Ph.D. (Agriculture)) -- University of Limpopo, 2021 / The rind physiological disorders incidence such as rind pitting is a challenge to the citrus industry as it affects appearance; and ultimately, acceptability and purchase in both local and international markets. Although the internal quality is not directly affected by rind pitting, fruit damaged by this disorder are rejected in the fresh fruit market. The susceptibility to this disorder varies among citrus fruit cultivars. Other factors impacting rind physiological disorders include; pre-harvest environmental conditions and postharvest storage conditions. However, the main cause of this disorder is still unknown. In South Africa, ‘Benny’ valencias are the most prone orange cultivars to rind pitting disorder within the sweet-orange-type. Therefore, the aim of this study was to investigate production site and postharvest treatments’ effect on physico-chemical, biochemical properties, antioxidants, rind soluble sugars and gene expression in relation to rind pitting development of ‘Benny’ valencia citrus fruit. During 2016 and 2017 seasons, the study was conducted, whereby, ‘Benny’ valencia citrus fruit were harvested from Tzaneen, Groblersdal and Musina in South Africa. After harvesting, the fruits were transported to the Agricultural Research Council- Tropical and Subtropical Crops (ARC-TSC) postharvest laboratory in Nelspruit for sorting, grading treatment, cold storage and post-storage quality evaluation. After sorting and grading, fruits were subjected to the following treatments: T1 = no wax plus dehydration, T2 = wax plus dehydration and T3 = wax plus no dehydration. Dehydrated treatments were applied for 3 days at relative humidity of ±45%, thereafter, fruit were stored at -0.6 and 4.5°C for 28 days plus 7 days shelf-life. After removal from cold storage plus 7 days shelf-life, fruit were analysed for rind pitting incidence (RPI), weight loss percentage (WL), firmness, total electrolyte leakage (TEL), total soluble solids (TSS), titratable acidity (TA) and TSS: TA ratio. xxvi Afterwards, fruit were peeled to remove flavedo, thereafter; the flavedo peels were freeze-dried, milled and stored at -21°C for further physiological analysis. Freeze dried flavedo peel was analysed for total flavonoids, total phenolics, vitamin C, soluble sugars (glucose, fructose and sucrose), antioxidant assays (FRAP, DPPH, ABST and ORAC) and genes. The results showed that rind pitting incidence was high on fruit subjected to wax plus no dehydration across all storage temperatures and production sites. Furthermore, results showed that fruit harvested from Musina exposed to T1 had higher incidence of rind pitting than those from Groblersdal and Tzaneen, irrespective of storage temperature. Meanwhile, fruit harvested from Musina had the highest TEL when compared with Groblersdal and Tzaneen irrespective of treatments and storage temperatures. A significantly higher (P<0.05) WL was observed in Musina fruit harvested from Tzaneen exposed to T3 at both storage temperatures. Moreover, increased TSS was observed after storage across all production site and postharvest treatments. The study showed that production site and postharvest treatments had a significant influence on rind pitting and total electrolyte leakage. Additionally, fruit treated with no wax + dehydration was found to be more susceptible to rind pitting. However, fruit sourced from Tzaneen had significantly (P<0.0001) high TPC and TFC, irrespective of postharvest treatments therefore, low rind pitting incidence. While rind vitamin C was higher in fruit from Groblersdal when compared with Tzaneen and Musina. However, low RPI was also observed in fruit sourced from Groblersdal. Fruit from Musina subjected to wax plus dehydration had higher RSA and low RPI at both temperatures when compared with fruit sourced from Groblersdal and Tzaneen. Therefore, wax plus dehydration resulted in low rind pitting with an increased accumulation of rind biochemical concentrations, xxvii irrespective of cold storage temperatures. These results suggested that there is a link between rind pitting and rind biochemical concentrations in the ‘Benny’ valencia citrus fruit. Moreover, fruit from Musina subjected to wax plus dehydration had higher antioxidant measured by DPPH and low RPI at both low storage temperatures when compared with fruit harvested from Groblersdal and Tzaneen. Furthermore, fruit harvested from Musina and treated with no wax plus dehydration, thereafter, stored at -0.6°C had low RPI with high antioxidant activity measured by FRAP than Tzaneen and Groblersdal regions in both seasons. With respect to sugars, fructose was not significantly (P<0.05) affected by production sites, postharvest treatments and cold storage temperature, hence, the low pitting incidence. The highest glucose was observed in fruit harvested from Groblersdal, irrespective of treatments and cold storage temperatures when compared with those from Tzaneen and Musina, low RPI was also observed in fruit harvested from Groblersdal. However, fruit harvested from Groblersdal treated with wax plus dehydration and stored at 4.5°C had higher sucrose and low RPI when compared with Tzaneen and Musina. Moreover, this study suggested that soluble sugars in ‘Benny’ valencia flavedo during cold storage is involved in rind pitting tolerance mediated by wax plus dehydration treatment. Three homologic genes: CsCP gene; CsNAC-domain protein gene; CsCP-F gene; were chosen to examine the relationship between their expression and citrus rind pitting through quantitative RT-PCR analysis in pitting and no-pitting fruits. Results showed that the expression of CsCP, CsNAC and CsCP-F genes were all higher in the pitting rind fruit harvested from Tzaneen and low in fruit with low pitting. Groblersdal and Musina fruit had low expression of genes and low rind pitting was observed. Therefore, findings suggested that CsCP, CsNAC and CsCP-F genes may xxviii be linked to non-chilling rind pitting and could serve as targets for future investigation. Generally, the overall results obtained in this study provided an understanding into the previous unknown complexities of citrus non-chilling rind pitting. Moreover, the study revealed that the studied factors had an influence on non-chilling rind pitting and physico-chemical properties of ‘Benny’ valencia citrus fruit. In addition, postharvest treatments resulted in low non-chilling rind pitting with an increased accumulation of rind biochemical concentrations. The fruit with high antioxidant capacity were found to be tolerant to rind pitting, whereas, fruit with low antioxidant capacity were found to be susceptible to rind pitting. Furthermore, soluble sugars are believed to be involved in the defence mechanisms against non-chilling rind pitting in the fruit. Gene expression changes also provided clues about the possible mechanisms involved in non-chilling rind pitting development. / National Research Fund, Agricultural Research Council Tropical and Subtropical Fruit Crops and Citrus Academy

Made available in DSpace on 2016-06-02T19:05:40Z (GMT). No. of bitstreams: 1 2695.pdf: 5053010 bytes, checksum: 2e6ff8d79ec3a3f85928bc9486a54956 (MD5) Previous issue date: 2009-09-28 / This dissertation presents the development of a computer vision system for bananas (Musa sapientum) analysis in post-harvest stage based on digital image processing techniques. The development used considerations about image acquisition, pre-processing, identification based on texture, percentage of brown spots and injuries on the fruits and classification of its maturity levels. The validation has been developed considering geometric patterns generated in laboratory, as well as real fruits. With the texture map it was possible to identify the existence of brown spots or injuries in a specific region of the images. The assessment of the level of maturation was performed considering both human observers and the computer vision system. The average of identification level of maturity was equal to 50% for human observers and 100% for computer vision. The results show identification rates of 80.40% for brown spots on the single image of banana, 97.70% for brown spots on the images of bundle of bananas, 97.80% for injuries for the set of single image of banana, and 75.30% for hand injuries considering the images of bundle of bananas. Besides, the method presents application for quality assessing of fruits in the post-harvest procedures. / Este trabalho apresenta o desenvolvimento de um sistema de visão computacional para análise de bananas (Musa sapientum), em estágio de pós-colheita, utilizando técnicas de processamento digital de imagens. Para o desenvolvimento foram consideradas as etapas de aquisição das imagens, pré-processamento, identificação baseada em textura, classificação em níveis de maturação e a obtenção do percentual de manchas marrons e injúrias. A validação foi desenvolvida considerando padrões geométricos gerados em laboratório, bem como considerando frutas reais. A obtenção do mapa de textura viabilizou a identificação da existência de manchas marrons ou injúrias em uma região da imagem. A avaliação método de classificação em nível de maturação foi realizada considerando os resultados obtidos com observadores humanos e visão computacional. A média da taxa de acerto dos observadores foi de 50% e a taxa de acerto da visão computacional foi de 100%. Além disso, os resultados da análise de manchas marrons e injúrias indicam uma taxa de acerto de 80,40% para manchas marrons em imagem de banana individual, 97,70% para manchas marrons em imagem de penca de bananas, 97,80% para injúrias em imagem de banana individual e 75,30% para injúrias em imagem de pencas. Adicionalmente, o desempenho global do sistema motiva a aplicação desta metodologia para avaliação da qualidade dos frutos no pós-colheita de bananas.

Made available in DSpace on 2015-03-26T13:36:38Z (GMT). No. of bitstreams: 1 texto completo.pdf: 399295 bytes, checksum: 3f7a6b3857d3216713ce9233ed752433 (MD5) Previous issue date: 2009-02-18 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Vegetables like leaves of tannia are subject to various factors which cause deterioration. Among these factors, mechanical damage triggers a series of physiological responses that occur at the site of the injury and surrounding tissues. The objective of this study was to evaluate the physiological responses of tannia leaves mechanical damaging, and whether these responses can be transmitted to tissues surrounding the site of injury. For this, the leaves were harvested and mechanical injuries were inflicted by using a needle. To verify that the changes resulting from injury extending to the region adjacent to the site of the damage were drilling, forming concentric circles of 3 diameters: 0.6 cm, circle A, located the needle injured area and 1.1 (B ) and 1.6 (C) cm around the circle, forming concentric rings. As control, was used the undamaged region from the leaf lamina. After 2, 4 and 6 hours of damaging, the discs were removed for the analysis of ethylene and CO2 production. The samples were also used for the assessment of weight loss, accumulation of soluble phenolic compounds, activity of phenylalanine ammonia lyase (PAL), total soluble sugars, non-reducing and reducing sugars, and starch after 30 minutes, 2, 4 and 6 hours of injury. Chlorophyll content was also determined after 30 minutes, 24, 48 and 72 hours. Intact and damaged discs were unfiltered with ACC to evaluate the activity of ACC oxidase and production of CO2, measured after 2, 4 and 6 hours of the tissue being damaged. The injury stimulated ethylene production by 39% in the disc B and 41% in CO2 production in the disc A, 6 hours after inflicting the damage. The experiment showed that addition of ACC induced an increase of 62% in ethylene production 4 hours after the injury and an increase of 40% in CO2 production in damaged discs. But, in the absence of ACC respiration was increased up to 4- fold in the injury discs. As the percentage of fresh matter, the injured discs showed lower percentage of mass compared to controls, from 2 hours after the damage, until the end of the experiment, and the reduction was more intense in the circle A; however, there was not a consistent reduction in the level of chlorophyll induced by the damage. The accumulation of phenols was stimulated after 4 and 6 hours after the treatment, especially in the damaged disc A, which showed 44 and 50% more soluble phenolic compounds compared to control discs, respectively at 4 and 6 hours. There was increase in the activity of PAL in the damaged disc A in all the analyzed times. The content of total soluble sugars, non-reducing sugar and starch were higher in damaged discs throughout the experiment. The levels of reducing sugars were higher in the damaged discs, allowing to suggest that occurred higher consumption of reserves at the site of injury, where the respiratory rate was also higher, however, this consumption was not sufficient to cause a depletion of carbohydrates in the damaged discs. / Produtos hortícolas, como a taioba, estão sujeitos a vários fatores que causam a deterioração. Dentre esses fatores, o dano mecânico desencadeia uma série de respostas fisiológicas que podem ocorrer no sítio da injúria e nos tecidos adjacentes. O objetivo deste trabalho foi avaliar as respostas fisiológicas em folhas de taioba danificadas, e se essas respostas podem ser transmitidas aos tecidos próximos do local da injúria. Para isto, folhas de taioba foram colhidas e injúrias físicas foram provocadas com o uso de uma agulha. Para verificar se as alterações resultantes da injúria se estendiam para a região vizinha ao local do dano foram feitas perfurações, formando círculos concêntricos de 3 diâmetros: 0,6 cm, círculo A, onde se localizavam os furos de agulha e 1,1 (B) e 1,6 (C) cm em torno do círculo A, formando anéis concêntricos. Como controle foi utilizada a região não danificada da folha. Após 2, 4 e 6 horas da realização do dano foram retiradas amostras para análise da produção de etileno e CO2. Amostras para avaliação da porcentagem de massa de matéria fresca, acúmulo de compostos fenólicos solúveis, atividade da enzima fenilalanina amônia liase (PAL), açúcares solúveis totais, não redutores, redutores e amido foram retiradas após 30 minutos, 2, 4 e 6 horas da imposição dos tratamentos; e o teor de clorofila foi verificado após 30 minutos, 24, 48 e 72 horas. Discos intactos e injuriados mecanicamente foram embebidos com ACC para análise da atividade da enzima ACC oxidase e da produção de CO2. Amostras foram retiradas após 2, 4 e 6 horas da realização do dano. O dano estimulou a produção de etileno em 39% no disco B e em 41% a produção de CO2 no disco A, 6 horas após a realização da injúria. No experimento com ACC após 4 horas, o dano induziu aumento de 62% na produção de etileno e de 40% na respiração. Porém, na ausência de ACC, houve estímulo da respiração de até 4 vezes nos discos injuriados. Quanto à porcentagem de massa de matéria fresca, constatamos que os discos injuriados, a partir de 2 horas, apresentaram menores porcentagens de massa comparados aos controles e que esta redução foi mais intensa no círculo A, entretanto, não houve uma consistente redução no teor de clorofila devido ao dano. Após 4 e 6 horas da realização do dano, ocorre estímulo ao acúmulo de fenóis, principalmente no disco A danificado, que apresentou 44 e 50% mais compostos fenólicos solúveis que o controle, respectivamente. Também se verificou maior atividade da PAL no disco A danificado, em todas as horas analisadas. O teor de açúcares solúveis totais, não redutores e amido foram maiores nos discos danificados durante todo o experimento. Já os teores de açúcares redutores foram maiores no disco A danificado, nos permitindo sugerir que há consumo de reservas no local da injúria, onde a taxa respiratória também foi maior, entretanto, esse consumo não é suficiente para se verificar esgotamento de carboidratos nos discos danificados.