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The Saccharomyces cerevisiae chitinase, encoded by the CTS1-2 gene, as an antifungal and biocontrol agentCarstens, Maryke,1976- 04 1900 (has links)
Thesis (MScAgric) -- University of Stellenbosch, 2002. / ENGLISH ABSTRACT: Fungi are an extremely diverse group of organisms and, by acting as pathogens, they can
colonise various other organisms, including humans, plants and animals. The effect of this is
usually detrimental, not only to agricultural crops and livestock, but also to human well-being.
The extensive farming of crops and livestock requires persistent control of fungal populations,
commonly through the use of chemical fungicides. However, the exclusive use of fungicides is
no longer a sustainable practice, as a result of serious problems, such as increasing fungicide
resistance in pathogen strains, the high costs of fungicides, as well as concern about the
environment. The search by producers and scientists for alternative control measures is an
ongoing process.
The fungal cell wall consists of polysaccharides that not only playa role in protection of the
fungi, but also in relaying signals for the invasion and infection of susceptible hosts. Chitin, a
polysaccharide composed of N-acteylglucosamine (GleNAc) residues linked by P-1,4 glucosidic
linkages, is one of the major components of the fungal cell wall, where it plays an important role
in the apical growth of the vegetative hyphae.
Chitinases (EC 3.2.1.14) are abundant proteins produced by a variety of microorganisms
and plants and are necessary for the hydrolysis of the chitin polymer. During the invasion of
many plant species by a pathogen, the production of a specific group of proteins, designated
pathogenesis-related (PR) proteins that include chitinases, is induced as part of their defence
response. Due to the facts that pathogenic fungi contain chitin in their cell walls and that plant
chitinases are induced upon pathogen attack, chitinases have been confirmed as an integral and
crucial part of the plant's natural defence response. Chitinases have increasingly been targeted
to upregulate plants' endogenous disease resistance mechanisms through transgenic
overexpression in a variety of hosts.
Several species of fungi, including various Trichoderma spp., are potent biocontrol agents
of plant pathogenic fungi and insects. The antagonistic activities of these biological control
agents towards phytopathogens are based on the secretion of extracellular hydrolytic enzymes,
such as cell wall-degrading chitinase enzymes. However, biological control is not restricted to
naturally occurring biocontrol agents. Through the process of genetic transformation, other
fungal or yeast species can be enhanced to produce their own chitinases or other antimicrobial
substances more effectively in order to yield potent biocontrol agents.
Various types of chitinases have been applied in the production of fungal resistant plants
and some research has been done on the application of chitinases, from a variety of
microorganisms, as biological control agents. In contrast, very little is known about the
antifungal activity of the Saccharomyces cerevisiae chitinase enzyme, encoded by the CTS1-2
gene. The CTS1-2 gene was utilised in this study as a candidate for overexpression in both
yeast and plant expression systems to analyse the ability of the encoding chitinase to inhibit
fungal growth.
The first objective of this study involved the high level expression and optimisation of the
secretion of the CTS1-2 gene in S. cerevisiae to render recombinant yeast with enhanced
antifungal abilities and with possible applications as a biocontrol agent to control plant pathogenic fungi. It was hypothesised that high-level expression and efficient secretion would
be prerequisites in a biocontrol yeast strain. To this end, two strong promoters and terminators
were included in the study and the secretion of the chitinase gene was evaluated by testing
three different secretion signals. The secretion signals included: the native CTS1-2 secretion
signal, the S. cerevisiae mating pheromone a-factor (MFa1) secretion signal, as well as the
Trichoderma reesei f3-xylanase 2 (XYN2) secretion signal. The phosphoglycerate kinase 1
(PGK1) and alcohol dehydrogenase 2 (ADH2) promoters and terminators were employed to
achieve high-level expression.
The results obtained from the analysis of the recombinant yeasts showed that the PGK1
promoter-terminator constructs yielded high level CTS1-2-expressing and chitinase-producing
strains of S. cerevisiae PRY488. The ability of the different secretion signals to efficiently
secrete the overexpressed chitinase was analysed and it was found that the non-native
secretion signals delivered significantly more protein to the extracellular environment. It was
thus evident that the performance of the MFa1 and XYN2 secretion signals was superior to that
of the native secretion signal. The antifungal activities of the recombinant chitinases produced
by these constructs were tested in in vitro assays against Botrytis cinerea. The enzymes led to
a significant reduction in hyphal development, caused by extreme structural damage to the
hyphal tips, the hyphal cell walls as well as the ability of the fungus to form reproductive and
survival structures, thereby confirming the antifungal abilities of this enzyme. The ADH2
promoter-terminator constructs yielded CTS1-2 transcripts, but no chitinase activity could be
detected with any of these strains. The reasons for this still remain unclear.
The second objective of this study was to assess the potential of the yeast chitinase gene to
upregulate defence against fungal infection in planta. In order to elucidate this, the CTS1-2
gene was constitutively overexpressed in tobacco plants, targeting the chitinase both to the
intra- and the extracellular environment. The results obtained showed that the transgenic
tobacco lines regenerated in this study stably integrated the transgene, exhibiting transgene
expression as well as the production of a biologically active yeast chitinase enzyme. The F,
progeny were rigorously tested for resistance to B. cinerea, and both in vitro and in planta
assays confirmed that the yeast chitinase increased the plant's tolerance to fungal infection;
some of the lines showed disease resistance of 65 and 70%. The plants expressing an
extracellularly targeted chitinase gene are still under evaluation. Interesting results are expected
relating to the effect of the chitinase on the plant surface with regards to disease resistance to
fungal pathogens.
In conclusion, the combined set of results from both the yeast and plant overexpression
studies has confirmed the strong antifungal effect of yeast chitinases. The yeast CTS1-2
chitinase could be instrumental in the development of a new generation of yeast strains with
improved antifungal capabilities. This enzyme could also play an important role in genetic
transformation technologies aimed at enhanced disease resistance. / AFRIKAANSE OPSOMMING: Swamme omsluit 'n uiterste diverse groep organismes wat mense, plante en diere deur
patogeniese aksie kan koloniseer. Die uitkoms hiervan op landbougewasse, die veebedryf en
menslike gesondheid is gewoonlik skadelik. Uitgebreide gewas- en veeboerderye benodig
voortdurende beheer van fungiese populasies, tipies deur van chemiese swamdoders gebruik te
maak. Die uitsluitlike gebruik van swamdoders is egter nie meer 'n lewensvatbare praktyk nie,
hoofsaaklik as gevolg van probleme soos die opbou van weerstand van patogeniese rasse teen
swamdoders, die hoë kostes van die middels, asook besorgheid oor die omgewing. Die soektog
na alternatiewe beheermaatreëls deur produsente en wetenskaplikes bly 'n aaneenlopende
proses.
Die swamselwand bestaan uit polisakkariede wat nie net In rol in die beskerming van die
swam speel nie, maar ook betrokke is in die oordrag van aanvals- en infeksieverwante seine in
'n vatbare gasheer. Chitien, 'n polisakkaried bestaande uit N-asetielglukosamien (GlcNAc)
residu's gekoppel deur 13-1,4glukosidiese bindings, is een van die hoofkomponente van die
swamselwand, waar dit 'n belangrike rol in die apikale groei van vegetatiewe hifes speel.
Chitinases (EC 3.2.1.14) is proteïene wat oorvloedig deur 'n verskeidenheid van
mikroërganismes en plante geproduseer word, waar hulle vir die hidrolise van die chitien
polimeer noodsaaklik is. Tydens die infeksie van verskeie plantspesies deur In patogeen, word
die produksie van 'n spesifieke groep proteïene, die sogenaamde patogeen-verwante (PR)
proteïene wat chitinases insluit, as deel van die plant se verdedigingsreaksie geïnduseer. Die
feit dat patogeniese swamselwande chitien bevat en dat plantchitinases tydens infeksie
geïnduseer word, het daartoe gelei dat dit bevestig is dat chitinases In integrale en kritiese deel
van die plant se natuurlike verdedigingsreaksie uitmaak. Chitinases word toenemend geteiken
in pogings om die plant se intrinsieke siekteweerstandsmeganismes te verbeter deur
transgeniese ooruitdrukking daarvan in 'n verskeidenheid van gashere.
Verskeie swamspesies, insluitend verskillende Trichodenna-spesies, is kragtige
bio-antagoniste van plantpatogeniese swamme. Die antagonistiese aksies van hierdie
biologiese beheeragente teenoor fitopatogene is gebaseer op die uitskeiding van ekstrasellulêre
hidrolitiese ensieme, soos die selwandverterende chitinase ensieme. Nietemin is biologiese
beheer nie net tot bio-antagoniste wat natuurlik voorkom beperk nie. Deur die proses van
genetiese transformasie kan ander swam- of gisspesies verbeter word om hul eie chitinases of
ander antimikrobiese substanse meer effektief te produseer, wat aanleiding sal gee tot kragtige
bio-antagoniste.
Verskeie tipes chitinases is al in die produksie van swambestande plante ingespan en
uitgebreide navorsing is gedoen op die toepassing van 'n reeks chitinases, afkomstig van 'n
verskeidenheid van mikroërganismes, as biologiese beheeragente. In teenstelling is baie min
bekend oor die antifungiese aktiwiteite van die Saccharomyces cerevisiae chitinase ensiem, wat
deur die CTS1-2 geen ge-enkodeer word. Die CTS1-2-geen is in hierdie studie gebruik vir
ooruitdrukking in beide gis- en plantuitdrukkingsisteme om die chitinase se vermoë om
swamgroei te inhibeer, te ondersoek. Die eerste oorkoepelende oogmerk van hierdie studie het hoë-vlak uitdrukking en
optimalisering van sekresie van die CTS1-2-geen in S. cerevisiae behels, met die toekomstige
doelwit om 'n rekombinante gis met verbeterde antifungiese eienskappe en met moontlike
toepassings as 'n bio-antagonis teen plantpatogeniese swamme te ontwikkel. Die hipotese was
dat hoë-vlak uitdrukking en voldoende sekresie voorvereistes vir 'n bio-antagonisras is. Omdié
rede is twee sterk promotors en termineerders by hierdie studie ingesluit en is die sekresie van
die chitinase-geen geëvalueer deur drie verskillende sekresieseine te toets. Die sekresieseine
sluit in: die wilde-tipe CTS1-2 sekresiesein, die S. cerevisiae paringsferomoon a-faktor (MFa1)
sekresiesein, en die Trichoderma reesei p-xilanase (XYN2) sekresiesein. Die fosfogliseraat
kinase 1 (PGK1) en alkohol dehidrogenase 2 (ADH2) promotors en termineerders is gebruik om
hoë-vlak uitdrukking te dryf.
Die resultate wat vanaf die analises van die rekombinante giste verkry is, het getoon dat die
PGK1 promotor-termineerder konstrukte hoë-vlak CTS1-2-uitdrukkende en
chitinase-produserende S. cerevisiae PRY488 rasse opgelewer het. Die vermoë van die
verskillende sekresieseine om die ooruitgedrukte chitinase voldoende uit te skei, is geanaliseer,
en daar is gevind dat die heteroloë sekresieseine aansienlik meer proteïene na die
ekstrasellulêre omgewing geloods het. Dit was dus duidelik dat die MFa1 en XYN2
sekresieseine beter as die wilde-tipe sekresiesein presteer het. Die antifungiese aktiwiteit van
die rekombinante chitinases wat deur hierdie konstrukte geproduseer is, is ook in in vitrotoetse
teen Botryits cinerea getoets. Die teenwoordigheid van die ensieme het gelei tot 'n aansienlike
afname in hife-ontwikkeling, veroorsaak deur ekstreme strukturele skade aan die hifepunte, die
hifeselwande, asook die vermoë van die swam om voortplanting- en oorlewingstrukture te vorm.
Die ADH2 promotor-termineerderkonstrukte het CTS1-2 transkripte vertoon, maar geen
chitinase-aktiwiteite kon in hierdie konstrukte waargeneem word nie. Die redes hiervoor is tot op
hede onbekend.
Die tweede oogmerk van hierdie studie was om die potensiaal van die gischitinase om
swaminfeksie in planta teë te werk, te ondersoek. Die CTS1-2-geen is konstitutief ooruitgedruk
in tabakplante, waarin die chitinase na beide die intra- en ekstrasellulêre omgewing geteiken is.
Resultate het getoon dat die geregenereerde transgeniese tabaklyne die transgeen stabiel
geïntegreer het, transgeenuitdrukking vertoon en dat 'n biologies aktiewe chitinase-ensiem
geproduseer is. 'n F1-generasie is aan strawwe toetse onderwerp om weerstand teen B. cinerea
te ondersoek. Beide die in vitro en in planta toetse het bevestig dat die gischitinase die plant se
verdraagsaamheid teenoor swaminfeksie verhoog het; sommige lyne het siekteweerstand van
tussen 65 en 70% getoon. Die plante wat 'n ekstrasellulêre chitinase produseer, word steeds
geëvalueer. Interessante resultate word verwag aangaande die effek van die chitinase op die
plant se oppervlak met betrekking tot siekteweerstand teen swampatogene.
Ten slotte, die gekombineerde stel resultate wat vanaf beide die gis- en
plantuitdrukkingstudies verkry is, het die sterk antifungiese effek van gischitinases bevestig. Die
gis CTS1-2 kan instrumenteel wees in die ontwikkeling van 'n nuwe generasie gisrasse met
verbeterde antifungiese eienskappe. Die ensiem kan ook 'n belangrike rol in genetiese
transformasietegnologieë, wat op verbeterde siekteweerstand gemik is, speel.
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Effect of shading and ethephon on the anthocyanin composition of ‘Crimson seedless’ (Vitis vinifera L.)Human, Michael Adriaan 12 1900 (has links)
Thesis (MScAgric (Viticulture and Oenology)--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: ‘Crimson Seedless’ is currently one of the most important and popular table grape
cultivars produced in South Africa, and as such it is of great economic value for table
grape producers. Major concerns with ‘Crimson Seedless’ is that it is prone to
inadequate colouring, and with increased yields the berry size decreases. An additional
difficulty is that methods used to increase berry size, further impede berry colouring. A
plant growth regulator (PGR) commonly used in table grape production, to enhance
colour formation, is ethephon (2-chloro-ethyl-phosphonic acid, 2-CEPA). In recent years
significant research has been done on the effect of sunlight on anthocyanin production
in grapes, although this has primarily been on wine grape cultivars. Currently, there is
limited knowledge on the effect of sunlight on table grapes, and how this might influence
their anthocyanin composition and content. The effect of ethephon on colour of grapes
and other fruit have been extensively researched and well documented. However, the
effect of ethephon on the anthocyanin composition of ‘Crimson Seedless’ is not well
known. The current study aimed to explore the effect of sunlight (by matter of exclusion)
and management practices, namely defoliation and ethephon application, on the
anthocyanin profile and content of ‘Crimson Seedless’. Four different treatments were
applied to two ‘Crimson Seedless’ vineyards, the first site located in Paarl, and the
second in De Doorns. The treatments were: 1. Naturally exposed bunches, 2. Exposed
bunches treated with ethephon, 3. Bunches kept in shade boxes, 4. Shaded bunches
treated with ethephon. At the De Doorns site an additional defoliation treatment was
superimposed over the above treatments. An HPLC technique was modified for the
separation and detailed profiling of ‘Crimson Seedless’ anthocyanins and was used to
analyse the effect of the reported treatments on the anthocyanin profile of berry skins.
The predominant anthocyanin in ‘Crimson Seedless’ is peonidin-3-glucoside (Pn-gluc),
and this was found to be significantly increased only by ethephon application, and was
not altered by sunlight or leaf removal. The responses of the other anthocyanin types
varied according to the respective treatments applied. However, a general observation
was that ethephon application more consistently increased the concentration of
anthocyanins in berry skins than did sunlight. Leaf removal had the least significant
effect on anthocyanin concentration. / AFRIKAANSE OPSOMMIMG: ‘Crimson Seedless’ is tans een van die belangrikste en gewildste tafeldruif cultivars wat
in Suid-Afrika verbou word en daarom is dit van groot ekonomiese waarde vir tafeldruifprodusente.
‘Crimson Seedless’ is egter daarvoor bekend dat dit te swak kleur (volgens
uitvoer spesifikasies) en tweedens is die cultivar geneig om kleiner korrels te ontwikkel
wanneer die oeslading vermeerder word. ‘n Addisionele probleem is dat die praktyke
wat in die industrie gebruik word om korrels te vergroot ‘n verdere negatiewe impak op
‘Crimson Seedless’ se kleur ontwikkeling kan veroorsaak. Die plant-groei-reguleerder
wat algemeen in tafeldruif verbouing gebruik word, ten einde beter gekleurde druiwe te
produseer, is ethephon (2-chloro-ethyl-phosphonic acid, 2-CEPA). In die laaste paar
jaar was daar baie navorsing gedoen oor die effek wat sonlig het op die antosianien
produksie van druiwe, maar navorsing was gefokus op wyndruif cultivars. Huidiglik is
daar beperkte tegniese kennis oor die effek wat sonlig op tafeldruiwe het, en hoe dit
moontlik die antosianien samestelling en inhoud kan beïnvloed. Daar is ook reeds
verskeie studies gedoen en data gepubliseer oor die invloed wat ethephon op die kleur
het van druiwe en ander vrugte, maar die invloed wat ethephon op die antosianien
samestelling van ‘Crimson Seedless’ het, is nie wel bekend nie. Die doel van hierdie
studie was om die effek van sonlig (deur uitsluiting) en bestuurspraktyke
(blaarverwydering en ethephon toediening) te bestudeer en hoe dit die antosianien
samestelling van ‘Crimson Seedless’ beïnvloed. Vier verskillende behandelings is
toegedien in twee ‘Crimson Seedless’ wingerde, die eerste proefperseel in die Paarl en
die tweede proefperseel in De Doorns. Die behandelings was: 1. Natuurlik blootgestelde
trosse, 2. blootgestelde trosse met ethephon, 3. Trosse met skadubokse omhul, 4.
Skaduboks trosse met ethephon. By De Doorns is ‘n addisionele blaarverwydering proef
bygebring. ‘n HPLC tegniek was aangepas om die antosianien samestelling en inhoud
van ‘Crimson Seedless’ te bepaal, en om die effek van die behandelings te ondersoek.
Die HPLC data het getoon dat peonodien-3-glukosied (Pn-gluc) die primêre antosianien
in ‘Crimson Seedless’ is met die hoogste inhoud van al die antosianiene. Pn-gluc was
betekenisvol beïnvloed deur ethephon toediening, terwyl die ander behandelings geen
betekenisvolle effekte daarop gehad het nie. Die effekte wat die ander antosianiene
gehad het, het gevarieer volgens die behandelings wat toegedien was. ‘n Algemene
observasie was dat ethephon toediening die antosianien konsentrasie in ‘Crimson
Seedless’ druiwe skille meer konsekwent vermeerder het as die sonlig blootstelling. Die
blaarverwydering het die minste betekenisvolle effek op die antosianien inhoud van
‘Crimson Seedless’ gehad.
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De la vigne au chai : viticulture et vinification en Bordelais après la guerre de Cent Ans (vers 1450 - vers 1480) / From vineyard to the wine storehouse : viticulture and vinification in Bordeaux area after the hundred years war (about 1450 - about 1480)Porcher, Kévin 25 October 2011 (has links)
De 1154 à 1453, Bordeaux se trouve sous l’obédience du roi d’Angleterre.L’ouverture du marché anglais favorise le développement d’un vignoble à vocation commerciale autour de la ville. De nombreux travaux sont consacrés à cette période faste du vignoble et du commerce du vin bordelais. En revanche, la situation du vignoble au lendemain de la fin de la guerre de Cent Ans (après la prise de Bordeaux par Charles VII en 1453) est très souvent restée dans l’ombre.Ce travail propose donc d’étudier les caractéristiques et les dynamiques du vignoble bordelais dans la seconde moitié du XVe siècle, après les crises de la fin du Moyen Âge. En raison de la nature des sources employées, l’approche adoptée est celle du point de vue des Bordelais sur le vignoble, ce qui permet d’analyser l’emprise urbaine sur les vignes des alentours. Nous verrons comment les stratégies foncières et économiques des élites urbaines, essentiellement composées de marchands, influencent l’évolution du vignoble bordelais après la guerre de Cent Ans. / From 1154 to 1453, Bordeaux is under the king of England's obedience. The opening of the English trade promotes the development of a turned-for-business vineyard around the town. Several researches are devoted to this lucky time for vineyardand Bordeaux wine trading. In return the state of the vineyard shortly after the end of the Hundred Years War (after the taking of Bordeaux by Charles VII in 1453) is very often remained in the background.Therefore this work purposes to study the Bordeaux vineyard characteristics and dynamics in the second half of the XVth century after the crisis of the end of the MidlleAges. On account of the nature of the used documents, the adopted approach is theBordeaux point of view about the vineyard, and this allows an analysis of the urbangrasp on the surrounding vineyards. We will see how the land and economic strategiesof the urban elites, mainly composed by merchants, influence the development of theBordeaux vineyard after the Hundred Years War.
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La vigne et l'olivier en Corse : études de géolinguistique et de sémantique lexicale / The vine and the olive tree in corsica : studies in geolinguistic and lexical semanticsTognotti, Aurelia Ghjacumina 13 December 2013 (has links)
Cette thèse s’inscrit dans le programme Nouvel Atlas Linguistique de la Corse et Banque de Données Linguistiques Corses et plus particulièrement dans la préparation du quatrième volume consacré à l’agriculture. A partir d’une collecte sur le terrain du lexique et des techniques relatifs à l’oléiculture et à la viticulture, une étude de géolinguistique et de sémantique lexicale est réalisée, à partir du corpus oral comprenant les données de la BDLC et d’enquêtes personnelles. L’examen de la répartition géolinguistique porte sur l’ensemble des variétés dialectales insulaires et est accompagné de commentaires étymologiques et sémantiques de chaque terme correspondant aux thèmes abordés. Pour conduire ce travail, nous nous sommes en particulier appuyés sur les travaux réalisés dans le reste du domaine italo-roman, notamment à travers un dépouillement systématique de dictionnaires étymologiques, historiques et dialectaux ; ce qui permet de donner une dimension comparatiste à notre étude. Cette recherche propose un développement de deux principaux axes : d’une part, l’évaluation de la diversité linguistique et la mise en évidence des rapports avec les aires voisines à la Corse et d’autre part, établir les processus de formation lexicale permettant, outre de retracer le cheminement de la langue, d’observer les caractéristiques des lexiques oléicole et viticole (lexique spécifique vs lexique général ; lexique hérité vs constructions motivées ; les analogies et les différences). / This thesisis part of the Program calledNew Linguistic Atlas of Corsica and LinguisticCorsican Data Bank and more specifically in the preparation of the fourth volume devoted to agriculture. From a field collection of vocabulary and techniques related to the viticulture and winegrowing, a study of geo-linguistic and lexical semantics has been done, from the spoken corpus data includingBLDC and personalsurveys. Examination of the distribution geolinguisticcovers all the islanddialects and isaccompanied by etymological and semanticcommentseachtermcorresponding to the topicdiscussed. To conductthiswork, weparticularlyrelied on the workdone in the rest of the Italian-Roman field -, includingthrough a systematicanalysis of etymologicaldictionaries, historical and dialectological ,whichallows to give a comparative dimension to ourstudy.This research proposes a development of two main areas: first, evaluate the linguisticdiversity and highlightrelationshipswithneighboring areas to Corsica and secondly, establishprocesses for lexical training, also to trace the language, observe the characteristics of the wine and olive lexicons (specificlexicon vs. generallexicon; lexiconinherited vs motivated constructions and the similarities and differences). / S’iscriviistatesi in u prugrammaNouvel Atlas Linguistique de la Corse è Banque de Données Linguistiques Corses è più particularmenti in a priparazioni di u quartuvulumu à prò di l’agricultura. À partasi di unaracoltaannant’àlocu è di u lessicu è di i tecnichi di a vigna è di l’alivu, hèfattuunustudiu di geolinguistica è di semanticalessicale, à partasi di un corpus uralichìcunteni i dati di a BDLC è di inchiestiparsunali. L’esamini di a ripartizionigeoliguisticatratta di l’insemi di i varietàdialettaliisulani è ghjèaccumpagnata di cummentietimulogichi è semantichi d’ugniterminicurrispundanti à i temaammintati. Da stradàistutravaddu, ci simuaiutatipà u più di i travaddirializatiind’è u restu di u duminiuitalorumanzu, in particularicù un spoddusistematicu di dizziunariaetimulogichi, storichi et dialettali ; ciòchìparmetti di dàuna misura cumparatista à u nosciustudiu. Istaricercapruponaunusviluppu di duiiassiprincipali : d’un cantu, a valutazioni di a diversitàlinguistica è a messa in luci di i leiaincù l’aghjivicini à a Corsica et d’un altrucantu, stabiliscia i prucessi di furmazionilessicalichìparmettani, aldilà di ritraccià l’andatura di a lingua, di fidighjà i caratteristichi di i lessichi di l’alivu è di a vigna (lessicuspecificu vs lessicughjinirali ; lessicueridatu vs custruzzionimutivati ; l’analugii è i sfarenzi).Parollichjavi : dialettulugia, geografialinguistica, corsica, aliva, vigna, etimulugia, semantisimu.
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The ecophysiological characterisation of terroirs in Stellenbosch : the contribution of soil surface colourWitbooi, Erna Hailey 03 1900 (has links)
Thesis (MScAgric (Viticulture and Oenology))--Stellenbosch University, 2008. / Soil is a component of the environment and sustains growth of several plants and animals.
It forms part of the biosphere and can be described as the interface between the
atmosphere and the lithosphere. The interaction between soil, climate and topography and
the resulting agricultural aptitude forms the concept of terroir. This relationship is complex
and it is difficult to quantify the contribution of each.
Grapevines are exposed to an array of soil types. Soils have varying colours, which can be
ascribed to their origin from different parent materials and pedogenetic factors. Historical
and experimental evidence points to the key role that soil physical conditions play in
determining grape berry composition, but other soil related factors may also play a role.
This study was conducted to investigate the effect of soil surface colour on the vegetative
and reproductive growth characteristics of Cabernet Sauvignon. The aim was to determine
whether a relationship exists between soil colour, reflective light quality below and inside
the grapevine canopy, vegetative growth of the grapevine and the berry and wine
composition.
The reflected light from soils was measured in three positions of the canopy and across
the light spectrum (300–2500 nm) for three different soil surface treatments (black, red and
grey). The effect of soil colour on vegetative parameters, yield and berry composition and
wine quality was investigated. Soil surface colour resulted in differences in the reflected
light quality below and in the canopy. The differences in the light quality were associated
with differences in vegetative parameters such as mean main leaf, with grey soils inducing
higher values. Potassium levels of the grapes and berry number per bunch appeared to be
influenced by soil surface colour throughout berry development with red and black soils
having higher levels of potassium and berry number per bunch than grey soils. Grape
ripening parameters were not influenced by soil surface colour, but the grey treatment had
a significantly more intense grape colour measured at 520 nm (red pigments).
It is assumed that the importance of soil colour is its association with the physical and the
pedogenetic properties that contribute to the grapevine water balance. From these results it can be concluded that soil surface colour appeared to have a direct effect on some
aspects of vegetative and reproductive growth, and berry composition, but the contribution
of different wavebands and mechanism of their effect deserves further study.
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Nutritional status of geologically different vineyards in HelderbergShange, Philisiwe Lawrancia 12 1900 (has links)
Thesis (MscAgric (Viticulture and Oenology))--University of Stellenbosch, 2009. / ENGLISH ABSTRACT: Little scientific information regarding the effect of different geological parent materials on
grapevine performance is currently available in South Africa. This aspect is of special
significance for the Helderberg area, where parent material may change from granite to shale
over a short distance. This results in shale- as well as granite-derived soils often occurring
within the same vineyard. The objectives of this study were to (i) quantify the nutritional status
and other soil properties of different parent materials (shale and granite) and overlying soils (ii)
investigate the impact of geological differences in the soil on the vine nutritional status and
certain vine parameters. This study was done over two seasons (2006/2007 and 2007/2008).
Two Sauvignon blanc and two Cabernet Sauvignon vineyard blocks were selected at two
different localities for each cultivar in the Helderberg area, South Africa. Shale- and granitederived
soils were identified within each block.
Kaolinite was the dominant mineral, whereas quartz and feldspar were sub-dominant. Traces of
mica were also present in some shale- and granite-derived soils. Granite- contained significantly
higher contents of coarse sand than shale-derived soils, whilst the opposite occurred in terms of
fine sand. These differences affected the water holding capacity, in general making it higher in
shale- than granite-derived soils. Shale-derived soils had higher concentrations of total K but
granite-derived soils had a higher ability to release K as they contained higher concentrations of
soluble K. The Q/I parameters, potential buffering capacity of K (PBCK) and equilibrium activity
ratio of K (ARK) showed no consistent responses to geological differences.
Potassium concentrations were higher in the leaf blades (obtained before harvest in 2007) from
Sauvignon blanc grapevines on granite- than on shale-derived soils. Potassium concentrations
in the Cabernet Sauvignon juice (obtained in 2007) tended higher in juice from granite- than
from shale-derived soils. In 2008, K concentrations tended higher in juice from shale- than from
granite-derived soils for both cultivars. The pH of the Sauvignon blanc juice (obtained in 2008)
tended higher in juice from shale-than from granite-derived soils, thus corresponding with the K
concentrations in the juice in this season. Nitrogen concentrations were higher in Cabernet
Sauvignon juice (obtained in 2007) and Sauvignon blanc juice (obtained in 2008) from shalethan
from granite-derived soils. In terms of vine water status, vines on granite-derived soils
appeared more stressed than those on shale-derived soils in both seasons at one of the
vineyards.
In these Sauvignon blanc and Cabernet Sauvignon vineyards, the K nutritional status was not
affected by geology in a consistent manner but there were some noticeable tendencies for a
specific cultivar during certain seasons. On account of vines being planted on shale- and
granite-derived soils within the same block, soil preparation was done similarly for both soils,
and they were exposed to similar irrigation schedules, canopy management strategies and
climatic conditions. Therefore, there is a high probability that all these practices may have
negated the effect of geology on the K status of soils and especially on juice K concentration at
the time of harvest. It was clear that seasonal differences and fertilisation affected the nutritional
status of the vines more than geology. / AFRIKAANSE OPSOMMING: In Suid-Afrika is daar tans min wetenskaplike inligting oor die effek van verskillende geologiese
moedermateriale op die prestasie van wingerd beskikbaar. Hierdie aspek is veral van belang in
die Helderberg-area, waar moedermateriaal oor ‘n baie kort afstand van graniet na skalie kan
wissel. Dit lei daartoe dat skalie-, sowel as granietgronde, dikwels binne dieselfde wingerd
voorkom. Die doelwitte van die studie was om: (i) die voedingstatus en ander grondkundige
eienskappe van die verskillende moedermateriale (skalie en graniet) en oorliggende gronde te
kwantifiseer (ii) die impak van geologiese verskille in die grond op wingerd se voedingstatus en
sekere wingerdkundige parameters, te ondersoek. Hierdie studie is oor twee seisoene
(2006/2007 en 2007/2008) gedoen. Twee Sauvignon blanc en twee Cabernet Sauvignon
wingerdblokke is geselekteer by twee verskillende lokaliteite vir elke kultivar in die Helderbergarea,
Suid-Afrika. Beide skalie- en granietgrond is binne elke blok geïdentifiseer.
Kaoliniet was die dominante mineraal, met kwarts en veldspaat sub-dominant, terwyl spore van
mika ook in beide skalie- en granietgronde gevind is. Granietgronde het betekenisvol hoër
hoeveelhede growwe sand bevat, terwyl skaliegronde meer fyn sand bevat het. Hierdie verskille
het ‘n effek op waterhouvermoë gehad en daartoe gelei dat waterinhoude oor die algemeen
hoër was vir skaliegronde. Skaliegronde het groter hoeveelhede totale K bevat, maar
granietgronde se vermoë om K vry te stel was hoër, omdat hulle ‘n hoër konsentrasie oplosbare
K bevat het. Die Q/I parameters, potensiële buffervermoë vir K (PBCK) en ewewig
aktiwiteitsverhouding vir K (ARK), is nie op ‘n konsekwente wyse deur geologiese verskille
beïnvloed nie.
Vir die Sauvignon blanc wingerde was kalium konsentrasies in blaarskywe (gemonster voor oes
in 2007) hoër vir graniet- as vir skaliegronde. Kalium konsentrasies in die sap vanaf Cabernet
Sauvignon (gemonster in 2007) het hoër geneig vir granietgronde. In 2008 het die kalium
konsentrasies, vir beide kultivars, hoër geneig in sap vanaf skaliegronde. Gedurende dié
seisoen het die pH van sap ook hoër geneig vir Sauvignon blanc vanaf skaliegronde, wat dus
ooreenstem met die K inhoud van die sap. Stikstof konsentrasies was hoër in sap vanaf
skaliegronde vir Cabernet Sauvignon (2007) en vir Sauvignon blanc (2008). In terme van die
wingerde se waterstatus, het stokke op die granietgrond, by een van die lokaliteite, geneig om
gedurende beide seisoene onder groter stremming te wees op graniet as op skaliegrond.
In hierdie Sauvignon blanc en Cabernet Sauvignon wingerde, is K voedingstatus nie op ‘n
konsekwente wyse deur geologie geaffekteer nie, maar gedurende sommige seisoene was daar
wel duidelike tendense vir ‘n spesifieke kultivar. Omdat die stokke binne dieselfde blok op
skalie- en graniet gronde geplant is, was grondvoorbereiding eenders vir die twee grondtipes
terwyl besproeiingskedule, lowerbestuur en klimaatstoestande ook identies was. Daar is dus ‘n
hoë waarskynlikheid dat al hierdie faktore daartoe kon bygedra het dat die effek van geologie
op die K status van van gronde versluier is, veral die effek op die K inhoud van sap teen oestyd.
Dit was duidelik dat seisoenale klimaatsverskile en bemestingspraktyke ’n groter effek as
geologie op die voedingstatus van die wingerd gehad het.
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Grape and Wine Production in the Four Corners RegionMielke, Eugene A., Dutt, Gordon R., Hughes, Sam K., Wolfe, Wade H., Loeffler, Gregory J., Gomez, Ricardo, Bryant, M. Douglas, Watson, John, Schick, Seth H. 04 1900 (has links)
No description available.
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Isolation and characterization of antifungal peptides from plantsDe Beer, Abre 03 1900 (has links)
Thesis (PhD (Viticulture and Oenlogy))--University of Stellenbosch, 2008. / Includes bibliography and list of tables and figures. / ENGLISH ABSTRACT: Over the last decade research has shown the importance of small antimicrobial peptides in the innate immunity of plants. These peptides do not only play a critical role in the multilayered defense systems of plants, but have proven valuable in the engineering of disease resistant food crops towards the ultimate aim of reducing the dependency on chemical fungicides. As the lists of isolated and characterized peptides grew, it became clear that other biological activities, in addition to the antimicrobial capacity, could be linked to some of these peptides; these alternative activities could have important applications in the field of medicine. This has made the defensin encoding genes prime targets for the agricultural and medical biotechnology sectors.
To this end we set out to evaluate South African flora for the presence of plant defensin sequences and to isolate plant defensin genes that might be useful in biotechnology applications. Moreover, by isolating and characterizing these novel peptides, also in an in planta environment and in interaction with fungal pathogens, important knowledge will be gained of the biological role and importance of the peptides in the plant body.
The plant host targets were South Africa Brassicaceae species including indigenous species, as well as Vitis vinifera, as the most important fruit crop in the world and since no defensins have been isolated from this economically important crop plant. The Brassicaceae family has been shown to be abundant in defensin peptides and several of the best characterized peptides with potent activity have been isolated from this family. Based on initial activity screens conducted on selected South African Brassicaceae spp. we concluded that these spp. contain promising antifungal peptide activities, warranting further efforts to isolate the genes and encoding peptides and to characterize them further. The preliminary activity screens used a peptide-enrichment isolation strategy that favored the isolation of basic, heat-stable peptides; these properties are characteristic features of plant antimicrobial peptides. These peptide fractions showed strong antifungal activities against the test organisms. A PCR-amplification strategy was subsequently designed and implemented, leading to the isolation of 14 novel defensin peptide encoding genes from four South African Brassicaceae spp., including the indigenous South African species Heliophila coronopifolia.
Amino acid sequence analysis of these peptides revealed that they are diverse in amino acid composition and share only 42% homology at amino acid level. This divergence in amino acid composition is important for the identification of new biological activities within closely related plant defensins. Single amino acid changes have been contributed with the divergent biological activities observed in closely related plant defensin peptides. Phylogenetic analysis conducted on the deduced amino acid sequences revealed that all the new defensins share a close relationship to other Brassicaceae members of the plant defensin superfamily and was furthest removed from the defensins isolated from the families Solanaceae and Poaceae. Classification
analysis of these peptides showed that they belong to subgroup A3 of the defensin superfamily.
A putative defensin sequence was also isolated from V. vinifera cultivar, Pinotage, and termed Vv-AMP1. Genetic characterization showed that only a single gene copy of this peptide is present within the V. vinifera genome, situated on chromosome 1. Genetic characterization of this peptide encoding gene within the Vitis genus showed that this gene has stayed conserved throughout the divergent evolution of the Vitis genus. Expression studies of Vv-AMP1 revealed that this gene is expressed in a tissue specific and developmentally regulated manner, being only expressed in grape berries and only at the onset of vèraison. Induction of Vv-AMP1 in grapevine leaf material could never be achieved through the external application of hormones, osmotic stress, wounding, or pathogen infection by Botrytis cinerea.
Deduced amino acid analysis showed that Vv-AMP1 encoded for a 77 amino acid peptide consisting of a 30 amino acid signal peptide and a 47 amino acid mature peptide, with putative antifungal activity. The Vv-AMP1 peptide grouped with the subclass B type defensins, which have been documented to have both antifungal and antibacterial activities. The Vv-AMP1 signal peptide directed the green fluorescent protein (GFP) reporter gene to the apoplastic regions in cells with high levels of accumulation in the vascular tissue and the guard cells of the stomata.
Recombinant Vv-AMP1 peptide was successfully purified from a bacterial host and shown to have a size of 5.495 kDa. Recombinant Vv-AMP1 showed strong antifungal activity at low concentrations against a broad spectrum of fungal pathogens, which included Verticillium dahliae (IC50 of 1.8 μg mL-1) and the necrotrophic pathogen Botrytis cinerea (IC50 of 12-13 μg mL-1). Antifungal activity of Vv-AMP1 did not induce morphological changes in fungal hyphae, but its activity was associated with induced membrane permeabilization in treated hyphae.
Vv-AMP1 was successfully introduced into Nicotiana tabacum as confirmed by Southern blot analysis and 20 individual lines were generated. Genetic characterization confirmed the integration and expression of the gene in the heterologous tobacco environment. The peptide was under control of its native signal sequence which has been shown to direct its product to the apoplastic regions of cells. The transgenic lines were analyzed to determine the presence and activity of the grapevine defensin peptide. Western blot analyses of partially purified plant extracts detected a signal of the expected size in both the untransformed control and the transgenic lines. Comprehensive analysis of EST databases identified three highly homologous sequences from tobacco that probably caused the background signal in the control. These crude protein extracts were able to inhibit the growth of V. dahliae in vitro when tested in a microtiter plate assay, but the inhibition could not be conclusively linked to the presence of the transgenic peptide, since non-expressing transgenic lines, included as controls, also showed inhibition. Similar results were obtained with infection studies, clearly showing that despite successful integration and expression of the transgene, the peptides was either not functional in the heterologous environment, or perhaps unstable
under the particular regulatory conditions. This peptide belongs to a subclass of peptides known for associated activities that might activate tight control by plant hosts if threshold levels are reached. These aspects need further investigation, specifically since it is in stark contrast to previous results obtained with defensins from a different subclass.
This study has also yielded significant other related resources that would be instrumental for further possible biotechnology exploitation of some of the novel peptides, but also to provide genetic constructs and plant material that would be invaluable to address fundamentally important questions such as the regulation and mode of action of defensin peptides, specifically in interaction with pathogen hosts. The novel peptides have been transformed to various hosts, including grapevine and these transgenic populations are available to facilitate the next rounds of research into this extremely promising group of antifungal peptides. / AFRIKAANSE OPSOMMING: In die laaste dekade het navorsing die belangrike rol van klein antimikrobiese peptiede in plantweerstandsmeganismes beklemtoon. Hierdie peptiede speel nie alleenlik 'n belangrike rol in die komplekse lae van plantweerstandstelsels nie, maar het ook hulle ekonomiese potensiaal getoon in die manipulering van siekteweerstandbiedendheid in voedselgewasse met die oorkoepelende doel om landbougewasse minder afhanklik van chemiese spuitstowwe te maak. Soos wat die hoeveelheid geïsoleerde en gekarakteriseerde peptiede toeneem, het dit duidelik geword dat ander biologiese aktiwiteite, bykomend tot die antimikrobiese kapasiteit, met sommige van dié peptiede verbind kan word; hierdie alternatiewe aktiwiteite het belangrike toepassing in veral die mediese veld. Dit het die defensin-koderende gene kernteikens vir die landbou- en mediese biotegnologiesektore gemaak.
In die studie is daar begin om die Suid-Afrikaanse blommeryk te evalueer vir die teenwoordigheid van plantdefensingene en om dié gene te isoleer wat van ekonomiese belang vir die biotegnologiebedryf kan wees. Deur die in vitro- én in planta karakterisering van die unieke plantdefensinpeptiede word daar gemik daarna om belangrike inligting in te win oor die biologiese rol van die peptiede binne die plantligggaam.
Die plantgashere wat geteiken is sluit in die Suid-Afrikaanse Brassicaceae-spesies, insluitende inheemse spesies, asook Vitis vinifera, wat as die belangrikste vrugtegewas ter wêreld beskou word. Die Brassicaceae-familie is welbekend daarvoor dat dit 'n ryk bron van plantdefensinpeptiede is en verskeie van die bes gekarakteriseerde antifungiese defensinpeptiede is van dié familie afkomstig. Aanvanklike aktiwiteitstoetse het getoon dat die Suid-Afrikaanse Brassicaceae-spesies belowende antifungiese aktiwiteit toon, wat die verdere isolering en karakterisering van dié gene en hul peptiedprodukte regverdig. Die aanvanklike aktiwiteitstoetse het 'n selektiewe peptiedverrykingstrategie gevolg wat die isolering van basiese, hittestabiele peptiede bevoordeel het; hierdie eienskappe is baie kenmerkend van plant-antimikrobiese peptiede. Die peptiedfraksies wat met hierdie metode geïsoleer is, het sterk antifungiese aktiwiteit teen die toetsorganismes getoon. Die resultate het gelei tot die ontwikkeling en toepassing van 'n polimerasekettingreaksie-strategie, wat daartoe gelei het dat 14 nuwe defensingene van vier Suid-Afrikaanse Brassicaceae-genera, insluitend die inheemse spesie Heliophila coronopifolia, geïsoleer kon word.
Afgeleide aminosuurvolgorde-analises van die nuwe defensinpeptiede het gewys dat hulle slegs 42% homologie het. Hierdie diversiteit in aminosuurvolgorde is belangrik vir die identifisering van nuwe biologiese aktiwitiete binne die groep van verwante peptiede. Navorsing het verder getoon dat enkel-aminosuurverskille bydra tot die diverse spektrum van biologiese aktiwiteite binne 'n groep van verwante defensinpeptiede. Filogenetiese analise van die aminosuurvolgordes het getoon dat al die nuwe defensinpeptiede 'n sterk verwantskap met plantdefensinpeptiede, wat van
ander Brassicaceae-spesies geïsoleer is, toon. Daarteenoor het dit die kleinste verwantskap getoon met plantdefensinpeptiede wat van die Solanaceae- en Poaceae-families geïsoleer is. Klassifikasiestudies het bewys dat die nuwe peptiede saam met subgroep A3 van die plantdefensin-superfamilie groepeer.
'n Moontlike plantdefensingeen, genaamd Vv-AMP1, is ook van die V vinifera-kultivar, Pinotage, geïsoleer. Genetiese karakterisering het aangedui dat slegs 'n enkele kopie van die geen in die V. vinifera-genoom teenwoordig en op chromosoom 1 geleë is. Genetiese karakterisering van Vv-AMP1 binne die Vitus-genus het gewys dat die geen binne die genus evolusionêr gekonserveerd is. Uitdrukkingstudies van Vv-AMP1 het verder bewys dat die geen uitgedruk word op 'n weefselspesifieke, ontwikkelingsgekoppelde wyse, naamlik slegs in druiwekorrels en slegs tydens rypwording. Vv-AMP1-uitdrukking kon nooit geïnduseer word in wingerdblare deur die uitwendige toediening van hormone, osmotiese stres, wonding of patogeeninfeksie deur Botrtys cinerea nie.
Ontleding van die afgeleide aminosuurvolgorde het gewys dat Vv-AMP1 kodeer vir 'n 77-aminosuurpeptied, wat uit 'n 30-aminosuurseinpeptied en 'n 47-aminosuur-aktiewe peptied met voorspelde antifungiese aktiwiteit bestaan. Die Vv-AMP1-peptied is gegroepeer met subgroep B van die plantdefensin-superfamilie, 'n subgroep wat vir beide antifungiese en antibakteriese aktiwiteit gedokumenteer is. Die Vv-AMP1-seinpeptied het die groen fluoressensie-indikatorproteïen (GFP) na die apoplastiese areas van die plantselle gelei, met hoë vlakke van lokalisering in die vaatbundelweefsel en sluitselle van die huidmondjies.
Die rekombinante Vv-AMP1-peptied is suksesvol geproduseer en uit 'n bakteriese produksieras gesuiwer, en het 'n molekulêre massa van 5.495 kDa gehad. Die gesuiwerde peptide het by lae konsentrasies 'n sterk aktiwiteit getoon teen 'n breë spektrum van fungiese patogene, wat Verticllium dahliae (IC50 van 1.8 μg mL-1) en die nekrotrofiese patogeen, B. cinerea (IC50 van 12-13 μg mL-1), ingesluit het. Vv-AMP1-aktiwiteit het geen ooglopende morfologiese veranderinge in die fungi-hifes veroorsaak nie, maar hulle aktiwiteit is verbind met 'n verhoogde membraandeurdringbaarheid in behandelde fungi-hifes.
Suksesvolle intergrasie van Vv-AMP1 in die Nicotiana tabacum-genoom is deur Southern-kladontledings bevestig en 20 individuele transgeniese lyne is ontwikkel. Genetiese karakterisering van die transgeniese lyne het gewys dat Vv-AMP1 suksesvol geïntegreer is en ook in die transgeniese tabakomgewing uitgedruk word. Die peptied is uitgedruk onder beheer van sy eie seinpeptied, wat die aktiewe produk na die apoplastiese areas van die plantselle teiken. Die transgeniese tabaklyne is ook ontleed om te bepaal of die wingerdpeptied suksesvol geproduseer word en sy aktiwiteit in die transgeniese omgewing behou. Western-kladanalise van semi-gesuiwerde plantproteïenekstrakte het 'n positiewe sein gelewer in beide die kontroleplante en die transgeniese plantlyne. Bestudering van tabakgeenuitdrukkings-databasisse het drie nukleotiedvolgordes opgelewer wat homologie met Vv-AMP1 toon en moontlik verantwoordelik kan wees vir die positiewe sein in die ongetransformeerde
kontroleplante. Kru proteïenekstrakte van die transgeniese tabaklyne het in vitro-aktiwiteit teen V. dahliae getoon. Geen oortuigende ooreenkoms kon egter gevind word tussen V. dahliae-inhibisie en die teenwoordigheid van die transgeniese Vv-AMP1-peptied nie, aangesien kontroleplante wat Southern-klad-positief is, maar nie geenuitdrukking toon nie, ook inhibisie van V. dahliae veroorsaak het. Soortgelyke resultate is met infeksiestudies verkry. Alle resultate dui daarop dat, al is daar suksesvolle integrasie en uitdrukking van die geen in tabak verkry, dat die Vv-AMP1 peptied óf onaktief óf onstabiel in die transgeniese tabakomgewing is. Die peptied behoort aan 'n subgroep peptiede met aktiwiteite wat, sodra sekere vlakke van peptied oorskry word, die moontlik streng kontrole op proteïenvlak in die gasheerplant kan uitlok. Sekere aspekte van die studie sal verder bestudeer moet word, aangesien die data teenstrydig is met data wat verkry is met soortgelyke plantdefensinpeptiede wat aan 'n ander subgroep behoort.
Die studie het baie hulpbronne gegenereer wat vir die biotegnologiesektor belangrik kan wees, veral op ekonomiese gebied. Verder is die geenkonstrukte en plantlyne wat ontwikkel is waardevol om fundamentele vrae rondom die regulering en meganisme van aksie van defensinpeptiede, spesifiek plantpatogeeninteraksie, te beantwoord. Die nuwe plantdefensingene is na verskeie gasheerplante, insluitende wingerd, getransformeer waar die transgeniese lyne die volgende rondte van navorsing oor die bestudering oor die belangrike groep van antifungiese peptiede, sal aanvul.
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The effect of partial rootzone drying and foliar nutrition on water use efficiency and quality of table grape cultivars Crimson seedless and DauphineVan Zyl, Tinake 12 1900 (has links)
Thesis (MScAgric (Viticulture and Oenology))--University of Stellenbosch, 2007. / The South African and international table grape industries are growing rapidly, which
necessitates the production of high quality export fruit at competitive production costs.
For this reason, alternative irrigation methods are required to utilise water optimally
while still attaining good quality table grapes. An increase in agricultural productivity
may be dependent on either the availability of more water for irrigation or an increase in
the efficiency of water use.
The first aim of this study was to evaluate the effectiveness of the Partial Rootzone
Drying (PRD) irrigation strategy in Crimson Seedless and Dauphine table grape
production. This irrigation system is based on the drying of half of the vine roots,
thereby allowing the plant to produce hormones like abscisic acid (ABA) in reaction to
water stress. The hormone production in turn results in stomatal closure and the
reduction of water loss via transpiration. The drying cycle is then repeated after 10 to 15
days on the other side of the vine, irrigating the previously dried roots. PRD will
encourage a consistent production of the stress hormone abscisic acid (ABA), without
actual water stress. This strategy reduces the amount of water used for irrigation,
without an accompanying loss in fruit yield, as compared to conventional techniques. In
this study, conventionally treated vines were irrigated according to historical block data
and PRD-treated vines were irrigated at the same times.
The second aim of this study was to monitor the efficacy of a foliar nutrient, Croplife.
This foliar nutrient allegedly improves the uptake of foliar applied nutrients, assists with
transport of all minerals through the leaves and enables the plant to attain higher pest
and disease resistance thresholds. Conventionally treated vines that did not receive
foliar nutrient treatment were compared to vines that received foliar nutrients as
prescribed by the manufacturer.
Vine cultivars Crimson Seedless and Dauphine, were grown under open hydroponic
principles with drip and drip irrigation respectively in this experiment. For the hydroponic
vines (Crimson Seedless), all vines were situated in the same row and 72 vines were
divided into mini-plots of three vines. Treatments were then assigned to an equal
number of plots at random. The same procedure was followed for the drip irrigated
vines (Dauphine) but the vines were situated in two rows of equal length. Treatment effects were followed from budburst until harvest, where after post-harvest analyses
were conducted.
The first aim, namely to show that PRD is an effective irrigation strategy for table grape
production in Crimson Seedless and Dauphine cultivars , has shown that vines did not
exhibit signs of stress even though they received only half the conventional amount of
water. This study was conducted over only one growth season and therefore no definite
conclusions could be drawn about the long term effectiveness of PRD on table grapes.
It did, however, confirm numerous results obtained from different studies on the use of
PRD in wine grape production.
The results obtained in the second part of the study were inconclusive and could not
show that Croplife is effective in improving the uptake and transport of applied foliar
nutrients. Because Crimson Seedless is cultivated under open hydroponic principles,
nutrients can be absorbed by the roots via the soil and micronutrients are also available
from chemical sprays during the season. There was no evidence to indicate that the use
of Croplife increased nutrient absorption and transport, neither did it supplement or
detract form the observed effect of PRD.
Despite the limitations experienced during this study, it has shown that the use of PRD
for table grape production may be a useful tool for improving water utilisation efficiency
in future. The strategy will have to be developed systematically through experimentation
to fully unlock the potential of the PRD management system for table grape production.
This study provides a good starting point for future research required to elucidate
numerous aspects of the PRD system and has clearly shown that established vineyards
can be switched to a PRD system without a loss in table grape quality. It is envisaged
that the advantages of this system could have a positive effect on the production of high
quality fruit for the international market.
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Influence of oxygen addition on the phenolic composition of red wineGeldenhuys, Lorraine 12 1900 (has links)
Thesis (MscAgric (Viticulture and Oenology))--University of Stellenbosch, 2009. / ENGLISH ABSTRACT: Tannins and colour components in red wine are important quality parameters. These factors can
be manipulated in the vineyard by grape growing techniques or in the cellar by different winemaking
practices. Grape seeds make a significant contribution to tannin concentration in wine
when compared to those from the skins and pulp. Tannins contribute to the ageing potential,
organoleptic properties and stabilisation of red wine colour. The colour of a red wine is also
influenced by malolactic fermentation, the biological process that transforms malic acid into
lactic acid which normally leads to an increase in pH. The subsequent change in pH alters the
anthocyanin equilibrium, the primary colour components in red wine. Oxygen contributes to the
polymerisation of anthocyanins over time to form more stable pigments that are less sensitive to
pH fluctuations and sulphur dioxide bleaching. Limited research has been done on the use of
oxygen after alcoholic fermentation and the impact it has on the phenolic composition of red
wines. Similarly, only a few studies have examined the impact of either the addition or removal
of seeds to the phenolic composition of a red wine in combination with oxygen addition.
Additionally, little published data seems to exist on the effect of different pHs on red wine’s
phenolic and colour development after oxygen addition.
In our results we have shown that it is possible to stabilise wine colour by adding
supplementary seeds before alcoholic fermentation. This led to an increase in colour intensity in
certain cases. Some red wines produced without seeds had significantly lower colour intensities.
This clearly suggests that catechins and proanthocyanidins are extracted from seeds and
contribute to wine colour as they combine with other pigments to stabilise wine colour.
Spectrophotometric and HPLC analyses have shown that the total phenolic content increased
with seed concentration. However, we have observed that a wine may possibly become
saturated with phenols when supplementary seeds are added. Anthocyanin concentrations
often decreased when oxygen was added, while polymeric phenols and polymeric pigments
sometimes increased.
When applying different oxygen dosages to a red wine on commercial scale with microoxygenation,
it was found that monomeric anthocyanins decreased as more oxygen was added
and this decrease in anthocyanins led to the formation of stable polymeric pigments. This
was reflected in the significant increase in colour intensity for the wines receiving oxygen. Small
differences were detected in the total phenol and tannin concentration for the control and
oxygenated wines. However, some of these phenolic and colour differences disappeared
during subsequent ageing of the wine.
When making wines of different initial pHs, we observed that the colour density decreased
as the pH increased. The application of oxygen reduced the decrease in colour during MLF,
especially at a lower pH. The addition of oxygen did not result in significantly different polymeric
pigment concentrations in the various pH treatments, although the results could have been
different if the wines were aged. However, pH differences in the range between 3.4 and 4.0 did
not significantly influence the phenol composition of the wines under our conditions. This study
led to a better understanding on the effect of oxygen additions under different conditions on red
wine's phenolic and colour composition. / AFRIKAANSE OPSOMMING: Tanniene en kleur komponente teenwoordig in rooiwyn is belangrike kwaliteit parameters.
Hierdie faktore wat wynkwaliteit beïnvloed kan gemanipuleer word in die wingerd deur verskeie
verbouingstegnieke toe te pas en in die kelder deur die toepassing van verskillende
wynbereidingsmetodes. Die bydrae van sade tot die finale tannienkonsentrasie in rooiwyn is
groot in vergelyking met dié van die pulp en doppe. Tanniene dra by tot die verouderingspotensiaal,
organoleptiese eienskappe en die stabilisasie van die wynkleur. Die kleur van ‘n rooi
wyn word ook beïnvloed deur appelmelksuurgisting (AMG), die biologiese proses wat appelsuur
omskakel na melksuur en ‘n gevolglike toename in die pH van die wyn veroorsaak. Hierdie
verandering in die pH van die wyn beïnvloed die antosianien ewewig, die primêre kleur
komponente teenwoordig in rooiwyn. Suurstof dra by tot die polimerisasie van antosianiene oor
tyd om meer stabiele kleur pigmente te vorm met ‘n hoër kleurintensiteit wat minder sensitief is
teenoor pH veranderinge en die bleikingseffek van swaweldioksied. Beperkte navorsing is
gedoen op die gebruik van suurstof na alkoholiese gisting en die impak daarvan op die
fenoliese samestelling van ‘n rooiwyn. Slegs ‘n paar studies het die invloed van die verwydering
of byvoeging van sade in kombinasie met suurstoftoediening op ‘n rooiwyn se fenoliese
samestelling ondersoek. Dit wil voorkom of beperkte gepubliseerde data beskikbaar is oor die
effek wat verskillende pH’s het op rooi wyn se fenoliese en kleurontwikkeling na suurstof
byvoeging.
Ons resultate het aangedui dat dit wel moontlik is om in sekere gevalle die kleur van ‘n
rooiwyn te stabiliseer deur addisionele sade by te voeg voor alkoholiese fermentasie. Hierdie
byvoeging het ‘n toename in kleurintensiteit tot gevolg gehad. Sekere wyne wat gemaak is
sonder sade het ‘n kenmerkend laer kleur intensiteit gehad. Hierdie bevinding is ‘n duidelike
bewys dat katesjiene en prosianidiene geëkstraheer word vanuit die sade en bydra tot wynkleur
deurdat hulle met ander pigmente verbind om die kleur sodoende te stabiliseer.
Spektrofotometriese en hoë druk vloeistof chromatografie (HDVC) analises het gewys dat die
totale fenoliese konsentrasie neem toe met ‘n toename in saad konsentrasie. Daar is egter
waargeneem dat ‘n wyn moontlik versadig kan raak met fenole wanneer addisionele sade
bygevoeg word. Antosianien konsentrasies het meestal afgeneem wanneer suurstof bygevoeg
is, maar polimeriese fenole en polimeriese pigmente het partykeer toegeneem.
Met die toediening van verskillende suurstof dosisse tot ‘n rooiwyn op kommersiële skaal
het ons bevind dat monomeriese antosianiene afneem wanneer meer suurstof bygevoeg word.
Hierdie afname in antosianiene het egter gelei tot die vorming van stabiele polimeriese
pigmente. Dié bevinding was gereflekteer in die toename in kleurintensiteit van wyne wat met
suurstof behandel is. Klein verskille was waargeneem vir die totale fenol en tannien
konsentrasies tussen die kontrole en wyne behandel met suurstof. Sekere van hierdie fenoliese
kleur verskille het egter afgeneem tydens die daaropvolgende veroudering van die wyne.
Wyne wat gemaak is met verskillende aanvanklike pH’s se kleurintensiteit neem af soos
die pH toeneem. Die toediening van suurstof het die kleurverlies tydens AMG verminder, veral
by ‘n laer pH. Die toediening van suurstof het nie verskillende polimeriese pigment
konsentrasies by verskillende pH’s veroorsaak nie, maar ‘n verskil kon moontlik waargeneem
word indien die wyne verouder was. pH verskille tussen 3.4 en 4.0 het egter nie die fenoliese
samestelling van die wyne onder ons omstandighede beduidend beïnvloed nie. Hierdie studie
het gelei tot meer kennis oor die effek van suurstoftoedienings onder verskillende kondisies op
rooiwyn se fenoliese en kleursamestelling.
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