Tomato fruit ripening is triggered by the demethylation of key genes, which alters their transcriptional levels thereby initiating and propagating a cascade of physiological events. What is unknown is how these processes are altered when fruit are ripened using postharvest practices to extend shelf-life, as these practices often reduce fruit quality. To address this, postharvest handling-induced changes in the fruit DNA methylome and transcriptome, and how they correlate with ripening speed, and ripening indicators such as ethylene, abscisic acid, and carotenoids, were assessed. This study comprehensively connected changes in physiological events with dynamic molecular changes. Ripening fruit that reached ‘Turning’ (T) after dark storage at 20°C, 12.5°C, or 5°C chilling (followed by 20°C rewarming) were compared to fresh-harvest fruit ‘FHT’. Fruit stored at 12.5°C had the biggest epigenetic marks and alterations in gene expression, exceeding changes induced by postharvest chilling. Fruit physiological and chronological age were uncoupled at 12.5°C, as the time-to-ripening was the longest. Fruit ripening to Turning at 12.5°C was not climacteric; there was no respiratory or ethylene burst, rather, fruit were high in abscisic acid. Clear differentiation between postharvest-ripened and ‘FHT’ was evident in the methylome and transcriptome. Higher expression of photosynthetic genes and chlorophyll levels in ‘FHT’ fruit pointed to light as influencing the molecular changes in fruit ripening. Finally, correlative analyses of the -omics data putatively identified genes regulated by DNA methylation. Collectively, these data improve our interpretation of how tomato fruit ripening patterns are altered by postharvest practices, and long-term are expected to help improve fruit quality.

Banana blossoms are rich in fiber and nutrients and are a popular plant-based, vegan alternative to fish. However undesirable browning, usually visible at the peduncle cut-end, negatively impacts consumer acceptability of banana blossoms. The aim of this work was to develop safe alternatives to prevent browning in banana blossoms. First, the activities of primary enzymes associated with tissue browning, i.e., polyphenol oxidase (PPO), peroxidase (POD) and phenylalanine ammonia lyase (PAL), were assayed. Our data showed that PPO and POD were the key enzymes responsible for blossom browning as they increased in activity, reaching a maximum at pH 7, as browning developed. In contrast, PAL activity decreased, and total phenolic content did not change as browning progressed, indicating PAL was not induced by cutting and may not be involved in blossom browning. Second, to find antibrowning agents for banana blossoms that can substitute for the use of sodium metabisulfite (SMS), different organic acids of varying concentrations were tested. Among organic acids studied, treatment with 3% (w/v) oxalic acid was the most effective method and thus could be a safe substitution for SMS to prevent browning in banana blossoms.

One problem with the pink pulp color of the ‘Thong Dee’ (TD) pummelo (Citrus maxima [Burm.] Merr.) is that it becomes pale during some harvesting periods. The cause of the pale pulp is not known. Therefore, the aim of this study was to determine the effect of growing temperature and rainfall on carotenoid contents and pulp color in the TD fruit. The experiments were conducted in 11 harvesting periods over two years from four orchards. The pale pink pulp coincided with low lycopene and was observed when the average daily minimum temperature two months before harvest was less than 20°C. Lycopene content and a*, which indicates pulp ‘redness’, positively correlated with the average daily minimum temperature two months before harvest (r = 0.6644 and r= 0.6013, respectively). In addition, TD pulp mineral nutrients, which include N, P, K, Ca, Mg, Zn, Cu, Fe, B, Mn, and Na, were not significantly related to the lycopene levels or the pale pink color in the pulp (P> .05). It is possible to conclude that the pale pulp of pummelo fruit is caused by the growing temperature during fruit development. This is the first study that comprehensively addresses the effects of environmental conditions on the pulp color of pummelo fruit. Abbreviations : TD: ‘Thong Dee’; MAP: Months after pollination; ABA: Abscisic acid; GAs: Gibberellic acids; MEP: 2-C-methyl-D-erythritol 4-phosphate; TSS: Total soluble solids; TA: Titratable acidity; HPLC: High performance liquid chromatography; N: Nitrogen; P: Phosphorus; K: Potassium; Ca: Calcium; Mg: Magnesium; Cu: Copper; Zn: Zinc; B: Boron; Fe: Iron; Mn: Manganese; Na: Sodium