Botrytis cinerea is the principal member of the species complex that causes bunch rot of grapes and gray mold disease on other hosts including fruits and ornamental crops. It has developed resistance to many fungicides, and isolates from eastern US strawberry fields have regularly been identified with resistance to several modes of action. During the 2011-2015 growing seasons, 487 isolates were collected from Virginia wine grapes, strawberries, and ornamental crops and evaluated for sensitivity to eight different fungicides by a germ tube elongation method; for a subset of isolates, a 24-well plate mycelial growth assay was also used, and baseline sensitivity to polyoxin-D was evaluated. Resistance to benzimidazoles and quinone outside inhibitors, and low-level resistance to iprodione were common. Boscalid resistance was common in wine grapes and ornamentals. Resistance to the hydroxyanilide fenhexamid during germ tube elongation was found in only 5% of wine grape isolates, but in 33% of isolates from strawberries and ornamentals. All of the fenhexamid-resistant isolates were identified as B. cinerea carrying various mutations in the erg27 gene. An additional subset of isolates was identified with moderate resistance to fenhexamid during mycelial growth, but not germination and germ tube growth. These were identified as B. cinerea HydR2 isolates, which possess an unknown mechanism of resistance towards fenhexamid in mycelial growth. Moderate resistance to cyprodinil was common, but in grape inoculation tests, moderately resistant isolates were controlled by a field rate of cyprodinil. Diminished sensitivity to fludioxonil and fluopyram was rare. Polyoxin-D controlled most isolates in mycelial growth tests at 100 µg/ml. / Master of Science in Life Sciences

Thesis (Ph. D.)--Oregon State University, 2007. / Printout. Includes bibliographical references. Also available on the World Wide Web.

Thesis (MScAgric)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: The microclimate environment around the bunch is complex. The spatial distribution of leaves as well as bunch position and morphology impact on the path of direct radiation received by the berries. Canopy microclimate is largely determined by the meteorological conditions (air temperature, solar radiation, wind speed and direction, relative humidity, and precipitation) as well as management practices (trellis/training system, canopy height, vine spacing, row orientation, canopy management practices, irrigation and soil variability and management). The fact that the grapevine continuously responds to its environment, adds to the complexity and dynamic nature of the microclimate that the bunches experience. Field studies involving the effect of the natural bunch environment (i.e. light and temperature conditions) on berry composition, are therefore a challenge, due to the difficulties in quantifying meteorological elements such as temperature and light, which can be hugely variable. There are different sensors available to assess bunch and berry temperature and it can be deployed in different ways within the grapevine canopy, but the difficulty remains in studying the variability that exists within a bunch. This study investigated the value of available sensor technology to measure bunch/berry temperature as well as the spatial and temporal variability on a bunch. Differences in temperature on an intra-berry level were assessed whereas the impact of canopy configuration and bunch orientation on the different sensor levels was also investigated. The contribution of macro- and mesoclimate on bunch and berry temperature was addressed by measuring at two locations (Robertson and Stellenbosch). The potential long term differences in temperature within a bunch with regard to thermal accumulation are discussed. Issues around sensor placement and some technical difficulties related to the sensors are discussed. The results indicated how the effects of mesoclimate were transferred through to the different sensors. A dominating effect of the sea breeze in Stellenbosch was found. Canopy configuration/architecture affected the light regime in the canopy, consequently impacting on bunch temperature variability, specifically in Stellenbosch where a "Ballerina" trellising system was used. Bunch orientation resulted in differences in the temporal variability of bunch/berry temperature and little variability was observed in temperature within the berry. Temperatures of berries situated at the back of the bunch were judged more optimal compared to exposed berries. Direct radiation caused extreme temperatures in exposed berries, which may be detrimental to berry composition and wine quality. This emphasized the importance of the canopy (trellis/training system and management practices) in protecting the bunch from extreme conditions. The large on-bunch spatial variability, observed from measurements with the thermal imager, demonstrated the importance of sensor placement in quantifying the bunch temperature regime; this is also relevant for the future development of berry temperature modelling. Thermal accumulation through the season also illustrated the variability that existed within a bunch, suggesting a potential long term effect on the berry composition. This study proved, in conditions similar to those that may prevail in the South African wine industry, that sensor type and positioning need to be carefully considered in any viticultural/oenological study where bunch microclimate and grape temperatures are assessed. / AFRIKAANSE OPSOMMING: Die mikroklimaat omgewing rondom die tros is kompleks. Die ruimtelike verspreiding van blare sowel as trosposisie en -morfologie het 'n impak op die pad waarlangs direkte straling ontvang word deur die korrels. Lowermikroklimaat word grootliks bepaal deur die meteorologiese kondisies (lugtemperatuur, sonstraling, windspoed en -rigting, relatiewe humiditeit en reënval) sowel as bestuurspraktyke (prieel/opleistelsel, lowerhoogte, wingerdstokspasiëring, ry-oriëntasie, lowerbestuurspraktyke, besproeiing asook grondvariasie en bestuur). Die feit dat die wingerdstok voortdurend reageer op sy omgewing dra by tot die kompleksiteit en dinamiese aard van die mikroklimaat wat die trosse ervaar. Veldstudies gemoeid met die effek van die natuurlike trosomgewing (d.w.s. lig- en temperatuurkondisies) op korrelsamestelling is daarom 'n uitdaging. Die rede hiervoor is dat dit problematies is om meteorologiese elemente soos temperatuur en lig, wat baie veranderlik kan wees, te kwantifiseer. Verskillende sensors is beskikbaar waarmee tros- en korreltemperatuur bepaal kan word en dit kan op verskillende wyses binne die wingerdstoklower aangewend word. Die bestudering van die variasie wat bestaan binne 'n tros is egter steeds problematies. Hierdie studie het die waarde ondersoek van die beskikbare sensortegnologie vir die meting van tros/korreltemperatuur en die ruimtelike en tydsvariasie op 'n tros. Verskille in temperatuur op 'n intra-korrelvlak is bepaal terwyl die impak van lowerkonfigurasie en trosoriëntasie op die verskillende sensorvlakke ook ondersoek is. Die bydrae van makro- en mesoklimaat tot tros- en korreltemperatuur is ondersoek deur te meet by twee verskillende liggings (Robertson en Stellenbosch). Die potensiële langtermyn verskille in temperatuur binne-in 'n tros met betrekking tot temperatuur akkumulasie word bespreek. Kwessies rakende sensorplasing en sommige tegniese probleme wat verband hou met sensors word bespreek. Die resultate het aangedui hoedat die effekte van mesoklimaat oorgedra is na die verskillende sensors. 'n Dominerende effek van die seebries is waargeneem in Stellenbosch. Lowerkonfigurasie/argitektuur het die ligregime in die lower beïnvloed en gevolglik 'n invloed gehad op die trostemperatuur veranderlikheid. Dit was veral die geval in Stellenbosch waar 'n "Ballerina" opleistelsel gebruik is. Trosoriëntasie het gelei tot verskille in tydsvariasie van tros/ korreltemperatuur en min variasie is waargeneem in temperatuur binne die korrel. Temperature van korrels wat voorkom aan die agterkant van die tros is beoordeel as meer optimaal vergeleke met blootgestelde korrels. Direkte straling het uiterste temperature in blootgestelde korrels veroorsaak wat nadelig kan wees vir korrelsamestelling en wynkwaliteit. Hierdeur is die belang van die lower (prieel/opleistelsel en bestuurspraktyke) om die tros te beskerm teen uiterste kondisies beklemtoon. Die groot ruimtelike variasie op 'n tros, soos waargeneem in metings met die termiese kamera, het die belangrikheid van sensorplasing in die kwantifisering van die trostemperatuur regime beklemtoon. Dit is ook relevant vir die toekomstige ontwikkeling van korreltemperatuur modellering. Termiese akkumulasie gedurende die seisoen is ook geïllustreer deur die veranderlikheid wat voorkom binne 'n tros, wat dui op 'n potensiële langtermyn effek op die korrelsamestelling. Hierdie studie het bewys, in kondisies wat algemeen voorkom in die Suid-Afrikaanse wynbedryf, dat sensortipe en -plasing sorgvuldig in ag geneem moet word in enige wingerd/wynkundige studie waar trosmikroklimaat en druiftemperature bepaal word. / Winetech and the National Research Foundation for their financial support of the project

A vitivinicultura é uma atividade extremamente importante no estado do Rio Grande do Sul, representando cerca de 50% das uvas produzidas e 90% dos vinhos em todo o país. Diferentes gêneros fúngicos são comumente encontrados infectando as bagas, os principais são Alternaria, Botrytis, Cladosporium e Aspergillus. Esta contaminação é influenciada por diferentes fatores, entre eles, características climáticas da região, variedades da uva, tipo de cultivo, entre outros. O gênero Aspergillus destaca-se dos demais, pois as espécies frequentemente encontradas nas uvas, os chamados Aspergillus seção Nigri, são potenciais produtores de Ocratoxina A, micotoxina nefrotóxica e possivelmente carcinogênica para humanos. Os objetivos deste trabalho foram a caracterização micotoxicológica de uvas das variedades Merlot e Cabernet Sauvignon, produzidas em três regiões vitivinícolas do Rio Grande do Sul, coletadas em dois estágios de maturação das bagas. As amostragens foram realizadas no inicio da mudança de cor e na colheita nas regiões da Campanha, Serra do Sudeste e Serra do Nordeste. Foram isolados oito gêneros fúngicos, com destaque para Alternaria, que foi predominante em todas as regiões, estágios de cultivo e nas duas variedades. Os Aspergillus seção Nigri foram predominantes no gênero Aspergillus, representando 88% dos isolados, que se destacaram na região da Campanha e na variedade Cabernet Sauvignon. O período da colheita demonstrou ser critico para a contaminação por Aspergillus negros na variedade Cabernet Sauvignon, enquanto na variedade Merlot, maior frequência desses fungos foi observada durante o início da mudança de cor. Uma cepa de Aspergillus japonicus foi capaz de produzir ocratoxina A na concentração de 148 ng/mL/106 conídios. Não foram encontrados níveis detectáveis de OTA nas amostras de uvas. A caracterização da contaminação fungica e por OTA em uvas cultivadas no estado é relevante para garantir a qualidade destes produtos e a segurança da população consumidora. / The viticulture is an important activity in Brazil. Rio Grande do Sul, the southern state of Brazil, responsible for almost 90% of wines production. Different fungal genera are commonly found infecting the berries, mainly Alternaria, Botrytis, Cladosporium and Aspergillus. Grape infection and fungal growth in influenced by different factors, including climatic characteristics of the region, grape varieties, crop type, among others. Among the genus Aspergillus, Aspergillus section Nigri stands out from the others, because its ability to produce ochratoxin A, mycotoxin with nephrotoxic characteristics and classified as a possible carcinogenic to humans. The aim of this study was the mycological characterization of wine grapes of Merlot and Cabernet Sauvignon varieties, cultivated at three wine producer regions of Rio Grande do Sul, collected during two stages of berries maturation. The sampling was conducted at the early ripeness and harvesting from the Campanha, Serra do Sudeste and Serra do Nordeste regions. Eight fungal genera were isolated, highlighting Alternaria, which was predominant in all regions, growing stages and varieties. Aspergillus section Nigri were prevalent in the genus Aspergillus, representing 88% of the isolates mainly at Campanha region as well as Cabernet Sauvignon veriety. The harvest period proved to be critical for contamination by Aspergillus section Nigri in C. Sauvignon variety; nevertheless, in Merlot, the greater frequency of these fungi was observed at early ripeness. One Aspergillus japonicus isolate was able to produce OTA at a concentration of 148 ng mL-1/106 conidia. No detectable levels of OTA were found in any grape samples. The characterization of fungal and OTA contamination in grapes cultivated in Rio Grande do Sul is extremely important to ensure the quality of these products and consumers safety.

A vitivinicultura é uma atividade extremamente importante no estado do Rio Grande do Sul, representando cerca de 50% das uvas produzidas e 90% dos vinhos em todo o país. Diferentes gêneros fúngicos são comumente encontrados infectando as bagas, os principais são Alternaria, Botrytis, Cladosporium e Aspergillus. Esta contaminação é influenciada por diferentes fatores, entre eles, características climáticas da região, variedades da uva, tipo de cultivo, entre outros. O gênero Aspergillus destaca-se dos demais, pois as espécies frequentemente encontradas nas uvas, os chamados Aspergillus seção Nigri, são potenciais produtores de Ocratoxina A, micotoxina nefrotóxica e possivelmente carcinogênica para humanos. Os objetivos deste trabalho foram a caracterização micotoxicológica de uvas das variedades Merlot e Cabernet Sauvignon, produzidas em três regiões vitivinícolas do Rio Grande do Sul, coletadas em dois estágios de maturação das bagas. As amostragens foram realizadas no inicio da mudança de cor e na colheita nas regiões da Campanha, Serra do Sudeste e Serra do Nordeste. Foram isolados oito gêneros fúngicos, com destaque para Alternaria, que foi predominante em todas as regiões, estágios de cultivo e nas duas variedades. Os Aspergillus seção Nigri foram predominantes no gênero Aspergillus, representando 88% dos isolados, que se destacaram na região da Campanha e na variedade Cabernet Sauvignon. O período da colheita demonstrou ser critico para a contaminação por Aspergillus negros na variedade Cabernet Sauvignon, enquanto na variedade Merlot, maior frequência desses fungos foi observada durante o início da mudança de cor. Uma cepa de Aspergillus japonicus foi capaz de produzir ocratoxina A na concentração de 148 ng/mL/106 conídios. Não foram encontrados níveis detectáveis de OTA nas amostras de uvas. A caracterização da contaminação fungica e por OTA em uvas cultivadas no estado é relevante para garantir a qualidade destes produtos e a segurança da população consumidora. / The viticulture is an important activity in Brazil. Rio Grande do Sul, the southern state of Brazil, responsible for almost 90% of wines production. Different fungal genera are commonly found infecting the berries, mainly Alternaria, Botrytis, Cladosporium and Aspergillus. Grape infection and fungal growth in influenced by different factors, including climatic characteristics of the region, grape varieties, crop type, among others. Among the genus Aspergillus, Aspergillus section Nigri stands out from the others, because its ability to produce ochratoxin A, mycotoxin with nephrotoxic characteristics and classified as a possible carcinogenic to humans. The aim of this study was the mycological characterization of wine grapes of Merlot and Cabernet Sauvignon varieties, cultivated at three wine producer regions of Rio Grande do Sul, collected during two stages of berries maturation. The sampling was conducted at the early ripeness and harvesting from the Campanha, Serra do Sudeste and Serra do Nordeste regions. Eight fungal genera were isolated, highlighting Alternaria, which was predominant in all regions, growing stages and varieties. Aspergillus section Nigri were prevalent in the genus Aspergillus, representing 88% of the isolates mainly at Campanha region as well as Cabernet Sauvignon veriety. The harvest period proved to be critical for contamination by Aspergillus section Nigri in C. Sauvignon variety; nevertheless, in Merlot, the greater frequency of these fungi was observed at early ripeness. One Aspergillus japonicus isolate was able to produce OTA at a concentration of 148 ng mL-1/106 conidia. No detectable levels of OTA were found in any grape samples. The characterization of fungal and OTA contamination in grapes cultivated in Rio Grande do Sul is extremely important to ensure the quality of these products and consumers safety.

A vitivinicultura é uma atividade extremamente importante no estado do Rio Grande do Sul, representando cerca de 50% das uvas produzidas e 90% dos vinhos em todo o país. Diferentes gêneros fúngicos são comumente encontrados infectando as bagas, os principais são Alternaria, Botrytis, Cladosporium e Aspergillus. Esta contaminação é influenciada por diferentes fatores, entre eles, características climáticas da região, variedades da uva, tipo de cultivo, entre outros. O gênero Aspergillus destaca-se dos demais, pois as espécies frequentemente encontradas nas uvas, os chamados Aspergillus seção Nigri, são potenciais produtores de Ocratoxina A, micotoxina nefrotóxica e possivelmente carcinogênica para humanos. Os objetivos deste trabalho foram a caracterização micotoxicológica de uvas das variedades Merlot e Cabernet Sauvignon, produzidas em três regiões vitivinícolas do Rio Grande do Sul, coletadas em dois estágios de maturação das bagas. As amostragens foram realizadas no inicio da mudança de cor e na colheita nas regiões da Campanha, Serra do Sudeste e Serra do Nordeste. Foram isolados oito gêneros fúngicos, com destaque para Alternaria, que foi predominante em todas as regiões, estágios de cultivo e nas duas variedades. Os Aspergillus seção Nigri foram predominantes no gênero Aspergillus, representando 88% dos isolados, que se destacaram na região da Campanha e na variedade Cabernet Sauvignon. O período da colheita demonstrou ser critico para a contaminação por Aspergillus negros na variedade Cabernet Sauvignon, enquanto na variedade Merlot, maior frequência desses fungos foi observada durante o início da mudança de cor. Uma cepa de Aspergillus japonicus foi capaz de produzir ocratoxina A na concentração de 148 ng/mL/106 conídios. Não foram encontrados níveis detectáveis de OTA nas amostras de uvas. A caracterização da contaminação fungica e por OTA em uvas cultivadas no estado é relevante para garantir a qualidade destes produtos e a segurança da população consumidora. / The viticulture is an important activity in Brazil. Rio Grande do Sul, the southern state of Brazil, responsible for almost 90% of wines production. Different fungal genera are commonly found infecting the berries, mainly Alternaria, Botrytis, Cladosporium and Aspergillus. Grape infection and fungal growth in influenced by different factors, including climatic characteristics of the region, grape varieties, crop type, among others. Among the genus Aspergillus, Aspergillus section Nigri stands out from the others, because its ability to produce ochratoxin A, mycotoxin with nephrotoxic characteristics and classified as a possible carcinogenic to humans. The aim of this study was the mycological characterization of wine grapes of Merlot and Cabernet Sauvignon varieties, cultivated at three wine producer regions of Rio Grande do Sul, collected during two stages of berries maturation. The sampling was conducted at the early ripeness and harvesting from the Campanha, Serra do Sudeste and Serra do Nordeste regions. Eight fungal genera were isolated, highlighting Alternaria, which was predominant in all regions, growing stages and varieties. Aspergillus section Nigri were prevalent in the genus Aspergillus, representing 88% of the isolates mainly at Campanha region as well as Cabernet Sauvignon veriety. The harvest period proved to be critical for contamination by Aspergillus section Nigri in C. Sauvignon variety; nevertheless, in Merlot, the greater frequency of these fungi was observed at early ripeness. One Aspergillus japonicus isolate was able to produce OTA at a concentration of 148 ng mL-1/106 conidia. No detectable levels of OTA were found in any grape samples. The characterization of fungal and OTA contamination in grapes cultivated in Rio Grande do Sul is extremely important to ensure the quality of these products and consumers safety.

Drosophila suzukii (Matsumura) (Diptera: Drosophila) is an invasive frugivore and has become a significant pest of small fruit, cherry and grape throughout the United States. It may be possible to determine if a Virginia vineyard is at risk of D. suzukii infestation by analyzing the biotic and abiotic factors around each vineyard. This pest is known to utilize a wide range of cultivated and wild host plants. A host plant survey was conducted at four vineyards in the Piedmont Region of Virginia to identify hosts used by D. suzukii around vineyards. The seasonal availability of host plants and adult emergence from them were tracked. Six host plant species of D. suzukii were identified, some available season-long. Monitoring D. suzukii in cultivated crops is crucial for the timing of spray applications. Homemade and commercially available baits and traps were deployed in two vineyards to determine the efficacy and selectivity towards D. suzukii. The homemade and commercially available baits that contained red wine caught the most D. suzukii, but none were exclusively attractive to D. suzukii. Wine grape susceptibility was assessed in laboratory choice and no-choice ovipositional bioassays. Ovipositional susceptibility was determined by measuring the physiological and morphological parameters using six wine grape varieties. More eggs were laid in grapes as penetration force decreased. Penetration force and not skin thickness was the limiting factor for oviposition. Survivorship of eggs laid in intact grapes was analyzed and survivorship to adulthood was dependent upon variety and survivorship usually exceeded 9% survival seen in previous studies. Larval developmental parameters of D. suzukii were affected by grape variety and the density of Z. indianus. D. suzukii mortality was increased in most cases when in competition with Z. indianus, but was less pronounced when reared in Viognier grapes. My Z. indianus oviposition study demonstrated that they will follow injury created by D. suzukii, and then the Z. indianus larvae may outcompete D. suzukii within the berries. These studies greatly improved our understanding of D. suzukii biology and ecology in Virginia vineyards. / Ph. D.

Botrytis bunch rot, caused by Botrytis cinerea, is a fungal disease that primarily affects the fruit of wine grapes. Infection of fruit consequently results in reduced yields and wine quality. These factors lead to significant economic losses for growers which prompts the implementation of management practices to control the disease. One objective of this study was to evaluate the level of resistance that populations of B. cinerea in the Central Coast region showed to various chemicals. A fungicide assay was conducted to determine resistant phenotypes to six fungicide active ingredients (pyrimethanil, iprodione, fenhexamid, fludioxonil, trifloxystrobin, boscalid). Thirty-five (2020) and 88 (2021) B. cinerea isolates were collected from Santa Maria, Cambria, Paso Robles, and Edna Valley in California and screened for resistance. The frequencies of populations (2020, 2021) showing resistance to each active ingredient were: pyrimethanil (94.3%, 81.8%), trifloxystrobin (97.1%, 100%), boscalid (77.1%, 77.3%), fenhexamid (8.6%, 25%). The majority of isolates were sensitive to iprodione (100%, 100%), fludioxonil (100%, 100%), fenhexamid (88.6%, 75%), and boscalid (22.9%, 22.7%). These results documented the accumulation of resistance in B. cinerea to various fungicides commonly used for Botrytis bunch rot management in California’s Central Coast. Another objective of this study was to determine the effective concentration of the six fungicides that reduces mycelial growth of the fungus by 50% (EC50). Seven B. cinerea isolates in 2020 and ten isolates in 2021 were selected and subjected to a sensitivity screening with serial dilutions of the different fungicide active ingredients. The fungicides found to have the highest EC50 values indicating reduced efficacy for inhibiting B. cinerea growth were Scala® (FRAC 9), Flint® (FRAC 11), and Endura® (FRAC 7). The fungicides found to have the lowest EC50 values indicating higher efficacy for inhibiting B. cinerea growth were Scholar® (FRAC 12) and Rovral® (FRAC 2). The results from this study provided information regarding the accumulated resistance of B. cinerea populations to certain chemical groups and therefore the efficacy of different fungicide active ingredients. This information can be utilized by growers as a tool to enhance and develop fungicide spray programs that effectively manage Botrytis bunch rot in Central Coast vineyards.

Thesis (MScAgric)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: In recent years South African wines have been under the spotlight due to references in the international wine media to a distinctive ‘burnt rubber’ character. Many winemakers and wine experts argued that the peculiar character could be ascribed to winemaking errors linked to mismanaged fermentation. An alternative possible source of the taint was identified in the coal tar creosote used as a wood preservative in vineyard trellis systems. South African regulations allow for the use of creosoted utility poles in agricultural land, but in Europe and USA their usage has been highly regulated and even banned for certain applications. Contamination of foodstuff by polycyclic aromatic hydrocarbons (PAHs) is one of the major motives for the banning of creosote in Europe and USA. Some of the compounds in the creosote mixture display very strong odour characteristics and for this reason it became the focus of attention for the present study. The overall aim of this study was to determine if vines trellised with creosoted posts could accumulate or absorb the various malodorous compounds deriving from the wood treatment onto the grape berries. These compounds could then be extracted from the grape berries into the wine during alcoholic fermentation, creating quality and sensory problems. Chapter 2 of this thesis gives an overview of the extensive literature that deals with methods of analysis of PAHs and malodorous phenols using both Gas Chromatography (GC), as well as High Performance Liquid Chromatography (HPLC). New methods for sample preparation, as well as analysis of PAHs using HPLC-Diode Array Detector (DAD), were developed and the results reported in Chapter 3. It was demonstrated that Sauvignon blanc experimental wines contained only chrysene at very low levels. The concentrations of chrysene found in the experimental wines are within the prescribed parameters as established by The Commission of the European Communities. Since no other PAH compounds were found in the samples analysed, it was concluded that the experimental wines were safe for human consumption and complied with EU regulations. The effect of vineyard posts on the sensorial characteristics of wine is discussed in Chapter 4. Creosoted poles were found to be responsible for an off-flavour described as ‘burnt rubber’ and ‘tarry’ in Merlot wines produced from grapes grown in close proximity to the posts. Following some of the reported findings, new guidelines have been introduced in the Integrated Production of Wine certification, which advise against the use of creosoted poles for vineyard trellising. This preliminary but important guideline will bring the South African wine industry a step closer to the fulfilling the obligations for food safety as required by the legislation of our major export partners. Future investigations are recommended to completely understand and evaluate the cumulative effect of creosoted posts in a fully trellised vineyard. / AFRIKAANSE OPSOMMING: Oor die afgelope paar jaar is Suid-Afrikaanse wyne onder die soeklig geplaas as gevolg van verwysings in die internasionale wynmedia na ‘n duidelike ‘gebrande rubber’-karakter. Baie wynmakers en wyndeskundiges het aangedui dat hierdie besonderse karakter toegeskryf kan word aan wynbereidingsfoute wat verband hou met gisting wat wanbestuur is. ‘n Alternatiewe moontlike oorsprong van die smaak is geïdentifiseer in die koolteer wat as ‘n houtpreserveermiddel in wingerdopleistelsels gebruik word. Suid-Afrikaanse regulasies maak voorsiening vir die gebruik van kreosoteerde nutspale in landbougrond, hoewel hulle gebruik in Europa en die VSA hoogs gereguleerd en in sommige gevalle selfs verbied is. Die besmetting van kossoorte deur polisikliese aromatiese koolwaterstowwe (polycyclic aromatic hydrocarbons (PAHs)) is een van die vernaamste redes vir die verbanning van kreosoot in Europa en die VSA. Sommige van die verbindings in die kreosootmengsel het baie sterk geurkenmerke en daarom is dit die fokus van die huidige studie. Die oorhoofse doelwit van hierdie studie was om te bepaal of wingerde wat op kreosoteerde pale opgelei is, die verskillende onwelriekende verbindings afkomstig van die houtbehandeling in die druiwekorrels kan akkumuleer of absorbeer. Hierdie verbindings sou dan tydens alkoholiese gisting uit die druiwekorrels in die wyn geëkstraheer kon word, wat aanleiding sou gee tot kwaliteits- en sensoriese probleme. Hoofstuk 2 van hierdie tesis verskaf ‘n oorsig van die breedvoerige literatuur wat handel oor metodes om PAH’s en onwelriekende fenole met behulp van beide gaschromatografie (GC) en hoëdrukvloeistofchromatografie (HPLC) te analiseer. Nuwe metodes is ontwikkel om monsters voor te berei en om PAH’s met behulp van ‘n HPLC-diode array detector (DAD) te analiseer. Die resultate word in Hoofstuk 3 gerapporteer. Daar is aangetoon dat die eksperimentele Sauvignon blanc-wyne chriseen teen baie lae vlakke bevat het. Die konsentrasies van chriseen wat in die eksperimentele wyne gevind is, is binne die voorgeskrewe parameters van die Kommissie van die Europese Gemeenskap. Aangesien daar nie ander PAHverbindings in die geanaliseerde monsters gevind kon word nie, is daar tot die gevolgtrekking gekom dat die eksperimentele wyne veilig is vir menslike verbruik en aan die EG-regulasies voldoen. Die effek van wingerdpale op die sensoriese kenmerke van wyn word in Hoofstuk 4 bespreek. Kreosoteerde pale is gevind wat verantwoordelik is vir ‘n wangeur in Merlot-wyne afkomstig van druiwe wat naby die pale gegroei het en wat as ‘gebrande rubber’ en ‘teeragtig’ beskryf is. Op grond van sommige van die gerapporteerde bevindings, is nuwe riglyne ingesluit in die sertifisering vir die Geïntegreerde Produksie van Wyn, wat aanbeveel dat kreosoteerde pale nie vir wingerdoplei gebruik word nie. Hierdie voorlopige, maar belangrike riglyn sal die Suid-Afrikaanse wynbedryf al beter in staat stel om te voldoen aan die voedselveiligheid regulasies wat vereis word deur die wetgewing van ons belangrikste uitvoervennote. Toekomstige ondersoeke moet aangewend word om die kumulatiewe effek van kreosoteerde pale in volledig opgeleide wingerde ten volle te verstaan en te evalueer. / Indaba Scholarship and Winetech for their financial support

Heat induced protein haze is a common problem in white wine. Grape derived pathogenesis related proteins slowly denature and aggregate during wine storage and this gives rise to light dispersing haze. Protein haze formation is currently prevented by removing proteins using bentonite, an aluminium silicate clay, but this method has drawbacks. A potential alternative or complementary method is the use of haze protective factors ( HPF ), specific mannoproteins from Saccharomyces cerevisiae that visually reduce protein haze. Hpf1p was originally isolated from Muscat Gordo Blanco wine and Hpf2p from a synthetic grape juice ferment. Based on partial amino acid sequences, putative structural genes, HPF1 and HPF2, for these proteins were identified. HPF1 has a homologue, HPF1 ', ( 71 % similarity ) in S. cerevisiae. Sequence analysis suggests that Hpf1p, Hpf1 ' p and Hpf2p are localised to the cell wall or plasma membrane. This study aimed to determine the biological function of the HPF genes in S. cerevisiae. HPF overexpression and deletion strains were constructed and analysed for cell wall related phenotypes. Under a number of conditions, including cold temperature and ethanol stress, the hpf1 Δ hpf1 ' Δ strain was more tolerant than the wild type strain. However, mating efficiency of the hpf1 Δ hpf1 ' Δ strain was significantly less than the wild type strain and this was found to be correlated with the persistence of a septum between the mating partners. The decreased mating efficiency was also mating type specific, only occurring in MAT α cells. This study also aimed to establish conclusively that the HPF genes do indeed encode proteins with haze protective properties. Haze protective activity of the material from ferment supernatants was assessed. Material from the HPF deletion strains exhibited significantly less haze protective activity than the wild type. Moreover, material derived from HPF1 and HPF1 ' overexpressors was more active than material from the wild type. A 6xHis - tagged Hpf2p was expressed and purified using immobilised metal affinity chromatography. This Hpf2p had significant haze protective activity. Modification of N - glycans of 6xHis - Hpf2p by Endoglycosidase H decreased its haze protective activity.visually reduce protein haze. Hpf1p was originally isolated from Muscat Gordo Blanco wine and Hpf2p from a synthetic grape juice ferment. Based on partial amino acid sequences, putative structural genes, HPF1 and HPF2, for these proteins were identified. HPF1 has a homologue, HPF1 ', ( 71 % similarity ) in S. cerevisiae. Sequence analysis suggests that Hpf1p, Hpf1 ' p and Hpf2p are localised to the cell wall or plasma membrane. This study aimed to determine the biological function of the HPF genes in S. cerevisiae. HPF overexpression and deletion strains were constructed and analysed for cell wall related phenotypes. Under a number of conditions, including cold temperature and ethanol stress, the hpf1 Δ hpf1 ' Δ strain was more tolerant than the wild type strain. However, mating efficiency of the hpf1 Δ hpf1 ' Δ strain was significantly less than the wild type strain and this was found to be correlated with the persistence of a septum between the mating partners. The decreased mating efficiency was also mating type specific, only occurring in MAT α cells. This study also aimed to establish conclusively that the HPF genes do indeed encode proteins with haze protective properties. Haze protective activity of the material from ferment supernatants was assessed. Material from the HPF deletion strains exhibited significantly less haze protective activity than the wild type. Moreover, material derived from HPF1 and HPF1 ' overexpressors was more active than material from the wild type. A 6xHis - tagged Hpf2p was expressed and purified using immobilised metal affinity chromatography. This Hpf2p had significant haze protective activity. Modification of N - glycans of 6xHis - Hpf2p by Endoglycosidase H decreased its haze protective activity. / Thesis (Ph.D.)--School of Agriculture and Wine, 2003.