Nutritional Contribution of an Undervalued Ancestral Cucurbita, Study of Sicana sp. Endocarp, Epicarp and Seeds Composition

Native to South America, the Sicana sp. fruits, known in Paraguay as “kurugua”, belongs to the Cucurbit family and is almost extinct in the region. The aim of this study was to determine the physicochemical characteristics, composition and antioxidant activity of “kurugua” with reddish peel color. The determinations were made by official and regional standardized methodologies on fresh weight (FW). The pulp has an alkaline pH (7.41 ± 0.11), and its main components are carbohydrates (9.44 ± 0.45 g·100 g−1), followed by dietary fiber (1.74 ± 0, 04 g·100 g−1), as minor proteins (0.53 ± 0.05 g·100 g−1) and lipids (0.08 ± 0.01 g·100 g−1). On the evaluated antioxidants compounds, they were higher in peel than in pulp as; total phenols (279.2 ± 12.1, 55.7 ± 10.3 mg of GAE·100 g−1), Vitamin C (9.67 ± 0.09, 7.84 ± 1.71 mg·100 g−1) and beta-carotene (0.37 ± 0.03, 0.19 ± 0.01 mg·100 g−1), respectively. Fresh seeds have a high moisture content (38.8%), dietary fiber (40.2%) and lipids (11.74%), they mineral composition showed a high content of Mg and Ca and a high content of micronutrients such as Cu, Mn, Fe and Zn, which can represent a great contribution to the daily requirements of the diet. The red kurugua fruits are a natural source of nutritious and bioactive compounds beneficial to health, with multiple potential applications in foodstuff, which should be promoted in healthy dietary guidelines for the benefit of the populations.

The Transcriptome and Metabolome Reveal Stress Responses in Sulfur-Fumigated Cucumber (Cucumis sativus L.)

Sulfur (S) fumigation is a commonly used sterilization method in horticultural facilities against fungal diseases. S fumigation damaged cucumber leaves, although the response mechanism is unclear. This study analyzes the growth, transcriptome, and metabolomic profiles of young and mature leaves, ovaries, and commercial cucumber fruits to decipher the mechanism of cucumber stress response under S fumigation. S fumigation significantly changed the photosynthetic efficiency and reactive oxygen species (ROS) in leaves, but not fruit development, fruit mass, and peel color. Transcriptome analysis indicated that S fumigation strongly regulated stress defense genes. The weighted gene co-expression network analysis revealed that S fumigation regulated ASPG1, AMC1 defense genes, LECRK3, and PERK1 protein kinase. The abscisic acid (ABA)-mediated model of regulation under S fumigation was constructed. Metabolome analysis showed that S fumigation significantly upregulated or downregulated the contents of amino acids, organic acids, sugars, glycosides, and lipids (VIP > 1 and P-value < 0.05). The opposite Pearson’s correlations of these differential metabolites implied that cucumber had different metabolic patterns in short-term and long-term S fumigation. Besides, the elevated levels of proline and triglyceride indicated that stress-responsive mechanisms existed in S-fumigated cucumber. Moreover, the comprehensive analysis indicated that S fumigation elevated secondary S-containing metabolites but decreased sulfate absorption and transportation in cucumber. Overall, our results provided a comprehensive assessment of S fumigation on cucumber, which laid the theoretical foundation for S fumigation in protected cultivation.

Bioactive Compounds, Sugars, and Sensory Attributes of Organic and Conventionally Produced Courgette (Cucurbita pepo)

Organic agriculture is considered one of the elements of sustainable food production and consumption, mainly due to its limited impact on the natural environment. At the same time, the quality features of organically produced foods, especially sensory attributes and health promoting values, are important factors determining consumers’ interest, and therefore play a key role in the organic sector’s development. The aim of this study was to investigate the sensory characteristics and concentrations of sugars and selected health-promoting bioactive compounds of organic courgette compared to conventionally grown courgette. In addition, untargeted metabolomic analysis of the courgette fruits was performed. The results of this study did not show a significant effect of the horticultural system (organic vs. conventional) on the concentrations of vitamin C, carotenoids, and chlorophylls in the courgette fruits. However, the fruits from the organic systems were significantly richer in sugars when compared to the conventionally cultivated ones (p = 0.038). Moreover, the organic fruits fertilized with manure contained significantly higher amounts of polyphenols, including gallic acid (p = 0.016), chlorogenic acid (p = 0.012), ferulic acid (p = 0.019), and quercetin-3-O-rutinoside (p = 0.020) compared to the conventional fruits. The untargeted analysis detected features significantly differentiating courgette fruits depending on the cultivar and horticultural system. Some significant differences in sensory values were also identified between fruits representing the two cultivars and coming from the horticultural systems compared in the study. Conventional courgettes were characterized by the most intensive peel color and aquosity, but at the same time were the least hard and firm compared to the fruits from the two organic systems. There was also a trend towards higher overall quality of the organically grown fruits. The presented study shows that the organic and conventional courgette fruits differ in a number of quality features which can influence consumers’ health and purchasing choices.

Identification and Application of BhAPRR2 Controlling Peel Colour in Wax Gourd (Benincasa hispida)

Peel color is an important factor affecting commodity quality in vegetables; however, the genes controlling this trait remain unclear in wax gourd. Here, we used two F2 genetic segregation populations to explore the inheritance patterns and to clone the genes associated with green and white skin in wax gourd. The F2 and BC1 trait segregation ratios were 3:1 and 1:1, respectively, and the trait was controlled by nuclear genes. Bulked segregant analysis of both F2 plants revealed peaks on Chr5 exceeding the confidence interval. Additionally, 6,244 F2 plants were used to compress the candidate interval into a region of 179 Kb; one candidate gene, Bch05G003950 (BhAPRR2), encoding two-component response regulator-like protein Arabidopsis pseudo-response regulator2 (APRR2), which is involved in the regulation of peel color, was present in this interval. Two bases (GA) present in the coding sequence of BhAPRR2 in green-skinned wax gourd were absent from white-skinned wax gourd. The latter contained a frameshift mutation, a premature stop codon, and lacked 335 residues required for the protein functional region. The chlorophyll content and BhAPRR2 expression were significantly higher in green-skinned than in white-skinned wax gourd. Thus, BhAPRR2 may regulate the peel color of wax gourd. This study provides a theoretical foundation for further studies of the mechanism of gene regulation for the fruit peel color of wax gourd.

Effects of mode and timing of calcium chloride application on tissue calcium concentration and acceptability of mango fruits

Mango (Mangifera indica L) production in Kenya directly supports approximately 200,000 farmers and many other beneficiaries. Despite this, its production suffers from post-harvest losses due to the fruits' short shelf life in ambient conditions. Calcium maintains cell integrity, strengthens the cell wall, membrane structure, and thus increases shelf life. A completely randomized block design with a split plot arrangement was used to compare the effect of spraying and immersion of ‘Van Dyke' mango fruits at maturity or 15 days later in calcium chloride at different concentrations (0.5%, 1%, 1.5%, or 0%) and times on the fruit ripening rate and organoleptic acceptance. The peel firmness (N), total soluble solids (0Brix), flesh color (Ho), beta carotene (mg/100ml), and carbon dioxide evolution (ml/kg/hr) of fruits were determined at time 0 and every two days for up to eight days in ambient conditions. Additionally, organoleptic characteristics, flesh firmness, calcium concentration (g/mg), and their correlations were determined. Fruits immersed in calcium chloride at maturity had higher retained peel firmness (10.6 N, 10.3 N), deeper flesh color (37.45, 36.78), lower total soluble solids (14, 13.8), a lower carbon dioxide evolution (30.7 ml/kg/hr), higher beta carotene and higher flesh calcium concentration than fruits exposed to other treatments. Fruits sprayed at maturity outperformed those sprayed 15 days later in the studied parameters. Flesh calcium content correlated positively with flesh firmness (r= 0.913, r= 0.852), flesh color (r= 0.828, r= 0.841), fruit aroma (r=0.8199, r=0.841), and negatively with skin shriveling (r=-0.778, r=-0.806) and fruit flavor (r=-0.811, r=-0.829). Flesh firmness correlated negatively with skin shriveling (r=-0.868, r=-0.788) and fruit flavor (r=-0.8869, r=-0.821), but positively with peel color (r=0.9115, r=0.856) and aroma (r=0.907, r=0.848). Skin shriveling was found to have a negative relationship with peel color (r=-0.944, r=-0.93) and aroma (r=-0.944, r=-0.938), but a positive relationship with fruit flavor (r=0.933, r=0.947). Peel color correlated positively with aroma (r=0.979, r=0.977) and negatively with fruit flavor (r=-0.962, r=-0.950), respectively. Despite the effectiveness of post-harvest calcium chloride immersion in extending fruit shelf life, optimal use is advised to avoid deteriorated pulp flavor and increased shriveling. More research is needed to determine how calcium chloride can be made available to the fruit while it is still attached to the tree.

PME and CaCl2 vacuum infusion maintains the firmness and physicochemical characteristics of tomato fruits

Tomato is a fruit of great commercial importance and highly cultivated. However, postharvest losses represent one of the main problems of this crop and can be minimized as alternative techniques. Therefore, the objective of the present work was to maintain tomato firmness by applying calcium chloride-associated pectin-methylesterase (PME) by the vacuum infusion method. Tomatoes of cultivar IAP-6 were submitted to vacuum infusion with water, vacuum infusion with 5% calcium chloride and vacuum infusion with PME associated with 5% calcium chloride, fruits without infusion were used as control. Fresh mass loss, fruit firmness, peel color, soluble solids content, pH, total acidity, PME activity and calcium activity were evaluated. The experiment was carried out in a completely randomized design in a 4x5 factorial scheme with three replications for 12 days, evaluated every 3 days. The means were compared using the Tukey test (p <0.05). Data were analyzed graphically with confidence interval (CI p <0.05). Regarding the loss of fresh mass there was an increase over time in all treatments. The PME + CaCl2 5% treatment was the most suitable for reducing firmness loss, as well as presenting the smallest variation of PME activity, as well as low levels of organic acids. Therefore, vacuum infusion with PME + CaCl2 in tomatoes maintains acceptable firmness and physicochemical characteristics as well as CaCl2 infusion.

Fruit quality and harvest point determination in white-fleshed dragon fruit

The objective of this study was to evaluate the quality of white-fleshed dragon fruit (Hylocereus undatus) at harvest and postharvest to determine fruit quality and the feasibility of harvesting the fruits at different outer fruit color stages. The treatments consisted of four peel color stages – S1 (<25% red peel), S2 (25%-49% red peel), S3 (50% to 75% red peel) and S4 (>75% red peel) – and two evaluation times (at harvest and one day after full red peel color), which corresponded to 1, 3, 5 and 7 days after harvest for the S4, S3, S2 and S1 color stages, respectively. The total, peel and pulp weights, pulp yield, peel thickness, pulp firmness, pH, total soluble solids and peel, scale and pulp colors were evaluated. The peel and scale colors are reliable indicators of fruit quality. It is possible to extend the postharvest shelf life of the fruits by harvesting at the S1 stage, but this negatively affects yield and final quality; the fruits are smaller and less sweet, making harvesting unfeasible at this timepoint. Despite the higher yield and quality of fruits harvested at a more advanced ripeness stage (S4), the postharvest shelf life is considerably reduced. Thus, fruits at stages S2 or S3 should be harvested to obtain higher yield and quality.

Can Sustained Deficit Irrigation Save Water and Meet the Quality Characteristics of Mango?

Mango is one of the most cultivated tropical fruits worldwide and one of few drought-tolerant plants. Thus, in this study the effect of a sustained deficit irrigation (SDI) strategy on mango yield and quality was assessed with the aim of reducing irrigation water in mango crop. A randomized block design with four treatments was developed: (i) full irrigation (FI), assuring the crop’s water needs, and three levels of SDI receiving 75%, 50%, and 33% of irrigation water (SDI75, SDI50, and SDI33). Yield, morphology, color, titratable acidity (TA), total soluble solids (TSS), organic acids (OA), sugars, minerals, fiber, antioxidant activity (AA), and total phenolic content (TPC) were analyzed. The yield was reduced in SDI conditions (8%, 11%, and 20% for SDI75, SDI50, and SDI33, respectively), but the irrigation water productivity was higher in all SDI regimes. SDI significantly reduced the mango size, with SDI33 generating the smallest mangoes. Peel color significantly changed after 13 days of ripening, with SDI75 being the least ripe. The TA, AA, and citric acid were higher in SDI75, while the TPC and fiber increased in all SDI levels. Consequently, SDI reduced the mango size but increased the functionality of samples, without a severe detrimental effect on the yield.

Comprehensive Analysis of Transcriptome and Metabolome Reveals the Flavonoid Metabolic Pathway Is Associated with Fruit Peel Coloration of Melon

The peel color is an important external quality of melon fruit. To explore the mechanisms of melon peel color formation, we performed an integrated analysis of transcriptome and metabolome with three different fruit peel samples (grey-green ‘W’, dark-green ‘B’, and yellow ‘H’). A total of 40 differentially expressed flavonoids were identified. Integrated transcriptomic and metabolomic analyses revealed that flavonoid biosynthesis was associated with the fruit peel coloration of melon. Twelve differentially expressed genes regulated flavonoids synthesis. Among them, nine (two 4CL, F3H, three F3′H, IFS, FNS, and FLS) up-regulated genes were involved in the accumulation of flavones, flavanones, flavonols, and isoflavones, and three (2 ANS and UFGT) down-regulated genes were involved in the accumulation of anthocyanins. This study laid a foundation to understand the molecular mechanisms of melon peel coloration by exploring valuable genes and metabolites.