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Comparative physiological and biochemical studies were conducted with apple varieties which were susceptible (Granny Smith and Lady Williams) and resistant (Crofton) to superficial scald, to understand the mechanisms of scald aetiology. This provided a basis for the development of alternatives to diphenylamine to control the disorder in cool stored apples. The research confirmed earlier research, which showed that the typical scald symptoms were the result of the deposition of brown pigments on the tonoplast in hypodermal and epidermal cells. It has been generally accepted that these pigments were formed by the action of polyphenol oxidase (PPO) following its release from chloroplasts, as a result of membrane damage caused by the oxidation products of alpha-farnesene. However, intact and functional chloroplasts were observed in severely scalded peel tissue. It was proposed that peroxidase (POD) might play a more important role in scald development. The concept that the concentration of alpha-farnesene or its products was related to the severity of scald was examined, and results indicated that differences in scald susceptability were related to the ability of apple tissue to cope with oxidative stress at low temperatures rather than the concentration of alpha-farnesene. If alpha-farnesene has a scald promoting role, it may be as a participant in a free radical chain reaction rather than an initiator. Studies were conducted on the phenolic compounds present in apple peel, which led to the proposal that phenolics might confer scald resistance by conserving other antioxidants and preventing peroxidation of membrane lipids. An holistic model of scald development was proposed, which indicated that scald results from a chilling stress since scald only occurs at temperatures below 4 degrees C and only in apples in which the capacity to protect membranes from oxidative stress is low. The model proposed that POD may have a more important role than PPO in scald development than previously thought. / Doctor of Philosophy (PhD)

Philosophiae Doctor - PhD / Apple (Malus x domestica) production in the Western Cape, South Africa, is one of the major contributors to the gross domestic product (GDP) of the region. The production of apples is affected by a number of diseases. One of the economically important diseases is apple scab that is caused by the pathogenic fungus, Venturia inaequalis. Research to introduce disease resistance ranges from traditional plant breeding through to genetic manipulation. Parallel disease management regimes are also implemented to combat the disease, however, such strategies are increasingly becoming more ineffective since some fungal strains have become resistant to fungicides. The recently sequenced apple genome has opened the door to study the plant pathogen interaction at a molecular level. This study reports on proteomic and transcriptomic analyses of apple seedlings infected with Venturia inaequalis. In the proteomic analysis, two-dimensional gel electrophoresis (2-DE) in combination with mass spectrometry (MS) was used to separate, visualise and identify apple leaf proteins extracted from infected and uninfected apple seedlings. Using MelanieTM 2-DE Gel Analysis Software version 7.0 (Genebio, Geneva, Switzerland), a comparative analysis of leaf proteome expression patterns between the uninfected and infected apple leaves were conducted. The results indicated proteins with similar expression profiles as well as qualitative and quantitative differences between the two leaf proteomes. Thirty proteins from the apple leaf proteome were identified as differentially expressed. These were selected for analysis using a combination of MALDI-TOF and MALDI-TOF-TOF MS, followed by database searching. Of these spots, 28 were positively identified with known functions in photosynthesis and carbon metabolism (61%), protein destination and storage (11%), as well as those involved in redox/response to stress, followed by proteins involved in protein synthesis and disease/defence (7%), nucleotide and transport (3%). RNA-Seq was used to identify differentially expressed genes in response to the fungal infection over five time points namely Day 0, 2, 4, 8 and 12. cDNA libraries were constructed, sequenced using Illumina HiScan SQTM and MiSeqTM instruments. Nucleotide reads were analysed by aligning it to the apple genome using TopHat spliceaware aligner software, followed by analysis with limma/voom and edgeR, R statistical packages for finding differentially expressed genes. These results showed that 398 genes were differentially expressed in response to fungal infection over the five time points. These mapped to 1164 transcripts in the apple transcripts database, which were submitted to BLAST2GO. Eighty-six percent of the genes obtained a BLAST hit to which 77% of the BLAST hits were assigned GO terms. These were classed into three ontology categories i.e. biological processes, molecular function and cellular components. By focussing on the host responsive genes, modulation of genes involved in signal perception, transcription, stress/detoxification, defence related proteins, transport and secondary metabolites have been observed. A comparative analysis was performed between the Day 4 proteomic and Day 4 transcriptomic data. In the infected and uninfected apple leaf proteome of Day 4, we found 9 proteins responsive to fungal infection were up-regulated. From the transcriptome data of Day 4, 162 genes were extracted, which mapped to 395 transcripts in the apple transcripts. These were submitted to BLAST2GO for functional annotation. Proteins encoded by the up-regulated transcripts were functionally categorised. Pathways affected by the up-regulated genes are carbon metabolism, protein synthesis, defence, redox/response to stress. Up-regulated genes were involved in signal perception, transcription factors, stress/detoxification, defence related proteins, disease resistance proteins, transport and secondary metabolites. We found that the same pathways including energy, disease/defence and redox/response to stress were affected for the comparative analysis. The results of this study can be used as a starting point for targeting host responsive genes in genetic manipulation of apple cultivars.

Apples growing in New Zealand, Argentina, Mexico, Michigan and Washington were used to provide the compositional data and to develop the analytical procedures for the use in verification of authenticity of apple juices. High Performance Liquid Chromatography (HPLC) techniques were applied for glucose, fructose, sucrose, sorbitol, malic, citric, quinic, shikimic, fumaric, chlorogenic acid, and hydroxymethylfurfural (HMF). L-malic acid was determined by an enzymic method. Sep-Pak C18 cartridge, anion exchange resin and millipore filter were used for sample preparation of HPLC. Influence of postharvest storage on sucrose and sorbitol content was observed but it had no effect on the glucose/fructose ratios. Quinic was the next most abundant acid in all the apple varieties examined. Paired t-test showed good agreement (p<0.01) between HPLC and enzymic determination for malic acid. Significantly high variability in chlorogenic acid content limits its utility. The influence of processing procedures on the phenolic compound was observed by comparison with commercial, self-pressed and gelatin treated apple juices. All apple juices showed two characteristic UV absorption maxima at around 280nm and 320nm, the ratio of the two maxima being relatively constant. First, second derivative spectra and fluorescence excitation and emission maxima were measured. As the order of derivative increased, the spectra became more complex and the resolution was enhanced. For the stable carbon isotope ratio analysis, juice, pulp, seeds and sugars, acids, and phenolics were fractionated using ion exchange resins and polyclar AT. Mass spectrometric measurements of ¹³C/ ¹²C ratio from whole juices showed low variability as compared to other fractions. Organic acids showed more negative values than the sugars. Phenolic fraction was most enriched in ¹²C when compared to the juice by as much as 4.6 ppt. The evidence suggests that postharvest storage and processing conditions played an important role in the variability of apple juice components. There are no marked differences in del ¹³C values with regard to apple variety or geographic origins. / Graduation date: 1985

Fruit juice concentrates- hard pear, soft pear, fig, prune, raisin, white grape, and pineapple, and sweeteners-invert beet, invert cane, and high fructose corn syrup (HFCS) were characterized by sugar profiles, nonvolatile acid profiles, UV spectral profiles, and mineral content. These fruit juices and sweeteners were also used to adulterate commercial apple juice at levels of 40%, 20%, and 10%. Sugar and nonvolatile acid analyses were performed by HPLC and isotopic carbon analyses were applied to selected samples. Data analysis included the application of Pattern Recognition methods and Chi-square test. Analysis by Pattern Recognition was restricted to sugar profiles because of the availability of an extensive data base on sugar composition of authentic apple juice, the compositional data base for the other components being limited. The "potential adulterants" were clearly distinguished from the cluster of authentic apple juice. Apple juice samples adulterated at 40% were at the perimeter and also distinguishable from the cluster, while the samples adulterated at 20% and 10% were intermingled within the cluster. Pattern Recognition methods were also used for classification of the authentic apple juice data base obtained from Mattick and Moyer (1983). Apple samples were classified by variety and geographical origin. Sucrose, glucose/fructose ratio, and sorbitol were important variables in the separability of the samples. Pattern Recognition methods are effective in classification of authentic juices and show potential as a powerful technique in discriminating between adulterated and authentic apple juice. / Graduation date: 1987

The British Columbia Apple industry, primarily located in the Southern Interior of the province, has undergone varying levels of tree removal and replanting as growers attempt to maximize profits. This study models their behaviour by using econometrics in a supply response model. The economic environment of the fruit industry is described. The variables affecting acreage responses to removals and replanting of new and traditional apple varieties are estimated using Ordinary Leased Squares in three separate equations. Data are pooled and aggregated at the regional level. Several versions of the original model are run to test for robustness of the variables and of the original model. The econometric models illustrated that the plantings of new varieties increases when expected profits from vintage trees decline. However, planting and removals of traditional varieties are positively related to excepted profits from vintage trees and this does not follow apriori expectations. More striking in the model is the regional differences and their responsiveness to removals and replanting. Regions with younger, better educated farmers replant to new varieties at a faster rate than other regions. Replant programs are shown to have a negative effect on the rate of replanting. These programs maintain basic criteria for their eligibility to funding and seemingly decreased the acres replanted. Increasing the monetary value of the replant grants results in the effect of increasing the acreage of traditional varieties being planted. Policy implications are examined in a post modelling analysis. The effects of top loading subsidy effects are shown to have decreased the acreage of trees replanted over time. These effects are shown to cause a dead weight loss to society of approximately $13 million over 20 years.

During the summer of 1920 the writer was engaged in studying the bionomics of the Apple Sucker, Psyllia Mali, in Nova Scotia, and, having occasion to make numerous dissections, he was struck by the lack of literature dealing with the anatomy of any members of this family, particularly with regard to the internal organs. Investigation showed many interesting and unusual features in the morphology of the insect and so the entire anatomy was chosen as the subject for this thesis. The field is a wide one, and it has not been found possible to follow out all points in full detail in the time available, with only preserved material with which to work. If there appears to be a hesitancy and uncertainty in describing certain structures, it must be borne in mind that the body of this insect is only 2.5 m.m. long, so that the individual organs and sclerites are in most cases extremely minute, rendering the work of dissection very delicate and trying. The writer hopes to follow up those points which have only been lightly touched upon, extending the field of investigation to related species, with the object of producing a more complete and valuable piece of work.

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Thesis (Ph. D.)--Virginia Polytechnic Institute and State University, 1989. / Vita. Abstract. Includes bibliographical references (leaves 168-179). Also available via the Internet.