Thesis (MScAgric)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: Citrus fruit exported from South Africa to markets such as the USA and China undergo a mandatory 24 day exposure of -0.6°C during shipment to kill any insect larvae in the fruit, however, this protocol causes chilling injury (CI). The aim of this study was firstly to determine the influence of various preharvest factors on chilling sensitivity. In addition, Near-Infrared (NIR) spectroscopy was tested as a potential management tool to identify variation in CI susceptibility of fruit and lastly the efficacy of thiabendazole (TBZ) applied in the packline to reduce CI was determined. Various factors influence the susceptibility of a navel orange fruit to CI including cultivar, micro-climate, harvest date, fruit size and rind colour. In this study it was found that ‘Washington’ was more susceptible to CI compared to ‘Navelina’ navel orange. Fruit from the coldest part of Citrusdal (Tharakama) had the highest incidence of CI, which concurred with literature. The incidence of CI was overall less when fruit were harvested in the middle of the commercial harvest window; however, the internal maturity at harvest does not appear to be related to the sensitivity of orange fruit to CI. Near infrared (NIR) spectroscopy was tested as a potential tool to predict fruit quality parameters in relation to CI. Analysing the NIR data with principal components analysis (PCA), score plots were obtained that separate fruit in clusters from the inside and outside of the canopy positions as well as different sizes and rind colours (green vs. orange). However, analysing data with partial least square regression (PLS) using fruit quality parameters (firmness, rind colour and mass), the NIR spectra obtained with the integrated sphere did not provide a good prediction model for CI index. Thiabendazole (TBZ) is reported to reduce the incidence of CI of citrus fruit and this fungicide was applied in a semi-commercial packline in the wax as well as the drench. The results of the application of different fungicides from the TBZ chemical group indicated that the TBZ dip treatments had the highest efficacy in reducing both the incidence and severity of CI and in addition were more effective when applied in warm (40°C) than cold water (10°C). Applications at the commercial recommended rate (20mL.L-1 and half of the commercial recommended rate were both effective in reducing the incidence of CI. Wax application was effective in reducing the incidence of CI however, the application of TBZ in the wax reduced the incidence of CI even more. For the successful reduction of CI incidence in commercial shipments of citrus fruit the focus should not be on a single factor but rather a strategy that encompasses pre-harvest factors that would influence rind quality as well as specific postharvest technologies know to decrease the impact of CI. / AFRIKAANSE OPSOMMING: Sitrus vrugte ondergaan 'n verpligte 24 dae blootstelling aan -0,6°C om moontlike insek-larwes te dood gedurende die uitvoer na markte soos die VSA en China, maar hierdie protokol veroorsaak koueskade. Die doel van hierdie studie was eerstens om die invloed van verskillende voor-oes faktore op koueskade-sensitiwiteit van nawel lemoene te bepaal. Daarbenewens is naby-infrarooi (NIR) spektroskopie as 'n potensiële tegniek getoets om variasie in koueskade-sensitiwiteit van nawel lemoene te identifiseer, en laastens is die effektiwiteit van thiabendazole (TBZ) toediening in die verpakkings lyn, om koueskade te verminder, ondersoek. Verskillende faktore soos kultivar, mikroklimaat, oesdatum, vruggrootte en skilkleur beïnvloed die koueskade-sensitiwiteit van sitrus. Hierdie studie het bevind dat die ‘Washington’ meer sensitief is vir koueskade as die ‘Navelina’ nawels. Vrugte afkomstig uit die koudste deel van Citrusdal (Tharakama) het die hoogste voorkoms van koueskade. In die algemeen was vrugte ge-oes in die middel van die kommersiële-venster die minste koueskade-sensitief, maar interne rypheid hou nie verband met koueskadesensitiwiteit nie. Naby-Infrarooi (NIR) spektroskopie is getoets as 'n potensiële instrument om vrugkwaliteit parameters te voorspel met betrekking tot koueskade. Deur ontleding van die NIR data met behulp van ‘Principal Components Analysis’ kon vrugte groepeer word volgens posisie (binne vs. buite blaredak), groottes en skilkleur. Deur ‘Partial Least Square Regression’ verdere data ontleding en met inagneming van vrugkwaliteit parameters (fermheid, skil kleur en massa), kon die NIR spektra wat verkry was egter nie 'n goeie voorspelling model vir koueskade verskaf nie. TBZ verminder die voorkoms van koueskade van sitrusvrugte na dit toegedien was in 'n semi-kommersiële verpakkingslyn in die waks, ‘drench’ of baddens. Die toediening van verskillende swamdoders van die TBZ chemiese groep in baddens, het aangedui dat die TBZ doop behandeling effektief was om die voorkoms van koueskade te verminder. Daarbenewens was TBZ meer effektief in verlaging van koueskade as dit toegedien word in warm (40°C) as koue (10°C) water, asook teen die volle (20mL.L-1) en die helfte van die aanbevole kommersiële dosis. Wakstoediening was effektief in die vermindering van die voorkoms van koueskade en byvoeging van TBZ in die waks het die effektiwiteit verhoog. Die suksesvolle vermindering van koueskade tydens kommersiële verskeping van sitrusvrugte moet egter nie fokus op 'n enkele faktor nie, maar op 'n strategie wat bestaan uit voor-oes faktore wat die vrugskil kwaliteit beïnvloed, sowel as spesifieke na-oes tegnologieë en hanteringsprotokolle wat bekend is vir die vermindering van koueskade. / Citrus Research International

Mamões \'Golden\' possuem importância econômica e social no Brasil com destaque dentre as frutas mais exportadas e consumidas. Porém, possuem curta vida útil e distintos comportamentos pós-colheita, bem como distúrbio do amolecimento precoce (DAP) com ocorrência esporádica. Isso culmina na dificuldade em alavancar as pesquisas de tecnologias de conservação. A hipótese de que o DAP tenha como causa fatores pré-colheita e o desbalanço hormonal, envolvendo a auxina (AIA), implicou no desenvolvimento deste estudo. Dentro deste contexto, o objetivo deste trabalho foi investigar o comportamento dos mamoeiros \'Golden\' diante de adversidades climáticas, simuladas com excesso de irrigação, e diante do desbalanço hormonal, induzido pela aplicação pré-colheita de reguladores vegetais. Para tal propósito o projeto foi desenvolvido em três etapas. A primeira foi com a avaliação do comprometimento fotossintético e nutricional de mamoeiros \'Golden\' em função de condições climáticas e estresse hídrico. A segunda foi com a avaliação física, química, fisiológica e níveis de AIA dos mesmos mamões \'Golden\' da primeira etapa. E a terceira foi com análise dos frutos na pós-colheita após aplicação de reguladores vegetais na pré-colheita [1-metilciclopropano (1-MCP), etefon e ácido 2,3,5-triiodo benzoico (TIBA)]. Na primeira e segunda etapa os mamoeiros foram conduzidos na região norte do Espírito Santo durante os meses de maio e outubro de 2012. Os tratamentos com lâminas de irrigação foram: controle = 33 mm de água e excesso = 70,6 mm de água durante 5 a 7 dias aplicados mensalmente. A atividade fotossintética e a nutrição mineral foram avaliadas logo após os tratamentos. Os frutos para avaliação na segunda etapa foram colhidos após 5 ou 7, 20 e 30 dias. As avaliações dos frutos foram durante 12 dias a 10 ± 1ºC e 85 ± 5% de UR. Na terceira etapa os mamoeiros foram conduzidos entre abril de 2012 e maio de 2013 em área experimental da ESALQ/USP em Piracicaba/SP. Os reguladores vegetais foram aplicados quando os frutos atingiram 120 dias após a antese. Os frutos foram colhidos quando a cor da casca atingiu o estádio 1 e foram analisados no estádio 5. Diante das duas primeiras etapas foi possível observar que as plantas e os frutos dos mamoeiros não apresentaram o DAP pelo excesso de água isoladamente, mas sim por um conjunto de fatores como temperaturas elevadas, altos índices pluviométricos, alto déficit de pressão de vapor e desbalanço nutricional. Porém, houve comprometimento do aparato fotossintético identificado, principalmente, pelo teste transiente da clorofila a, redução dos níveis de AIA e de 1-aminociclopropano-1-ácido carboxílico (ACC) naqueles frutos com excesso de irrigação. Os resultados da terceira etapa demonstraram que a formação fisiológica dos frutos tem relação com os graus dias acumulados e que as mudanças no comportamento pós-colheita, possivelmente, ocorrem em maior proporção em função dos teores de etileno endógeno do que dos teores de AIA livre. / \'Golden\' papayas have economic and social importance in Brazil, especially among the most exported and consumed fruit. However, have a short shelf life and postharvest distinct behaviors, as well as sporadic occurrence of \"early softening disorder\" (ESD). This culminates in difficulty leveraging research conservation technologies. The hypothesis that ESD has a cause preharvest factors and hormonal imbalance involving auxin (IAA) resulted in the development of this study. Within this context, the aim of this study was to investigate the behavior of papaya \'Golden\' before climatic adversities, simulated with excessive irrigation, and before the hormonal imbalance induced by preharvest application of plant growth regulators. For this purpose the project was developed in three stages. The first was to review the photosynthetic and nutritional impairment of papaya \'Golden\' due to climatic conditions and drought stress. The second was with the physical, chemical, and physiological assessment of these levels IAA \'Golden\' papaya the first step. And the third was to analyze the fruits after application of plant growth regulators on preharvest [methylcyclopropane - 1 (MCP - 1), ethephon and 2,3,5 - triiodo benzoic acid (TIBA)]. In the first and second stage, papayas were conducted in the northern region of the Espírito Santo during the months of May and October 2012. The irrigation treatments were: control = 33 mm and excess water = 70.6 mm water for 5 or 7 days applied monthly. Photosynthetic activity and mineral nutrition were evaluated after treatments. Fruit for evaluation in the second stage were harvested after 5 or 7, 20 and 30 days. The fruits of the reviews were storage for 12 days at 10 ± 1 ºC and 85 ± 5 % RH. In the third stage, papayas were conducted between April 2012 and May 2013 in an experimental field of ESALQ/USP in Piracicaba/SP. Growth regulators were applied when fruit reached 120 days after anthesis. Fruit were harvested when the color of the shell reached the stage 1 and were analyzed in stage 5. Given the first two stages was observed that plants and fruit did not show ESD by excess water alone, but by a set of factors such as high temperatures, heavy rainfall, high vapor pressure deficit and nutritional imbalance. However, there was impairment of the photosynthetic apparatus identified mainly by the transient testing chlorophyll a reduction in the levels of IAA and a 1-aminocyclopropane-carboxylic acid 1 (ACC) in fruit over- irrigation. Third stage showed that physiological fruit formation is related to accumulated growing degree days and those changes in post-harvest behavior, possibly occur to a greater extent depending on the levels of endogenous ethylene than IAA free.

Mamões \'Golden\' possuem importância econômica e social no Brasil com destaque dentre as frutas mais exportadas e consumidas. Porém, possuem curta vida útil e distintos comportamentos pós-colheita, bem como distúrbio do amolecimento precoce (DAP) com ocorrência esporádica. Isso culmina na dificuldade em alavancar as pesquisas de tecnologias de conservação. A hipótese de que o DAP tenha como causa fatores pré-colheita e o desbalanço hormonal, envolvendo a auxina (AIA), implicou no desenvolvimento deste estudo. Dentro deste contexto, o objetivo deste trabalho foi investigar o comportamento dos mamoeiros \'Golden\' diante de adversidades climáticas, simuladas com excesso de irrigação, e diante do desbalanço hormonal, induzido pela aplicação pré-colheita de reguladores vegetais. Para tal propósito o projeto foi desenvolvido em três etapas. A primeira foi com a avaliação do comprometimento fotossintético e nutricional de mamoeiros \'Golden\' em função de condições climáticas e estresse hídrico. A segunda foi com a avaliação física, química, fisiológica e níveis de AIA dos mesmos mamões \'Golden\' da primeira etapa. E a terceira foi com análise dos frutos na pós-colheita após aplicação de reguladores vegetais na pré-colheita [1-metilciclopropano (1-MCP), etefon e ácido 2,3,5-triiodo benzoico (TIBA)]. Na primeira e segunda etapa os mamoeiros foram conduzidos na região norte do Espírito Santo durante os meses de maio e outubro de 2012. Os tratamentos com lâminas de irrigação foram: controle = 33 mm de água e excesso = 70,6 mm de água durante 5 a 7 dias aplicados mensalmente. A atividade fotossintética e a nutrição mineral foram avaliadas logo após os tratamentos. Os frutos para avaliação na segunda etapa foram colhidos após 5 ou 7, 20 e 30 dias. As avaliações dos frutos foram durante 12 dias a 10 ± 1ºC e 85 ± 5% de UR. Na terceira etapa os mamoeiros foram conduzidos entre abril de 2012 e maio de 2013 em área experimental da ESALQ/USP em Piracicaba/SP. Os reguladores vegetais foram aplicados quando os frutos atingiram 120 dias após a antese. Os frutos foram colhidos quando a cor da casca atingiu o estádio 1 e foram analisados no estádio 5. Diante das duas primeiras etapas foi possível observar que as plantas e os frutos dos mamoeiros não apresentaram o DAP pelo excesso de água isoladamente, mas sim por um conjunto de fatores como temperaturas elevadas, altos índices pluviométricos, alto déficit de pressão de vapor e desbalanço nutricional. Porém, houve comprometimento do aparato fotossintético identificado, principalmente, pelo teste transiente da clorofila a, redução dos níveis de AIA e de 1-aminociclopropano-1-ácido carboxílico (ACC) naqueles frutos com excesso de irrigação. Os resultados da terceira etapa demonstraram que a formação fisiológica dos frutos tem relação com os graus dias acumulados e que as mudanças no comportamento pós-colheita, possivelmente, ocorrem em maior proporção em função dos teores de etileno endógeno do que dos teores de AIA livre. / \'Golden\' papayas have economic and social importance in Brazil, especially among the most exported and consumed fruit. However, have a short shelf life and postharvest distinct behaviors, as well as sporadic occurrence of \"early softening disorder\" (ESD). This culminates in difficulty leveraging research conservation technologies. The hypothesis that ESD has a cause preharvest factors and hormonal imbalance involving auxin (IAA) resulted in the development of this study. Within this context, the aim of this study was to investigate the behavior of papaya \'Golden\' before climatic adversities, simulated with excessive irrigation, and before the hormonal imbalance induced by preharvest application of plant growth regulators. For this purpose the project was developed in three stages. The first was to review the photosynthetic and nutritional impairment of papaya \'Golden\' due to climatic conditions and drought stress. The second was with the physical, chemical, and physiological assessment of these levels IAA \'Golden\' papaya the first step. And the third was to analyze the fruits after application of plant growth regulators on preharvest [methylcyclopropane - 1 (MCP - 1), ethephon and 2,3,5 - triiodo benzoic acid (TIBA)]. In the first and second stage, papayas were conducted in the northern region of the Espírito Santo during the months of May and October 2012. The irrigation treatments were: control = 33 mm and excess water = 70.6 mm water for 5 or 7 days applied monthly. Photosynthetic activity and mineral nutrition were evaluated after treatments. Fruit for evaluation in the second stage were harvested after 5 or 7, 20 and 30 days. The fruits of the reviews were storage for 12 days at 10 ± 1 ºC and 85 ± 5 % RH. In the third stage, papayas were conducted between April 2012 and May 2013 in an experimental field of ESALQ/USP in Piracicaba/SP. Growth regulators were applied when fruit reached 120 days after anthesis. Fruit were harvested when the color of the shell reached the stage 1 and were analyzed in stage 5. Given the first two stages was observed that plants and fruit did not show ESD by excess water alone, but by a set of factors such as high temperatures, heavy rainfall, high vapor pressure deficit and nutritional imbalance. However, there was impairment of the photosynthetic apparatus identified mainly by the transient testing chlorophyll a reduction in the levels of IAA and a 1-aminocyclopropane-carboxylic acid 1 (ACC) in fruit over- irrigation. Third stage showed that physiological fruit formation is related to accumulated growing degree days and those changes in post-harvest behavior, possibly occur to a greater extent depending on the levels of endogenous ethylene than IAA free.