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Thesis (MScAgric)--Stellenbosch University, 2011. / ENGLISH ABSTRACT: Commercial production of the southern highbush blueberries (SHB) ‘Jewel’, ‘Emerald’, ‘Star’, ‘Snowchaser’ and ‘Bluecrisp’ started recently in the Western Cape. In South Africa, no research has been conducted on pruning and pollination of SHB, and various questions regarding these practices have arisen. Six experiments were conducted to evaluate the self-compatibility and the effect of cross-pollination on berry characteristics of ‘Star’, ‘Emerald’, ‘Jewel’, ‘Bluecrisp’ and ‘Snowchaser’. The effect of cross-pollination on fruit set, berry weight, berry diameter and fruit development period is cultivar dependant. ‘Bluecrisp’ appears self-incompatible and ‘Misty’ or ‘Emerald’ can be recommended as cross-pollinators. ‘Snowchaser’ seems self-compatible and solid block plantings can be recommended. ‘Misty’ and ‘Emerald’ would be recommended as cross-pollinators for ‘Star’ and ‘Jewel’ respectively, even though these cultivars will set an adequate crop when self-pollinated. Although ‘Emerald’ seem self-compatible, the fruit set tends to vary greatly and cross-pollination with ‘Jewel’, ‘Misty’ and ‘Bluecrisp’ is recommended to obtain early maturing berries of the required size. Another season’s data is required before final conclusions can be drawn. In order to establish sustainable summer pruning strategies for South African growing conditions that will maximise yield and berry quality for SHB, two pruning trials were conducted. In the first trial, the severity of pruning of ‘Star’, ‘Emerald’ and ‘Jewel’ was evaluated. We established that summer pruning is a compromise between total yield and desired berry size. All the pruning treatments reduced total vegetative growth and shoot number, but increased individual shoot length. Summer pruning increased berry weight and diameter by reducing total yield, but also by developing better quality bearing wood. Vigorous laterals stimulated by pruning seize growth later thereby delaying reproductive bud initiation and harvest. An increase in the severity of pruning increased the level to which the plants responded. No pruning and ‘light pruning’ gave the highest yields, but one more season’s data will clarify whether successive light pruning is sustainable. “Standard pruning” resulted in a well-balanced plant with an intermediate yield and berry size. Heading of one-year-shoots as part of the pruning strategy is not recommended for any of the cultivars. “Severe pruning” will only be recommended for young, newly established plantings where vegetative growth is the main objective. A second trial was conducted to study the effect of time of summer pruning. At Teeland, delaying pruning resulted in a decrease in total new growth and shoot number thereby reducing yield. This was probably due to progressively more buds that became endodormant. For all three cultivars, pruning as soon as possible after harvest would therefore be recommended. At Lushof, the effect of time of summer pruning was not significant. This could be due to the fact that plants were younger and more vigorous or because the area is warmer and growth continued for longer. One more season’s data is needed before any final conclusions are drawn. / AFRIKAANSE OPSOMMING: Kommersiële verbouing van die “southern highbush” bloubessies (SHB) ‘Jewel’, ‘Emerald’, ‘Star’, ‘Snowchaser’ en ‘Bluecrisp’ is ’n nuwe ontwikkeling in die Wes-Kaap. In Suid-Afrika is nog geen navorsing oor die snoei en bestuiwing van SHB onderneem nie, en verskeie vrae het oor hierdie praktyke ontstaan. Ses eksperimente is gedoen om die self-verenigbaarheid, sowel as die effek van kruisbestuiwing op bessie-eienskappe van ‘Star’, ‘Emerald’, ‘Jewel’, ‘Bluecrisp’ en ‘Snowchaser’ te evalueer. Die effek van kruisbestuiwing op vrugset, bessiegewig, bessiedeursnee en vrugontwikkelingsperiode is kultivar spesifiek. ‘Bluecrisp’ blyk self-onverenigbaar te wees en kruisbestuiwing met ‘Misty’ of ‘Emerald’ word aanbeveel. ‘Snowchaser’ blyk self-verenigbaar te wees en suiwer blok aanplantings kan dus aanbeveel word. ‘Misty’ en ‘Emerald’ word onderskeidelik as kruisbestuiwers vir ‘Star’ en ‘Jewel’ aanbeveel, alhoewel beide kultivars ‘n goeie oes sonder kruisbestuiwing kan lewer. Vir ‘Emerald sal kruisbestuiwing met ‘Jewel’, ‘Misty’ of ‘Bluecrisp’ aanbeveel word, indien vroeë, groot bessies belangrik is. ’n Tweede seisoen se data word benodig om bogenoemde te bevestig voor finale aanbevelings gemaak kan word. Twee snoeiproewe is uitgevoer om volhoubare somersnoei-strategieë te ontwikkel wat die opbrengs en kwaliteit van bessies onder Suid-Afrikaanse groeitoestande sal maksimeer. In die eerste snoeiproef is die intensiteit van snoeisnitte vir ‘Star’, ‘Emerald’ en ‘Jewel’ ondersoek. Daar is vasgestel dat totale opbrengs en bessiegrootte teen mekaar opgeweeg moet word wanneer strafheid van snoei ge-evalueer word. Somersnoei verminder totale vegetatiewe groei en aantal nuwe lote, maar vermeerder lootlengte en bessiegrootte. Somersnoei het ‘n toename in bessiegrootte tot gevolg deur dat die totale opbrengs verminder, maar ook deur die kwaliteit van draende lote te verbeter. Meer groeikragtige lote gestimuleer deur somersnoei, staak verlengingsgroei later in die seisoen wat dan lei tot later bloknopinisiasie en oes. Geen snoei, sowel as “ligte snoei” het gelei tot die grootste opbrengs na die afloop van een seisoen, maar nog ‘n seisoen se data word benodig om vas te stel of dit volhoubaar is. “Standaard snoei’” lei tot ‘n goed gebalanseerde plant met ‘n gemiddelde opbrengs en bessiegrootte. “Harde snoei” sal slegs aanbeveel word vir nuwe aanplantings waar vegetatiewe groei die hoof prioriteit is. Om die tydsbereking van somersnoei aan te spreek, is ‘n tweede snoeiproef uitgevoer. Op Teeland, het ‘n uitstel van somersnoei gelei tot ‘n afname in vegetatiewe groei en aantal lote en dit het dan gelei tot ‘n afname in opbrengs. Hierdie was moontlik die gevolg van meer knoppe wat mettertyd in endodormansie ingegaan het. Op Lushof het die tydsberekening van somersnoei geen betekenisvolle effek gehad nie. Dit kan moontlik toegeskryf word aan die jonger, groeikragtige plante, of aan die langer groeiseisoen weens die warmer klimaat in die area. Nog ‘n seisoen se data word egter benodig voor enige finale gevolgtrekkings gemaak kan word.

Modified atmosphere packaging storage combines an atmosphere of higher carbon dioxide and lower oxygen levels than air, with chilling temperatures to extend shelf-life of fresh fruits. In three modified atmosphere packaging storage trials, blueberries were packaged in film bags with different gas permeabilities, and stored at about 4°C. Storage of blueberries in packages of a film with intermediate gas permeability produced an aerobic atmosphere and a relatively low carbon dioxide level, resulting in rapid growth of yeast and molds on blueberries. Packaging blueberries in a film with very low gas permeability created a high carbon dioxide almost anaerobic atmosphere, which successfully inhibited yeast and mold growth on blueberries for up to eight weeks. The possibility of yeast inhibition by antifungal compounds accumulated in blueberries stored under modified atmosphere packaging conditions was investigated by using the disk diffusion assay. The results of these assays showed the absence of antifungal activity against two Rhodotorula species, a Zygosaccharomyces species, a Cryptococcus species, a Debaryomyces species, and indicated that the inhibition of yeast growth was due to low temperature, high carbon dioxide level and anaerobic conditions. The effects of temperature and atmosphere composition were investigated by using natural flora of blueberry juice and two yeast isolates grown in sterilized juice. At 21°C, yeast growth was slow in the presence of carbon dioxide and absence of oxygen. At low temperature, yeast growth was slow in the presence of oxygen, but was inhibited in the anaerobic, high carbon dioxide environment. It is proposed that the micro-aerobic environment of modified atmosphere packaging storage might have allowed slow desaturation of yeast membrane fatty acids which enabled yeasts to maintain membrane fluidity and function at low .temperature. Furthermore, yeast growth during storage of modified atmosphere packaged blueberries may be affected by low temperature and high carbon dioxide conditions. / Land and Food Systems, Faculty of / Graduate

No description available.

Sitka black-tailed deer (Odocoileus hemionus sitkensis Sm.) prefer understory forages growing beneath a forest canopy despite a greater abundance of the same plant species in forest clearings. This research examined responses of the deciduous shrub - blueberry (Vaccinium ovalifolium), to test the hypotheses that 1) forage is less nutritious and less palatable when grown in clearings than in forest understories, and that 2) changes in the plant carbon/nitrogen (C/N) ratio in response to light and nitrogen supply determine forage nutritional quality. Responses to irradiance and nitrogen supply were examined with respect to plant physiology, morphology, biochemistry and nutritional quality in three phases : 1) under controlled conditions in a growth room, 2) with manipulations in a field experiment and 3) along natural gradients of light and nitrogen in the native forests. The results were highly consistent from the growth room to the field. Light strongly affected plant physiological responses, including photosynthesis, relative growth rates and growth efficiency, whereas nitrogen had little effect. In regression analyses, leaf morphological properties, including specific leaf weight and leaf succulence, were the best predictors of relative growth rates (R2=.67). Irrespective of nitrogen supply, the biochemical properties of sun leaves included higher concentrations of starch, nonstructural carbohydrates and % lignin + cutin in the cell wall, but lower concentrations of structural polymers, total nitrogen, free amino acids, and ratio of free amino acids : total N, compared to shade leaves. Sun leaves also were slightly higher in digestible energy, much lower in digestible nitrogen and presumably less palatable due to higher tannin concentrations, compared to shade leaves. Tannins were directly correlated to specific leaf weight (R2=.89). Regression equations based upon specific leaf weight, leaf succulence and leaf structural polymers accurately predicted field values for digestible nitrogen (R2=.91) and digestible energy (R2=.96) in foliage. Nutritional properties of blueberry forage grown under variable irradiance in the natural stands matched predictions based upon results from the growth room and field. Compared to even-aged stands and oldgrowth, leaves of plants grown in clear-cuts were similar in digestible energy, much lower in digestible nitrogen, and presumably less palatable due to higher tannin concentrations. / Graduation date: 1990

Το Vaccinium corymbosum (Ericaceae) είναι ένας ψηλός θάμνος, ο οποίος καλλιεργείται σε περιοχές της Αμερικής και της Ευρώπης για τους υψηλής διατροφικής αξίας καρπούς του (κυανά μύρτιλλα: blueberries). Στη χώρα μας, καλλιέργεια μύρτιλλων γίνεται κυρίως στην περιοχή της Δράμας. Οι περισσότερες μελέτες εστιάζουν στην ανάλυση των συστατικών των καρπών, ενώ η φυτοχημική σύσταση των φύλλων δεν έχει μελετηθεί εκτενώς. Η παρούσα εργασία, στόχο είχε την ανάλυση των κυριότερων φαινολικών συστατικών των φύλλων του φυτού, με χρήση χρωματογραφικών μεθόδων ανάλυσης. Τα αποξηραμένα φύλλα, τα οποία χρησιμοποιήθηκαν στην παρούσα διατριβή, προέρχονται από τις ποικιλίες ‘Bluecrop’ και ‘Patriot’, βιολογικής καλλιέργειας στην περιοχή της Δράμας. Προετοιμάστηκε αφέψημα των αποξηραμένων φύλλων, το οποίο στη συνέχεια εκχυλίστηκε διαδοχικά, με οξικό αιθυλεστέρα (AcOEt) και βουτανόλη (BuOH). Κατόπιν και με σκοπό τον εύκολο προσδιορισμό των φαινολικών ενώσεων, πραγματοποιήθηκε όξινη υδρόλυση (90 oC, 2 h, 50% μεθανόλη) όλων των κλασμάτων: Crude (αφέψημα), AcOEt, BuOH και Aqueous. Η ανάλυση των συστατικών πραγματοποιήθηκε με Υγρή Χρωματογραφία Υψηλής Απόδοσης με Ανιχνευτή Συστοιχίας Φωτοδιόδων (HPLC-DAD) και ύστερα με Υγρή Χρωματογραφία Υπερυψηλής Απόδοσης (UPLC-MS) με Φασματόμετρο Μάζας, το οποίο διαθέτει υβριδικό αναλυτή τετραπόλου – χρόνου πτήσης (Q-TOF). Για την HPLC-DAD ανάλυση χρησιμοποιήθηκε στήλη αντίστροφης φάσης (Luna C-18), με σύστημα βαθμιδωτής έκλουσης με τρείς διαλύτες: διάλυμα οξικού αμμωνίου (CH3COONH4-10 mM), ακετονιτρίλιο και μεθανόλη (Μαργιάννη, 2011). Επιπλέον, για την ποσοτικοποίηση των κυριότερων φαινολικών συστατικών χρησιμοποιήθηκε σύστημα βαθμιδωτής έκλουσης με δύο διαλύτες: διάλυμα CH3COONH4-10 mM και ακετονιτρίλιο (τροποποίηση Tsao et al., 2003). Στην ανάλυση UPLC-ESI-MS χρησιμοποιήθηκε στήλη αντίστροφης φάσης (BEH C18), με σύστημα βαθμιδωτής έκλουσης με δύο διαλύτες: 0.1% μυρμηκικό οξύ σε H2O και ακετονιτρίλιο. Τα αποτελέσματα έδειξαν, αρχικά, ότι κανένα από τα κλάσματα δεν περιέχει ανθοκυανίνες, ενώ το AcOEt κλάσμα είναι περισσότερο εμπλουτισμένο σε φαινολικά συστατικά, σε σχέση με τα άλλα κλάσματα. Με χρήση της UPLC-ESI-MS ανάλυσης, προσδιορίσθηκαν διάφορα συστατικά μεταξύ των οποίων φαινολικά οξέα και φλαβονοειδή. Ενδιαφέρον παρουσίασε το γεγονός ότι το Aqueous κλάσμα περιείχε μόνο φαινολικά οξέα. Η επιλογή της μεθόδου της όξινης υδρόλυσης, φαίνεται να ήταν ικανοποιητική, αφού τα άγλυκα τμήματα των γλυκοζυλιωμένων φλαβονολών, αλλά και τα προϊόντα διάσπασης του εστερικού δεσμού του χλωρογενικού οξέος, προσδιορίσθηκαν εύκολα με την UPLC-ESI-MS ανάλυση. Στα επιμέρους δείγματα ποσοτικοποιήθηκαν, με χρήση HPLC-DAD ανάλυσης τα εξής φαινολικά συστατικά: χλωρογενικό οξύ, ρουτίνη, υπεροζίτης, ισοκερσιτρίνη και κερκετίνη. Συνεπώς, το αφέψημα των καλλιεργούμενων μύρτιλλων είναι μία καλή πηγή φαινολικών συστατικών. / Vaccinium corymbosum (Ericaceae) is a tall shrub, which is cultivated in parts of America and Europe for their fruits (blueberries), which possess high nutritional value. In our country, blueberries are mainly cultivated in the area of Drama. Many studies focus on the analysis of the constituents of fruits, while the phytochemical composition of leaves has not been studied in detail. The present study aimed the analysis of the main components of blueberry leaves, using chromatographic techniques. Dried leaves (var ‘Bluecrop’ and ‘Patriot’) were obtained from the Cooperative ‘‘Biodrama’’. The decoction of dried leaves was prepared and then extracted sequentially with ethyl acetate and butanol. In order to easily identify the phenolic compounds, all fractions (Crude or decoction, AcOEt, BuOH and Aqueous) were hydrolysed in acid conditions (90 oC, 2 h, 50% MeOH). The components of the fractions were analyzed firstly by High Performance Liquid Chromatography with Diode Array Detector (HPLC-DAD) and then with Ultra High Performance Liquid Chromatography (UPLC-MS) with Mass Spectrometry. The mass spectrometer features hybrid quadrupole - time of flight (Q-TOF) analyzer. For the HPLC-DAD analysis a reverse phase column (Luna C-18) was used with a gradient elution system with three solvents: ammonium acetate (CH3COONH4-10 mM), acetonitrile (AcCN) and methanol (MeOH) (Margianni, 2011). Moreover, the quantification of the major phenolic components system was done with a gradient elution system of CH3COONH4-10 mM and AcCN (modified from Tsao et al., 2003). UPLC-ESI-MS was performed on a reverse phase column (BEH C18) with a gradient elution system with two solvents: 0.1% formic acid in H2O and AcCN. Firstly, the results showed that none of the fractions contain anthocyanins while AcOEt fraction is more enriched in phenolic compounds, in comparison to the other fractions. Using UPLC-ESI-MS analysis, we identified several components including phenolic acids and various flavonoids. Interestingly, the Aqueous fraction contained only phenolic acids. The choice of the method of acid hydrolysis appears to be satisfactory for identification purposes, since the aglycones of glycosylated flavonols, and the cleavage products of the chlorogenic acid, was determined easily by UPLC-ESI-MS analysis. The phenolic compounds: chlorogenic acid, rutin, hyperoside, isoquercitrin and quercetin were quantified in blueberry leaf decoction using HPLC-DAD. Therefore, the decoction of cultivated blueberries is a good source of phenolic compounds.

Bluberries (Vaccinium sp.) are rich in polyphenols that are responsible for lowering the risk of developing several chronic degenerative diseases. However, the effect of food matrix interactions on the bioaccessibility and bioavailability of polyphenols is not well understood. In this research free and complexed polyphenols found in blueberry extracts were characterized and their antioxidant activity as well as antiproliferative activities against colon cancer cells (HT-29) and normal colon cells (CRL-1790) were evaluated. The blueberry food matrix and different carbohydrate-rich synthetic matrices were characterized and their biological activities assessed alone and in complexed state with polyphenols. The degradation of polyphenols during their transit through the gastrointestinal tract (GIT) was evaluated using an in vitro digestion model. Biological activities of blueberry polyphenols and their parent metabolites produced during colonic fermentation were estimated by in vitro antioxidant assays and cell proliferation analysis using HT-29 and CRL-1790 cell lines. HPLC analysis revealed the presence of 7 phenolic compounds and 13 anthocyanins in all samples. Although the concentration of the polyphenols varied among the samples, free and complexed polyphenols showed significant antioxidant and antiproliferative activities. Polyphenol complexes were analyzed using transmission electron microscopy (TEM) revealing the presence of electron dense complexes ranging from 100 – 200 nm. Pectinase treatment disrupted the structure of the complexes, suggesting the pectin nature of the polyphenol complexes. The antioxidant- and antiproliferative activities of the blueberry food matrix alone was below 10% compared to almost 90% and 70% of free and complexed polyphenols, respectively. Polyphenols and anthocyanins were highly stable during simulated gastric digestion step with approximately 93% and 99% of recovery, respectively. The intestinal digestion process decreased the polyphenol- and anthocyanin- contents by 49% and 15 % respectively. During colonic digestion, the complex polyphenol mixtures were degraded to a limited number of phenolic compounds. Only acetylated anthocyanins were detected in low amounts after the colonic digestion process. After simulated colonic digestion, the isolated catabolites showed lowered antioxidant activity and cell growth inhibition potential. Understanding the interactions that occur among polyphenols and different food matrices may help to produce more stable foods with better bioavailability. / The National Council of Science and Technology of Mexico (CONACYT)