The populations of aphidophagous insects in low-spray and conventional programs were surveyed in Virginia apple orchards. Two sampling methods were utilized;aphid colony collection and beating tray collection. The low-spray blocks employed the use of mating disruption for control of the key direct pests, codling moth, Cydia pomonella (Linnaeus), and leafrollers. The abundance and diversity of aphid predators in low-spray mating disruption programs and conventionally controlled apple orchards was compared. Both sampling methods suggested that aphid predators were more plentiful in the mating disruption blocks. Several mating disruption blocks were found to accumulate significantly more predator-days and diversity than the matched control blocks. The reduction of insecticide input into the low-spray blocks may have allowed higher populations of aphidophagous insects to occur. Aphid populations in mating disruption blocks sometimes declined faster and had less resurgence than those in the conventionally controlled blocks. The tufted apple bud moth (TABM), Platynota idaeusalis (Walker), populations in four apple orchards in Winchester, Virginia, were compared for resistance to azinphosmethyl. These orchards were suspected by the growers to have resistant populations of TABM. Pheromone traps with insecticide incorporated into the adhesive were used to collect and test the moths. The results were not analyzed due to the low number of moths collected and high variability in mortality. / Master of Science

Dissertation (PhD)--University of Stellenbosch, 2001. / ENGLISH ABSTRACT: The basic biology of Eriosoma lanigerum (Hausmann) and its natural enemy, Aphelinus mali (Haldeman), was investigated in the Western Cape Province of South Africa. The first instar nymph can be identified by the absence of cornicles and the adult female by the presence of the vulva. Body length and distance between cornicles can be used to distinguish between the 2nd , 3rd and 4th instars. The development of E. lanigerum was negatively influenced by temperatures above 27DC. The net replacement rate (Ro) and intrinsic rate of increase (rm) peaked at 20DC. The theoretical lower and upper threshold temperatures for development were estimated at 4.48DC and 28.07DC, respectively. Crawlers of E. lanigerum migrated from the roots up into the trees during spnng to start new infestations. Colonies became visible from December and maximum colony numbers were reached from the end of summer until autumn, at which time most of the colonies were parasitised by A. mali. Colony numbers declined at the end of autumn after high parasitism and the appearance of winged E. lanigerum. The aphid overwintered on the tree. Chemical sprays, rain during spring and high temperature influenced population numbers negatively. E. lanigerum can be monitored by counting the unparasitised colonies in leaf axils of half of each of 25 trees per 2 hectare plot with 5 unparasitised colonies as the economic threshold. Sampling error was high at 40% but increasing the number of trees did not reduce it. Presence-absence sampling, which will reduce the time required for monitoring, did not seriously compromise the reliability of decisions regarding the necessity for intervention. Chemicals containing nitrogen usually sprayed for bitterpit control stimulated the settling of E. lanigerum crawlers on Granny Smith trees, while fruit weevil barriers for the control of Phlyctinus callos us Boh. limited crawler movement into the trees but did not prevent colonisation. All the postembryonic developmental stages of E. lanigerum were parasitised by A. mali. Complete parasitism of the population was never reached as younger instars sheltered under other aphids and mummified aphids. Development of A. mali was not influenced negatively by high temperatures. The minimum developmental temperature and number of degree days needed for development of the larval stage and emergence of the adult from the mummy were .6.72°C and 172.41°D, and 10.27°C and 109.89°D respectively. Mummies collected during early winter survived long periods of cold storage in postdiapause. The rrummum threshold temperature for postdiapause development of A. mali was ·10.15°C. Most chemicals tested against A. mali adults were highly toxic to the wasp, except endosulfan and two growth regulators, flufenoxuron and fenoxycarb. The mortality of adults exposed to the fungicides tested was low within the first 24 hours. The percentage emergence from the mummies was high for all chemicals tested, but more than 60% of the adults died soon after emergence from mummies treated with chlorpyrifos. Nearly 30% of the adults died soon after they emerged from carbaryl (XLR-Plus) and fenthion treated mummies. The growth regulators, flufenoxuron and fenoxycarb, did not influence fecundity adversely. / AFRIKAANSE OPSOMMING: Die basiese biologie van Enosoma lanigerum (Hausmann) en sy natuurlike vyand, Aphelinus mali (Haldeman), in die Weskaap Provinsie van Suid-Afrika isondersoek. Die eerste instar nimf kan aan die afwesigheid van kornikels en die volwassenes aan die teenwoordigheid van die vulva uitgeken word. Die liggaamslengte en afstand tussen die kornikels kan gebruik word om tussen instar 2, 3 en 4 te onderskei. Die ontwikkeling van E. lanigerum word nadelig deur temperature bo 27°C beïnvloed. Die netto vervangingstempo (Ro) en intrinsieke tempo van toename (rm) was die hoogste by 20°C. Die teoretiese minimum en maksimum temperatuur drempelwaardes vir ontwikkeling was 4.48°C en 28.07°C onderskeidelik. In die lente beweeg E. lanigerum kruipers op vanaf die wortels tot in die bome om nuwe kolonies te begin. Kolonies is sigbaar vanaf Desember en die hoogste koloniegetalle word aan die einde van die somer tot die herfs bereik, wanneer die meeste van die kolonies dan ook deur A. mali geparasiteer word. Teen laat-herfs neem koloniegetalle af as gevolg van hoë parasitisme en die verskyning van gevleuelde E. ,lanigerum. E. lanigerum oorwinter op die appelboom. Chemiese behandelings, reën gedurende die lente en hoë temperatuur beïnvloed koloniegetalle nadelig. E. lanigerum kan deur die aantal ongeparasiteerde kolonies in die blaaroksels van die helfte van 25 bome per 2 hektaar blok te tel, met 5 ongeparasiteerde kolonies as die ekonomiese drempelwaarde, gemonitor word. Die steekproefnemingsfout was hoog (40%), maar kon nie verminder word deur die aantal bome wat gemonitor is te verhoog nie. Steekproefneming, vir aan- of afwesigheid van kolonies, wat monitortyd sal verminder, het min invloed op die betroubaarheid van besluitnemings oor die noodsaaklikheid van bespuitings gehad. Stikstofbevattende chemikalieë, wat vir die beheer van bitterpit gespuit word, stimuleer vestiging van E. lanigerum kruipers op Granny Smith bome, terwyl snuitkewerversperrings, vir die beheer van Phlyctinus callosus Boh., die opwaartse beweging van kruipers in die bome beperk, maar nie kolonievorming van E. lanigerum verhoed nie. Alle postembrioniese ontwikkelingstadiums van E. lanigerum is deur A. mali geparasiteer. Totale parasitisme is nooit bereik nie, omdat jonger instars onder ander bloedluise en gemummifiseerde bloedluise skuil. Die ontwikkeling van A. mali word nie deur hoë temperature benadeel nie. Die minimum ontwikkelingstemperatuur en graaddae, nodig vir ontwikkeling van die larwale stadium en die verskyning van die volwassene uit die mummie, was 6.72°C met 172.4loD en 10.27°C met 109.89°D, onderskeidelik. Mummies wat vroeg in die winter versamel is, het lang periodes van koelopberging oorleef. Die minimum temperatuur drempelwaarde vir A. mali ontwikkeling in postdiapouse was 10.15°C. Die meeste van die chemikalieë wat getoets is, was hoogs toksies vir die volwasse wesp, behalwe endosulfan en die twee groeireguleerders, flufenoxuron en fenoxycarb. Die mortaliteit van volwassenes wat aan swamdoders blootgestel is, was laag binne die eerste 24 uur na blootstelling. Die persentasie uitkoms vanuit mummies was hoog vir al die chemikalieë wat getoets is, maar met chlorpyrifos het 60% van die volwassenes net na uitkoms doodgegaan. Ongeveer 30% van die volwassenes is dood na verskyning vanuit mummies wat met carbaryl (XLR-Plus) en fenthion gespuit is. Die groeireguleerders, flufenoxuron en fenoxycarb, het nie die vrugbaarheid van die parasiet merkbaar beïnvloed nie.

This study examines three commercially driven swedish news organizations that cover consumer electronics in some way. These are: MacWorld, Dagens Industri and Ny Teknik. The aim of this study is to analyze the policies and ethical guidelines regarding consumer electronics of each news organization and see how these translate to the finished articles. This study also aims to examine if the articles from each news organization can be interpreted as native advertising and/or adverising for the product. To achieve this, qualitative interviews have been conducted with representatives from each news organization, about their guidelines and general attitudes regarding consumer electronics. Furthermore, a qualitative content analysis of 13 articles in total has been conducted. To limit this study, one product has been chosen as the analysis object. This product is the Apple Watch and all the analyzed articles has a focus on the product. The results show that the policies and ethical guidelines about consumer electronics where very similiar between the three news organizations. All three were strongly against native advertising and any other form of favouritism. They emphazied that their credibilty towards their audience was the most important thing and that their focus were on what was important and interesting for the audience, not financial gain. However, the representatives, did say that they experienced their reporting about consumer electronics as difficult, and descibed it as a balancing act. The content analysis show that all of the articles about the Apple Watch had similarities to native advertisning and regular advertising for the product, and that they could be interpreted as such. There was a discrepancy between the policies and the actual articles. The interviews painted a picture of the ideal and morally correct way of reporting about consumer electronics. The articles on the other hand did not always live up to these standards. However, this should not be interpreted as if the media organizations were immoral and lied about their use of native advertising. Yet, this study illustrates the difficulty in reporting about consumer electronics without it being interpreted as advertising, and supports previous calls for revised guidelines and definitions about what is and what is not considered native adverising.

Disease management in organic apple orchards in Vermont is focused on controlling diseases with sulfur fungicides. The objective of this two year study was to evaluate the target and non-target effects of an organic disease management system containing agricultural biostimulants compared to two sulfur-based systems on foliar and fruit diseases, pest and beneficial arthropods, tree growth, yield and fruit quality on four cultivars, `Ginger Gold', `Honeycrisp' and `Liberty' and `Zestar!'. Trees were arranged in a complete randomized design of five three-tree replications in a certified organic orchard. The two sulfur-based systems differed in the number of applications; in the third system, sulfur was replaced with biostimulants including pure neem oil, liquid fish, an activated microbial inoculant plus equisetum and stinging nettle teas. Each biostimulant application also included kelp meal, unsulfured organic molasses and yucca extract emulsifier. The biostimulant system did not successfully manage apple scab and rust diseases as well as the sulfur-based fungicide systems, and had variable results with other diseases. No differences were observed among the three systems in tree growth parameters; however, the length of the study may not have been sufficient to determine effects. Differences in the incidence of disease among the three systems were reflected in extrapolated figures for gross income per hectare which takes into account fruit yield and quality. In the higher fruit-bearing year of the study, it was estimated that the gross income per hectare of the biostimulant system would be significantly lower than the reduced-sulfur system and the full-sulfur system by at least $5,800 and $12,000, respectively. In that same year, it is estimated that the full-sulfur system would have generated approximately $6,500 more gross income per hectare than the reduced-sulfur system suggesting the number of sulfur sprays can influence fruit quality and income. The use of the agricultural biostimulants had very limited non-target effects and when present, they were beneficial in suppressing insect pest incidence and/or damage on foliage compared to one or both of the sulfur-based fungicide systems. However, many insect pests or their damage were not observed on the foliage or had incidence of less than 1% in any of the systems. The biostimulant system did appear to suppress European red mites in both years compared to both sulfur-based systems when data were averaged across cultivars. On fruit, no differences in non-target impacts on arthropod pests were observed among the three systems except for surface-feeding Lepidoptera and San Jose scale damage. In a separate phytophagous mite study on the cultivar `Zestar!' leaf samples were evaluated for the number of motile phytophagous mites every 14 days from 1 July through 26 August each year. When there were differences, the biostimulant system had less mite incidence per leaf than one or both of the sulfur-based systems in both years. The difference in the number of sulfur sprays did not have a major effect on the mite populations. In summary, the use of the biostimulant system resulted in insufficient disease management which led to lower estimated gross income compared to the sulfur-based systems. These results show more research and further evaluation of new organic disease management tools, including the use of agricultural biostimulants, are necessary before growers consider replacing the use of standard sulfur fungicides for disease management in Vermont orchards.

This master thesis focuses on the Apple's iPad in the educational institutions and provides reader with the compact overview about the device in this field. Firstly, it shows the strategy of the company in the Europe and the Czech Republic. Secondly, there are mentioned iPad competitors from the different perspectives and the comparison. Thirdly, iPad usage in the schools; if it is even suitable device for this field and how students and educators can benefit from it. This is followed by the survey among the high school and university students. The questionnaire was divided into the two groups -- non-iPad users and iPad users. And lastly the thesis shows various case studies from the different schools and how the iPad can be implemented into the curriculums. Also contains recommendations and the best practises from the different high schools and universities, which can be inspiring for the new iPad pilot projects.

On April 1, 1976, Steve Jobs and Steve Wozniak entered into a partnership agreement to found Apple Computer. In the decade that followed, Apple experienced remarkable growth and success, as Jobs catapulted Apple to the Fortune 500 list of top‐flight companies faster than any other company in history. Under direction of Jobs, Apple, an idea that started in a garage, transformed into a major force in the computer industry of the 1980s. Though Jobs' leadership undoubtedly influenced Apple’s success during this time, in 1995, he was forced to resign, when conflicts mounted at the executive level. Using Kenneth Burke’s theory of identification and the dramatistic process, this thesis examines Jobs’ discourse through a series of interviews and textual artifacts. First, I provide a framework for Jobs' acceptance and rejection of the social order at Apple, and then consider the ways in which Jobs identified with employee and consumer audiences on the basis of division. Analysis shows that Jobs identified with individual empowerment, but valued separation and exclusivity. Jobs' preference to create identification through division, therefore, established the foundation for new identifications to emerge. The findings of this study suggest that division has significant implications for creating unity. / Graduation date: 2012

Behovet av att analysera volatilt minne från Macintosh-datorer med OS X har blivit allt mer betydelsefull på grund av att deras datorer blivit allt populärare och att volatil minnesanalysering blivit en allt viktigare del i en IT-forensikers arbete. Anledningen till att volatil minnesanalysering blivit allt viktigare är för att det går att finna viktig information som inte finns lagrad permanent på datorns interna hårddisk. Problemet som låg till grunden för det här examensarbetet var att det uppenbart fanns brist på undersökningsmetoder av det volatila minnet för Mac-datorer med OS X.Syftet med detta arbete var därför att undersöka möjligheten att utvinna information från ett volatilt minne från en Mac-dator med OS X genom att kartlägga och bedöma olika undersökningsmetoder. För att göra denna undersökning har litteraturstudier, informella intervjuer, egna kunskaper och praktiska försök genomförts.Slutsatsen blev att möjligheten att utvinna information från det volatila minnet från en Mac-dator med OS X är relativt begränsad. Det största problemet är själva dumpningen av minnet. Många av dumpningsmetoderna som finns att tillgå kräver administrativa rättigheter. Vid analysering av en minnesdump bör man aldrig förlita sig på en analysmetod då olika analysmetoder ger olika resultat som kan vara till nytta för en vidare undersökning av en Mac-dator. / The need to analyze volatile memory on Macintosh computers with OS X has become increasingly important due to the fact that their computers have become more popular and volatile memory analysis has become a more important part of an IT-forensics work. The reason volatile memory analysis has become more important is that it's possible to find information that’s not stored permanently on the computer’s hard drive. The problem that formed the basis for this thesis was that it was obvious there was a lack of methods of investigation of the volatile memory for Macs running OS X.The aim of this work was therefore to investigate the possibility of extracting information from a volatile memory from a Mac computer with OS X by identifying and assessing different methods of investigation. To do this investigation, literature studies, informal interviews, own knowledge and practical attempts have been conducted.It was concluded that the ability to extract information from the volatile memory from a Mac-computer with OS X is relatively limited. The biggest problem is the dumping of the memory. Many of the available dumping methods require administrative rights. When analyzing a memory dump you should never rely on one analyze method since different analyze methods give different results that can be useful for further investigation of a Mac-computer.

Syftet med denna studie har varit att undersöka huruvida Apple, ett av världens största varumärken, anpassar sina reklamfilmer efter den lokala kulturen i USA och UK. För att genomföra den tvärkulturella studien användes en kombination av semiotisk textanalys och litteraturstudie. Två nivåer användes för att analysera materialet, först ett makroperspektiv över samtliga 81 reklamfilmer och sedan ett mikroperspektiv över de åtta filmer som hade en motsvarighet i respektive land. Resultatet visade att Apple anpassar sina reklamfilmer på ett flertal områden. Makroanalysen visade flera övergripande strukturella skillnader, samt att flera av de reklamfilmer som var exklusiva i respektive land anknöt till lokala kulturella företeelser och fenomen. Mikroanalysen visade flera syntagmatiska och paradigmatiska skillnader, både i de verbala och visuella tecknen.

Philosophiae Doctor - PhD / Apple scab, powdery mildew and woolly apple aphid are a major concern for apple breeders and producers. Control of these diseases is a significant economic and marketing priority for the South African apple industry. Application of chemicals and orchard management practices are the main methods for controlling these diseases. These diseases require an average of 15 chemical sprays per season, which leads to increased production costs for the farmer. The increased cost of chemical based control programs and demand from consumers for ‘organic apples’ grown with very little to no chemical sprays makes it important to breed for commercial apple cultivars with endogenous disease resistance genes (R-genes). The use of genetic tools (apple genetic linkage maps and the apple genome sequence) to track and introgress endogenous R-genes in breeding and to confer durable disease resistance in commercial apple cultivars will lead to a more cost effective means of disease control for apple producers. Historically, most breeding programmes rely on recurrent conventional breeding systems. This involves the crossing of apple selections showing resistance to a given disease with a susceptible elite variety. This is followed by phenotyping the progeny to identify trees exhibiting segregating field resistance. Several crosses and backcrossing are required to produce resistant varieties and to fix the resistance trait using this breeding strategy. This breeding technique is time consuming, especially in perennial tree species such as apples, which have a long juvenile period. Molecular markers have enabled the building of genetic maps, which has allowed for tracking of the inheritance of genes contributing towards the observed resistances. This has given breeders the opportunity to start the implementation of marker-assisted-breeding (MAB) and marker-assistedselection (MAS). MAB and MAS greatly reduce the time required to select for favourable genotypes, given that MAB facilitates efficient selection for inherited traits at the seedling stage. With the publication of the apple genome sequence, the identification of the genes involved in disease resistances has been made possible and this will allow researchers to venture into cisgenics for apples, which will further reduce the time required for the introgression of desirable genes into commercial cultivars. The main thrust of this research was to generate dense genetic linkage maps for three mapping populations segregating for apple scab, woolly apple aphid and powdery mildew resistance. The three mapping populations are ‘Mildew Resistant’ x ‘Golden Delicious’, ‘Russian Seedling’ x ‘Golden Delicious’ and Malus platycarpa x ‘Mildew Resistant’ and are Malus full-sib outbreed mapping populations. The generation of the genetic maps was for use in the subsequent identification candidate disease resistance QTLs/genes that can be implemented in apple cisgenics. Integrated genetic maps using SSRs, DArTs and SNP marker data were generated for all the three crosses. The integrated map of ‘Mildew Resistance’ x ‘Golden Delicious’ consists of 1, 563 markers with a total map length of 1, 298.8 cM. The ‘Russian Seedling’ x ‘Golden Delicious’ genetic map is composed of 979 markers with a total map length of 1, 729.9 cM. The Malus platycarpa x ‘Mildew Resistant’ integrated map has 616 markers and a total map length of 1,324.3 cM. Due to the fragmentation of some of the linkage groups in the ‘Russian Seedling’ x ‘Golden Delicious’ and in the Malus platycarpa x ‘Mildew Resistant’ genetic maps, a phylogenetic analysis was performed to evaluate the genetic distances between the parents of the crosses in order to understand the cause of the fragmentation of these two integrated genetic maps. QTLs were detected through the statistical correlation of the phenotypic and map data using restricted Multiple QTL Mapping (rMQM) from MapQTL® 6.0. The genome-wide LOD score minimum QTL detection thresholds were determined using 10 000 permutations for each population. The minimum QTL detection threshold for accepting a putative QTL was then determined to be 4.5 for ‘Mildew Resistant’ x ‘Golden Delicious’ and 4.6 for both the ‘Malus platycarpa’ x ‘Mildew Resistant’ and ‘Russian Seedling’ x ‘Golden Delicious’ mapping populations. A total of 17 putative QTLs were detected for the ‘Mildew Resistant’ x ‘Golden Delicious’ population, 10 putative QTLs for the Malus platycarpa x ‘Mildew Resistant’ population and nine putative QTLs for the ‘Russian Seedling’ x ‘Golden Delicious’ population were detected for the three diseases under study. The two putative QTLs for apple scab resistance detected on LG 02 of the ‘Russian Seedling’ x ‘Golden Delicious’ map coincided with the loci previously identified as encoding two apple scab resistance genes Vh2 and Vh4 on ‘Russian apple’. The QTL for apple scab resistance identified on the proximal QTL of LG 02 co-localized with SNP marker R_8936738_Lg2 on the loci where Vh4 was previously identified. The distal QTL on LG 02 shown to encode the Vh2 R-gene was linked with the SNP marker R_32981524_Lg2. With ‘Russian apple’ being known to carry a natural pyramid of R-genes for apple scab on LG 02, therefore, the ‘Russian Seedling’ used in this study was screened by a set of 14 SSR markers to determine if it was related to ‘Russian apple. The 14 SSRs produced identical alleles to those amplified by ‘Russian apple’, which means “Russian Seedling’ and ‘Russian apple’ are closely related or identical. The LG 02 pseudo-chromosome sequence was extracted from the NCBI database housing the apple genome sequence and was then used to mine for the putative R-genes within the two QTL regions. The region corresponding to the Vh2 loci, which was roughly a 600 kb region, had two clusters of ABC (PDR) disease resistance related genes. These were predicted using a full Pfam domain search and were only detected on the negative strand. The 60 kb region corresponding to the Vh4 loci comprised a cluster of LRR domains that were also detected on the negative strand using a full Pfam domain search. This 60 kb region was further analysed using Phytozome and Genome Database for Rosaceae (GDR) leading to two candidate disease resistance genes being identified. Ten consensus gene sequences were present within the 60 kb region, with only two transcripts MDP0000657246 and MDP0000128458 identified as being disease resistance related genes. The MDP0000657246 was identified on the contig MDC000294 of the Malus x domestica reference genome as being a Leucine Rich Repeat protein kinase family, which is one of the most abundant disease resistance family mainly involved in the gene-for-gene resistance mechanism. The MDP0000128458 locus was identified on contig MDC015161 as being a Ser/Thr phosphatase 7. The Ser/Thr phosphatase genes have been associated with the regulation of MAP kinase cascades that have been shown to induce the hypersensitive response (HR) in tobacco. Therefore these two genes are likely to be the loci associated with the hypersensitive response associated with the infection of apples with race 4 of apple scab, carrying the Vh4 apple scab resistance gene. Recurrent putative QTLs were detected that still need to be validated in order to be used for MAB. The ‘Russian Seedling’ x ‘Golden Delicious’ cross produced a single powdery mildew resistance QTL located on LG08 and conferring a 1:1 resistance to susceptible phenotypic segregation ratio. These results indicate that the source of the resistance thus was a single dominant resistance gene. The ‘Mildew Resistant’ x ‘Golden Delicious’ mapping population also showed two stable QTLs one for powdery mildew on LG 03, which co-segregated with SNP GD_LG03snp00866 and in addition SNP R_13071892_Lg10 was also identified to be co-segregating with the QTL for apple scab resistance on LG10. However, none of these recurrent QTLs co-localized with known genes or QTLs. For the phylogenetic analysis, re-sequenced data using the Illumina® sequencing technologies and the apple SNP chip data for ‘Russian Seedling’, ‘Mildew Resistant’, Malus platycarpa, a Chinese accession of Malus sieversii and ‘Anna’ where used to infer relatedness of the five genotypes. The Chinese accession of Malus sieversii was included in the analysis since ‘Russian Seedling’ was thought to be relatively close genetically. Whilst ‘Anna’ is known to be a low chilling cultivar of Malus x domestica (Borkh) and therefore would add in the phylogenetic placement of ‘Mildew Resistant’ and Malus platycarpa. These were sequenced to coverage of approximately 60X for ‘Russian Seedling’ and 6X for the other four genotypes. The sequence data was aligned to the reference Malus x domestica cv Golden Delicious mitochondrial genome sequence. Phylogenetic analysis was then performed using both the data from the apple SNP-chip and the aligned mitochondrial genomes. The results from both sets of data supported the putative evolutionary distances between the five genotypes. ‘Russian Seedling’ and M. sieversii were closely related, while both were genetically divergent from the closely related ‘Anna’ and ‘Golden Delicious’ commercial cultivars. This analysis however indicated that ‘Mildew Resistant’ was relatively closely related to ‘Golden Delicious’ and hence the low number of markers showing segregation distortions for the ‘Mildew Resistant’ x ‘Golden Delicious’ population in the 17 LGs of the integrated map. However, the other two mapping population exhibited a high number of markers with segregation distortions. Markers which are closely associated with disease resistance to apple scab powdery mildew and woolly apple aphid resistance will play a major role in the identification of the genes responsible for the resistances being observed. The identification of the two candidate genes for the Vh4 gene associated with apple scab resistance will be the platform from which a cisgenic programme can be implemented in the South African apple breeding program.

Recent demands for minimally-processed foods, has led to the exploration of plant-derived essential oil (EO) compounds as an alternative means of preservation. While some of these compounds are effective against foodborne pathogens, their strong aroma and "spicy" flavor are not compatible with the flavor of juice. The purpose of this research was to evaluate the antimicrobial activity of three EO compounds (thymol, eugenol, and trans-cinnamaldehyde) alone and in combination with three naturally-occurring apple aroma compounds (hexanal, trans-2-hexenal and 1-hexanol) in order to identify combinations that lower the concentrations needed to destroy foodborne pathogens in apple juice. The standard agar dilution method (SAD) and the Spiral Gradient Endpoint method (SGE) were compared for their abilities to determine minimum inhibitory concentrations (MIC) of the EO compounds. Both methods produced similar patterns of inhibition; however, the MICs produced by the SGE system were significantly higher than those produced by the SAD method of analysis (P<0.05). Since the results produced by the SAD method were more comparable with those published in literature, this method was selected for further testing. In general, the EO compounds were significantly more effective against the test pathogens (Listeria monocytogenes, Salmonella Typhimurium and Staphylococcus aurues) than were the apple aroma compounds (P<0.05). Cinnamaldehye exhibited the highest degree of activity, followed by thymol and eugenol. Eugenol was the only compound that acted synergistically with the apple aroma compounds. The most effective compounds (cinnamaldehyde, eugenol and trans-2-hexenal) were then used to inactivate L. monocytogens and S. Typhimurium in preservative-free apple juice. In most cases, treatment with 0.05% of each compound resulted in a 5 log CFU/ml reduction in bacterial numbers following one day of storage at 4°C or 25°C. Likewise, treatment with antimicrobial combinations (containing 0.025% of trans-2-hexenal in combination with 0.025% trans-cinnamaldehyde or eugenol) also resulted in a 5 log CFU/ml reduction in bacterial numbers, following one day of storage at 4°C or 25°C. Since these combinations contained half the effective concentration of the essential oil compounds, they may be used to preserve the microbial quality of apple juice, while reducing the likelihood of off flavors in the final juice product. / Ph. D.