vi, 128 leaves : photos, tables ; 30 cm / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Plant Pathology, 1978

Thesis (MSc Food Sc)--Stellenbosch University, 2003. / ENGLISH ABSTRACT: Post-storage quality of the stone fruit, apricots and peaches, is the major factor determining their suitability for canning after cold storage in South Africa. Short harvesting periods and the limited capacity of the factory to process the large quantities of fruit within two days after delivery, necessitates cold storage until canning. Apricots develop internal breakdown, whereas peaches develop internal breakdown accompanied by loosening of the skin and adhesion of the flesh to the stone. The deterioration takes place within the fruit during a cold storage period of one to two weeks. The tendency of the fruit to develop internal defects can, to date, not be identified prior to storage and are only discovered after destoning during canning. Near infrared spectroscopy (NIRS) combined with chemometrics were investigated as a non-destructive method to predict post-storage quality in Bulida apricots and clingstone peach cultivars. Near infrared (NIR) spectra (645-1201 nm), measured on the intact fruit just after harvesting, were correlated with subjective quality evaluations performed on the cut and destoned fruit after cold storage. The cold storage periods for apricots were four weeks (2002 season) and three and two weeks for peach cultivars for the 2002 and 2003 seasons, respectively. Soft independent modelling by class analogy (SIMCA) and multivariate adaptive regression splines (MARS) were applied to the spectral and reference data to develop models for good and poor post-storage quality. The ability of these models to predict post-storage quality was evaluated in terms of recognition (sensitivity) and rejection (specificity) of the samples in independent validation sets. Total correct classification rates of 50.00% and 69.00% were obtained with Bulida apricots, using SIMCA and MARS, respectively. Classification results with apricots showed that MARS performed better than SIMCA and is thus recommended for this application. Total correct classification rates of 53.00% to 60.00% (SIMCA) and 57.65% to 65.12% (MARS) were obtained for data sets of combined peach cultivars within seasons and over both seasons. Additional aspects of fruit quality were investigated to identify possible indices of post-storage quality. Classification trees were used to find correlations between the post-storage quality and the fruit mass, diameter, firmness and soluble solids content (SSC). Among these, fruit diameter and firmness were the major indices of post-storage quality. Accurate predictions of firmness could not be achieved by near infrared spectroscopy (NlRS), making the combination of NIRS and classification trees not yet suitable for predicting post-storage quality. NIRS was further used to predict poststorage SSC within seasons in Bulida apricots and intact peach cultivars. This confirmed sufficient NIR light penetration into the intact fruit and also provided a further application of NIRS for ripeness evaluation in the canning industry. Validations on peach samples obtained correlation coefficients (r) of 0.77-0.85 and SEP-values of 1.35-1.60 °Brix using partial least squares (PLS) regression. MARS obtained r = 0.77-0.82 and SEP = 1.42-1.55 °Brix. Predictions of sse in apricots were less accurate, with r = 0.39-0.88, SEP = 1.24-2.21 °Brix (PLS) and r = 0.51-0.82, SEP = 1.54-2.19 °Brix (MARS). It is suggested that the accuracy of sse measurements, and the subsequent predictions, were affected by the cold storage periods as well as internal variation within the fruit. This study showed that a combination of NIRS and chemometrics can be used to predict post-storage quality in intact peaches and apricots. A small scale feasibility study showed that 4% (R117 720) (apricot industry) and 3% (R610 740) (peach industry) of production losses can be saved if this method is implemented in the South African canning industry. Although it was difficult to assign specific chemical components or quality attributes to the formulation of the storage potential models, important hidden information in the spectra could be revealed by chemometric classification methods. NIRS promises to be a useful and unique quality evaluation tool for the South African fruit canning industry. Several recommendations are made for the canning practices to reduce losses and for future research to improve the current prediction models. / AFRIKAANSE OPSOMMING: Die kwaliteit van die steenvrugte, appelkose en perskes, is die hoof bepalende faktor vir hul geskiktheid vir inmaakdoeleindes na koelopberging in Suid-Afrika. Die vrugte moet opgeberg word by lae temperature vir een tot twee weke, aangesien die oestydperk kort is en die kapasiteit van die fabriek te beperk is om die groot hoeveeheid vrugte dadelik in te maak. Tydens hierdie opbergingstydperk vind agteruitgang in die vrugte plaas. Dit word in appelkose gekenmerk deur interne verval en in perskes gekenmerk aan interne verval, tesame met enlos skil en die vaskleef van die vrugvlees aan die pit. Tot dusver, bestaan daar geen metode om hierdie tipe agteruitgang in vrugte voor opberging te identifiseer nie. Dit word eers na opberging opgemerk wanneer die vrugte ontpit word. Naby-infrarooi spektroskopie (NIRS), gekombineerd met chemometriese metodes is gebruik om opbergingspotensiaal in Bulida appelkose en taaipitperske kultivars te bepaal. enKorrelasie is gemaak tussen naby-infrarooi (NIR) spektra, gemeet op die heel vrugte voor opberging en subjektiewe evaluering van kwaliteit, geïdentifiseer op die gesnyde vrugte na opberging. Die opbergingstydperke vir perskes was vir drie en twee weke vir die 2002 en die 2003 seisoene, onderskeldeflk, terwyl die appelkose vir vier weke opgeberg is. Twee chemometriese metodes, "soft independent modelling by class analogy" (SIMCA) en "multivariate adaptive regression splines" (MARS) is gebruik om die spektra en ooreenstemmende subjektiewe data te kombineer en modelle is ontwikkel vir goeie en swak opbergingspotensiaal. Die vermoë van die modelle om die vrugkwaliteit na die opbergingstydperk te voorspel, is geêvalueer in terme van herkenning en verwerping van vrugtemonsters in onafhanklike toetsstelle. Totale korrekte klassifikasies van 50.00% and 69.00% is verkry vir Bulida appelkose, met SIMCA en MARS, onderskeidelik. Die klassifikasie resultate het gewys dat MARS beter gevaar het as SIMCA en word dus sterk aanbeveel vir hierdie toepassing. Totale korrekte klassifikasies van 53.00% tot 60.00% (SIMCA) and 57.65% tot 65.12% (MARS) is verkry vir gekombineerde perskekultivars tussen seisoene en oor seisoene. Verdere aspekte van vrugkwaliteit is geêvalueer om enmoontlike indeks van opbergingspotensiaal te verkry. Klassifikasiebome is gebruik om en korrelasie te vind tussen kwaliteit na opberging en vrugmassa, deursnee, fermheid en totale oplosbare vastestowwe (TOV). Diameter en fermheid het die meeste gekorreleer met die kwaliteit na opberging. Voorspellings van fermheid deur die gebruik van naby infrarooi spektroskopie (NIRS) was ~gter nie akkuraat nie. Dus word die kombinasie van klassifikasiebome en NIRS om opbergingspotensiaal te voorspel nie tans aanbeveel nie. NIRS is verder gebruik om TOV te voorspel binne seisoene in heel Bulida appelkose en perskekultivars. Dit is uitgevoer om voldoende NIR ligpenitrasie in die vrugte te bevestig en ook om 'n verdere toepassing van kwaliteitsbepaling (as indeks van soetheid en rypheid) vir die inmaakindustrie te verskaf. Validasies is op perskemonsters uitgevoer en korrelasiekoêffisiente (r) van 0.77-0.85 en voorspellingsfoute van 1.35-1.60 °Brix is verkry met "partial least squares" (PLS) regressie. MARS het r = 0.77-0.82 and voorspellingsfoute = 1.42-1.55 °Brix verkry. Die akkuraatheid van die TOV meetings en gevolglike voorspellings is waarskynlik beïnvloed deur interne variasie binne die vrugte sowel as die opbergings tydperke wat verloop het tussen metings. Hierdie studie wys dat NIRS en chemometriese metodes wel gebruik kan word om opbergingspotensiaal in heel perskes in appelkose te voorspel. 'n Kosteberekening het gewys dat besparings van 4% (R117 720) (appelkoos industrie) en 3% (R610 740) (perske industrie) moontlik is indien NIRS en MARS geïmplementeer word. Alhoewel dit moeilik was om spesifieke chemiese komponente en .sekere kwaliteitsaspekte aan die ontwikkeling van die modelle te koppel, is belangrike verborge informasie in die spectra uitgebring deur chemornetriese metodes. NIRS beloof om 'n bruikbare en unieke kwaliteitskontrole maatstaf te wees vir die Suid-Afrikaanse inmaakindustrie. Verskeie aanbevelings is gemaak vir die inmaakpraktyke om verliese te voorkom en ook vir toekomstige navorsing om die huidige klassifikasiemodelle te verbeter.

M.Sc.(Agric) / Department of Horticultural Sciences

Submitted by Milena Rubi (milenarubi@ufscar.br) on 2017-08-08T17:44:33Z No. of bitstreams: 1 GHIOTTO_Thais_2016.pdf: 18907197 bytes, checksum: 0779f8ac869df152bdd7747df97a15e5 (MD5) / Approved for entry into archive by Milena Rubi (milenarubi@ufscar.br) on 2017-08-08T17:44:43Z (GMT) No. of bitstreams: 1 GHIOTTO_Thais_2016.pdf: 18907197 bytes, checksum: 0779f8ac869df152bdd7747df97a15e5 (MD5) / Approved for entry into archive by Milena Rubi (milenarubi@ufscar.br) on 2017-08-08T17:44:49Z (GMT) No. of bitstreams: 1 GHIOTTO_Thais_2016.pdf: 18907197 bytes, checksum: 0779f8ac869df152bdd7747df97a15e5 (MD5) / Made available in DSpace on 2017-08-08T17:44:55Z (GMT). No. of bitstreams: 1 GHIOTTO_Thais_2016.pdf: 18907197 bytes, checksum: 0779f8ac869df152bdd7747df97a15e5 (MD5) Previous issue date: 2016-05-09 / Não recebi financiamento / Megastigmus transvaalensis is an exotic wasp that attacks Brazilian pepper tree drupes Schinus terebinthifolius in native forests and areas of restoration and ecological restoration in Brazil. The parasitism begins with the oviposition M. transvaalensis in drupes S. terebinthifolius where the larvae hatch and remain internally feeding of nutrients and tissue, affecting germination. The aim of this work was to study the effect of temperature, rainfall and humidity in the population dynamics of M. transvaalensis and determine the parasitism rate and sex ratio of this wasp in drupes S. terebinthifolius. The study was performed with yellow sticky traps and collection of S. terebinthifolius drupes in seasonal semideciduous forest during August 2014 to September 2015, in the region of Sorocaba, São Paulo, Brazil. The capture of insects through the sticky traps proved satisfactory, and thus can be applied to the monitoring of small Hymenopteros. Populations of M. transvaalensis were negatively correlated with the maximum temperature and population peak in the fall of 2015, meaning that when the maximum temperature has reduced, there is a higher incidence of insect field. The parasitism rate of S. terebinthifolius drupes ranged from zero to 36.34% during this period, making this value an aggravating factor for the emergence of new individuals, since this phytophagous wasp has the potential to be spread throughout Brazil and It poses a threat to the natural regeneration of S. terebinthifolius. The sex ratio of M. transvaalensis was 0.42 and 0.08 in the laboratory field. The bio-ecology and the damage caused by M. transvaalensis in drupes S. terebinthifolius warrant further studies to integrated management / Megastigmus transvaalensis é uma vespa exótica que ataca drupas de aroeira-pimenteira Schinus terebinthifolius em florestas nativas e em áreas de recomposição e restauração ecológica no Brasil. O parasitismo inicia com a oviposição de M. transvaalensis nas drupas de S. terebinthifolius, onde as larvas internamente eclodem e permanecem alimentando-se dos nutrientes e tecidos, prejudicando a germinação. O objetivo desse trabalho foi estudar o efeito da temperatura, precipitação e umidade na flutuação populacional de M. transvaalensis e determinar o índice de parasitismo e razão sexual dessa vespa nas drupas de S. terebinthifolius. O estudo foi realizado com armadilhas adesivas amarelas e coleta de drupas de S. terebinthifolius em fragmento de floresta estacional semidecidual, durante agosto de 2014 a setembro de 2015, na região de Sorocaba, São Paulo, Brasil. A captura dos insetos através das armadilhas adesivas se mostrou satisfatória, podendo assim ser aplicada para o monitoramento de pequenos Hymenopteros. As populações de M. transvaalensis apresentaram correlação negativa com a temperatura máxima e pico populacional no outono de 2015, significando que, quando a temperatura máxima apresenta redução, há maior incidência do inseto em campo. O índice de parasitismo das drupas de S. terebinthifolius variou de zero a 36,34% no período avaliado, tornando este valor um agravante para o surgimento de novos indivíduos, uma vez que, essa vespa fitófaga tem potencial de ser disseminado por todo Brasil e representa ameaça para a regeneração natural de S. terebinthifolius. A razão sexual de M. transvaalensis foi de 0,42 no laboratório e 0,08 em campo. A bioecologia e os danos causados por M. transvaalensis em drupas de S. terebinthifolius justificam mais estudos visando o manejo integrado dessa vespa fitófaga.

Total soluble solids (TSS) is a reliable indicator of melon eating quality, with a minimum standard of 10% recommended. The state of Australian melon production with respect to this quality criterion was considered within seasons, between growing districts and over seasons. It was concluded that improvement in agronomic practice and varietal selection is required to produce sweeter melons. The scientific literature addressing melon physiology and agronomy was summarised, as a background to the work that is required to improve melon production practices in Australia. The effect of source sink manipulation was assessed for commercially grown and glasshouse grown melon plants. The timing of fruit thinning, pollination scheduling, the application of a growth inhibitor and source biomass removal were assessed in relation to fruit growth and sugar accumulation. Results are interpreted against a model in which fruit rapidly increase in weight until about two weeks before harvest, with sugar accumulation continuing as fruit growth ceases. Thus treatment response is very dependant on timing of application. For example, fruit thinning at 25 days before harvest resulted in further fruit set and increased fruit weight but did not impact on fruit TSS (at 9.8%, control 9.3%), while thinning at 5 days before harvest resulted in a significant (Pless than 0.05) increase in fruit TSS (to 10.8%, control 9.3%) and no increase in fruit weight or number. A cost/ benefit analysis is presented, allowing an estimation of the increase in sale price required to sustain the implementation of fruit thinning. The effect of irrigation scheduling was also considered with respect to increasing melon yield and quality. To date, recommended practice has been to cause an irrigation deficit close to fruit harvest, with the intent of 'drying out' or 'stressing' the plant, to 'bring on' maturity and increase sugar accumulation. Irrigation trials showed that keeping plants stress-free close to harvest and during harvest, facilitated the production of sweeter fruit. The maintenance of a TSS grade standard using either batch based (destructive) sampling or (non-invasive) grading of individual fruit is discussed. On-line grading of individual fruit is possible using near infrared spectroscopy (NIR), but the applicability of the technique to melons has received little published attention. Tissue sampling strategy was optimised, in relation to the optical geometry used (in commercial operation in Australia), both in terms of the diameter and depth of sampled tissue. NIR calibration model performance was superior when based on the TSS of outer, rather than inner mesocarp tissue. However the linear relationship between outer and middle tissue TSS was strong (r2 = 0.8) in immature fruit, though less related in maturing fruit (r2 = 0.5). The effect of fruit storage (maturation/senescence) on calibration model performance was assessed. There was a negligible effect of fruit cold storage on calibration performance. Currently, the agronomist lacks a cost-effective tool to rapidly assess fruit TSS in the field. Design parameters for such a tool were established, and several optical front ends compared for rapid, though invasive, analysis. Further, for visualisation of the spatial distribution of tissue TSS within a melon fruit, a two-dimensional, or hyper-spectral NIR imaging system based on a low cost 8-bit charge coupled device (CCD) camera and filter arrangement, was designed and characterised.

Isolates of Monilinia fructicola (Wint.) Honey obtained from stone fruit orchards in Hawkes Bay, North Island and from Californian fruit exported to New Zealand, were tested for resistance to methyl benzimidazole carbamate (MBC). Resistant isolates from the North Island had EC₅₀ values of >30,000, and most isolates from the imported fruit had of values approximately 1.5 mg a.i./l carbendazim. Sensitive isolates failed to grow on 1 mg a.i./l carbendazim. A detached peach shoot system was used in controlled conditions for estimation of values for incubation period, latent period and rate of spore production on flowers (cv Glohaven). The same variables and the rate of colonisation of host tissue were measured on fruit (cv Fantasia) in controlled conditions. An inoculum density of 1x10⁴ spore/flower or fruit greatly increased fitness in vivo compared to an inoculum density of 1x10² spore/flower (fruit). Isolates varied considerably, but there was no consistent relationship between the degrees of resistance and fitness. This was in contrast to earlier studies with dicarboximide resistant strains of M. fructicola. The survival in the field of 10 isolates resistant or sensitive to MBC or dicarboximide fungicides on twig cankers and mummified fruit was compared. The ability to produce conidia on twig cankers inoculated in late spring 1989 was maintained by all sensitive and MBC resistant isolates for at least 1 year. The production of conidia on mummified fruit inoculated in February 1990 decreased after 2-3 months in the field but some conidia were still produced on all fruit in the following spring. Dicarboximide resistant isolates produced less conidia than either the MBC resistant and the sensitive isolates. The pathogenicity and fitness of all isolates were similar to the original values after survival for 1 year. A technique was developed to produce apothecia reliably from inoculated peach (cv Black Boy) and nectarine (cv Fantasia) fruit in controlled conditions in the laboratory. The fruit were inoculated with resistant or sensitive isolates, or combinations, and were incubated for 8 weeks at 25°C (±1°C) with 12 hours photoperiod of fluorescent light (Sylvania 2x65 W, daylight) to produce mummified fruit. The fruit were then buried in moist autoclaved peat moss for 10 weeks at 25°C (±1°C) in the dark to form stromata. These fruit were then hydrated with running tap-water (total hardness (CaCO₃) = 47 g/m³ and conductivity at 20°C = 12.7 mS/m) for 72 hours. The hydrated mummified fruit were placed in moist peat moss and were incubated for 13-14 weeks at 8°C (±0.5°C) in the dark. At the end of this period, stipe initials were visible. Differentiation of stipe initials into mature apothecia occurred within 15-20 days after transfer to 12°C (±2 °C) with a 12 hour photoperiod of fluorescent and incandescent light. All isolates produced apothecia when treated in this way. A technique for isolation of ascospore sets in linear arrangement was developed for tetrad analysis of the inheritance of resistance. At least 3 hours of fluorescent and incandescent light at 12°C (±2°C) was essential to allow ascospore ejection from individual asci taken from apothecia previously maintained in a 12 hour photoperiod at 12°C (±1°C). A water film on the surface of water agar was necessary to hold a set of ejected ascospores in linear sequence. Single ascospores were obtained in sequence with the aid of a micromanipulator. Genetic analysis of MBC resistant isolates was carried out on ascospores derived from apothecia produced in the laboratory. Analysis of ascospore sets in linear arrangement and ascospore populations indicated that resistance to >30,000 mg a.i./l carbendazim (high-resistant) is governed by a single major gene and is affected by gene conversion mechanisms. Crossing over was frequent, suggesting that recombination of resistance with other characters, such as pathogenicity and fitness, may occur readily. The segregation ratio (1:1) from most resistant isolates revealed that heterokaryons containing both resistant and sensitive alleles were common in resistant populations and that resistance is dominant. Allozyme analysis of ascospore progeny through electrophoresis revealed a narrow genetic base of M. fructicola in New Zealand. The technique for reliable apothecial production in controlled conditions developed in this study provided an important step for the determination of the biology of M. fructicola strains resistant to MBC fungicides, and the complexity of its life cycle. Genetic heterogeneity in field populations can be conserved in one isolate through heterokaryosis, thus providing for adaptability of the pathogen to the changing environmental conditions. Knowledge on genetic variability, overwintering ability, pathogenicity and fitness factors may be useful for future management strategies of stone fruit brown rot. Special emphasis should be made in particular to prevent primary infection on blossoms, which would delay the establishment of recombinant strains of M. fructicola and the onset of brown rot epidemics.

<p>Istraživanja u okviru ove disertacije obuhvataju ispitivanje fizičkih, hemijskih i biolo&scaron;kih osobina svežeg i osu&scaron;enog ko&scaron;tičavog voća i razvoj inovativnog tehničkog re&scaron;enja su&scaron;enja voća u vakuumu. Dobijeni rezultati istraživanja daju doprinos formiranju baze naučnih znanja u vezi sa karakteristikama ko&scaron;tičavog voća osu&scaron;enog različitim tehnikama su&scaron;enja: konvektivnim su&scaron;enjem, vakuum su&scaron;enjem i liofilizacijom (su&scaron;enjem zamrzavanjem). Projektovan inovativni prototip vakuum su&scaron;are sa ejektorskim sistemom omogućava očuvanje biolo&scaron;ki aktivnih komponenata voća uz mogućnost smanjenja investicionih tro&scaron;kova i tro&scaron;kova održavanja opreme. Takođe je uspe&scaron;no prikazana mogućnost primene analize glavnih komponenata (eng. Principal Component Analysis, PCA), ve&scaron;tačke neuronske mreže (eng. Artificial Neural Networks, ANN) i matematičkog modelovanja za opisivanje funkcionalne zavisnosti primenjenih parametara su&scaron;enja i fizičkih, hemijskih i biolo&scaron;kih osobina osu&scaron;enog voća, optimizaciju procesa su&scaron;enja, kao i za pronalaženje modela koji najbolje opisuje proces su&scaron;enja.</p> / <p>Research in the framework of the thesis includes investigation of physical, chemical and biological properties of fresh and dried stone fruit and the development of an innovative technical solution for fruit vacuum drying. The obtained results contribute to the formation of the scientific base of knowledge, regarding the characteristics of stone fruit dried by different drying techniques: convective drying, vacuum drying and lyophilization (freeze drying). The designed innovative prototype of a vacuum dryer with an ejector system enables the preservation of biologically active fruit compounds with the possibility of reducing investment and equipment maintenance costs.<br />The possibility of application of Principal Component Analysis (PCA), Artificial Neural Networks (ANN) and mathematical modeling for describing the functional dependence between applied drying parameters and physical, chemical and biological properties of dried fruit, optimization of the drying process, as well for finding the model that best describes the drying process was presented in this work.</p>