The aim of this study was to investigate plant species to develop a product with the potential of protecting plants or plant products against plant fungal pathogens. Hexane, dichloromethane, acetone, and methanol leaf extracts of six plant species (Bucida buceras, Breonadia salicina, Harpephyllum caffrum, Olinia ventosa, Vangueria infausta and Xylotheca kraussiana) were evaluated for antifungal activity against seven plant fungal pathogens (Aspergillus niger, A. parasiticus, Colletotrichum gloeosporioides, Penicillium janthinellum, P. expansum, Trichoderma harzianum and Fusarium oxysporum). These plant species were selected from more than 400 plant species evaluated in the Phytomedicine Programme that had good activity against two animal fungal pathogens. All the leaf extracts were active against at least one or more of the phytopathogenic fungi in a serial microdilution assay. Of the six plant species, B. buceras had the best antifungal activity against four of the fungi, with MIC values as low as 0.02 mg/ml and 0.08 mg/ml against Penicillium expansum, P. janthinellum, Trichoderma harzianum and Fusarium oxysporum. The number of active compounds in the plant extracts was determined using bioautography with the above-mentioned plant pathogens. No active compounds were observed in some plant extracts against the fungal plant pathogens indicating possible synergism between metabolites responsible for the antifungal activity of the extract. B. salicina and O. ventosa were the most promising plant species, with at least three antifungal compounds. The antioxidant activities of plant extracts were determined using the qualitative method by spraying TLC chromatograms developed in three eluent systems BEA, CEF and EMW with 1, l-diphenyl -2 picrylhydrazyl (DPPH). The plant extracts of five of these species did not have a strong antioxidant activity. The methanol extract of X. kraussiana was the most active radical scavenger in the DPPH assay amongst the six medicinal plants screened. Based on good activity against Aspergillus niger and A. parasiticus, leaf extracts of the six plant species were also tested for antifungal activity against A. fumigatus, a very important animal fungal pathogen. The acetone extracts of B. buceras, B. salicina, V. infausta and X. kraussina had good antifungal activity against the animal pathogens, with MIC values ranging between 0.02 and 0.08 mg/ml. This indicates that crude extracts of these species may be more valuable in combating Aspergillus infections in animals than in humans. Based on the results discussed above, B. salicina was selected for in-depth study. Serial exhaustive extraction was used to extract plant material with solvents of increasing polarities namely, hexane, chloroform, acetone and MeOH. Amongst the four extractants, MeOH extracted the largest quantity of plant material 12.3% (61.5g), followed by acetone 5.6% (27.8 g), hexane 2.6% (12.8 g) and chloroform 2.1% (10.3 g). The chloroform fraction was selected for further work because it had the best antifungal activity against A. niger, C. gloeosporioides, P. janthinellum and T. harzianum and the bioautography assay showed the presence of several antifungal compounds in the chloroform fraction. Column chromatography was used in a bio-assay guided fractionation and led to isolation of four compounds. The antimicrobial activity was determined against seven plant pathogenic fungi and three bacteria, including the Gram-positive Staphylococcus aureus (ATCC 29213) and the Gram-negative Escherichia coli (ATCC 25922) and Pseudomonas aureus (ATCC 27853). The isolated compounds had good antifungal activity against A. parasiticus with an MIC of 10 μg/ml, while in other cases it ranged from 20 to 250 μg/ml. Amongst the four compounds tested, only three had a clear band, indicating that the growth of the pathogenic fungi was inhibited in the bioautography assay. Nuclear magnetic resonance spectroscopy (NMR) and mass spectroscopy (MS) were used for identification of isolated compounds. Only one compound was identified as the triterpenoid ursolic acid. Ursolic acid has been isolated from several plant species and has antifungal activity against Candida albicans (Shai et al. 2008). This is the first report on the isolation of antifungal compounds from leaves of Breonadia salicina. The other compounds isolated appeared to be mixtures of fatty acids based on mass spectroscopy and the structures were not elucidated. The cytotoxicity of acetone extracts and the four isolated compounds were determined against Vero cells using a tetrazolium-based colorimetric (MTT) assay. The acetone extract was selected based on good in vitro antifungal activity and was used in an in vivo fruit experiment. The acetone extract was less toxic toward the Vero cells with an LC50 of 82 μg/ml than ursolic acid and compound 4 which had LC50 values of 25 and 36 μg/ml respectively. Compounds 2 and 3 had low toxicity against the cells with LC50 values greater than 200 μg/ml. The potential use of the extract or isolated compound(s) against three plant fungal pathogens Penicillium expansum and P. janthinellum as well as P. digitatum (isolated from infected oranges) were tested after treating the oranges with the extract and ursolic acid. The model used gave good reproducible results. The concentration that inhibited growth correlated reasonably well with MIC values determined by serial microplate dilution. There were substantial differences in the susceptibility of the different isolates tested. The activity of ursolic acid was in the same order as that of the crude acetone leaf extract of B. salicina. The LC50 of the extract varied from 1 to 1.8 mg/ml. Penicillium digitatum was more resistant to amphotericin B in comparison to other Penicillium species. It has been reported that the fungus was resistant to the three fungicides: sodium ï-phenylphenate (ï-phenylphenol), imazalil, and thiabendazole used commercially in the fruit industry to reduce postharvest decay (Holmes and Eckert 1999). The toxicity of the extract to Vero cells was in the order of 10 times lower than the LC50 of the extracts to the fungal pathogens. Although much work still has to be done, there is good potential that a commercial product can be developed from an acetone leaf extract of B.salicina leaves, especially if the activity of this extract can be improved by removing inactive compounds. The results confirm the traditional use of B. salicina and demonstrate the potential value of developing biopesticides from plants. / Thesis (PhD)--University of Pretoria, 2009. / Paraclinical Sciences / unrestricted

Submitted by Angela Maria de Oliveira (amolivei@uepg.br) on 2018-10-19T12:57:01Z No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) Iohann Metzger .pdf: 2446573 bytes, checksum: b496303d3bde21c766b8b82d72b53870 (MD5) / Made available in DSpace on 2018-10-19T12:57:01Z (GMT). No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) Iohann Metzger .pdf: 2446573 bytes, checksum: b496303d3bde21c766b8b82d72b53870 (MD5) Previous issue date: 2018-08-01 / A cultura da ameixeira apresenta um enorme potencial de crescimento no Brasil, as pesquisas no brasil para o desenvolvimento de novas variedades, tiram como base os materiais de origem asiáticos, implantados nos estados, do sul do pais, sendo realizados diversos cruzamentosvisando a obtenção de variedades adaptadas ao clima, resistentes a doenças e com maiores períodos de armazenamento de seus frutos, período de armazenamento é menor do que outras frutíferas principalmente porque a ameixa é uma fruta climatérica e apresenta continuidade nos seus processos de maturação, respiração e transposição após ser colhida. Desta forma são necessárias estratégias de colheita e armazenamento para aumentar a vida útil dos frutos e de transporte, fatores que causam elevação nos preços dos frutos para o consumidor. Este trabalho teve como objetivo conhecer o desenvolvimento climatérico dos frutos, a capacidade de armazenamento e de qualidade dos frutos de ameixeira japonesa (Prunus salicina Lind), genótipos de ameixa japonesa desenvolvidos no programa de melhoramento genético do Instituto Agronômico do Paraná. Foram realizados dois experimentos. O primeiro foi realizado comquatro genótipos, armazenados em temperatura ambiente e temperatura refrigerada a 1°C e analisada suas qualidades em oito épocas de armazenamento. Para o segundo experimento foram utilizadosdois genótipos de ameixa, armazenados em temperatura ambiente erefrigerado 1°C, e tratados ou não com Etefom, e nove épocas de avaliação. As análises realizadas nos frutos em cada uma das épocas foram, diâmetro, massa e firmeza dos frutos, perda de massa fresca, coloração L,A,B e transformação do ângulo Hue, sólidos solúveis, acidez titulável, ratio e pH. A capacidade de armazenamento dos frutos em condições de temperatura ambiente é menor do que se comparados com os frutos quando armazenados em temperatura refrigerada nos dois experimentos.Os frutos de todos os genótipos no momento da colheita apresentaram diâmetro superior a 44,00mm, e massa dos frutos superior a 50gramas sendo estes resultados de maior expressão na qualidades fisicas dos frutos, em relação as qualidades quimicas dos frutos é possivel observar que no momento da colheita foram obtidos resultados de SS superiores a 9° Brix, e com o avanço da maturação os valores de SS chegaram proximos de 15°Brix, enquanto que a AT no momento da colheita apresentava valores de 1,00% e após o armazenamento os valores obtidos foram inferiores a 0,5%.Conclui-se com este trabalho que todos os genótipos estudados apresentam comportamento climatérico, com diferentes periodos de armazenamentos e capacidades distintas seja quando estes frutos, são armazenados em temperatura ambiente ou em temperatura refrigerada 1°C, ocorreu em todos os genótipos variçoes entre os momentos de colheita e final do armazenamento, sendo os resultados de maior expressão obtidos na perda de massa fresca dos frutos armazenados em temperatura refrigerada 1°C com aplicação de Etefom, e elevação do ratio e SS, nos frutos em ambos os locais de armazenamento. / The plum cultivation has enormous potential for growth in Brazil, research in Brazil for the development of new varieties, based on the Asian origin materials, implanted in the states, in the south of the country, with several crosses being carried out in order to obtain resistant to diseases and with longer periods of storage of their fruits, storage period is lower than other fruits, mainly because the plum is a climacteric fruit and presents continuity in its maturation, respiration and transposition processes after being harvested . In this way, harvest and storage strategies are required to increase fruit shelf life and transport, factors that cause a rise in fruit prices for the consumer. The objective of this work was to know the climacteric development of fruits, storage capacity and quality of Japanese plum fruits (Prunus salicina Lind), Japanese plum genotypes developed in the breeding program of the Agronomic Institute of Paraná. Two experiments were carried out. The first one was carried out with four genotypes, stored at room temperature and refrigerated temperature at 1 ° C and analyzed for their qualities in eight storage periods. For the second experiment, two plum genotypes were used, stored at room temperature and refrigerated at 1 ° C, and treated or not with Etefom, and nine evaluation periods. Fresh fruit weight loss, L, A, B color and Hue angle transformation, soluble solids, titratable acidity, ratio and pH were analyzed in the fruits at each time point. The storage capacity of fruits at ambient temperature conditions is lower than when compared to fruits when stored at refrigerated temperature in the two experiments. Fruits of all genotypes at harvest had a diameter greater than 44.00 mm, and mass of fruits greater than 50grams being these results of greater expression in the physical qualities of the fruits, in relation to the chemical qualities of the fruits it is possible to observe that at the moment of the harvest SS results were obtained higher than 9 ° Brix, and with the advancement of the maturity values of SS reached close to 15 ° Brix, while TA at the time of harvest had values of 1.00% and after storage the values obtained were less than 0.5%. It is concluded with this work that all the genotypes studied climatic behavior, with different storage periods and different capacities, when stored in or in refrigerated temperature 1 ° C, all the genotypes occurred between the harvesting and the final moments of the storage, with the highest expression results obtained in the loss of fresh mass of the fruits stored in refrigerated temperature 1 ° C with application of Etefom , and elevation of the ratio and SS in fruits at both storage sites.

ENGLISH ABSTRACT: The export of Japanese plums from South Africa is challenging, since most cultivars are prone to develop chilling injury (CI) when stored at low temperatures. This injury manifests as gel breakdown or internal browning in the mesocarp tissue of the fruit on removal from low storage temperature conditions, i.e. in the consumer’s fruit basket, who subsequently does not buy plums again. Loss of cell membrane integrity and oxidative stress are, respectively, the primary and secondary physiological responses to CI. The main aim of this study was to investigate changes in cell membrane composition and levels of antioxidants in plums throughout fruit development and maturation, during forced air cooling (FAC) and storage under different temperature regimes. ‘Sapphire’ (a chilling susceptible cultivar) accumulated high levels of glutathione and polyunsaturated fatty acids (PUFAs) during fruit development. Therefore, the cultivar is protected against lipid peroxidation while developing on the tree, but the high levels of PUFAs, which are easily oxidised, may cause this cultivar to be chilling susceptible when stored at low temperatures. It is suggested that the high levels of monounsaturated fatty acids (MUFAs), which are not easily oxidised, and ascorbic acid that accumulated in ‘Angeleno’ (a chilling resistant cultivar) during fruit development, render this cultivar CI resistant during long-term cold-storage. When stored at -0.5 °C, CI development increased at a higher rate, ethylene evolution rates were higher and water soluble antioxidant activity (HAA), ascorbic acid and glutathione levels, and the MUFA:PUFA ratio were lower in H2 (more mature) ‘Sapphire’ plums than H1 fruit (less mature). Therefore, concurrent with H2 fruit having lower levels of antioxidants to quench free radicals caused by chilling stress, their cell membranes were more vulnerable to oxidation due to their phospholipid fatty acid composition. H2 fruit also had higher levels of saturated fatty acids, and hence less fluid cell membranes than H1 fruit when stored at -0.5 °C. An intermittent warming (IW) regime delayed symptom appearance and reduced CI severity in plums significantly compared to storage at -0.5 °C. Fruit stored under the IW regime had a more optimal phospholipid fatty acid composition and lower membrane sterol levels under shelf-life conditions to keep the membranes fluid. It also had higher levels of HAA and lipid soluble antioxidant activity, ascorbic acid and glutathione, which rendered fruit better protected against oxidation. Elevated storage temperatures (2.5 °C to 7.5 °C) caused higher levels of lipid peroxidation or low ascorbic acid levels and poor fruit quality compared to the IW regime in ‘Sapphire’ plums. ‘Laetitia’ plums stored at 5 °C and 7.5 °C had significantly less CI than under the IW regime, but softened quicker due to higher ethylene evolution rates. ‘Sapphire’ tolerated both long and short FAC durations, but a slower initial FAC rate prevented CI manifestation and caused a higher HAA after cold-storage in this fruit. ‘Laetitia’ cooled with a slower initial FAC rate and for a longer duration resulted in the best fruit quality and had higher HAA, total phenolic, phospholipid and saturated phospholipid fatty acid concentrations during storage. / AFRIKAANSE OPSOMMING: Die uitvoer van Japanese pruime vanaf Suid-Afrika hou talle uitdagings in, want die meeste van die kultivars ontwikkel koueskade wanneer hulle by lae temperature opgeberg word. Koueskade manifesteer as gelverval of interne verbruining in die mesokarpweefsel van die vrugte wanneer die vrugte verwyder word uit die lae opbergingstemperatuuromstandighede, m.a.w. in die verbruiker se vrugtemandjie, wat nie weer pruime koop nie. Verlies aan selmembraanintegriteit en oksidatiewe druk is, respektiewelik, die primêre and sekondêre fisiologiese reaksies op koueskade. Die hoofdoel van hierdie studie was om die veranderinge in selmembraansamestelling en antioksidantkonsentrasie in pruime te ondersoek tydens vrugontwikkeling en volwassewording, tydens geforseerde lugverkoeling (GLV) en tydens opberging onder verskillende temperatuurregimes. ‘Sapphire’ (‘n koueskade sensitiewe kultivar) het hoër konsentrasies van glutatioon en polionversadigde vetsure (POV) tydens vrugontwikkeling geakkumuleer. Dié kultivar is dus voldoende beskerm teen lipiedperoksidasie tydens vrugontwikkeling aan die boom, maar die hoë konsentrasies van POVs, wat maklik oksideer, mag veroorsaak dat hierdie kultivar meer koueskadesensitief is wanneer dit by lae temperature opgeberg word. Die hoë konsentrasies van mono-onversadigde vetsure (MOV), wat nie maklik oksideer nie, en askorbiensuur wat in ‘Angeleno’ (‘n koueskade weerstandbiedende kultivar) geakkumuleer het tydens vrugontwikkeling, verleen moontlik weerstandbiedendheid teen koueskade aan hierdie kultivar tydens langtermyn koelkopbering. Tydens opberging by -0.5 °C het koueskade ontwikkeling vinniger toegeneem, was etileenvrystellingstempos hoër en die wateroplosbare antioksidantaktiwiteit (HAA), askorbiensuuren glutatioonkonsentrasies en die MOV:POV verhouding laer in H2 (meer volwasse) ‘Sapphire’ pruime as in die H1 vrugte (minder volwasse). Dus, tesame met die laer antioksidantkonsentrasies in die H2 vrugte om die vry radikale veroorsaak deur koelopbering te verminder, was hul selmembrane ook meer vatbaar vir oksidasie a.g.v. die vetsuursamestellling van hul membraanfosfolipiede. Die H2 vrugte het ook ‘n hoër konsentrasie van versadigde vetsure, en dus minder vloeibare membrane as die H1 vrugte gehad tydens opberging by -0.5 °C. Die dubbeltemperatuurregime (DT) het simptoomontwikkeling vertraag en koueskade-intensiteit betekenisvol verminder in vergelyking met pruime wat by -0.5 °C opgeberg is. Vrugte wat met die DT regime opgeberg is, het ‘n meer optimale fosfolipiedvetsuursamestelling en laer konsentrasie van membraansterole tydens gesimuleerde raklewe gehad wat meer vloeibare membrane verseker het. Hierdie behandeling het ook hoër HAA en lipiedoplosbare antioksidantaktiwiteit (LAA), askorbiensuur- en glutatioonkonsentrasies gehad wat die vrugte beskerm het teen oksidatiewe druk. Verhoogde opbergingstemperature het hoër vlakke van lipiedperoksidasie of lae askorbiensuurkonsentrasies asook swak vrugkwaliteit in ‘Sapphire’ pruime veroorsaak in vergelyking met die DT regime. ‘Laetitia’ pruime wat by 5 °C en 7.5 °C opgeberg is, het betekenisvol minder koueskade gehad in vergelyking met die DT regime, maar het vinniger sag geword a.g.v. hoër etileenvrystellingstempos. ‘Sapphire’ kon lang en kort GLV tye weerstaan, maar ‘n stadiger inisiële GLV spoed het die manifestasie van koueskade voorkom en het ‘n hoër HAA in die vrugte tot gevolg gehad na koelopberging. ‘Laetitia’ wat met ‘n stadiger inisiële GLV spoed en oor ‘n langer tyd verkoel is, het die beste vrugkwaliteit, en hoër HAA, totale fenool-, fosfolipied- en versadigde fosfolipiedvetsuurkonsentrasies as die ander behandelings tydens koelopberging gehad

Thesis (MScAgric)--Stellenbosch University, 2008. / ENGLISH ABSTRACT: Stone fruit is susceptible to chilling injury and intermittent warming has been shown to alleviate chilling injury during cold storage. A dual temperature storage regime was developed in South Africa for plums based on the principles of intermittent warming. The regime consists of an initial period at -0.5°C, a variable duration warming period at 7.5°C, followed by -0.5°C. Refrigerated integral containers were designed to maintain product temperature and not to reduce product temperature, per se. Considering that dual temperature shipment requires significant refrigeration and effective distribution of cool air to remove sensible- and respiratory heat, the capacity of integral containers to ship plums successfully at dual temperature is questioned. The objectives of this study were, firstly, to analyse pulp temperature data and possibly identify different temperature zones within containers shipping plums at dual temperature. Secondly, to understand the underlying processes differentiating the temperature zones and thirdly, to determine the effect of container performance on fruit quality. Three processes were identified as important characteristics of pulp temperature data sets recorded during dual temperature shipping, namely cooling down, heating up and over heating in the container. The order of importance differed according to the cultivar shipped and the container’s performance. Three temperature zones were identified in dual temperature containers, where the average pulp temperature, time to heat up and time to cool down for each temperature zone increased along the length, across the width from the left to the right and up the container system. The variable temperature conditions were possibly due to a variation in delivery air temperature, poor airflow and the effect of increased respiration and, therefore, production of vital heat by the fruit. The cooling down process was identified as the most important process discriminating the temperature zones. With the exception of ‘Fortune’, variable temperature conditions found within integral containers shipping plums at dual temperature had a significant influence on the fruit firmness post-shipment, where deterioration levels increased from the front to the door end of the container due to an increase in pulp temperature. However, it was also shown that fruit firmness prior to shipment could have a determining effect on differences found. It could not be proven that variable temperature conditions resulted in significantly higher levels of internal defects within the integral container. Temperature zones could not be identified within refrigerated integral containers shipping plums at single temperature, suggesting that the containers are able to maintain the temperature well throughout the container area. A constant 2°C storage temperature could possibly replace the commercial dual temperature regime in the case of ‘Pioneer’ plums due to improved fruit firmness, similar colour development to the control and less sensible heat produced in the container resulting in a more stable container environment. However, unacceptably high levels of shrivel and internal browning were found. / AFRIKAANSE OPSOMMING: Steenvrugte is vatbaar vir koueskade en dit is bewys dat periodieke verwarming gedurende koelopberging koueskade kan verlig. Die dubbeltemperatuur opbergingsregime is in Suid- Afrika ontwikkel vir pruime en is gebaseer op die beginsels van periodieke verwarming. Die regime bestaan uit ‘n inisiële periode by -0.5°C, ‘n variërende periode by 7.5°C, gevolg deur -0.5°C. Verkoelde integrale houers is ontwerp om produktemperature te handhaaf en nie soseer om produktemperatuur te verlaag nie. Die kapasiteit van integrale houers om pruime suksesvol teen dubbeltemperatuur te verskeep word dus bevraagteken, in ag geneem dat dubbeltemperatuurverskeping betekenisvolle verkoeling en effektiewe verspreiding van koue lug vereis om die waarneembare- en respiratoriese hitte te verwyder. Die doelwitte van die studie was eerstens om die pulptemperatuurdata te analiseer en moontlik verskillende temperatuursones binne houers wat pruime teen dubbeltemperatuur verskeep te identifiseer. Tweedens, om die onderliggende prosesse wat die temperatuursones van mekaar onderskei te verstaan, en derdens om die effek van die houer se werkverrigting op vrugkwaliteit te bepaal. Drie prosesse is geïdentifiseer as belangrike eienskappe van pulptemperatuur datastelle aangeteken gedurende dubbeltemperatuurverskeping, naamlik afkoeling, opwarming en oorverhitting wat binne die houer plaasvind. Die volgorde van belangrikheid het gevarieer afhangende van die kultivar verskeep en die houer se werkverrigting. Drie temperatuursones is geïdentifiseer binne integrale houers wat pruime teen dubbeltemperatuur verskeep, waar die gemiddelde pulptemperatuur, die opwarmingstyd en die afkoelingstyd vir elke temperatuursone in die lengte, oor die wydte van links na regs en van onder na bo in die houersisteem toegeneem het. Die variërende temperatuur toestande kan moontlik toegeskryf word aan ‘n variasie in leweringstemperatuur, swak lugvloei en die effek van toenemende respirasie, en dus die produksie van hitte vrygestel deur die vrugte. Die afkoelingsproses is geïdentifiseer as die belangrikste proses wat die temperatuursones van mekaar onderskei. Behalwe in die geval van ‘Fortune, het variërende temperatuurtoestande in integrale houers wat pruime teen dubbeltemperatuur verskeep ‘n betekenisvolle invloed op die vrugfermheid na verskeping gehad, waar vrugveroudering toegeneem het van voor in die houer na die deur van die houer as gevolg van ‘n toename in pulptemperatuur. Daar is egter bewys dat die vrugfermheid voor verskeping ook ‘n bepalende effek kon hê op die fermheidsverskille. Dit kon nie bewys word dat die variërende temperatuurtoestande betekenisvol hoër vlakke van interne defekte binne die integrale houer veroorsaak het nie. Temperatuursones kon nie geïdentifiseer word binne verkoelde integrale houers wat pruime teen enkeltemperatuur verskeep het nie, wat dus impliseer dat die houers daartoe instaat is om temperatuur goed te onderhou binne die houer. ‘n Konstante 2°C opbergingstemperatuur kan moontlik die kommersiële dubbeltemperatuurregime vervang in die geval van ‘Pioneer’ pruime as gevolg van verbeterde vrugfermheid, soortgelyke kleurontwikkeling as die dubbeltemperatuurregime en minder hitte geproduseer binne die houer deur die pruime, wat ‘n meer stabiele houeromgewing veroorsaak. Onaanvaarbare hoë vlakke van verrimpeling en interne verbruining is egter gevind.

Memoria para optar al título profesional de: Ingeniero Agrónomo Mención: Manejo de Suelos y Aguas / Con el objetivo de evaluar cuantitativamente la efectividad de la aplicación de una pulverizadora hidroneumática modificada, se midió el depósito del caldo de aplicación sobre las hojas de Prunus salicina Lindl., en un huerto plenamente productivo ubicado en la Comuna de Peumo, Región de O´Higgins, Chile. Se evaluaron 4 tratamientos, diferenciados en el volumen de agua aplicado por hectárea y el número de boquillas utilizadas en la máquina: 1.200 L∙ha-1 y 56 boquillas; 1.200 L∙ha-1 y 28 boquillas; 600 L∙ha-1 y 56 boquillas; y 600 L∙ha-1 y 28 boquillas; cada uno con 4 repeticiones. Para cuantificar el depósito sobre las hojas, se utilizó una solución de Azul Brillante FD&C-1 en agua como caldo de aplicación de los cuatro tratamientos, recolectando, inmediatamente seco el residuo, 10 muestras por repetición compuestas por 3 hojas cada una, a las cuales se les midió la superficie y el depósito de la solución mediante espectrofotometría UV. Los valores del depósito logrado fueron expresados como μL del caldo de aplicación por cm2 de hoja. El comportamiento del depósito en hojas a distintos niveles de cubrimiento conservó proporcionalidad, logrando obtener aproximadamente la mitad del depósito en hojas al emplear 600 L∙ha-1 respecto al depósito logrado al emplear 1.200 L∙ha-1. Por su parte, el número de boquillas no logra por sí sólo un efecto en el depósito sobre hojas. Un análisis de varianza de dos factores permitió establecer que el depósito en hojas es afectado por la interacción entre el cubrimiento utilizado y el número de boquillas. / With the aim to quantitatively evaluate the effectiveness of an application with a modified hydropneumatic sprayer, spray deposition was measured on leaves of Prunus salicina Lindl. in a fully productive orchard (Peumo, O'Higgins Region, Chile). Four treatments were evaluated, differentiated by water volume applied per hectare and the number of nozzles of the machine: 1,200 L∙ha-1 and 56 nozzles; 1,200 L∙ha-1 and 28 nozzles; 600 L∙ha-1 and 56 nozzles; and 600 L∙ha-1 and 28 nozzles; each with 4 replications. To quantify the deposit on the leaves, a solution of Brilliant Blue FD&C-1 in water was used as the spray solution of the four treatments, then 10 samples per repeat composed by three leaves each were collected, to measure the surface and the deposit of the solution by UV spectrophotometry. The achieved deposit values were expressed as μL∙cm-2 leaf. Deposit behavior at different levels of coverage maintained proportionality, achieving about half the deposit in leaves by using 600 L∙ha-1 respect to the deposit when using 1,200 L∙ha-1. Meanwhile, the number of nozzles by itself fails effect in the deposit on leaves. ANOVA of two factors showed that interaction between the spray coverage used and the number of nozzles was significant.

Thesis (MSc)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: The export of Japanese plums from South Africa is challenging. Exporting late season plums require fruit to last as long as 8 weeks in cold-storage. Prolonged storage periods can cause some cultivars to develop a shrivelled appearance due to moisture loss. Moisture loss from perishable commodities manifests mainly as shrivelling due to a loss in the turgidity of the surface cells of the fruit, or weight loss. ‘African DelightTM’ (highly susceptible to shrivel), ‘Laetitia’ (shrivel susceptible), ‘Sapphire’ (shrivel susceptible) and ‘Songold’ (not shrivel susceptible) plums were investigated by means of fluorescent microscopy for cracks and openings in the fruit peel. Only ‘African DelightTM’ had open hairline cracks in its peel, and fruit with wider cracks were associated with higher water vapour permeabilities. Open lenticels were found in the peels of ‘African DelightTM’, ‘Laetitia’ and ‘Sapphire’ plums. For ‘Songold’ no peel cracking or open lenticels were observed. The fact that the cuticle of this cultivar is mostly intact may be the reason why it is not susceptible to postharvest shrivel manifestation. The water vapour permeance of the fruit peel determines how easily fruit lose moisture. In this study it was determined to what extent fruit, trees, orchards, harvest date and cultivar contribute to the total variation in plum peel water vapour permeability. The permeabilities of ‘African DelightTM’, ‘Laetitia’, and ‘Songold’ were determined weekly from 4 weeks before harvest until post optimum maturity. Fruit to fruit variation made the largest contribution towards the total variation (> 45%), followed by harvest date (> 20%) and orchard (> 15%) effects. The permeability across all cultivars increased two-fold as fruit became over mature. The contribution of cultivar differences to fruit peel permeability varied greatly between seasons (42% in 2013/2014 and 5% in 2014/2015). Differences between cultivars may include cuticle thickness and composition, micro cracks in the peel and/or open lenticels. Current handling protocols suggest that fruit should be cooled as soon as possible after harvest, but this is not always possible. ‘African DelightTM’ plums were exposed to various handling scenarios in order to determine the handling protocol with the least risk of moisture loss. The control consisted of packaging and cooling the fruit within 6 h of harvest. Fruit quality was comparable or even better than the control when the fruit were pre-cooled to 0 °C and 15 °C for up to 72 h. High vapour pressure deficits caused fruit to lose more moisture, especially when fruit were exposed to ambient temperatures for 48 h and 72 h. It is recommended that handling protocols for plums should be followed stringently in order to reduce mass loss and shrivel manifestation. Since other studies found that silicate (Si) has positive effects on fruit quality, we applied potassium silicate preharvest to ‘African DelightTM’ trees. However, we did not find significant differences between treatments regarding crack width or crack incidence in the fruit peel, shrivel, decay, internal browning, gel breakdown or aerated tissue levels. Currently preharvest potassium silicate applications are not recommended to improve plum quality. / AFRIKAANSE OPSOMMING: Die uitvoer van die Japanese pruime uit Suid-Afrika is 'n uitdaging, omrede daar verwag word dat laatseisoen kultivars tot 8 weke in koelopberging moet bly. Lang opbergingsperiodes veroorsaak dat sommige kultivars 'n verrimpelde voorkoms ontwikkel a.g.v. vogverlies. Vogverlies uit vars produkte manifesteer hoofsaaklik as verrimpeling a.g.v. 'n verlies in die turgiditeit van die selle in en onder die vrugskil, en as massaverlies. ‘African DelightTM’ (hoogs vatbaar vir verrimpeling), ‘Laetitia’ (vatbaar vir verrimpeling), ‘Sapphire’ (vatbaar vir verrimpeling) en ‘Songold’ (nie vatbaar vir verrimpeling) pruime is ondersoek deur middel van fluoressensie mikroskopie vir krake en openinge in die vrugskil. Slegs ‘African DelightTM’ het oop haarlyn krake in sy skil gehad en vrugte met wyer krake het ʼn hoër waterdamp deurlaatbaarheid gehad. Oop lentiselle is gevind in die skille van ‘African DelightTM’, ‘Laetitia’ en ‘Sapphire’ pruime. ‘Songold’ het geen krake of oop lentiselle getoon nie. Die feit dat ‘Songold’ se kutikula meestal ongeskonde was, mag die rede wees waarom hierdie kultivar nie vatbaar vir verrimpeling is nie. Die waterdamp deurlaatbaarheid van 'n vrugskil bepaal hoe maklik vrugte vog verloor. In hierdie studie is bepaal tot watter mate vrugte, bome, boorde, oesdatum en kultivar bydra tot die totale variasie in die pruimskil se waterdamp deurlaatbaarheid. Die deurlaatbaarheid van ‘African DelightTM’, ‘Laetitia’, en ‘Songold’ is weekliks bepaal vanaf 4 weke voor die verwagte oesdatum tot die vrugte oorryp was. Vrug tot vrug variasie het die grootste bydrae tot die totale variasie gemaak (> 45%), gevolg deur oesdatum (> 20%) en boord (> 15%). Die skildeurlaatbaarheid van al die kultivars het verdubbel in die tyd van net voor oes tot die vrugte oorryp was. Die kultivar se bydrae tot die deurlaatbaarheid van die vrugskil het baie gewissel tussen seisoene (42% in 2013/2014 en 5% in 2014/2015). Verskille in skil-deurlaatbaarheid tussen kultivars kan kutikula-dikte en -samestelling, mikro-krake in die skil en/of oop lentiselle insluit. Huidige hanteringsprotokolle stel voor dat vrugte so spoedig moontlik afgekoel word na oes, maar dit is nie altyd moontlik nie. In hierdie studie is 'African DelightTM' pruime is blootgestel aan verskeie hantering scenario's om die hanteringsprotokol met die laagste risiko vir vogverlies te bepaal. Die kontrole vrugte is gepak en onder geforseerde verkoeling geplaas binne 6 ure na oes. Vrugkwaliteit was vergelykbaar of selfs beter in vergelyking met die kontrole wanneer die vrugte voorverkoel is tot 0 °C en 15 °C vir tot 72 uur. Hoë dampdrukverskille het veroorsaak dat vrugte meer vog verloor, veral wanneer vrugte aan kamertemperatuur blootgestel was vir 48 h en 72 h na oes. Dit word aanbeveel dat hanteringsprotokolle vir pruime streng gevolg moet word om massaverlies en verrimpeling te beperk. Aangesien ander studies gevind het dat silikaat (Si) ‘n positiewe uitwerking op vrugkwaliteit het, het ons kaliumsilikaat vooroes aan ‘African DelightTM’ bome toegedien. Daar was egter geen beduidende verskille tussen behandelings met betrekking tot kraakbreedte of kraakvoorkoms in die vrugskil of t.o.v. gehalte eienskappe soos die voorkoms van verrimpeling, bederf, interne verbruining, gelverval of deurlugte weefsel nie. Tans word voor-oes kaliumsilikaat spuite nie aanbeveel om pruimkwaliteit te verbeter nie.

Made available in DSpace on 2017-07-25T19:29:53Z (GMT). No. of bitstreams: 1 Alexandre Pavanello.pdf: 2830870 bytes, checksum: 6cfe2c059418ba0841f20c1f7b9ba383 (MD5) Previous issue date: 2012-05-10 / Fundação Araucária de Apoio ao Desenvolvimento Científico e Tecnológico do Paraná / Fruit thinning is one of the main practice to produce good quality fruit today. It promotes a balance between vegetative growth and production, increases fruit size and avoids alternation of production. Thinning can be done during flowering, but its often done later after fruit set, which can be defined best fruiting. Manual thinning of large number of plants is not practical or economical. An alternative is chemical thinning, which involves the application of chemicals on flowering or right after flowering and leads to fruit abscission, reducing or eliminating manual thinning. The objectives of this trial was to evaluate the effect of different concentrations of ethephon (2-chloroethylphosphonic) in chemical thinning of plum cvs. Irati, Reubennel during the harvest of 2010/2011 and 2011/2012 and its economic feasibility in Arapoti-PR. East central region of Paraná. The following characteristics were evaluated, number of fruits per branch, per plant, production, medium weight, firmness, soluble solids, pH, acidity and color. In the season 2010/2011, it was observed that increased concentration of ethephon linearly decreased the number of fruit caliber I, II, III, since the gauge IV had a higher number of fruits on the estimated concentration of 0.093 mL L ethephon and necessary to drive studies at lower concentrations, which were made in 2011/2012 harvest. In this harvest, the estimated concentration of 0.07 mL L ethephon, cv. Irati produced 23 kg/plant and the cv. Reubennel 73 kg/plant having satisfactory quantity of fruit size III and IV. The use of ethephon decreased the firmness of the fruits for cv. Irati and did not influenced the cv. Reubennel. None of the concentrations of ethephon affected the physical and chemical quality of fruits in relation to total soluble solids, pH and acidity for both crops and cvs. Economical evaluation of both cvs., showed that productivity and net income of treatment with etehephon gave better results than other treatments. Manual thinning showed a higher percentage gave better results than other treatments. Manual thinning showed a higher percentage of fruit size III and IV but at higher cost, which is difficult to sustain in time, due to high cost and availability of skilled labor force in the region, which indicates that chemical thinning will be a good economical alternative. / O raleio de frutos é uma das práticas mais importantes para se produzir frutos de qualidade. Promove equilíbrio entre o crescimento vegetativo e produtivo, aumento no tamanho dos frutos e evita alternância da produção. O raleio pode ser realizado durante a floração, mas é frequentemente feito mais tarde, após a fixação dos frutos, onde pode se definir melhor a frutificação. O raleio manual de um grande número de plantas não é prático nem econômico. A alternativa é o raleio químico, o qual consiste na aplicação de produtos químicos na floração ou logo após, provocando a abscisão de frutos, diminuindo ou eliminando, a atividade do raleio manual. Nesse contexto, os objetivos deste trabalho foram avaliar o efeito de diferentes concentrações de ethephon (ácido 2-cloroetilfosfônico), para o raleio químico das ameixeiras cvs. Irati e Reubennel, nas safras 2010/2011 e 2011/2012 e sua viabilidade econômica, no município de Arapoti – PR, região centro leste do Paraná. As seguintes características foram avaliadas: número de frutos por ramo, por planta, produção, massa médio, firmeza, sólidos solúveis, pH, acidez e coloração. Na safra 2010/2011, concluiu-se que o aumento na concentração de ethephon diminuiu linearmente o número de frutos de calibre I, II e III, já o calibre IV apresentou maior número de frutos na concentração estimada de 0,093 mL Lˉˡ de ethephon, sendo necessário realizar estudos com menores concentrações, as quais foram feitas na safra 2011/2012. Nesta safra, a concentração estimada de 0,07 mL Lˉˡ de ethephon, a cv. Irati produziu 23 kg/planta e a cv. Reubennel 73 kg/planta, apresentando quantidade satisfatória de frutos calibre III e IV. A utilização de ethephon diminui a firmeza dos frutos para cv. Irati e não influenciou a cv. Reubennel. Nenhuma das concentrações de ethephon afetou a qualidade física e química dos frutos, em relação ao teor de sólidos solúveis, pH e acidez, para ambas cvs e safras. Na análise econômica, em ambas cvs., a produtividade e a receita líquida para o tratamento com ethephon, foi superior aos demais. O tratamento com raleio manual apresentou maior porcentagem de frutos calibre III e IV, porém o alto custo, a dificuldade e disponibilidade de mão-de-obra para o raleio manual, fazem com que o raleio químico venha a ser usado cada vez mais.

Made available in DSpace on 2017-07-25T19:31:03Z (GMT). No. of bitstreams: 1 Alexandre Pozzobom.pdf: 2410959 bytes, checksum: 345f13c6c1a806e223fa350c8d0ff379 (MD5) Previous issue date: 2016-06-10 / Fundação Araucária de Apoio ao Desenvolvimento Científico e Tecnológico do Paraná / The harvest of fruits of high quality provides increased market value for the fruit grower. A effective fruit thinning is of the most important steps to provide good commercialization. The increased occurrence of hail storms during the growing period resulted in the installation of protective hail nets. This study aimed to evaluate the effects of chemical and mechanical thinning in plums and hand, chemical and mechanical thinning in apples for different hail nets.. For thinning in plums, mechanical thinning was more efficient when compared to chemical thinning. The mechanical thinning treatment reduced fruit set, number of fruit per tree and yield, however it increased fruit size, fruit weight and promoted higher vegetative growth, an important factor to avoid alternating production every year. For apple thinning, mechanical thinning was an effective fruit thinner. It was observed that some treatments like CT-BA required around 300 hours or more per hectare of hand thinning to achieve a satisfactory thinning efficacy. The black hail nets showed a reduction in red colour in apples. The thinning efficacy value (TEV) for hand thinning was 93%, for mechanical thinning was 74%, for chemical thinning with Metamitron was 62% and for chemical thinning with Benzyladenine was 54%. / A colheita de frutos com qualidade proporciona ao produtor agregar valor na venda da fruta. Realizar o raleio dos frutos de maneira eficiente é uma das práticas que proporcionam ao fruticultor melhorar a rentabilidade na produção. Devido as frequentes chuvas de granizo no período de produção de frutas, alguns fruticultores optam por implantar telas antigranizo. Neste contexto, os objetivos deste trabalho foram avaliar os efeitos do raleio químico e mecânico em ameixeira e do raleio manual, químico e mecânico em macieiras sobre diferentes telas antigranizo. Para os raleios em ameixeira, os tratamentos com raleio mecânico foram mais eficientes comparados aos tratamentos com raleio químico. O raleio mecânico reduziu o pegamento de frutos, o número de frutos e a produtividade. Entretanto, proporcionou aumento no tamanho e peso dos frutos e maior crescimento vegetativo, o que pode evitar a alternância de produção. Para o raleio em macieiras, o raleio mecânico foi o mais efetivo. Para o tratamento com benziladenina, foram necessárias mais de 300 horas por hectare de raleio manual para alcançar um raleio eficaz. A utilização de tela preta proporciona redução na coloração vermelha dos frutos de maçã. O Valor da Eficácia do Raleio (VER) para o tratamento com raleio manual foi de 93%, com raleio mecânico de 74%, com raleio químico Metamitron de 62% e o raleio químico Benziladenina 54%.

A ameixeira Gulfblaze, também conhecida como FLA 87-7, é uma cultivar de ameixa japonesa que se destaca pelo tamanho do fruto, precocidade de produção e resistência a escaldadura das folhas, doença que tem sido entrava a produção de ameixas no Brasil. Essa cultivar foi incorporada ao Banco Ativo de Germoplasma (BAG) do IAC por volta das décadas de 60 e 70, mas ainda há poucos trabalhos no tocante a informações sobre sua a fisiologia, conservação e armazenamento pós-colheita. As ameixas apresentam, geralmente, um curto período pós-colheita, sendo necessárias tecnologias para aumentar seu tempo de armazenamento e a manutenção da qualidade, as quais visam, sobretudo, a minimização dos efeitos deletérios causados pelo etileno, desde a maturação até o momento da chegada ao consumidor. Para sugerir melhorias no manejo e conservação da qualidade pós-colheita e promover maior longevidade da ameixa \"Gulfblaze\", alguns experimentos foram realizados. Desses experimentos, surgiram três trabalhos. O primeiro trabalho investigou o ponto de colheita ideal baseado no estado de maturação. No segundo, foi investigado o uso da refrigeração associado ao 1-MCP para prolongar o tempo de armazenamento. E no terceiro, foi testada a hipótese de que a aplicação do etileno poderia reiniciar o processo regular de amadurecimento de frutos refrigerados, interrompido pelo 1-MCP, e uniformizar o amadurecimento. A ameixa \"Gulfblaze\" apresenta padrão climatérico de amadurecimento, e quando colhida com casca apresentando 50 a 75% da coloração característica da cultivar apresentam maturação regular e maior potencial para comercialização e consumo, com longevidade comercial de 10 dias em temperatura ambiente (25°C). Sob essas condições, a firmeza dos frutos no momento da colheita é adequada ao transporte e são visualizados melhores resultados para os índices de qualidade, tais como sólidos solúveis e relação sólidos solúveis/acidez titulável, ao longo do período de armazenamento. A aplicação de 1-MCP retarda o pico climatérico em ameixa \"Gulfblaze\". Aplicação de 450 nL L-1 de 1-MCP seguido do armazenamento a 1°C mantém a qualidade desses frutos durante 36 dias de armazenamento refrigerado, proporcionando firmeza, cor e sabor adequados a comercialização e consumo mesmo após seis dias de armazenamento a 25°C. A aplicação de etileno em ameixa \"Gulfblaze\" tratada com 1-MCP não provocou aumento na atividade respiratória e na produção de etileno, tampouco antecipou o climatérico. Embora a perda de massa e a acidez titulável nos frutos tratados com 1-MCP e etileno tenha sido maior que nos demais tratamentos, essa combinação permitiu a manutenção da coloração da casca mais próxima daquela observada na colheita e proporcionou maiores valores para o teor de sólidos solúveis e atividade antioxidante. A aplicação de 1-MCP e etileno aos 18 dias proporcionou maior conteúdo de antocianina na casca e maior teor de vitamina C na polpa. A aplicação do 1-MCP inibiu o surgimento de injúrias por frio, mesmo em frutos tratados com etileno. / The Gulfblaze plum, also known as FLA 87-7, is a Japanese plum cultivar that stands out for fruit size, earliness and resistance to the leaf scald disease, which has been hindering the production of plums in Brazil. This cultivar was incorporated into the Active Germplasm Bank of IAC around the \'60s and \'70s, but there are few papers related to information about their physiology, conservation and post-harvest storage. Plums have a short post-harvest period, and further technology is necessary to increase their shelf life and maintain quality, primarily by minimizing the deleterious effects of ethylene from ripening until the time of arrival to the consumer. In order to suggest improvements in the management and conservation of postharvest quality and promote longevity plum \'Gulfblaze\', some experiments were carried out. Three studies resulted from these experiments: The first study investigated the point of ideal harvest based on ripeness, the second one investigated refrigeration associated with 1-MCP to extend the storage time, and the third paper tested the hypothesis that the application of ethylene could restart the regular process of maturation of chilled fruit, interrupted by 1-MCP, and uniform ripening. \'Gulfblaze\' plums exhibit a climacteric ripening pattern, and when harvested within 50-75% of a cultivar\'s characteristic color, they have regular maturation with an brand longevity of 10 days at room temperature (25°C). In that condition, the fruit has greater potential for marketing and consumption, with a proper firmness transport at harvest and better results for the quality indexes such as soluble solids and soluble solids / titratable acidity during the storage period. The application of 1-MCP slows the climacteric peak in \'Gulfblaze\' plums. Application 450 nL L-1 1-MCP followed by storage at 1°C maintains the quality of the fruit during 36 days of cold storage, providing firmness, color and flavor suitable for marketing and consumption even after six days of storage at 25°C. The application of ethylene in \'Gulfblaze\' plums treated with 1-MCP did not cause an increase in respiratory activity and ethylene production, nor did it anticipate the climacteric. Although weight loss and titratable acidity in fruit treated with 1-MCP and ethylene was higher than other treatments, this combination allowed the maintenance of the peel color closer to that observed at harvest, and it gave higher values for the solids and soluble antioxidant activity. The application of 1-MCP and ethylene in the 18th day showed higher content of anthocyanin in the skin and higher content of vitamin C in the pulp. The application of 1-MCP inhibited the incidence of chilling injuries, even in ethylene treated fruit.

Submitted by Claudia Rocha (claudia.rocha@udesc.br) on 2018-02-27T14:30:45Z No. of bitstreams: 1 PGPV16MA207.pdf: 1304865 bytes, checksum: 7b2854584ba3fabd5f5a4cf59285f1f4 (MD5) / Made available in DSpace on 2018-02-27T14:30:45Z (GMT). No. of bitstreams: 1 PGPV16MA207.pdf: 1304865 bytes, checksum: 7b2854584ba3fabd5f5a4cf59285f1f4 (MD5) Previous issue date: 2016-07-28 / Capes / ‘Laetitia’ plums develop internal browning during cold storage. The severity of this disorder is associated with factors such as harvest time, storage time, and oxidative stress. The occurrence of this disorder and rapid ripening of fruits during storage are the main challenges after harvesting plums. Methods such as initial low oxygen stress (ILOS) and heat treatments and ethanol vapor application can be alternatives for controlling internal browning and delaying ripening of fruits. The aim of this study was to evaluate the effect of ILOS, heat treatments and ethanol vapor application on both ripening of fruits and internal browning in ‘Laetitia’ plums cold stored, as well as on the oxidative stress on fruit pulp tissues. The fruits used in the experiments were from commercial orchards located in the municipalities of Urubici, Santa Catarina, 2014/15 and 2015/16 seasons and Vacaria, Rio Grande do Sul, 2014/15. In experiment 1, the following treatments were evaluated: control, ethanol vapor application (0.15%), heat treatment (37ºC/24 h), heat treatment (40ºC/6 h), heat treatment (37°C/24 h) + ethanol vapor application (0.15%), and heat treatment (40ºC/6 h) + ethanol vapor application (0.15%). In experiment 2, the following treatments were evaluated: maintenance of the fruits for 48 h under environmental conditions (20°C ± 5°C/63% ± 2% RH), and five periods of ILOS (1.0 kPa O2) (0, 12, 24, 48, and 72 h) under environmental conditions. Each treatment was performed four times, and an experimental unit comprised 20 fruits. Fruits were stored (1±0.2°C e 92±2% de RH) during 35 days. In experiment 1, heat treatment at both temperatures resulted in a lower incidence of internal browning. The combination of heat treatment at 40°C for 6 h plus ethanol vapor application reduced the ethylene production rate, severity of internal browning, concentration of phenolic compounds, and antioxidant activity. It also maintained greater flesh firmness and POD and SOD activities. In experiment 2, fruits from the treatments with ILOS, at 2014/15, showed lower ethylene production and respiratory rates, less internal browning, as well as greater SOD enzyme activity. Fruits that presented a reddish epidermis color and had a greater fruit compression force and flesh firmness during the 48 and 72 h of ILOS treatment. ILOS treatment for 12 and 24 h led to decreased H2O2 production and greater SOD activity. In fruits from 2015/16, ILOS treatment for 12 h provided greater fruit compression force and flesh firmness and lower ethylene production rate, with less internal browning, lipid peroxidation, and POD and SOD activities / Ameixas ‘Laetitia’ desenvolvem escurecimento de polpa durante o armazenamento refrigerado e a severidade do distúrbio está associada a fatores como ponto de colheita, tempo de armazenamento, estresse oxidativo, entre outros. A ocorrência deste distúrbio e o rápido amadurecimento dos frutos durante o armazenamento caracterizam os principais desafios para a pós-colheita de ameixas. Tratamentos como o estresse inicial por baixo oxigênio (ILOS), tratamento térmico e o etanol podem ser alternativas para o controle do escurecimento de polpa e retardo do amadurecimento dos frutos. O objetivo deste trabalho foi avaliar o efeito do estresse por baixo oxigênio, do tratamento térmico e da aplicação de vapor de etanol sobre o amadurecimento e o escurecimento de polpa em ameixas ‘Laetitia’ armazenadas sob refrigeração, bem como sobre o estresse oxidativo no tecido da polpa dos frutos. Os frutos foram provenientes de pomares comerciais situados nos municípios de Urubici, SC, nas safras 2014/15 e 2015/16, e Vacaria, RS, na safra de 2014/15. No experimento 1, os tratamentos avaliados foram controle, aplicação de vapor de etanol (0,15%), tratamento térmico (37ºC/24 h), tratamento térmico (40ºC/6 h), tratamento térmico (37°C/24 h) + vapor de etanol (0,15%) e tratamento térmico (40ºC/6 h) + vapor de etanol (0,15%). Para o experimento 2, os tratamentos avaliados foram manutenção dos frutos em condições ambiente por 48 horas (20±5ºC/UR de 63±2%) e cinco períodos de ILOS (1,0 kPa O2) (0, 12, 24, 48, 72 horas) em condições ambiente. Cada tratamento foi composto de quatro repetições e unidade experimental constituída de 20 frutos. Os frutos foram armazenados (1±0,2°C e 92±2% de UR) durante 35 dias. No experimento 1 o tratamento térmico, em ambas as temperaturas, resultou em menor incidência de escurecimento de polpa. A combinação de tratamento térmico 40°C por 6 horas mais aplicação de vapor de etanol reduziu a taxa de produção de etileno, a severidade do escurecimento de polpa e a concentração de compostos fenólicos e atividade antioxidante e manteve maior firmeza da polpa e atividade da POD e SOD. No experimento 2 os frutos dos tratamentos com ILOS, safra 2014/15, apresentaram menor taxas de produção de etileno e respiratória e menor incidência de escurecimento da polpa, bem como maior atividade da enzima SOD. Os frutos com cor da epiderme menos vermelha e maior força para compressão do fruto e firmeza de polpa foram observados em ILOS por 48 e 72 horas. Menor quantidade de H2O2, e maior atividade da SOD foram obtidos nos tratamentos com ILOS por 12 e 24 horas. Em frutos da safra 2015/16, o tratamento com ILOS por 12 horas proporcionou maior força para compressão do fruto e firmeza de polpa e menor taxa de produção de etileno, incidência de escurecimento da polpa, peroxidação de lipídios e atividade da POD e SOD