Thesis (M. Sc. (Horticulture)) -- University of Limpopo, 2018 / ‘Hass’ avocado fruit changes skin colour from green to purple and then black during ripening. However, markets importing South African avocado fruit have been complaining about the ‘Hass’ skin colour not changing to purple/black during ripening. Thus, the study aimed to investigate the effect of tree girdling, harvest time and ripening temperature on ‘Hass’ avocado fruit skin colour development during ripening. The mature ‘Hass’ avocado fruit were harvested from girdled and non-girdled trees during early (April), mid- (May) and late (June) harvest times. Upon arrival, in the laboratory fruit were cold stored at 5.5°C for 28 days. After storage, fruit were ripened at 25, 21 and 16°C for 8, 6 and 4 days, respectively. After withdrawal from clod storage fruit were evaluated for skin colour development, ripening and physiological disorders (chilling injury). Fruit from girdled trees showed high maturity (low moisture content) when compared with fruit from non-girdled trees during early and mid-harvest. With respect to skin colour development, the results indicate that skin eye colour development of fruit from girdled and non-girdled trees minimally increased from emerald green (1) to olive green (3) across all harvest times, ripening temperature and ripening duration. However, late season fruit from non-girdled trees improved to purple (4) when ripened at 21°C when compared with fruit from girdled trees. In terms of objective colour, lightness, hue angle and chroma decreased for fruit from girdled and non-girdled trees, across all harvest times, ripening temperature and ripening duration. Lightness and hue angle of fruit from girdled trees were slightly reduced when compared with fruit from non-girdled trees, throughout all harvest times, ripening temperature and duration. Early and mid-season fruit harvested from girdled trees showed rapid decrease of chroma when compared with fruit from non-girdled trees, throughout ripening temperature and x duration. In terms of softening, fruit from girdled trees showed higher firmness loss and ripening percentage within 6 (16°C) and 4 (21 and 25°C) days when compared with fruit from non-girdled trees during early and mid-harvest, whereas, late harvest fruit from girdled trees reached higher ripening percentage and firmness loss within 4 days throughout ripening temperatures. With respect to cold damage, late harvested fruit from girdled trees showed higher external chilling injury when compared with non-girdled trees, throughout ripening temperature. In general, girdling treatment improved fruit maturity, ripening rate and firmness loss. However, the incidence of variable skin colouring of ‘Hass’ avocado fruit during ripening was also prevalent in early harvested fruit from girdled tree, irrespective of ripening temperature. Keywords: girdling, harvest time, physiological disorder, ripening temperature, variable colouring

Thesis (M.Sc. (Horticulture)) --University of Limpopo, 2018 / ‘Hass’ avocado fruit changes skin colour from green to purple and then black during ripening. However, markets importing South African avocado fruit have been complaining about the ‘Hass’ skin colour not changing to purple/black during ripening. Thus, the study aimed to investigate the effect of tree girdling, harvest time and ripening temperature on ‘Hass’ avocado fruit skin colour development during ripening. The mature ‘Hass’ avocado fruit were harvested from girdled and non-girdled trees during early (April), mid- (May) and late (June) harvest times. Upon arrival, in the laboratory fruit were cold stored at 5.5°C for 28 days. After storage, fruit were ripened at 25, 21 and 16°C for 8, 6 and 4 days, respectively. After withdrawal from clod storage fruit were evaluated for skin colour development, ripening and physiological disorders (chilling injury). Fruit from girdled trees showed high maturity (low moisture content) when compared with fruit from non-girdled trees during early and mid-harvest. With respect to skin colour development, the results indicate that skin eye colour development of fruit from girdled and non-girdled trees minimally increased from emerald green (1) to olive green (3) across all harvest times, ripening temperature and ripening duration. However, late season fruit from non-girdled trees improved to purple (4) when ripened at 21°C when compared with fruit from girdled trees. In terms of objective colour, lightness, hue angle and chroma decreased for fruit from girdled and non-girdled trees, across all harvest times, ripening temperature and ripening duration. Lightness and hue angle of fruit from girdled trees were slightly reduced when compared with fruit from non-girdled trees, throughout all harvest times, ripening temperature and duration. Early and mid-season fruit harvested from girdled trees showed rapid decrease of chroma when compared with fruit from non-girdled trees, throughout ripening temperature and x duration. In terms of softening, fruit from girdled trees showed higher firmness loss and ripening percentage within 6 (16°C) and 4 (21 and 25°C) days when compared with fruit from non-girdled trees during early and mid-harvest, whereas, late harvest fruit from girdled trees reached higher ripening percentage and firmness loss within 4 days throughout ripening temperatures. With respect to cold damage, late harvested fruit from girdled trees showed higher external chilling injury when compared with non-girdled trees, throughout ripening temperature. In general, girdling treatment improved fruit maturity, ripening rate and firmness loss. However, the incidence of variable skin colouring of ‘Hass’ avocado fruit during ripening was also prevalent in early harvested fruit from girdled tree, irrespective of ripening temperature. Keywords: girdling, harvest time, physiological disorder, ripening temperature, variable colouring

Made available in DSpace on 2015-03-26T13:36:42Z (GMT). No. of bitstreams: 1 texto completo.pdf: 807492 bytes, checksum: ecca2fba2120cf3ee786b7d412fce672 (MD5) Previous issue date: 2010-07-28 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Pruning is a key agronomic practice in coffee (Coffea canephora) plantation management, but little is known on a scientific basis about the ideal time to conduct it. Furthermore, studies associating variations in photosynthesis, as affected by the fruit ripening pattern, are missing in coffee. In this study, the effects of different pruning times, conducted between harvest and flowering, in clones of robusta coffee, displaying varying fruit ripening patterns (early, intermediate and late maturation periods), were examined by specifically evaluating growth, photosynthesis and starch accumulation. Treatments consisted of different pruning periods as follows: early maturation clones (03 and 67) were pruned at 0, 30, 60 and 90 days after fruit harvest (DAH); intermediate maturation clones (120 e 16) pruned at 0, 30 and 60 DAH; and late maturation clones (19 and 76) pruned at 0 and 30 DAH. The branch growth rate and gas exchange parameters (net photosynthesis rate, stomatal conductance and internal-to-atmospheric CO2 concentration ratio), maximum photochemical efficiency of photosystem II, and leaf starch concentration all were unaffected by the pruning treatments, regardless of clones. Other chlorophyll a fluorescence parameters were only marginally affected by pruning. On the other hand, some gas exchange variables and starch contents were altered in response to the fruit ripening patterns. The late maturation clones, compared to the other ones, showed lower net photosynthesis rates (~25%) and lower leaf starch content (~20%). In any case, for the late ripening clones, as their fruits have a longer grain-filling period and maturation time, their lower photosynthetic rates, starch content and leaf-to-fruit ratio could be offset, in the long-term, by their lower sink strength. In summary, the results suggest that is indifferent to perform the pruning immediately after fruit harvest, as usually recommended, or afterwards before flowering. / Embora a poda em lavouras de Coffea canephora seja uma prática necessária, pouco se sabe, em bases científicas, a respeito da época ideal para a sua realização. Ademais, em café, nenhum estudo foi feito, até o presente, tentando associar as variações da fotossíntese, em função do padrão de maturação de frutos. Procurou-se investigar, neste estudo, os efeitos de podas realizadas em diferentes épocas entre a colheita e a florada, em clones de café robusta, com distintos períodos de maturação de frutos (precoce, intermediário e tardio), avaliando-se, especificamente, o crescimento, a fotossíntese e o acúmulo de amido. Clones de maturação precoce (clones 03 e 67) foram podados em quatro diferentes épocas: 0, 30, 60 e 90 dias após a colheita (DAC); nos clones intermediários (120 e 16), a poda foi realizada aos 0, 30 e 60 DAC; nos tardios (19 e 76), realizou-se a poda aos 0 e 30 DAC. A taxa de crescimento de ramos e as trocas gasosas (taxa de fotossíntese líquida, condutância estomática e a razão entre as concentrações interna e ambiente de CO2) não foram afetadas pelos tratamentos de poda, independentemente do clone estudado. Não se verificou, também, efeitos da poda sobre as concentrações foliares de amido e sobre a eficiência fotoquímica máxima do fotossistema II. Outros parâmetros de fluorescência da clorofila a foram apenas afetados marginalmente pelos tratamentos de poda. As principais diferenças ora observadas dizem respeito às variáveis associadas à fotossíntese e aos teores de amido, em função, particularmente, do padrão de maturação dos frutos. Os clones de maturação tardia, comparados aos demais clones, exibiram menor taxa de fotossíntese líquida (~25%) e menor teor foliar de amido (~20%). Em todo o caso, nos clones de maturação tardia, como os frutos têm um período maior de enchimento e maturação, os menores valores da taxa fotossintética, de teores de amido e de razão área foliar/massa de frutos podem ser compensados, no longo prazo, pela menor força do dreno. Em suma, demonstrou-se que é indiferente proceder-se à poda imediatamente após a colheita, conforme usualmente recomendado, ou posteriormente, antes da florada.

Submitted by Luciana Ferreira (lucgeral@gmail.com) on 2015-11-19T12:44:41Z No. of bitstreams: 2 Dissertação - Ruver Rodriques Feitosa Ramalho - 2015.pdf: 3672502 bytes, checksum: 9452919a961824a1718a9111d9ee60ad (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2015-11-19T12:46:53Z (GMT) No. of bitstreams: 2 Dissertação - Ruver Rodriques Feitosa Ramalho - 2015.pdf: 3672502 bytes, checksum: 9452919a961824a1718a9111d9ee60ad (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) / Made available in DSpace on 2015-11-19T12:46:53Z (GMT). No. of bitstreams: 2 Dissertação - Ruver Rodriques Feitosa Ramalho - 2015.pdf: 3672502 bytes, checksum: 9452919a961824a1718a9111d9ee60ad (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) Previous issue date: 2015-09-23 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / The composition of essential oils and the content of phenolic compounds in fruits of three varieties of pitanga (fruits red, red-orange and purple) were analyzed for four ripening stages. The analysis of variance (two-way ANOVA) showed that the anthocyanins differ significantly between the three pitanga varieties, especially at the final stage. Levels of flavonoids varied during maturation differently for each variety, and only at the third stage the levels of these metabolites were similar for the three varieties. No differences were observed in tannin concentrations during fruit ripening and total phenols between the three varieties. Through analysis by GC/MS was possible to identify a total of 28 substances in essential oils of pitanga fruit. The red variety was characterized by the presence of germacrone (39.67-46.54%) curzerene (14.36- 15.75%) and atractylone (6.90-10.10%), while the red-orange presents as major compounds: selina-1,3,7(11)-trien-8-one (36.06-41.22%) and selina-1,3,7(11)-trien-8- one epoxide (19.36-34.28%). The purple variety contains germacrone (51.56-56.80%), curzerene (4.10-5.11%), atractylone (0.72-1.50%), selina-1,3,7(11)-trien-8-one (11.04- 14.31%) and selina-1,3,7(11)-trien-8-one epoxide (3.70-5.86%). Total sesquiterpenes are the major constituents of the fruits of the three varieties at all stages of maturation, and the oxygenated sesquiterpenes were more abundant in red and purple varieties, while hydrocarbons sesquiterpenes were dominant in the red-orange variety. Generally no significant differences were observed in the concentrations of the major volatile compounds of the three varieties during the period of maturation, only the orange-red variety showed variations in the total levels of sesquiterpenes and monoterpenes. It was concluded that the composition of essential oils and anthocyanin levels are the factors that distinguish the three varieties, while in relation to the ripening process the anthocyanins, flavonoids, phenolic compounds and some minor constituents of the oils have varied significantly. / A composição de óleos essenciais e os teores de compostos fenólicos em frutos de três variedades de pitanga (frutos vermelho, vermelho-laranja e roxo) foram analisados durante quatro estádios de maturação. A análise de variância (ANOVA two-way) mostrou que os teores de antocianinas diferem significativamente entre as três variedades de pitanga, principalmente no último estádio. Teores de flavonóides variaram durante a maturação de forma diferente para cada variedade e somente no terceiro estádio os níveis destes metabólitos foram iguais para as três variedades. Não foram observadas diferenças nas concentrações de taninos durante o amadurecimento dos frutos e de fenóis totais entre as três variedades. Através de análise por CG/EM foi possível identificar no total 28 substâncias nos óleos essenciais dos frutos de pitanga. A variedade vermelha foi caracterizada pela presença de germacrona (39,67-46,54%), curzereno (14,36-15,75%) e atractilona (6,90-10,10%), enquanto a variedade vermelhaalaranjada possui como compostos majoritários: selina-1,3,7(11)-trien-8-one (36,06- 41,22%) e epóxido de selina-1,3,7(11)-trien-8-one (19,36-34,28%). A variedade roxa contém tanto germacrona (51,56-56,80%), curzereno (4,10-5,11%) e atractilona (0,72- 1,50%) quanto selina-1,3,7(11)-trien-8-one (11,04-14,31%) e epóxido de selina- 1,3,7(11)-trien-8-one (3,70-5,86%). Os sesquiterpenos totais são os constituintes majoritários dos frutos das três variedades em todos os estádios de maturação, sendo que os sesquiterpenos oxigenados foram mais abundantes nas variedades vermelha e roxa, enquanto os hidrocarboneto sesquiterpênicos foram dominantes na variedade vermelha-alaranjada. Em geral não foram observadas diferenças significativas nas concentrações dos compostos voláteis majoritários das três variedades durante o período de maturação, somente a variedade vermelho-alaranjada apresentou variações nos teores totais de sesquiterpenos e monoterpenos. Concluiu-se que a composição dos óleos essenciais e os níveis de antocianinas são os fatores que mais distinguem as três variedades, em relação ao processo de amadurecimento dos frutos temos que antocianinas, flavonóides, fenóis totais e alguns constituintes minoritários dos óleos variaram de forma significativa.

A enzima sacarose-fosfato sintase foi parcialmente purificada de bananas fisiologicamente imaturas (70 dias após a antese), fisiologicamente maturas pré-climatéricas (110 dias após a antese) e climatéricas (130 dias após a antese). De acordo com os resultados apresentados a SPS de banana é uma enzima constituída de subunidade de 116 kD, apresentando peso molecular nativo de 440 kD por filtração em gel e bandas de 180, 240 e 686 kD por eletroforese em gel de poliacrilamida, nos três estágios estudados. Uma sequência parcial do gene da SPS foi amplificado através de PCR, donado e seu sequenciamento indicou que a enzima de banana apresenta elevada homologia com as de outras fontes vegetais. A análise dos níveis de proteina e mRNA durante o desenvolvimento e amadurecimento do fruto permitem correlacionar o aumento de atividade com o aumento na expressão do gene da SPS. Não foram observadas alterações significativas no estado de ativação, sugestivas de modificação covalente como mecanismo de ativação durante o amadurecimento. / Sucrose-phosphate synthase (SPS) was purified ITom bananas at different deveIopmental stages (70, 110 and 130 days after anthesis), corresponding to tissue with different composition. Banana SPS have a subunit of 116 kD and the native enzyme have a molecular weight around 440 kD by gel fiItration and bands of 180, 240 and 686 kD by eIectrophoresis in alI stages studied. A 952 base pair polymerase chain reaction product of SPS was cloned and showed that banana SPS has a high homology with the enzyme from other species. Enzyme activity, Protein and mRNA leveI point to an increase in SPS expression during ripening. The increase in SPS activity was not correlated to changes in the activation state. The results indicate that the increase in SPS expression is an important regulatory event during banana fruit ripening.

O amadurecimento é um processo complexo e geneticamente programado através do qual o fruto adquire características próprias (níveis de açúcar e acidez, cor, amaciamento, sabor e aroma, entre outras) que o torna atraente aos consumidores. O tomate (Solanum lycopersicum) tem sido largamente utilizado como modelo para os estudos sobre amadurecimento de frutos devido à sua importância nutricional e econômica e aos avanços no entendimento de sua genética e bioquímica. Neste fruto, um conjunto de 20 a 30 substâncias voláteis, entre álcoois, aldeídos, cetonas e ésteres, contribuem para o aroma, sendo elas derivadas principalmente de aminoácidos, ácidos graxos e carotenóides. O hormônio etileno está intimamente relacionado com as alterações metabólicas que ocorrem no amadurecimento, inclusive na geração desses compostos voláteis, através da ativação de fatores de transcrição que regulam genes codificadores de enzimas envolvidas nesse processo. Embora se saiba bastante a respeito da bioquímica que produz compostos de aroma e o envolvimento do etileno nesse processo, pouco se sabe sobre o mecanismo de sua regulação. Além disso, o etileno não é o único regulador do amadurecimento, pois há vários indícios de que as auxinas também estão envolvidas neste processo. Embora crescente, este campo ainda encontra-se pouco explorado quando comparado aos avanços obtidos sobre o papel do etileno no amadurecimento de frutos. Os dados são ainda mais escassos no que se refere a regulação das vias de biossíntese dos compostos voláteis. Assim, este trabalho visa avaliar como a interação entre o ácido indol-3-acético (AIA), a auxina mais abundante em plantas, e o etileno influencia a produção do aroma em frutos de tomateiro. Para tal, tomates da cultivar Micro-Tom foram tratados com AIA e etileno, isoladamente e em conjunto. Os resultados mostraram que os grupos de frutos caracterizaram-se por possuir diferentes perfis de compostos voláteis. Os tratamentos com AIA e etileno+AIA ocasionaram atraso no acúmulo de compostos voláteis derivados de isoprenóides, assim como na transcrição de genes envolvidos na síntese desses compostos: carotenoid cleavage dioxygenases 1A e 1B (S/CCD1A e S/CCD1B). A mudança da cor verde para a vermelha e o acúmulo de licopeno também foram atrasados em resposta a estes dois tratamentos. Foram também avaliados os níveis de transcritos de genes envolvidos na síntese de voláteis derivados de ácidos graxos, sendo eles lipoxigenases (S/LOX), hidroperóxido liases (S/HPL) e álcool desidrogenases (S/ADH), além dos níveis da produção de etileno, e AIA na forma livre e conjugados. Os resultados mostraram-se robustos em relação aos impactos nos perfis de compostos voláteis, causados pelos mesmos tratamentos hormonais, em frutos de tomateiro da variedade Grape. Os dados sugerem que a auxina possui importante papel na formação de compostos voláteis do aroma em frutos de tomateiro, regulando de forma negativa este metabolismo. Esse efeito modulador ocorre provavelmente por meio de interações com o etileno. / Fruit ripening is a complex and genetically programmed process through the fruit acquires characteristics (sweetness and acidity, color, softening, flavor and aroma, etc.) that make it attractive to consumers. The tomato fruit (Solanum lycopersicum) has been widely used as a model for studies on fruit ripening due to its nutritional and economic importance and advances in the understanding of its genetics and biochemistry. A set of 20 to 30 volatile substances, including alcohols, aldehydes, ketones and esters, which were derived from amino acids, fatty acids and carotenoids, contribute to the flavor. The hormone ethylene is closely related to the metabolic changes that occur in the maturation, including the generation of these volatile compounds, through the activation of transcription factors that regulate genes encoding proteins involved in this process. Although the knowledge about the biochemistry pathways that produces flavor compounds and the involvement of ethylene have advanced, little is known about the regulation of this process. In addition, ethylene is not the unique hormone that plays this role on fruit ripening. There is a growing body of evidence indicating the involvement of auxin in the maturation. The role of other hormonal classes is still little explored when compared to progress made on the role of ethylene in fruit ripening, especially regarding the regulation of the biosynthetic pathways of volatile compounds. This study aim to assess how the interaction between the indole-3-acetic acid (IAA), the most abundant auxin in plants, and ethylene influence the production of tomato fruit aroma. To do this, fruit from tomato cultivar Micro-Tom were treated with IAA and ethylene, separately and in combination. The results showed that the fruit groups characterized by having different profiles of volatile compounds. The treatment with IAA and IAA + ethylene caused delay in accumulation of volatile compounds derived from isoprenoid, as well as in the transcription of genes involved in the synthesis of these compounds: carotenoid cleavage dioxygenases 1A and 1B (S/CCD1A and S/CCD1B). The change from green to red and the accumulation of lycopene were also delayed in response to these two treatments. We also assessed the levels of transcripts of genes involved in the synthesis of volatile compounds derived from fatty acids (lipoxygenases [S/LOX], hydroperoxide lyases [S/HPL] and alcohol dehydrogenases [S/ADH]), besides the levels of ethylene production, and IAA in free and conjugated form. The results were robust with respect to impacts on volatile compounds profiles, caused by the same hormone treatments in tomato variety Grape. The data suggest that auxin plays an important role in the synthesis of volatile compounds in tomato fruit, negatively regulating this metabolism. This modulating effect likely occurs through crosstalks with ethylene.

O mamão papaia (Carica papaya L.) é uma fruta tropical de grande relevância comercial uma vez que o Brasil é o maior produtor mundial e terceiro maior exportador da fruta. Contudo, por ser uma fruta climatérica, tem uma vida pós-colheita limitada, devido ao rápido Amaciamento da polpa. Neste trabalho foi realizada uma investigação proteômica comparativa de polpa do mamão verde e maduro. Várias centenas de componentes protéicos (spots) foram resolvidos em géis 2-DE (faixa de pH 4-7) utilizando a eletroforese diferencial em gel (DIGE) e posteriormente as imagens geradas foram analisadas pelo programa PDQuest. Os spots diferencialmente expressos foram retirados do gel, digeridos e sequenciados (ESI-Q-TOF-MS/MS). Em geral, as proteínas diferencialmente expressas foram associadas ao metabolismo do etileno, resposta ao estresse, metabolismo de carbono e outros importantes processos fisiológicos. Os papéis de algumas das proteínas identificadas foram discutidos em relação à qualidade dos frutos do mamão. Este estudo fornece a primeira caracterização das mudanças no proteoma da polpa do mamão durante o amadurecimento. Deste modo a identificação de proteínas envolvidas na instalação ou desenvolvimento do amadurecimento pode contribuir para o entendimento deste processo e, também, gerar subsídios para avanços tecnológicos visando à qualidade e diminuição das perdas pós-colheita. / Papaya (Carica papaya L.) fruit is a relevant tropical crop since Brazil is the world\'s largest producer and third largest exporter of fruit. However being a climacteric fruit, has a limited green life due to the rapid pulp softening. We report here a comparative proteomic investigation of fruit pulp from unripe and ripe papayas. Several hundreds of protein components were resolved on 2-DE gels (pH range 4-7) using the differential gel electrophoresis (DIGE) approach, and images were analyzed by PDQuest. The variable components were excised, in-gel digested and were analyzed by ESI-Q-TOF-MS/MS. In general, the differentially expressed proteins were associated to ethylene metabolism, stress response, carbon metabolism and other important physiological processes. The roles of some of the identified proteins were discussed in relation to papaya fruit quality. To the best of our knowledge, this investigation provides the first characterization of the changes in papaya fruit pulp proteome during ripening. Thus the identification of proteins involved in the installation or development of the ripening may contribute to the understanding of this process and also provide subsidies for technological advances aimed at quality and reduction of post harvest losses.

Thesis (M.Sc. Agriculture (Horticulture)) -- University of Limpopo, 2017 / Avocado ‘Hass’ fruit characteristically change skin colour from green to deep purple or black during ripening. However, there is an ongoing debate about the use of ‘Hass’ avocado fruit skin colour change as an indicator for ripening and whether pre- and post-harvest factors can alter this relationship. Thus, the aim of the study was to investigate the effect of harvest season, harvest time, ripening temperature and ripening days on ‘Hass’ avocado fruit skin colour change during ripening. The experiment was carried out as 2 x 3 x 3 x 5 factorial with three replicates. The experiment consisted of four treatment factors: 2 x harvest season (2014 and 2015), 3 x harvest time (May-early, June-mid and July-late), 3 x ripening temperature (16, 21 and 25°C) and 5 x ripening days (0, 2, 4, 6 and 8). Fruit were stored at industry recommended temperature of 5.5°C. After storage, fruit were ripened at 16, 21 and 25°C, therefore, evaluated at 0, 2, 4, 6 and 8 days for subjective and objective skin colour, fruit firmness, ripening percentage and chilling injury. Harvest season, harvest time, ripening temperature and ripening days had a significant effect (P<0.001) on ‘Hass’ avocado fruit skin subjective colour development during ripening. However, amongst the treatment factors; harvest time, ripening temperature and ripening days were the predominant factors in skin subjective colour development variation. Hence, late harvest fruit showed an improved skin colour development at higher temperature (25°C) at day 4 to ripening when compared with early and mid-harvest fruit. Moreover, skin lightness showed a decreasing trend during all harvest time and ripening temperature throughout days to ripening during 2014 and 2015 harvest season. Furthermore, ripening at higher temperature (25°C) resulted in rapid decrease on fruit firmness when compared with lower temperature (16°C), irrespective of harvest season and harvest time. In addition, mid-season fruit showed significantly higher chilling damage during the 2014 harvest season. In conclusion, the study showed that harvest season, harvest time, ripening temperature and ripening days factors had a significant influence on ‘Hass’ avocado fruit skin colour development, firmness and susceptibility to chilling injury. / Agricultural Sector Education Training Authority (AgriSeta) and Postharvest Innovation Programme (PHI)

Fruit of Capsicum annuum L. (capsicum or pepper) are one of the major sources of red food colourant and pungency for spice production. In the spice production industry, fruit are mechanically harvested at different ripeness stages and fruit colour needs to be synchronised before being processed. However, even though capsicum ripens normally on the plant it often fails to ripen fully and turn red once harvested at the green stage. Attempts to promote ripening of harvested fruits have had limited success and the reason for this has been unclear. This project, therefore, investigated ripening behaviour on and off the plant of capsicum fruit grown in Australia and examined effects of pre- and postharvest applications on ripening of green harvested fruit. To examine ripening behaviour on and off the plant, capsicum fruit from three different cultivars (a mild paprika type cv. “Papri Queen”, a cayenne chilli cv. “Caysan”, and a sweet type bell pepper cv. “Aries”) were either allowed to ripen naturally on the plant or harvested at three different maturity stages: light green, deep green and breaker. Harvested fruit were stored individually at room temperature and several ripening characteristics including internal ethylene (C2H4) and carbon dioxide (CO2) concentration, extractable colour, 1-aminocyclopropane-1-carboxylic acid (ACC) synthase and oxidase activity, and total soluble solid content (TSSC) were studied during storage. There was very limited involvement of C2H4 during ripening of capsicum and the change in ACC synthase and ACC oxidase (two enzymes in C2H4 biosynthesis pathway) activity was not closely related to that of C2H4. However, it appeared that colour development in cv. “Papri Queen” was closely associated with what C2H4 production did occur while a climacteric-like peak of C2H4 could be observed in all fruit from cv. “Caysan”. For all three cultivars, the level of internal CO2 concentration, extractable colour and TSSC were greater in fruit ripened on the plant followed by fruit harvested at the breaker, deep green and light green stage, respectively. Fruit harvested at the light green stage failed to change colour properly and had very low levels of internal CO2 concentration and TSSC while fruit harvested from the breaker stage onwards ripened normally and developed sufficient colour for spice processing. This may suggest a role of external carbon-supply during ripening. To study the effect of the external-carbon supply during ripening, the stem of fruit were cinctured when fruit reached the light green stage and fruit were left to ripen on the plant. Cincturing delayed colour development of fruit by approximately five days but cinctured fruit were still able to turn red and develop extractable colour higher than the acceptable level of 140 ASTA units. Cincturing did not significantly alter other ripening behaviour such as CO2 concentration or TSSC. The lack of external carbon-supply is, therefore, unlikely to play a major role in the failure of green harvested fruit to ripen. To study the effect of application of plant growth regulators (both pre- and postharvest), an effective method of solution application utilising cincturing was firstly developed. Different plant growth regulator solutions including ethephon, naphthalene acetic acid, abscisic acid, jasmonic acid, sucrose, and different combinations of these were applied to fruit at the light green stage to study preharvest effects on ripening parameters during storage. Only treatment with high concentrations of ethephon increased the extractable colour higher than the acceptable level of 140 ASTA units and induced the complete degradation of chlorophyll. To study effects of postharvest application, 10 µL of various plant growth regulators was dropped into the hole created on the stem of harvested fruit for ten consecutive days. Treatment with ethephon significantly increased extractable colour and degraded chlorophyll content of fruit. Pre- and postharvest ethephon treatment strongly up-regulated Capsanthin-capsorubin synthase (Ccs) gene expression in a manner similar to the up-regulation of Ccs observed in fruit ripened on the plant. This explains the effect of C2H4 on colour development and also indicates the possible reason for the failure of green harvested fruit to ripen. However, the Ccs gene expression and chlorophyll degradation induced by ethephon was not visible until 14 days after harvest which indicated it may not be a direct effect and other signal transduction factors may be involved. When fruit are ripened on the plant, colour development may, therefore, be induced by ripening-related factors (other than C2H4) which is possibly inhibited or inactivated when fruit are harvested at the green stage. C2H4 application to fruit at this stage may help to reactivate or recover these factors which in turn induce colour development. Thus, although capsicum fruit show typical non-climacteric behaviour, C2H4 appears to be involved in some aspects of the ripening process. / http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1294648 / Thesis(Ph.D.)-- School of Agriculture, Food and Wine, 2007

Les derniers acteurs de la voie de signalisation à l’éthylène sont des facteurs de transcription appelés ERF (Ethylene Response Factors). La connaissance de leur rôle spécifique dans la régulation des processus développementaux dépendant de l’éthylène reste limitée. Les travaux présentés dans la thèse concernent la caractérisation fonctionnelle du gène Sl-ERF.B3, un membre de cette grande famille de régulateurs transcriptonnels dans la tomate (Solanum lycopersicum). Utilisant une stratégie répresseur dominant ; il est montré en particulier que ce gène intervient dans la mise en place de la réponse à l’éthylène et dans le contrôle de la maturation du fruit. L’expression d’une construction ERF.B3-SRDX, une version chimérique de Sl-ERF.B3 fusionné à un domaine répresseur de type EAR, entraine des phénotypes pléotropiques aussi bien dans la signalisation de l’éthylène que dans le développement des parties végétatives et des organes reproducteurs. Ainsi, une altération de la triple réponse à l’éthylène est constatée chez les lignées transgéniques et au stade adulte, les plantes présentent des phénotypes d’épinastie des feuilles, de sénescence prématurée des fleurs et d’abscission accélérée des fruits. L’ensemble de ces observations est corrélée avec une modification de l’expression de gènes impliqués dans la biosynthèse et la réponse à l’éthylène. Ces données suggèrent que ERF.B3 intervient dans un mécanisme de rétro-control de la réponse à l’éthylène en agissant à la fois sur les gènes de biosynthèse et de signalisation de l’hormone. Au niveau du fruit, la sur-expression d’ERF.B3-SRDX entraine une modification du processus de maturation avec un retard notable de l’avènement de l’acquisition de la compétence à murir. Cependant, une fois la maturation initiée, elle s’accompagne d’une forte production d’éthylène et d’une accélération du ramollissement du fruit. A l’inverse, l’accumulation de pigment est inhibée par altération de la voie de biosynthèse des caroténoïdes. Ces données phénotypiques sont corrélées avec le niveau d’expression des gènes clés impliqués dans ces processus. Les résultats indiquent que dans les lignées transgéniques, il y a découplage de certaines caractéristiques de la maturation du fruit et permettent de mettre en lumière le rôle d’ERF.B3 dans la régulation des processus de développement dépendant de l’éthylène chez la tomate. / Ethylene Response Factors (ERFs) are known to be the last transcription factors of the ethylene transduction pathway. Their specific role in ethylene-dependent developmental processes remains poorly understood. This work demonstrated a specific role of Sl- ERF.B3, a member of the ERF gene family in tomato (Solanum lycopersicum), in mediating ethylene response and fruit ripening through a dominant repressor strategy. ERF.B3-SRDX dominant repressor etiolated seedlings displayed partial constitutive ethylene-response in the absence of ethylene and adult plants exhibited typical ethylenerelated alterations such as leaf epinasty, premature flower senescence and accelerated fruit abscission. The multiple symptoms related to enhanced ethylene sensitivity correlate with the altered expression of ethylene biosynthesis and signaling genes, suggesting the involvement of Sl-ERF.B3 in a feedback mechanism regulating components of ethylene production and response. In addition, over-expression of ERF.B3-SRDX in tomato results in alterations in both fruit morphology and ripening process. The attainment of competence to ripen is dramatically delayed in ERF.B3-SRDX fruits but once ripening proceeds it is associated with high climacteric ethylene production and enhanced fruit softening while pigment accumulation is strongly reduced. Moreover, a number of genes involved in the fruit ripening process showed expression pattern deviating from that of wild type. These data suggest a putative role of Sl-ERF.B3 in the transcriptional network underlying the ripening process and uncover a mean for uncoupling some of the main features of fruit ripening such as fruit softening and pigment accumulation. Overall, the study highlighted the importance of an ERF gene in ethylene-mediated developmental processes such as plant growth and fruit ripening.