A healthy lifestyle includes fruits and vegetables consumption. Tomato is one of the most consumed vegetables, although it is susceptible to physical damage through postharvest handling, thus leading to important losses. Softening is an important variable during tomato ripening; excessive softening is undesirable and leads to postharvest losses. TomloxB plays an important role in ripening, mainly in the loss of cellular integrity caused by fatty acids released from the lipid matrix of membranes that initiate oxidative deterioration, which is in turn carried into senescence. In order to increase postharvest life, we produced transgenic tomato plants via Rhizobium radiobacter with tomato lipoxygenase B (TomloxB) antisense constructs under control of the cauliflower mosaic virus (CaMV) 35S promoter. Lipoxygenase activity and firmness were measured in tomato fruit and the fatty acids profile was determined. Transgenic fruits were maintained for 40 days at room temperature in optimal conditions, whereas wild type fruits remained in similar conditions for only six days. Firmness in pink and red stages was significantly lower in wild type fruits than in two transgenic lines. Linolenic acid was the most important fatty acid consumed by lipoxygenase in both turning and pink stages of ripening. Lipoxygenase activity was smaller in transformed fruits in comparison with the wild type. These results suggest that silencing the TomloxB gene promoted significant changes in the physiology of transformed tomatoes, being the increase in postharvest life the most important.

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Lipoxygenase (LOX) enzyme activity and their putative isoforms were investigated during postharvest life in chayote fruit (Sechium edule Jacq. Sw. cv. “virens levis”). Possible associations of LOX with fruit quality parameters are discussed. Five LOX isoforms were identified (SeLOX‐1 to −5) displaying different activity patterns during ripening and senescence as well as in roots, stems, and leaves. The probable role of SeLOX‐5 as a specific isoform linked to senescence was examined. The highest relative activity of LOX was registered in fruit tissue, followed by leaves, stem, and roots. Correlations were found between LOX and fruit composition variables such as the contents of linoleic (LA) and linolenic (LNA) acids, weight loss, CO2 and ethylene production rates. LOX activity, and LA and LNA concentration decreased from Day 1 to Days 13–17, when early seed germination events became visible, indicating a transition stage between late fruit ripening and early senescence characterized by a deteriorative process. Practical applications Detrimental effects on fruit composition variables such as dehydration, weight loss, wilting, and sprouting symptoms, have been reported as the main causes that reduce the commercial quality and shelf life in chayote fruit and prevent their export to distant markets. To the best of our knowledge, the association of lipoxygenase (LOX) enzymes to non‐climacteric fruit ripening—like chayote—or their loss of commercial quality during prolonged shelf life has not yet been described. This is the first study that explores the role of chayote LOX activity in fruit, identifies various specific LOX isoforms associated to ripening or to the senescence process and provides new evidence that supports the hypothesis that putative LOX isoforms might be related to several postharvest detrimental effects on chayote fruit. This information could be useful to food processors or packers to pursue better profitability and consumer satisfaction.

Research background. TomloxB is the main isoform of lipoxygenase associated with ripening and senescence of fruits. On the other hand, ethylene, a gaseous hormone, is essential for the regulation of ripening in climacteric fruits like tomatoes. However, the relationship between TomloxB and ethylene production has not been thoroughly studied. Therefore, we aim to assess the effect of exogenous ethylene in transgenic tomatoes that contain a silenced TomloxB gene, and subsequently evaluate lipoxygenase activity, 1-aminocyclopropane-1-carboxylic acid oxidase and ethylene production; as well as to quantify the expression of the genes encoding 1-aminocyclopropane-1-carboxylic acid oxidase and TomloxB.Experimental approach. To investigate the effect of lipoxygenase and 1-aminocyclopropane-1-carboxylic acid oxidase activity, fruits harvested at the stages of break, turning and pink were used. Tomatoes at break stage collected from transgenic and wild type plants were used to determine ethylene production and gene expression. Genetically modified and wild type tomato fruits were exposed to 100 μL/L exogenous ethylene. Lipoxygenase activity was measured spectrophotometrically. Activity of 1-aminocyclopropane-1-carboxylic acid oxidase and ethylene production were determined by gas chromatography. Oligonucleotides for differentially expressed genes: 1-aminocyclopropane-1-carboxylic acid oxidase and TomloxB were used to determine gene expression by real-time PCR.Results and conclusions. The data showed that silencing of TomloxB caused a reduction in lipoxygenase activity and ethylene production in tomato fruits, and also reduced 1-aminocyclopropane-1-carboxylic acid oxidase activity. Hence, the addition of exogenous ethylene increased lipoxygenase activity in all treatments and 1-aminocyclopropane-1-carboxylic acid oxidase activity only in transgenic lines at break stage, consequently there was a positive regulation between TomloxB and ethylene, as increasing the amount of ethylene increased the activity of lipoxygenase. The results suggest that lipoxygenase may be a regulator of 1-aminocyclopropane-1-carboxylic acid oxidase and production of ethylene at break stage.Novelty and scientific contribution. These results lead to a better understanding of the metabolic contribution of TomloxB in fruit ripening and how it is linked to the senescence-related process, which can lead to a longer shelf life of fruits. Understanding this relationship between lipoxygenase and ethylene can be useful for better post-harvest handling of tomatoes.

La guanábana (Annona muricata L.) es una fruta climatérica que posee una vida útil corta (6 a 8 días). Esta característica limita su transporte y comercialización. El objetivo del presente trabajo fue conocer el efecto de algunos pretratamientos sobre el oscurecimiento superficial en guanábana. Se evaluó el efecto del tratamiento hidrotérmico a 50 °C durante 20 min, la aplicación del fungicida Azoxystrobin® a 300 mg L-1 y el recubrimiento Semperfresh® (1:20) sobre la respuesta a la maduración y oscurecimiento superficial en frutos de guanábana almacenados a 16 ±2 °C y 25 ±2 °C. Se observó una vida útil de 7 días en los tratamientos almacenadas a 25 ±2 °C y de 9 días para los almacenadas a 16 ±2 °C, comparadas con el testigo que fue de seis días. La combinación de fungicida y el recubrimiento fue la condición que produjo los mejores resultados, debido a que se retardó el oscurecimiento de la cáscara. Los mejores tratamientos que evidenciaron el mayor control frente a las pudriciones y la antracnosis fueron la aplicación del fungicida y el tratamiento hidrotérmico-fungicida con 46 y 38.5% de severidad de pudriciones, respectivamente. La temperatura de 16 ±2 °C fue la mejor en mantener los frutos viables por más tiempo. El tratamiento hidrotérmico causó un oscurecimiento acelerado en la cáscara.