowers and shoot dry weight. In overwintering, fertilization treatments that resulted in low substrate electrical conductivity going into dormancy, 5.0 kg·m controlled release fertilizer 15N-3.9P-10K or 150 mg·l-1 N using 15N-2.2P-12.5K applied using constant liquid feed, resulted in the highest survival rates of <i>Echinacea</i> cultivars. As a monitoring tool, SPAD measurements were not successful in predicting tissue N levels in <i>Echinacea</i> hybrids. Twenty-one hybrid cultivars acquired as stage 3 tissue culture plantlets were grown under one of three photoperiods (10-hour, 16-hour, or 24-hour) for 10 weeks before being transplanted to larger containers and grown under natural daylength until flowering. Providing <i>Echinacea</i> hybrid cultivars with a 16-hour photoperiod during liner production resulted in plants which flowered soonest without negative effects on growth. The need for height control PGRs varied by cultivar; however, overall height control PGRs controlled flower stalk height and increased market rating.

Master of Science / Department of Horticulture, Forestry, and Recreation Resources / Jack Fry / Zoysiagrass (Zoysia spp.) is more heat and drought resistant and requires fewer cultural inputs than cool-season (C3) turfgrasses; however, its widespread use may be limited by an extended period of winter dormancy, the disease Rhizoctonia large patch (Rhizoctonia solani Kühn AG-2-2 LP), and lack of cold hardiness. Objectives of these 2012-2014 field studies were to evaluate: 1) turfgrass colorants and overseeding for color enhancement; 2) three colorant application volumes on color persistence; 3) colorants applied at two volumes, once or sequentially, on buffalograss (Buchloë dactyloides) and zoysiagrass; 4) the impact of nitrogen source and application timing on large patch severity; and 5) winter hardiness and turf quality of new experimental lines. The colorants Ultradwarf Super and Green Lawnger provided acceptable lawn-height ‘Chisholm’ zoysiagrass color for 7 to 9 and 19 to 24 weeks after treatment (WAT), respectively. Chisholm receiving a sequential application of either product in mid-winter (14 WAT) maintained an acceptable color level after that point until mid-May (28 WAT). Overseeding with annual ryegrass did not provide acceptable color for more than 4 weeks. Evaluation of the colorants Green Lawnger, Endurant, and Wintergreen Plus showed that acceptable Chisholm color at lawn-height occurred for 8 to 14 WAT at 80 gallons per acre (GPA) and 16 to 26 WAT at 240 GPA. Buffalograss at lawn-height receiving a single autumn colorant application had acceptable color for 8 to 12 WAT at 100 GPA or 8 to 14 WAT at 160 GPA. ‘Meyer’ zoysiagrass maintained at a 0.5 inch height receiving a single autumn colorant application had acceptable color for 8 to 18 WAT at 100 GPA or 14 to 18 WAT at 160 GPA. No differences in large patch occurred between spring and fall applications of ammonium sulfate and calcium nitrate, nor between those treatments and summer-applied urea. Applying fertilizer in spring when soils reached 21 ºC increased green cover on some rating dates compared to applications in fall when soil temperatures fell to 21 ºC but differences were minimal. Out of 985 experimental zoysiagrass lines planted in the field, about 25 were identified for further evaluation for cold hardiness, large patch resistance, and turf quality.

Thesis (PhD(Agric) (Horticulture))--University of Stellenbosch, 2009. / ENGLISH ABSTRACT: Branch architecture is the position and length of lateral shoots along a main axis, and is dependant on competitions (dominance) among meristems and lateral shoots. In areas with inadequate winter chilling, branch architecture is altered, the dynamics of which are poorly understood. The aim of this work was to better understand the dynamics underlying plant architecture. In the first part of the study, the dynamics of apple branch architecture were characterized for two cultivars, Golden Delicious and Granny Smith, in areas with differing degrees of inadequate winter chilling (a warm area and a cool area). In an additional study, progeny of a mapped ‘Telamon’ (columnar habit) and ‘Braeburn’ (normal habit) population were used to quantify branch architecture in an effort to develop quantitative trait loci (QTLs) for branching habit. Although branch architecture could be quantified, it was difficult to relate these to known qualitative branching habits, as the columnar gene is dominant and limited the number of progeny that were not columnar. With the exception of organogenesis in the season preceding growth, acrotonic tendencies (number of growing laterals, lateral length, fruit set) were not related to temporal (primigenic) dominance of the distally located buds or flowers within an axis. In the warm area, both relative time of budburst and flowering among buds within an axis did depict a loss of acrotony (positional dominance of the distally located buds and shoots within an axis). The first buds to burst and flower in the warm area had the greatest ability to grow out and set fruit, respectively, regardless of position within the shoot, implicating a role for primigenic dominance when chill unit accumulation was inadequate. Overall, temporal (primigenic) dominance in the warm area, and positional dominance (acrotony) in the cool area dictated lateral outgrowth and development. / AFRIKAANSE OPSOMMING: Takargitektuur verwys na die posisie en lengte van laterale lote soos dit oor die hoofas versprei voorkom. Dit is afhanklik van kompetisie (dominansie) tussen meristeme en laterale lote. In areas met onvoldoende winterkoue word takargitektuur verander, maar die dinamika van hierdie veranderinge word nog nie goed verstaan nie. Die doel van hierdie navorsing was om die onderliggende dinamika wat plantargitektuur beïnvloed beter te verstaan. In die eerste deel van die studie is die dinamika van appeltakargitektuur van twee cultivars Golden Delicious en Granny Smith, in twee areas met verskillende mate van onvoldoende winterkoue bestudeer (’n warm en ’n koel area). In ’n verdere studie is die nageslag van ‘n ‘Telemon’ (kolomgroeiwyse) en ‘Braeburn’ (normale groeiwyse) kruising gebruik om takargitektuur te kwantifiseer. Dit is gedoen in ’n poging om kwantitatiewe eienskapslokusse vir vertakking te ontwikkel. Alhoewel takargitektuur kwantifiseer kon word, was dit moeilik om dit in verhouding te bring met kwalitatiewe vertakkingspatrone daar die kolomgroeiwyse-geen dominant is en die aantal indiwidue in die nageslag wat nie ’n kolomgroeiwyse gehad het nie beperk was. Met die uitsondering van organogenese in die seisoen wat groei voorafgaan, is akrotoniese neigings (aantal laterale lote, laterale lootlengte, vrugset) nie beïnvloed deur tydelike (primigeniese) dominansie van distale knoppe of blomme binne ’n as nie. In die warm area het beide relatief tot knopbreek en blomtyd binne ’n assestelsel die verlies aan akrotonie beskryf (posisionele dominansie van distale knoppe en lote in assestelsel). Die eerste knoppe wat bot en blom in die warm area het die beste vermoë om te groei en vrugte te set, onafhanklik van hul posisie. Dit impliseer die rol van primigeniese dominansie wanneer ’n gebrek aan winterkoue ervaar word. Algemeen gesien was dit tydelike (primigeniese) dominansie in warm areas en posisionele dominansie (akrotonie) in die koeler area wat lateraal bot en ontwikkeling bepaal het.

Stellenbosch University. Faculty of AgriSciences. Dept. of Horticulture. / Thesis (PhD (Agric))--Stellenbosch University, 2006. / ENGLISH ABSTRACT: Market preferences for larger fruit have forced producers to adopt cultural practices that will ensure bigger fruit even if this comes at the expense of reduced total yields. In order to obtain acceptable fruit size there must be an adequate supply of photosynthetic carbon products especially during the cell division stage of fruit growth. Competition between fruits and between fruit and vegetative growth, as well as adverse climatic conditions, may limit the carbon supply to the fruits at this critical period and thus limit the final fruit size. Growers are showing renewed interest in the use of girdling or scoring in combination with the usual fruit thinning program to achieve growth control and increase fruit size. A new and milder chemical growth retardant, prohexadione-calcium (ProCa), is now also available for vegetative growth control of apple trees. [n this study, the effects of, and potential interaction between scoring, ProCa and fruit thinning were investigated, with respect to shoot and fruit growth, yield and photosynthetic capacity, in 'Royal Gala" 'Fuji' and 'Cripps' Pink' apple trees. ProCa decreased final extension shoot length in all three cultivars. Extension shoots were generally more sensitive than bourse shoots to scoring and ProCa. ProCa seems to be a more effective way of controlling shoot growth than scoring, with 'Fuji' and 'Cripps' Pink' being more sensitive than 'Royal Gala' to the application of ProCa. Scoring led to increased fruit growth rates during the first 40 days after full bloom (DAFB), and culminated in better fruit size at harvest. Scoring improved the total soluble solids concentration (TSS) of 'Fuji' and 'Cripps' Pink' compared to control and ProCa treatments. ProCa inhibited shoot growth effectively, but no evidence was found for improved carbon allocation to fruits and reproductive buds. Yield efficiencies of scored trees were significantly improved in all cultivars during the second season, due to better reproductive bud development after the first year of scoring. On 'Royal Gala' and 'Cripps' Pink', the efficiency of scoring to stimulate reproductive bud development on old and new spurs declined after 4 weeks after full bloom (WAFB). In 'Fuji', scoring later than I WAFB led to a decreasing positive response on old and new spurs. In contrast, reproductive bud development on long shoots increased with later scoring (6 and 8 W AFB) on all cultivars. It seems that the most beneficial time of scoring is 2-4 W AFB, as early as possible during the cell division stage offruit growth, but not before natural drop has occurred. The combination of early-season scoring and application of ProCa seems to hold potential for increasing carbon allocation to the fruit and improving fruit size and quality attributes. Scoring early in the season reduced photosynthetic capacity, and this reduction in carbon availability led to earlier cessation of shoot growth as well as shorter shoots. Later in the season, reduced fruit numbers led to a decrease in photosynthesis. The optimum temperature range for photosynthesis was found to adjust according to seasonal temperature variations. The harvest-induced reduction in sink strength changed stomatal sensitivity to higher temperature. Due to a reduced demand for carbohydrates by the plant, the maximum rate of photosynthesis (Amax) was reduced post-harvest. Following this reduction in sink strength and Am .. , stomata became more sensitive to high leaf temperatures, thus restricting water loss. Pre-harvest there was a strong demand for carbohydrates, therefore stomata were kept open at higher temperatures to ensure a high rate of C02 incorporation, but at a cost with regard to water use efficiency. The sharp increase in dark respiration (Rd) in leaves and fruit with an increase in temperature would mean that significant carbohydrate shortages could occur in trees during source limited periods early in the season, especially under warm weather conditions commonly experienced in the Western Cape region. / AFRIKAANSE OPSOMMING: Die effek van omgewings- en interne faktore op koolstofproduksie en -allokasie in appelbome (Malus domestlca Borkh.). Mark voorkeur vir groter vrugte forseer produsente om tegnieke te gebruik wat groter vrugte sal verseker selfs al beteken dit verlaagde totale opbrengste. Om aanvaarbare vruggrootte te bereik moet daar voldoende voorsiening van fotosinteties geproduseerde koolstofprodukte aan die vrug wees, veral gedurende die selverdelingstadium van vruggroei. Kompetisie tussen vrugte, en tussen vrugte en vegetatiewe groei sal die voorsiening van koolstof gedurende die kritieke stadium aan die vrug beperk en so vruggroote benadeel. Daar is dus hernude belangstelling in die gebruik van ringelering in kombinasie met die gewone vrug uitdunprogramme om groei te beheer en vruggrootte te verbeter. 'n Nuwe, sagter chemiese groeireguleerder, proheksadioon-kalsium (ProCa) is ook nou beskikbaar vir groeibeheer op appelbome. In hierdie studie is die effekte van, en moontlike interaksie tussen ringelering, ProCa en vruguitdunning ondersoek ten opsigte van loot- en vruggroei en opbrengs, sowel as die effekte op gaswisseling op 'Royal Gala', 'Fuji' en 'Cripps' Pink' appelbome. ProCa veroorsaak korter lote in aJ drie kultivars. Verlengingslote is meer sensitief as beurslote vir ringelering en ProCa. ProCa is effektiewer as ringelering om lootgroei te beheer, en 'Fuji' en 'Cripps' Pink' is sensitiewer as 'Royal Gala'. Ringelering lei tot verbeterde vruggroeitempos gedurende die eerste 40 dae na volblom en verbeterde vruggrootte by oes. Ringelering verbeter die totale oplosbare vastestotkonsentrasie (TOVS) van 'Fuji' en 'Cripps' Pink' in vergelyking met kontrole- en ProCa-behandelings, onderskeideHk. ProCa inhibeer lootgroei effektief, maar geen bewyse van verbeterde koolstomllokasie na vrugte en reproduktiewe knoppe is gevind nie. Opbrengseffektiwiteit van geringeleerde borne verhoog gedurende die tweede seisoen van ringelering weens beter reproduktiewe knopontwikkeling. Ringelering later as 4 weke na volblom (WNVB) is minder effektief om reproduktiewe knopontwikkeling op ou en nuwe spore in 'Royal Gala' en 'Cripps' Pink' te stimuleer. Die positiewe effek van ringelering op reproduktiewe knoppe op 'Fuji' verminder sodra dit later as I WNVB gedoen word. Op langlote het 'n laat ringelering (6 en 8 WNVB) die beste effek op reproduktiewe knopontwikkeling. Die mees voordelige tyd om te ringeIeer was 2-4 WNVB, so vroeg as moontlik gedurende die selverdelingstadium van vruggroei, maar nie voor natuurlike vrugval voltooi is nie. Die kombinasie van vroei! ringelering en die toediening van ProCa het potensiaal om koolstofallokasie na die vrug te verbeter, met die gepaardgaande verbetering in vruggrootte en -kwaliteit. RingeJering vroeg in die seisoen inhibeer fotosintese en hierdie verlaging in koolstof beskikbaarheid het tot gevolg dat lootgroei vroei!r gestaak word. Later in die seisoen veroorsaak verlaagde vruggetalle 'n afname in fotosintese. Die optimum temperatuur vir fotosintese verander na gelang van heersende lugtemperature. Die oes-geinduseerde verlaging in sinksterkte verander stomatale sensitiwiteit vir hoo temperature. Weens 'n verJaagde aanvraag vir koolhidrate deur die plant word fotosintese verlaag na-oes. Weens die verlaging is stomata sensitiewer vir hoer temperature en beperk dus waterverlies. V oor oes is daar 'n hoo aanvraag na koolhidrate dus word stomata oop gehou selfs by hoe temperature ten koste van watergebruiksdoeltreffendheid. Die skerp styging in donker respirasie in blare en vrugte met 'n verhoging in temperature sal beteken dat koolhidraat-tekorte kan ontstaan in bome gedurende die bron-beperkte periodes vroeg in die seisoen, veral onder warm toestande 500S wat algemeen ervaar word in die Wes Kaap.

Dissertation (PhD (Agric))--University of Stellenbosch, 2003. / ENGLISH ABSTRACT: Leaf blackening is a particular problem limiting vase life and marketability of Protea cut flowers. This research investigated suppression of Protea leaf blackening with a specific focus on Protea cv. Sylvia (P. eximia x P. susannae) cut flowers. Leaf blackening decreased significantly with decreasing storage temperatures m 'Sylvia' proteas and this was attributed to lower respiration rate and conservation of carbohydrate. Low storage temperatures were beneficial in short term handling procedures encountered during airfreight. However, use of low temperatures alone during the longer sea freight period was unsatisfactory in either maintaining or extending 'Sylvia' protea vase life. Cooling of 'Sylvia' proteas under vacuum significantly suppressed leaf blackening and was of greater benefit than forced air cooling. Although removal of the uppermost leaves delayed leaf blackening in short term storage no significant benefit was found for longer storage periods. Girdling directly beneath the 'Sylvia' protea flowerhead significantly reduced leaf blackening and in combination with low storage temperatures (O°C) enabled a significant extension in both storage and vase life of 'Sylvia' proteas. 'Sylvia' proteas did not exhibit a climacteric respiration peak during 96 h storage at O°C. Exposure to ethylene did not increase Protea leaf blackening or have a detrimental effect on vase life of either proteas or pincushions evaluated. No beneficial response to sucrose supplementation was found in 'Sylvia' proteas. Analysis of the sugar content of both flowerhead and leaves indicated that glucose supplementation might be of benefit and was investigated. Holding solutions of 2.5 % glucose significantly extended vase life due to a significant reduction in leaf blackening. Vase life was terminated due to flowerhead collapse instead of leaf blackening for the first time in 'Sylvia' protea cut flowers. Vase life was significantly extended by 2:3% glucose pulse solutions and leaf blackening significantly suppressed with increasing glucose pulse concentration. Solution uptake was facilitated by use of high intensity PAR lights in the early morning and was attributed to increased stomata opening and a consequent increase in both transpiration and glucose solution uptake. The faster uptake of glucose solutions in shoots harvested in the afternoon was attributed to higher shoot temperatures and consequent transpiration rate to those harvested in the morning. There was a significant reduction in uptake time with increasing pulse temperature, which enabled vacuum cooling to be performed earlier further benefiting storage and vase life extension. Enclosure of 'Sylvia' proteas in polyethylene (PE) lined cartons did suppress leaf blackening in non-pulsed shoots. However, this had no practical significance on useful vase life, which was terminated at this point due to excessive leaf blackening. Water loss appears to have a minimal influence on 'Sylvia' protea leaf blackening. Shading at four and three weeks prior to harvest coincided with a period of significant flowerhead dry mass increase. It is thought that shading at this point, concurrent with an increased carbohydrate demand by the developing flower head resulted in a temporary limitation in carbohydrate supply resulting in the appearance of preharvest leaf blackening. It would appear that proteas do not store large quantities of carbohydrate. Although accentuating winter light conditions by shading did result in a decrease in carbohydrate content the fact that carbohydrate content was already low precluded shading from having a significant impact on postharvest leaf blackening. The finding that glucose was beneficial in extension of both storage and vase life of 'Sylvia' proteas directed research into its use for other Protea and Leucospermum cut flowers. Significant differences in the response to glucose supplementation were found in both Protea and Leucospermum (pincushions). The significant difference in sensitivity to glucose concentration in 'Pink Ice' proteas (phytotoxic at 2:4%) and 'Susara' proteas (no apparent toxicity), in conjunction with a lack of response in 'Cardinal' proteas, a hybrid from the same parents as 'Sylvia' indicates the need to direct future research to individual cultivars. Glucose supplementation had no beneficial effect on vase life of 'Scarlet Ribbon' and 'Tango' pincushions, whilst significantly extending vase life of 'Cordi', 'Gold Dust', 'High Gold' and 'Succession' pincushions. / AFRIKAANSE OPSOMMING: Blaarverswarting is 'n spesifieke probleem wat die vaasleeftyd en die bemarkbaarheid van Protea snyblomme beperk. In hierdie navorsing is ondersoek ingestel na die onderdrukking van Protea blaarverswarting met spesifieke fokus op die snyblomme van die kv. Sylvia (P. eximia x P. susannae). Die voorkoms van blaarverswarting by 'Sylvia' het merkbaar afgeneem tydens die verlaging van bergingstemperature. Hierdie afname is toegeskryf aan 'n laer respirasietempo en die behoud van koolhidrate. Lae bergingstemperature in die korttermyn hantering van die produk tydens lugvrag was voordelig. Die gebruik van lae temperature, slegs tydens die langer verskeepingsperiode, was egter onbevredigend vir vaasleeftyd verlenging en onderhoud van 'Sylvia' protea. Die afkoeling van 'Sylvia' proteas onder vakuum het blaarverswarting in 'n groot mate onderdruk en het beter resultate gelewer as geforseerde lugverkoeling. Alhoewel die verwydering van die heel boonste blare blaarverswarting by korttermynopberging vertraag het, het dit geen merkbare voordele vir langer bergingsperiodes ingehou nie. Ringelering direk onder die blomkop van die 'Sylvia' protea het blaarverswarting aansienlik verminder, en saam met lae bergingstemperature (O°C) het dit 'n merkbare verlenging in beide die bergingstyd en die vaasleeftyd van 'Sylvia' proteas teweeggebring. 'Sylvia' proteas het geen klimakteriese respirasiekruin tydens 'n bergingsperiode van 96 uur teen O°C getoon nie. Blootstelling aan etileen het nie die Protea blaarverswarting laat toeneem of 'n nadelige effek op die vaasleeftyd van die proteas of speldekussings wat geevalueer is, gehad nie. Geen voordelige reaksie op sukrose-byvoeging is in 'Sylvia' proteas gevind nie. 'n Analise van die suikerinhoud van beide die blomkoppe en die blare het aangetoon dat 'n glukose-byvoeging moontlik voordelig kon wees, en hierdie aspek is ondersoek. Met stooroplossings van 2,5 % glukose is die vaasleeftyd aansienlik verleng omdat daar 'n merkbare afname in blaarverswarting was. Vir die eerste keer in die geval van die 'Sylvia' protea, het die vaasleeftyd van die snyblomrne tot 'n einde gekom omdat die blornkoppe uitmekaar gebreek het en nie omdat blaarverswarting ingetree het nie. Die vaasleeftyd is aansienlik verleng met ~ 3% glukose-pulsoplossings, en blaarverswarting is merkbaar onderdruk met die verhoging van hierdie oplossings se glukosekonsentrasie. Die opname van die oplossings is gefasiliteer deur hoe intensiteit PAR (fotosinteties-aktiewe radiasie) ligte vroeg in die oggend, en is toegeskryf daaraan dat meer huidmondjies oopgegaan het. Dit het gelei tot 'n toename in transpirasie en 'n toename in die opname van die glukose-oplossing. Die feit dat glukose-oplossings vinniger opgeneem is deur lote wat in die middag geoes is, is toegeskryf daaraan dat loottemperature dan hoer is as soggens en gevolglik lei tot 'n vinniger transpirasietempo. Daar was 'n merkbare afname in die opnametyd wanneer die temperatuur van die pulsoplossings verhoog is. Vakuumafkoeling kon dus vroeer toegepas word, wat 'n verlenging in bergingstyd en vaasleeftyd tot gevolg gehad het. Verpakking van 'Sylvia' proteas in kartonne wat met poli-etileen uitgevoer is, het blaarverswarting van lote wat nie aan pulsering onderwerp is nie, onderdruk. Hierdie maatreel het egter geen praktiese waarde met betrekking tot vaasleeftyd nie; die vaasleeftyd het tot 'n einde gekom as gevolg van omvangryke blaarverswarting. Dit lyk asof waterverlies weinig invloed het op die blaarverswarting van' Sylvia' proteas. Die vermoede bestaan dat lae koolhidraatvlakke proteas ontvanklik maak vir blaarverswarting. Alhoewel die beklemtoning van winterligtoestande deur beskaduwing gelei het tot 'n afname in koolhidraatinhoud, was hierdie inhoud reeds laag en blaarverswarting na die oes is nie beinvloed nie. Beskaduwing tydens die vier en drie weke voor oestyd het saamgeval met 'n tydperk van aansienlike toename in die droe massa van die blomkop. Die vermoede bestaan dat beskaduwing tydens hierdie fase, saam met die toename in die ontwikkelende blomkop se behoefte aan koolhidrate, aanleiding gegee het tot 'n tydelike beperking in koolhidraatvoorraad wat die voorkoms van blaarverswarting voor die oes tot gevolg gehad het. Die bevinding dat glukose voordelig is vir die verlenging van beide die bergingstyd en die vaasleeftyd van 'Sylvia' proteas het die navorsing gerig om ook ondersoek in te stel na die gebruik daarvan vir ander Protea en Leucospermum snyblomme. Merkbare veranderinge is gevind in die reaksie op glukosebyvoegings in beide Protea en Leucospermum (speldekussings). Die opmerklike verskil in sensitiwiteit vir glukosekonsentrasie in 'Pink Ice' proteas (fitotoksies by ~ 4%) en 'Susara' proteas (geen klaarblyklike toksisiteit), saam met 'n gebrek aan reaksie by 'Cardinal' proteas, 'n hibried van dieselfde ouers as 'Sylvia', dui aan dat verdere navorsing op individuele kultivars toegespits sal rnoet word. Glukosebyvoegings het geen voordelige uitwerking op die vaasleeftyd van 'Scarlet Ribbon' en 'Tango' speldekussings gehad nie, terwyl dit die vaasleeftyd van 'Cordi', 'Gold Dust', 'High Gold' en 'Succession' speldekussingkultivars merkbaar verIeng het.

Thesis (PhD(Agric)--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: The bright colouration of involucral leaves in Leucadendron is unfortunately transient in nature. Undesirable colour changes render this cut flower unmarketable, resulting in a considerable loss of profit. A deeper understanding of the mechanism leading to colour change is needed to form the framework on which future manipulation strategies can be built. Yellow Leucadendron possess the ability to degreen and regreen naturally, a phenomenon linked to the controlled degradation of chlorophyll and the lesser degradation of carotenoids, which then impart the yellow colour. This colour change is directly linked to the development of the inflorescence. Involucral leaves degreen towards anthesis and are entirely yellow at full bloom. They begin to regreen again when the last florets on the cone have wilted. Deconing before flowering completely inhibits the colour change. Deconing at full bloom, results in leaves regreening sooner. Therefore the inflorescence appears to be the origin of the cue for colour change. Any factor that expedites the death of the florets, results in sooner regreening of involucral leaves. Ultra-structurally, the degreening and regreening resulted from a transdifferentiation of mature chloroplasts to gerontoplast-like plastids, which upon regreening completely redifferentiated into fully functional chloroplasts. In the red Leucadendron cultivar Safari Sunset, the photosynthetic pigment degradation pattern is identical to that of yellow cultivars. However, colour expression is complexed by the presence of anthocyanins. Anthocyanin concentration was shown to be directly related to the opening of the flower head rather than to the phenological development of the inflorescence. With opening, the previously shaded inner involucral leaf surfaces are exposed to higher levels of irradiance and respond by turning red, presumably for photoprotection. Similar to yellow cultivars, any factor leading to the death of the florets before flowering, not only prevents the degreening of involucral leaves, but also prevents the opening of the flower head and therefore the associated change in anthocyanin levels. The ecological significance of regreening was also investigated. What does a female Leucadendron plant stand to gain by regreening rather than discarding the involucral leaves? Regreened involucral leaves were shown not to play a significant role in providing photosynthates for the developing cone. Although the presence of regreened involucral leaves were shown to provide protection against high irradiance and radiant heating of the cone, they were not essential to ensure survival of the cone. The small floral bracts were shown to be very capable of adaptation. The most plausible reason for regreening is therefore assumed to be based on a cost-benefit relationship. As most Leucadendron are adapted to grow on very nutrient poor soils, the question should maybe be rephrased. Why waste valuable resources? Sclerophyllous leaves, like the involucral leaves, are costly to make and therefore reusing, rather than discarding them does seem a sensible strategy for survival. / AFRIKAANSE OPSOMMING: Leucadendron snyblomme word gekenmerk deur die helder kleure van hul omwindselblare. Die helder kleure is egter slegs vir 'n kort periode aanwesig waarna die snyblomme onbemarkbaar word, met aansienlike verlies aan potensiele inkomste. Die ontwikkeling van manipulasies ten einde die bemarkbare periode van Leucadendron te verleng, berus op die verkryging van 'n dieper insig in die meganisme van kleurverandering. Die kleurveranderinge van geel Leucadendron omwindselblare is te wyte aan 'n unieke vermoë tot die gereguleerde degradasie en heropbou van chlorofiele en karotenoiede onder direkte beheer van die ontwikkelende bloeiwyse. Met die aanvang van blom, lei groter proporsionele degradasie van chlorofiele tot geleidelike vergeling van omwindselblare. Die hele blomhofie verkry uiteindelik met volblom 'n helder geel kleur. Sodra die laaste blommetjies doodgaan, neem chlorofiel- en karotenoiedsintese weer in aanvang en binnekort is die omwindselblare weer net so groen soos voor die aanvang van blom. Die geel verkleuring kan verhoed word deur die keël voor blom uit te breek. Enige faktor wat die dood van die blommetjies versnel, asook die uitbreek van keël tydens volblom, lei tot die vroeëre aanvang van vergroening. Die degradasie van plastiedpigmente hang nou saam met die differensiasie van volwasse chloroplaste tot gerontoplast-agtige plastiede wat op hul beurt weer tydens vergroening tot volkome funksionele chloroplaste herdifferensieer. Soortgelyk aan geel Leucadendron kultivars, vind die veranderinge in plastiedpigmente ook plaas tydens blom van die rooi kultivar, Safari Sunset. Kleurveranderinge in 'Safari Sunset' is egter meer ingewikkeld vanweë die aanwesigheid van variërende konsentrasies antosianiene. Antosianienkonsentrasies en rooi kleur neem toe tydens blom vanwee die blootstelling van die beskutte adaksiale binnekante van omwindselblare aan hoe irradiasie met die oopvou van die blomhofie. Die akkumulasie van antosianiene het moontlik 'n fotobeskermende funksie. Kleurveranderinge in 'Safari Sunset' kan, soos in geel kultivars, voorkom word deur blom te verhoed. Antosianiensintese word voorkom deurdat die blomhofie geslote bly en is nie direk gekoppel aan blom soos wat met plastiedpigmente die geval is nie. Die belang van vergroening is ondersoek na aanleiding van die vraag oor wat dit 'n vroulike Leucadendron baat om omwindselblare te behou na die afloop van blom? Die bydrae van foto-assimilasie deur omwindselblare tot die ontwikkeling van keels is beperk. Alhoewel omwindselblare wel keels teen hoe irradiasie en stralingsverhitting beskerm, is die blomskutblare in staat om aan te pas by hierdie kondisies. Die mees waarskynlike verklaring vir die behoud van die omwindselblare na blom berus moontlik op 'n koste-voordele verwantskap. Alhoewel nie essensieel nie, is die beperkte bydrae van die omwindselblare na die afloop van blom tot die oorlewing en welstand van die keel waarskynlik genoegsaam om hul behoud te regverdig. Verskeie Leucadendron spesies groei in gronde wat baie arm is aan nutriente. Sklerefiele blare, soos die van Leucadendron, is verder duur om te vervaardig. Dit maak dus sin om hulle vir meer as een funksie te herontplooi eerder as om hulpbronne te belê in meer gespesialiseerde en minder durende blombykomstighede. Dus dui die behoud van omwindselblare dalk op 'n strategie wat gemik is op die behoud en besparing van beperkte hulpbronne.

Thesis (PhD(Agric) (Horticulture))--University of Stellenbosch, 2011. / Includes bibliography. / ENGLISH ABSTRACT: Mealiness, a soft, dry textural disorder of ‘Forelle’ pear (Pyrus communis L.), is a problem for the South African fruit export industry. Soft, dry textural disorders seem to be related to changes in cell wall breakdown. The aim of this work was, therefore, to investigate the occurrence of mealiness‐associated changes in the cell wall and elucidate the mechanism by which mealiness occurs in ‘Forelle’ pear, as well as to characterise cell wall changes occurring during normal ripening. Mealy ‘Forelle’ tissues had significantly lower total galacturonic acids associated with the middle lamella (water‐ and CDTA‐soluble fractions). The water‐soluble pectin of mealy tissues was depolymerised at an earlier stage of ripening. The widespread disintegration of cell‐to‐cell adhesion in mealy cell walls only, suggests that the middle lamella and the plasmodesmata are more broken down. In mealy ‘Forelle’ tissues there was no indication of less broken down high molecular weight polyuronides in the CDTA fraction, normally associated with these dry, soft textures. The pectins from mealy tissues were more broken down and both mealy and non‐mealy tissue polyuronides depolymerised. Furthermore, there was a lack of light toluidine staining in the larger air spaces, which would indicate such water‐insoluble pectins. These data suggest that the formation of high molecular weight pectate gels is unlikely in mealy ‘Forelle’ pear. The slight increase in the galactose content in mealy tissues in CDTA‐ and Na2CO3‐soluble fractions and slight decrease in the 1 M KOH glycan fraction during later stages of ripening (6+11, 9+7, 9+11; weeks at ‐0.5°C plus days at 15°C) may indicate that galactose loosely interlinked into the glycan fraction broke down sooner for mealy tissues. This didn’t increase molecular size profiles in the CDTA fraction. Arabinose content was slightly higher in the 4 M KOH fraction and slightly lower in mealy tissues of water‐ and CDTA fractions. This did not influence the molecular weight of the glycans compared to those in the nonmealy tissues. ‘Forelle’ data therefore seem to be more congruent with a decrease in intercellular adhesion as the mechanism by which mealiness occurs, rather than the formation of high molecular weight pectins taking up the cellular fluid. ‘Forelle’ pear water‐soluble pectin content increases with increased ripening. High amounts of watersoluble pectin and low amounts of Na2CO3‐soluble pectin suggests that solubilisation of rhamnogalacturonan‐I pectins must have taken place during early ripening (at a fruit firmness of > 4.7 kg (7.9mm tip). Galactose and glucose in the pectin fraction dramatically decreased after fruit ripened to a firmness of 4.5 kg, whereafter they remained unchanged. This was also the period in which fruit softened the most and the biggest increase in pectin water‐solubility occurred. It is not known whether these events are coincidental, or linked causally. Rhamnose and arabinose extractability increased in the water fraction and xylose, fucose and mannose increased in glycan fractions with ripening. The biggest changes in polyuronide solubilisation and depolymerisation occurred in water‐ and CDTA fractions between storage and ripening durations of 3+7 (4.7 kg) and 6+4 (2.7 kg). / AFRIKAANSE OPSOMMING: Melerigheid, ʼn sagte droë tekstuur afwyking van ‘Forelle’ pere (Pyrus communis L.), is ʼn probleem vir die Suid Afrikaanse vrugte uitvoerbedryf. Sagte, droë tekstuur afwykings blyk betrekking te hê op selwandafbraak veranderinge. Die doel van die studie was dus om die melerigheid‐geassosieerde veranderinge in die selwand te ondersoek, sowel as om vas te stel wat die meganisme betrokke is by melerigheid ontwikkeling in ‘Forelle’ pere. Die selwand veranderinge gedurende normale rypwording is ook gekarakteriseer. Melerige ‘Forelle’ weefsel het betekenisvol laer totale galakturoonsuur wat geassosieer is met die middellamella (water‐ en CDTA‐oplosbare fraksies). Die water‐oplosbare pektien van melerige weefsel was op ʼn vroeër stadium van rypwording gedepolimeriseer. Die wydverspreide disintegrasie van sel‐tot‐sel adhesie, slegs in melerige selwande, dui aan dat die middellamella en die plasmodesmata meer afgebreek is. Daar is geen indikasie van hoë molekulêre massa poliuroniedes in die CDTA fraksie van melerige ‘Forelle’ weefsel, wat gewoonlik geassosieer word met droë, sagte teksture nie. Die pektiene van melerige weefsel was meer afgebreek en melerige en nie‐melerige weefsel se poliurone was gedepolimeriseer. Daar was ook geen ligte toluïdien verkleuring in die groter intersellulêre lugruimtes nie, wat ʼn aanduiding sou wees van wateronoplosbare pektiene. Hierdie data dui dus aan dat die vorming van hoë molekulêre pektien jel in melerige ‘Forelle’ pere onwaarskynlik is. Die klein toename in galaktose inhoud in die CDTA‐ en Na2CO3‐ oplosbare fraksies en ʼn klein afname in 1 M KOH glikaan fraksie tydens latere rypheidstadiums (6+11, 9+7, 9+11; weke by ‐0.5°C plus dae by 15°C), kan beteken dat los verweefde galaktose in die glikaan fraksie vroeër afgebreek het in melerige weefsels. Die molekulêre grootte profiel is nie verander in die CDTA fraksie nie. Arabinose inhoud was bietjie hoër in die 4 M KOH fraksie en bietjie laer in melerige weefsel van die water‐ en CDTA fraksies. Die molekulêre massa van die glikane was klaarblyklik onbeïnvloed hierdeur. ‘Forelle’ data blyk dus meer saam te stem met die meganisme waar ʼn vermindering in intersellulêre adhesie ʼn rol speel in melerigheid, eerder as die meganisme waar hoë molekulêre pektien selvloeistowwe bind. ‘Forelle’ peer water‐oplosbare pektieninhoud neem toe met toenemende rypheid. Hoë vlakke wateroplosbare pektien en lae vlakke Na2CO3‐oplosbare pektien stel voor dat die oplossing van rhamnogalakturonan‐I pektiene gedurende vroeë rypwording moes plaasgevind het (by ʼn fermheid van > 4.7 kg (7.9mm punt). Galaktose en glukose in die pektienfraksie het drasties verminder nadat vrugte tot ʼn fermheid van 4.5 kg ryp geword het, waarna hul onveranderd gebly het. Dit was ook die periode waarin vrugte die meeste sag geword het en die grootste toename in poliuronied wateroplosbaarheid gevind is. Dit is nie bekend of die gebeure toevallig of oorsaaklik verbind is nie. Rhamnose en arabinose ekstraheerbaarheid het vermeerder in die water fraksies, en xylose, fukose en mannose het vermeerder in die glikaan fraksies gedurende rypwording. Die grootste verandering in oplosbaarheid en depolimerisasie het plaasgevind in die water‐ en CDTA fraksies tussen opberging en rypwordingsperiodes van 3+7 (4.7 kg) en 6+4 (2.7 kg).

Thesis (PhD(Agric))--Stellenbosch University, 2013. / ENGLISH ABSTRACT: The development and application of science-based tools for determining optimum fruit maturity and postharvest handling protocols to maintain quality and reduce losses during postharvest handling and marketing is essential to maintain the competitiveness of the emerging pomegranate industry in South Africa. Currently, there are no quality standards for the South African pomegranate industry, neither is there a general consensus on the optimal harvest maturity indices for fruit cultivars. These information are important to ensure the delivery of good quality fruit to consumers, particularly for long supply chains. The overall aims of this study were (a) to develop science-based management tools for determining optimum maturity indices and storage performance of pomegranate fruit cultivars grown in South Africa, and (b) to characterise the physico-chemical and pharmacological properties of selected cultivars relevant to postharvest handling and industrial applications. In Section II, seasonal studies on pomegranate (‘Baghwa’ and ‘Ruby’) fruit growth and the evolution of maturity indices during development were conducted. Significant increases in total soluble solids (TSS), sugars (glucose and fructose) and anthocyanin composition, coupled with significant decline in titratable acidity (TA), organic acids and total phenolics (TP) occurred with advancing fruit maturity. Fruit at advanced maturity stages were characterized by intense pigmentation of peel and aril, which coincided with maximum accumulation of anthocyanins. Among all the major maturity indices investigated, TSS, BrimA and anthocyanins did not show significant (p<0.05) seasonal variability, and strong correlations were found among the indices. In combination, these indices accounted for fruit juice sugar content, acidity and colour and could serve as reliable markers to determine optimal maturity for both pomegranate cultivars. The studies in Section III focused on characterization of postharvest quality including nutritional, medicinal and antioxidant properties of fruit parts. Quality attributes of eight commercial cultivars were analysed by cluster analysis, which enabled the cultivars to be separated into two clusters (cluster 1 = ‘Ruby’, ‘Arakta’ and ‘Ganesh’; cluster 2 = ‘Bhagwa’, ‘Acco’ and ‘Herskawitz’) and two ungrouped cultivars (‘Molla de Elche’ and ‘Wonderful’) based on important quality attributes (size, texture, colour, soluble solids, acidity, juiciness and phenolics). Furthermore, pomegranate fruit peel extracts were studied to highlight their potential for value-adding in pharmaceutical and other industrial applications. The results showed that fruit peels of the investigated cultivars possess strong antibacterial, antioxidant and antityrosinase activities, and hence could be exploited as potential sources of natural antimicrobial and antioxidant agents, as well as a potential tyrosinase inhibitor. The research reported in Section IV investigated the effects of harvest maturity and storage conditions on postharvest quality and nutritional value of ‘Bhagwa’ and ‘Ruby’ cultivars. Fruit harvested at commercial maturity were stored at 5±0.3°C, 7±0.5°C and 10±0.4°C with 92±3% RH and at room temperature (20±2.2°C, 65±5.5% RH) for 16 weeks. Fruit physiological responses and quality were affected by storage condition, with the maximum levels of respiration occurring at higher temperature and extended storage duration. Fruit colour and antioxidant capacity varied slightly among storage temperatures, with total soluble solids and titratable acidity decreasing gradually over time at different temperatures. Considering that fruit stored at 5°C and 92% RH had significantly reduced weight loss, low incidence of physiological disorders and best results in maintaining flavour attributes (TSS and TA, TSS:TA ratio), the investigated cultivars may be stored at 5°C and >92% RH for 8 - 12 weeks. In paper 9 (Section IV), the research investigated the relationships between instrumental and sensory measurements of pomegranate fruit at different harvest maturities during storage and shelf life. Mature ‘Bhagwa’ fruit harvested at different times could not be discriminated by sensory attributes assessed by a trained panel. However, TSS (R2 = 0.677) and juice content (R2 = 0.512) were the two most decisive quality attributes at shelf life related to harvest maturity status. For ‘Ruby’, however, a combination of instrumental and sensory attributes appeared to be influential in discriminating mature fruit harvested at different times, with TSS:TA ratio being the most decisive (R2 = 0.654) in distinguishing different fruit harvests, followed by sweet taste (R2 = 0.474) and hue angle (R2 = 0.431). The results showed that to ensure the best post-storage quality of ‘Bhagwa’, the optimum harvest maturity was between 167 - 175 DAFB (H2 and H3) when fruit reached maximum TSS level (>16°Brix; H3) and juice content (>65 mL/100 g aril; H2). However, for ‘Ruby’, this study indicated that the optimum harvest date was at 143 DAFB (H2) when TSS:TA ratio was >55, which coincided with significantly higher sensory rating for sweet taste after shelf life of fruit at H2 than H1 and H3, respectively. The results from this thesis provide new understanding and better insights on fruit characteristics of major pomegranate cultivars grown in South Africa. Overall, the study provides new knowledge on science-based tools for assessing fruit readiness for harvest as well as storage conditions to maintain fruit postharvest quality and reduce losses. It also provides scientific information on phytochemical contents and antioxidant compounds in fruit to promote value-adding of pomegranate as a good raw material with potential applications in health food products and other industrial applications such as pharmaceuticals and cosmetics. / AFRIKAANSE OPSOMMING; Die ontwikkeling en toepassing van wetenskapgegronde instrumente vir die bepaling van optimale vrugrypheid en naoes-hanteringsprotokolle om gedurende die naoes-hantering en -bemarking van vrugte gehalte te behou en verliese te verminder, is noodsaaklik om die mededingendheid van die ontluikende granaatbedryf in Suid-Afrika te verseker. Tans is daar nie enige gehaltestandaarde vir die Suid-Afrikaanse granaatbedryf óf algemene eenstemmigheid oor die optimale oesrypheidsaanwysers vir vrugtekultivars nie. Hierdie inligting is belangrik om die naoes-lewering van uithalervrugte aan verbruikers te verseker, veral vir lang verskaffingskettings. Die oorkoepelende doelwitte van hierdie studie was (a) om wetenskapgegronde bestuursinstrumente te ontwikkel vir die vasstelling van optimale rypheidsaanwysers en bergingsprestasie van granaatkultivars wat in Suid-Afrika verbou word, en (b) om die fisiko-chemiese eienskappe en farmakologiese kenmerke van gekose kultivars te tipeer. In deel II is seisoenale studies oor granaatgroei en die ontwikkeling van rypheidsaanwysers gedurende groei onderneem. Namate vrugte ryp geword het, is beduidende toenames in totale oplosbare vaste stowwe (TSS), suikers (glukose en fruktose) en antosianien-samestelling opgemerk, sowel as ’n beduidende afname in titreerbare suur (TA), organiese suur en totale fenol (TP). Vrugte in gevorderde stadia van rypheid is gekenmerk deur intense pigmentasie van die skil en aril, wat met maksimum opbou van antosianien verband gehou het. Van ál die belangrike rypheidsaanwysers wat ondersoek is, het TSS, BrimA en antosianien onbeduidende (p<0.05) seisoenale veranderlikheid getoon, en is sterk verbande tussen die aanwysers opgemerk. Gesamentlik sou die aanwysers kon rekenskap gee van sapsuikerinhoud, -suurgehalte én -kleur, en sou dit dus as betroubare rypheidsmerkers kon dien om optimale rypheid vir albei granaatkultivars te bepaal. Die studies in deel III het gekonsentreer op die tipering van die naoes-kenmerke, onder meer die voedings-, medisinale en antioksidant-kenmerke van vrugtedele. Kenmerke van agt kommersiële kultivars is deur middel van groepsontleding bestudeer, waarvolgens die kultivars op grond van belangrike kenmerke (grootte, tekstuur, kleur, oplosbare vaste stowwe, suurgehalte, sappigheid en fenol) in twee groepe (groep 1 = ‘Ruby’, ‘Arakta’ en ‘Ganesh’; groep 2 = ‘Bhagwa’, ‘Acco’ en ‘Herskawitz’) en twee niegegroepeerde kultivars (‘Molla de Elche’ en ‘Wonderful’) ingedeel is. Ten einde die toegevoegde waarde van granaatskille vir farmaseutiese en kosmetiese doeleindes te bevorder, is skilekstrakte ook bestudeer. Die resultate toon dat die vrugteskille van die bestudeerde kultivars oor sterk antibakteriese, antioksidant- en antitirosinase- eienskappe beskik. Daarom kan die skil van die granaatkultivars as moontlike bron van natuurlike antimikrobiese en antioksidant-agense sowel as ’n moontlike tirosinase-inhibitor ontgin word. Die navorsing in deel IV het ondersoek ingestel na die uitwerking van oesrypheid en bergingsomstandighede op die naoes-gehalte en -voedingswaarde van die kultivars ‘Bhagwa’ en ‘Ruby’. Vrugte wat op kommersiële rypheid geoes is, is vir 16 weke by 5±0.3 °C, 7±0.5 °C en 10±0.4 °C met 92±3% RH, sowel as by kamertemperatuur (20±2.2 °C, 65±5.5% RH) geberg. Die bergingsomstandighede het die fisiologiese reaksies en gehalte van die vrugte beïnvloed: Maksimum vlakke van respirasie het teen hoër temperature en met verlengde berging voorgekom. Die kleur en antioksidantvermoë van die vrugte het effens tussen bergingstemperature verskil, en totale oplosbare vaste stowwe en titreerbare suur het mettertyd geleidelik by verskillende temperature afgeneem. Gedagtig daaraan dat die vrugte wat teen 5 °C en 92% RH geberg is beduidend minder gewigsverlies, ’n lae voorkoms van fisiologiese afwykings en die beste resultate in blywende geurkenmerke (TSS en TA, TSS:TA-verhouding) getoon het, kan die bestudeerde kultivars vir 8 tot 12 weke teen 5 °C en >92% RH geberg word (navorsingstuk 8). In navorsingstuk 9 (deel IV) is daar ondersoek ingestel na die verhouding tussen instrument- en sintuiglike metings van granate in verskillende stadia van oesrypheid gedurende berging en raklewe. Geen verskil in sintuiglike kenmerke kon bespeur word by ryp ‘Bhagwa’- vrugte wat op verskillende tye geoes is nie. Tog was TSS (R2 = 0.677) en sapinhoud (R2 = 0.512) die twee bepalendste gehaltekenmerke wat betref oesrypheidstatus gedurende raklewe. By ‘Ruby’ kon ’n kombinasie van instrument- en sintuiglike kenmerke egter wél tussen stadia van oesrypheid onderskei, met die TSS:TA-verhouding die bepalendste (R2 = 0.654) in die onderskeid tussen verskillende vrugteoeste, gevolg deur ’n soet smaak (R2 = 0.474) en skakeringshoek (R2 = 0.431). Die resultate toon dat die beste nabergingsgehalte vir ‘Bhagwa’ verkry word by ’n optimale oesrypheid van 167–175 DAFB (H2 en H3), wanneer vrugte die maksimum TSS-vlak (>16°Brix; H3) en sapinhoud (>65 mL/100 g aril; H2) bereik het. Vir ‘Ruby’ dui hierdie studie op ’n optimale oesdatum van 143 DAFB (H2) met ’n TSS:TA-verhouding van >55, wat verband gehou het met ’n beduidend hoër telling vir soet smaak by H2 eerder as by H1 en H3 ná raklewe. Die resultate van hierdie tesis bied ’n beter begrip van, en insig in, die vrugtekenmerke van granaatkultivars wat in Suid-Afrika verbou word. Oor die algemeen bied die studie wetenskaplike inligting om moontlik die toegevoegde waarde van granate as ’n goeie bron van minerale elemente sowel as farmaseutiese, kosmetiese en antioksidant-verbindings te bevorder. Dit bied ook kennis oor die ontwikkeling van wetenskapgegronde instrumente vir die vasstelling van optimale vrugrypheid en naoes-hanteringsprotokolle om gedurende die naoes-hantering en -bemarking van granate vruggehalte te behou en verliese te verminder.

Thesis (PhD(Agric))--Stellenbosch University, 2013. / ENGLISH ABSTRACT: The aim of this study was to develop non-destructive methods to predict external and internal quality of citrus fruit. A critical review of the literature identified presymptomatic biochemical markers associated with non-chilling rind physiological disorders. The prospects for the use of visible to near infrared spectroscopy (Vis/NIRS) as non-destructive technology to sort affected fruit were also reviewed. Initial studies were conducted to determine the optimum condition for NIRS measurements and to evaluate the accuracy of this technique and associated chemometric analysis. It was found that the emission head spectroscopy in diffuse reflectance mode could predict fruit mass, colour index, total soluble solids, and vitamin C with high accuracy. Vis/NIRS was used to predict postharvest rind physico-chemical properties related to rind quality and susceptibility of ‘Nules Clementine’ to RBD. Partial least squares (PLS) statistics demonstrated that rind colour index, dry matter (DM) content, total carbohydrates, and water loss were predicted accurately. Chemometric analysis showed that optimal PLS model performances for DM, sucrose, glucose, and fructose were obtained using models based on multiple scatter correction (MSC) spectral pre-processing. The critical step in evaluating the feasibility of Vis/NIRS was to test the robustness of the calibration models across orchards from four growing regions in South Africa over two seasons. Studies on the effects of microclimatic conditions predisposing fruit to RBD showed that fruit inside the canopy, especially artificially bagged fruit, had lower DM, higher mass loss, and were more susceptible to RBD. The study suggested that variations in microclimatic conditions between seasons, as well as within the tree canopy, affect the biochemical profile of the rind, which in turn influences fruit response to postharvest stresses associated with senescence and susceptibility to RBD. Principal component analysis (PCA) and PLS discriminant analysis (PLS-DA) models were applied to distinguish between fruit from respectively, inside and outside tree canopy, using Vis/NIRS signal, suggesting the possibility of using this technology to discriminate between fruit based on their susceptibility to RBD. Results from the application of optical coherence tomography (OCT), a novel non-destructive technology for imaging histological changes in biological tissues, showed promise as a potential technique for immediate, real-time acquisition of images of rind anatomical features of citrus fruit. The study also demonstrated the potential of Vis/NIRS as a non-destructive tool for sorting citrus fruit based on external and internal quality. / AFRIKAANSE OPSOMMING: Die studie het ten doel gestaan om nie-destruktiewe meeting metodes te toets en ontwikkel wat die interne en eksterne-kwaliteit van sitrusvrugte kan voorspel. In ʼn litratuuroorsig is biochemies verandering in die skil en wat geassosieer word met die ontwikkeling van fisiologies skildefekte geïdentifiseer, asook is die moontlikheid ondersoek om Naby Infrarooi spektroskopie (NIRS) as ‘n nie-destruktiewe tegnologie te gebruik om vrugte te sorteer. Eerstens was die optimale toestande waarby NIRS meetings van sitrusvrugte geneem moet word asook die akkuraatheid van die toerusting en chemometrika data-ontleding beproef. Daar is gevind dat die uitstralings-kop spektrofotometer in diffusie-weerkaatsings modus vrugmassa, skilkleur, totale opgeloste stowwe asook vitamien C akkuraat kan voorspel. Daarna van NIRS gebruik om na-oes fisies-chemiese eienskappe wat verband hou met skilkwaliteit en vatbaarheid vir skilafbraak van ‘Nules Clementine’ mandaryn. Deur gebruik te maak van “Partial least squares” (PLS) statistieke was gedemonstreer dat die skilkleur, droë massa (DM), totale koolhidrate en waterverlies akkuraat voorspel kon word. Chemometriese analises het ook getoon dat optimale PLS modelle vir DM, sukrose, glukose en fruktose verkry kan word deur modelle te skep wat gebaseer is op “Multiple scatter correction” (MSC) spektrale voor-verwerking. ʼn Belangrike stap in die ontwikkeling van NIRS gebaseerde indeling is om die robuustheid van die kalibrasiemodelle te toets en was gedoen deur vrugte te meet en sorteer van vier boorde en oor twee seisoene. ʼn Verder eksperiment om die impak van mikroklimaat op die skil se vatbaarheid vir fisiologiese defekte te ontwikkel het getoon dat vrugte wat binne in die blaardak ontwikkel (lae vlakke van sonlig) ʼn laer DM, hoër gewigsverlies het en was ook meer vatbaar vir skilafbraak. Die resultate dui daarop dat verskille in mikroklimaat oor die seisoen asook in die blaardak die skil se biochemiese profiel beïnvloed, wat lei tot ʼn negatiewe reaksie op na-oes stres en verhoogde voorkoms van fisiologiese skilafbraak. Die ontwikkelde “Principal component analysis” (PCA) en PLS-diskriminant analise modelle was daarna suksesvol toegepas om vrugte te skei na NIRS meetings, op die basis van vrugpossies in die blaardak. Nuwe, nie-destruktiewe tegniek, nl. “Optical coherence tomography” (OCT) was suksesvol getoets as manier om ʼn fotografiese beeld te skep van histologiese veranderinge in die skil. Die resultate dui op die potensiaal van die onontginde tegnologie om intak biologiese-materiaal te analiseer. Hierdie studie het getoon dat daar wesenlike potensiaal is om NIRS verder te ontwikkel tot ʼn tegnologie wat gebruik kan word om vrugte te sorteer gebaseer op eksterne (skil) asook interne (pulp) eienskappe