Thesis (MSc .(Plant Production)) -- University of Limpopo, 2016 / Delayed fruit harvest (DFH) or on-tree-fruit storage is a strategy being considered to extend the harvest season of late maturing ‘Reed’ avocado. However, avocado fruit growth beyond physiological maturity is accompanied by alterations in chemical and physical properties. Thus, the study aimed to investigate the effects of delayed harvest on tree productivity, mineral nutrition and post-harvest quality of late maturing ‘Reed’ avocado and further to evaluate the fruit quality response to varying ripening temperature regimes. As treatments, fruit were harvested early, mid and late in the season, with one month apart from each harvest during 2013 and 2014 seasons. Yield and fruit size were recorded at harvest. During each harvest time, two sets of fruit samples were collected to determine the fruit nutritional content while the second set was cold stored at 5.5°C for 28 days. After storage, fruit were ripened at 16, 21 or 25°C and evaluated for post-harvest disorders, pathological diseases and fruit physico-chemical properties. Yield dropped from 42 to 12 kg/tree from early to late harvest during 2013, while treatments showed no effect during 2014. Furthermore, treatments had no effect on fruit size during both seasons. Phosphorus content decreased by 40 and 23% from early to late harvest time during 2013 and 2014 seasons, respectively. Similar decreasing patterns were observed for K, Ca and Mg content. Zinc content remained constant during 2013; however, mid-season fruit maintained higher zinc levels during 2014 season when compared to early and late harvest time. Protein content was constant for early and mid-season fruit but significantly decreased during the late harvest in both seasons. Moisture content decreased from 74.0 to 65.0% from early to late harvest during both seasons. Starch, oil and ash content were high during late harvest time in both seasons; while crude fibre was high during the mid-harvest time when compared with early and late harvest time. Internal chilling injury increased with maturity and ripening temperature. In both seasons, higher temperatures induced higher anthracnose incidences during early and mid-harvest compared with late harvest time. Similarly, vascular browning was high on fruit ripened at 16°C during early and mid-harvest time but decreased on late harvest fruit during 2013. However, low ripening temperatures induced high incidences of vascular browning during 2014 season. Stem-end rot was high on fruit ripened at 16°C than 21 and 25°C during 2014 season. xvi Physico-chemical quality parameters showed similar behaviour in both seasons. Fruit lightness increased with ripening time regardless of ripening temperature during the early harvest, but remained constant during mid and late harvest. Hue angle (h0) and Chroma (C*) values were slightly reduced during ripening. Fruit ripened at 25°C had the highest respiration rate and reached a climacteric peak earlier (day 2) than fruit ripened at 21 and 16°C (day 4). Fruit firmness and weight loss were high and rapid at 25°C followed by 21 and 16°C regardless of the harvest time. Delayed harvest had no effect on yield and fruit size. Generally, nutritional content of avocado fruit increased with fruit maturity. Furthermore, fruit maturity played a major role in the response of fruit to ripening temperature. Higher temperature enhanced fruit ripening, but was conducive for development of post-harvest diseases. Keywords: Harvesting time, nutrition, yield, fruit size, ripening temperature, post-harvest quality

Dietary fiber (DF) consumption is related with several healthy benefits such as the decreasing risk of colon cancer development. The DF is not digested by the digestive enzymes and reach to colon where is fermented by the colonic microbiota. The fermentation process releases metabolites as short chain fatty acids (SCFA) such as butyrate, propionate and acetate. Besides the fermentation process, the DF can directly interact with intestinal epithelial cells inducing mechanism that can also be related with the associated DF consumption benefits. The lack of information regarding DF and colon cancer are due to the complexity of both the cancer and the DF structure. The papayas DF are derived from the fruit cell wall, and they are probably naturally modified during ripening through a massive polysaccharide hydrolysis, because papayas show a very fast pulp softening. Due to the lack of information about DF and their beneficial effects to human health as well as the possibility of the natural papaya ripening to modifying the DF presented in the fruit pulp, the present thesis had as the primary objectives: 1) to evaluate how the cell-wall degrading enzymes affect the fruit cell wall solubilization and molecular weight; 2) to investigate the direct effects of the papaya pectin derived from unripe to ripe papayas in cancer cell lines, in galectin-3 interaction and in HEK cells expressing pattern recognition receptors (PRR); 3) to evaluate the human colonic in vitro fermentation using DF from unripe and ripe papayas as substrates; 4) to conduct an in vivo experiment using rats with pre-neoplastic colon lesions while receiving a diet with DF from unripe and ripe papayas. The endopolygalacturonases were the main enzymes acting on the solubilizing papaya cell wall pectin affecting both the papaya firmness and pectin structure. Overall, the papayas DF showed a ripening dependent structureeffects. In the cancer cell lines experiments, the ripe papayas pectin showed a more pronounced effects in inducing cancer cell death, inhibiting cancer cells migration and aggregation, activating PRR as toll-like receptors and inhibiting the pro-metastatic protein galectin-3. The DF from papayas also showed different aspects in colonic in vitro fermentation regarding the DF utilization by the bacteria and the bacteria abundance profile. Lastly, the animals receiving the diet with the DF from ripe papayas had less aberrant crypt foci in colon than the animals that received the DF from unripe papayas or cellulose (AIN-93G DF). Therefore, the study of papaya DF was carried out both during papaya ripening and its biological effects in vitro and in vivo, generating unprecedented results relating the endogenous biochemical changes of the fruits during maturation with the possible beneficial effects of their ingestion for health human. / O consumo de fibras alimentares (FA) está relacionado com vários benefícios à saúde como a diminuição no risco do desenvolvimento de câncer de cólon. A FA não é digerida pelas enzimas digestivas do trato gastrointestinal sendo fermentada pela microbiota intestinal do cólon. Como subproduto do processo de fermentação há a liberação de ácidos graxos de cadeia curta (SCFA) - como o butirato, o propionato e o acetato. Além do processo de fermentação, a FA pode interagir diretamente com as células epiteliais do intestino, induzindo mecanismos que também podem estar relacionados com os benefícios associados ao consumo de FA. A falta de informação sobre a FA e o câncer de cólon é, em partes, devido à complexidade de ambos, tanto do câncer quanto da estrutura da FA. As FA do mamão papaia são derivadas da parede celular da fruta apresentando diferentes estruturas dependendo do ponto de amadurecimento do fruto. Esse fato ocorre, pois, durante o amadurecimento do mamão papaia, existe uma extensa hidrólise dos polissacarídeos presentes na parede celular, diminuindo rapidamente a firmeza da polpa do fruto. Devido à falta de informações sobre FA e seus efeitos benéficos à saúde humana que são dependentes da sua estrutura, bem como a possibilidade do amadurecimento do mamão papaia naturalmente modificar as FA presentes na polpa dos frutos, a presente tese teve como principais objetivos: 1) avaliar como as enzimas que degradam a parede celular do mamão papaia afetam a solubilização e o peso molecular da parede celular do fruto; 2) investigar os efeitos diretos da pectina derivada de mamões verdes e maduros em linhagens de células de câncer, na interação com a galectina-3, e em células do tipo HEK que expressam receptores de reconhecimento de padrões (RRP); 3) avaliar a fermentação colônica humana in vitro utilizando as FA de mamões verdes e maduros; 4) avaliar em ratos com lesões pré-neoplásicas no cólon o efeito do consumo de ração com ou sem FA de mamões papaias verdes e maduros. As endopoligalacturonases foram relacionadas como as principais enzimas que atuam solubilizando a pectina da parede celular do mamão, afetando tanto a firmeza da polpa do fruto quanto a solubilização da pectina durante o amadurecimento. De modo geral, as FA dos mamões exerceram um efeito estruturadependente de acordo com a maturação do fruto. Nos experimentos utilizando linhagens de células de câncer, a pectina do mamão papaia maduro apresentou efeitos mais pronunciados na indução da morte e na inibição da migração e da agregação das células, bem como ativando os RRP, como por exemplo, os receptores do tipo toll-like, além de inibir a proteína pró-metastática galectina-3. As FA dos mamões também apresentaram diferentes resultados na fermentação colônica in vitro quanto à utilização das FA pelas bactérias do intestino, e também no perfil de crescimento dessas bactérias. Por fim, os animais que receberam a dieta com as FA dos mamões maduros apresentaram menor incidência de focos de criptas aberrantes do que os animais que receberam as FA provenientes de mamões verdes ou de celulose (FA da ração AIN-93G). Portanto, o estudo das FA dos mamões foi efetuado tanto durante o amadurecimento dos mamões quanto dos seus efeitos biológicos in vitro e in vivo, tendo gerado resultados inéditos relacionando as alterações bioquímicas endógenas dos frutos durante o amadurecimento com os possíveis efeitos benéficos da sua ingestão para a saúde humana.

Durante o amadurecimento ocorrem profundas alterações na composição química dos frutos e a expressão gênica desempenha papel fundamental no controle desse processo. Apesar da importância comercial do mamão, as informações a respeito da expressão gênica durante o amadurecimento são limitadas. Assim, nessa tese, técnicas de estabelecimento de perfis de RNA mensageiro, como Differential Display-PCR, cDNA-AFLP e Cross-Species Microarray, foram aplicadas para a identificação de genes com expressão alterada. Alguns genes ligados ao metabolismo e transporte de açúcares, de lipídeos e carotenóides, à degradação de parede celular e stress, e fatores de transcrição dependentes e independentes de hormônios vegetais pareceram apresentar diferenças de expressão durante o amadurecimento do mamão papaia. O isolamento dos genes diferencialmente expressos permitiu traçar um panorama da expressão gênica do fruto e, dessa maneira, a relação das funções dos genes com o amadurecimento do mamão contribuiu para o aumento do entendimento acerca da qualidade pós-colheita do fruto. / Ripening affects the quality of fleshy fruits by changing the chemical composition, and gene expression regulates most part of these transformations. Although papaya fruit is an important Brazilian crop, there are restricted studies concerning its ripening and gene expression. In this work, it is described the use of some RNA profiling techniques, such as Differential Display-PCR, cDNA-AFLP and Cross-Species Microarray, to identify ripening-related genes in papaya fruit. Using these techniques, some differentially expressed genes during papaya fruit ripening were isolated. Their functions were associated with metabolism and transport of sugars, lipids and carotenoids, cell wall disassembly, stress and transcription factors dependent and independent of plant hormones. In this way, it was proposed a pattern of gene expression during papaya fruit ripening, at least for those isolated genes, and the assemblage of these data with other authors data can locate fruit handling to a better level, minimizing postharvest losses and increasing papaya fruit shelf-life.

Durante o amadurecimento ocorrem profundas alterações na composição química dos frutos e a expressão gênica desempenha papel fundamental no controle desse processo. Apesar da importância comercial do mamão, as informações a respeito da expressão gênica durante o amadurecimento são limitadas. Assim, nessa tese, técnicas de estabelecimento de perfis de RNA mensageiro, como Differential Display-PCR, cDNA-AFLP e Cross-Species Microarray, foram aplicadas para a identificação de genes com expressão alterada. Alguns genes ligados ao metabolismo e transporte de açúcares, de lipídeos e carotenóides, à degradação de parede celular e stress, e fatores de transcrição dependentes e independentes de hormônios vegetais pareceram apresentar diferenças de expressão durante o amadurecimento do mamão papaia. O isolamento dos genes diferencialmente expressos permitiu traçar um panorama da expressão gênica do fruto e, dessa maneira, a relação das funções dos genes com o amadurecimento do mamão contribuiu para o aumento do entendimento acerca da qualidade pós-colheita do fruto. / Ripening affects the quality of fleshy fruits by changing the chemical composition, and gene expression regulates most part of these transformations. Although papaya fruit is an important Brazilian crop, there are restricted studies concerning its ripening and gene expression. In this work, it is described the use of some RNA profiling techniques, such as Differential Display-PCR, cDNA-AFLP and Cross-Species Microarray, to identify ripening-related genes in papaya fruit. Using these techniques, some differentially expressed genes during papaya fruit ripening were isolated. Their functions were associated with metabolism and transport of sugars, lipids and carotenoids, cell wall disassembly, stress and transcription factors dependent and independent of plant hormones. In this way, it was proposed a pattern of gene expression during papaya fruit ripening, at least for those isolated genes, and the assemblage of these data with other authors data can locate fruit handling to a better level, minimizing postharvest losses and increasing papaya fruit shelf-life.

Thesis (M.Sc. Agriculture (Horticultrure)) -- University of Limpopo, 2017 / The current South African ‘Hass’ type avocado cultivars are inadequate to enhance competitiveness, cultivar diversity and profitability. In an effort to ensure competitiveness and maintain sustainability, the Agricultural Research CouncilInstitute for Tropical and Subtropical Crops (ARC-ITSC) as one the South African Avocado Industry’s (SAAI) main stakeholder, has bred and selected new superior ‘Hass’ type avocado selections. However, the cold storage potential and associated physico-chemical ripening properties of these selections (‘Jalna’, ‘OA 184’ and ‘Balboa’) have not been documented. Therefore, the objective of this study was to evaluate the effect of cold storage on internal and external physico-chemical ripening variables of the new ‘Hass’ type avocado selections. New ‘Hass’ type avocado fruit maturity was evaluated using moisture content, thereafter, harvested, sorted, graded and stored under two temperature regimes (2.0°C and 5.5°C) for 28 days to simulate export conditions. The experiment was a completely randomised factorial design with three treatment factors; temperature regimes (2.0°C and 5.5°C), days to ripening and ‘Hass’ type avocado selections fruit and control (commercial ‘Hass’) replicated three times. After withdrawal from cold storage, fruit were ripened at ambient temperature and evaluated for electrical conductivity, external chilling injury, fruit water loss, skin colour change, ripening percentage, firmness, respiration rate and seed:fruit weight ratio. Results indicated that treatment factors had no significant effect on moisture content (P=0.733) and chilling injury (P=0.776). Treatment factors had a significant effect on electrical conductivity (P=0.004), skin colour parameters; eye colour (P<0.001), hue angle (P<0.001), lightness (P=0.011) and chroma (P=0.042). Selection ‘Jalna’ fruit started changing colour whilst in storage (2.0°C and 5.5°C). Furthermore, ‘Hass’ type avocado selection fruit followed a declining pattern for lightness, chroma and hue angle in agreement with commercial ‘Hass’. Moreover, results indicated that treatment factors had a significant effect (P<0.001) on respiration rate, fruit firmness, ripening percentage and seed:fruit weight ratio. Selection ‘Jalna’ and ‘OA 184’ desynchronised mesocarp softening with exocarp due to genetically non-softening exocarp. Treatment factors had no significant effect (P=0.998) on fruit water loss during ripening. Selection ‘OA 184’ fruit showed export potential due to its good storage, ripening physico-chemical and shelf-life properties. Studies on cold sterilisation would add more value on generated scientific information, as such would enable the SAAI to gain access to high paying export markets. In addition, the selections should be planted and evaluated in other avocado producing region