Determination of Quality Parameters in Mangetout (Pisum sativum L. ssp. arvense) by Using Vis/Near-Infrared Reflectance Spectroscopy.

Pisum sativum L. ssp. arvense, is colloquially called tirabeque or mangetout because it is eaten whole; its pods are recognized as a delicatessen in cooking due to its crunch on the palate and high sweetness. Furthermore, this legume is an important source of protein and antioxidant compounds. Quality control in this species requires the analysis of a large number of samples using costly and laborious conventional methods. For this reason, a non-chemical and rapid technique as near-infrared reflectance spectroscopy (NIRS) was explored to determine its physicochemical quality (color, firmness, total soluble solids, pH, total polyphenols, ascorbic acid and protein content). Pod samples from different cultivars and grown under different fertigation treatments were added to the NIRS analysis to increase spectral and chemical variability in the calibration set. Modified partial least squares regression was used for obtaining the calibration models of these parameters. The coefficients of determination in the external validation ranged from 0.50 to 0.88. The RPD (standard deviation to standard error of prediction ratio) and RER (standard deviation to range) were variable for quality parameters and showed values that were characteristic of equations suitable for quantitative prediction and screening purposes, except for the total soluble solid calibration model.

The ethylene receptors CpETR1A and CpETR2B cooperate in the control of sex determination in Cucurbita pepo.

High-throughput screening of an ethyl methanesulfonate-generated mutant collection of Cucurbita pepo using the ethylene triple-response test resulted in the identification of two semi-dominant ethylene-insensitive mutants: etr1a and etr2b. Both mutations altered sex determination mechanisms, promoting conversion of female into bisexual or hermaphrodite flowers, and monoecy into andromonoecy, thereby delaying the transition to female flowering and reducing the number of pistillate flowers per plant. The mutations also altered the growth rate and maturity of petals and carpels in pistillate flowers, lengthening the time required for flowers to reach anthesis, as well as stimulating the growth rate of ovaries and the parthenocarpic development of fruits. Whole-genome sequencing allowed identification of the causal mutation of the phenotypes as two missense mutations in the coding region of CpETR1A and CpETR2B, each one corresponding to one of the duplicates of ethylene receptor genes highly homologous to Arabidopsis ETR1 and ETR2. The phenotypes of homozygous and heterozygous single- and double-mutant plants indicated that the two ethylene receptors cooperate in the control of the ethylene response. The level of ethylene insensitivity, which was determined by the strength of each mutant allele and the dose of wild-type and mutant etr1a and etr2b alleles, correlated with the degree of phenotypic changes in the mutants.

Oxidative Stress Associated with Chilling Injury in Immature Fruit: Postharvest Technological and Biotechnological Solutions.

Immature, vegetable-like fruits are produced by crops of great economic importance, including cucumbers, zucchini, eggplants and bell peppers, among others. Because of their high respiration rates, associated with high rates of dehydration and metabolism, and their susceptibility to chilling injury (CI), vegetable fruits are highly perishable commodities, requiring particular storage conditions to avoid postharvest losses. This review focuses on the oxidative stress that affects the postharvest quality of vegetable fruits under chilling storage. We define the physiological and biochemical factors that are associated with the oxidative stress and the development of CI symptoms in these commodities, and discuss the different physical, chemical and biotechnological approaches that have been proposed to reduce oxidative stress while enhancing the chilling tolerance of vegetable fruits.

Advances in Postharvest Preservation and Quality of Fruits and Vegetables.

Numerous agricultural regions face the daunting task of providing high-quality fresh fruits and vegetables to increasingly competitive markets [...].

Use of Sub-Atmospheric Pressure Storage to Improve the Quality and Shelf-Life of Marmande Tomatoes cv. Rojito.

In this study, the feasibility of storing Marmande tomatoes (Solanum lycopersicum, cv Rojito) under hypobaric conditions was evaluated. The fruits were sorted into four lots of 72 fruits each. One lot was considered as a control, and the fruits were kept in the open box, while the fruits of the rest of the three remaining lots were enclosed in airtight containers and subjected to 101, 75 and 50 Kpa, respectively. Control fruits and airtight containers were kept at room temperature, and every three days from the beginning of the experiment the following main quality parameters were analysed: ethylene production rate, firmness, colour, total solids content, ascorbic acid, total phenolics and pigments, as well as a sensory analysis carried out by panellists. The results show that sub-atmospheric storage led a reduction in ethylene production, which was associated with a delay in ripening. The differences in the evolution of pigments were very significant, while a large degradation of chlorophylls was observed in the control fruits and in those kept at 101 kPa, in the fruits kept at 75 kPa and 50 kPa the degradation was much slower. In relation to carotenoid pigments, it was observed that sub-atmospheric treatments delayed their appearance compared to control and 101 kPa fruits. In relation to other quality parameters, it was found that control fruit and fruit held at 101 kPa softened more rapidly than fruit under sub-atmospheric conditions, whose loss of firmness was more gradual with differences found only at 9 and 12 days of storage with respect to fruit firmness at harvest. The appearance of these fruits was evaluated with the same score as at the time of harvesting, during 9 of the 12 days of the experiment, then a positive effect of sub-atmospheric treatments was also found in the sensory analysis. The results suggest that sub-atmospheric storage could be a suitable method of increasing the shelf-life of fruits.

Genetic and Pre- and Postharvest Factors Influencing the Content of Antioxidants in Cucurbit Crops.

Cucurbitaceae is one of the most economically important plant families, and includes some worldwide cultivated species like cucumber, melons, and squashes, and some regionally cultivated and feral species that contribute to the human diet. For centuries, cucurbits have been appreciated because of their nutritional value and, in traditional medicine, because of their ability to alleviate certain ailments. Several studies have demonstrated the remarkable contents of valuable compounds in cucurbits, including antioxidants such as polyphenols, flavonoids, and carotenoids, but also tannins and terpenoids, which are abundant. This antioxidant power is beneficial for human health, but also in facing plant diseases and abiotic stresses. This review brings together data on the antioxidant properties of cucurbit species, addressing the genetic and pre- and postharvest factors that regulate the antioxidant content in different plant organs. Environmental conditions, management, storage, and pre- and postharvest treatments influencing the biosynthesis and activity of antioxidants, together with the biodiversity of this family, are determinant in improving the antioxidant potential of this group of species. Plant breeding, as well as the development of innovative biotechnological approaches, is also leading to new possibilities for exploiting cucurbits as functional products.

Involvement of ethylene receptors in the salt tolerance response of Cucurbita pepo.

Abiotic stresses have a negative effect on crop production, affecting both vegetative and reproductive development. Ethylene plays a relevant role in plant response to environmental stresses, but the specific contribution of ethylene biosynthesis and signalling components in the salt stress response differs between Arabidopsis and rice, the two most studied model plants. In this paper, we study the effect of three gain-of-function mutations affecting the ethylene receptors CpETR1B, CpETR1A, and CpETR2B of Cucurbita pepo on salt stress response during germination, seedling establishment, and subsequent vegetative growth of plants. The mutations all reduced ethylene sensitivity, but enhanced salt tolerance, during both germination and vegetative growth, demonstrating that the three ethylene receptors play a positive role in salt tolerance. Under salt stress, etr1b, etr1a, and etr2b germinate earlier than WT, and the root and shoot growth rates of both seedlings and plants were less affected in mutant than in WT. The enhanced salt tolerance response of the etr2b plants was associated with a reduced accumulation of Na+ in shoots and leaves, as well as with a higher accumulation of compatible solutes, including proline and total carbohydrates, and antioxidant compounds, such as anthocyanin. Many membrane monovalent cation transporters, including Na+/H+ and K+/H+ exchangers (NHXs), K+ efflux antiporters (KEAs), high-affinity K+ transporters (HKTs), and K+ uptake transporters (KUPs) were also highly upregulated by salt in etr2b in comparison with WT. In aggregate, these data indicate that the enhanced salt tolerance of the mutant is led by the induction of genes that exclude Na+ in photosynthetic organs, while maintaining K+/Na+ homoeostasis and osmotic adjustment. If the salt response of etr mutants occurs via the ethylene signalling pathway, our data show that ethylene is a negative regulator of salt tolerance during germination and vegetative growth. Nevertheless, the higher upregulation of genes involved in Ca2+ signalling (CpCRCK2A and CpCRCK2B) and ABA biosynthesis (CpNCED3A and CpNCED3B) in etr2b leaves under salt stress likely indicates that the function of ethylene receptors in salt stress response in C. pepo can be mediated by Ca2+ and ABA signalling pathways.

Effectiveness of Chemical and Thermal Treatments on Control Rhizopus Stolonifer Fruit Infection Comparing Tomato Cultivars with Different Sensitivities to Cracking.

Tomatoes are among the most important horticultural crops; however, it is estimated that 30% of tomato yield is lost due to postharvest rot due to Rhizopus stolonifer, a fungus which requires lesions to initiate the infectious process. Tomato fruit cracking is a physiopathy which causes significant economic losses, since cracking is the door used by the fungus. In this experiment, 14 cultivars of tomato of different types were used. Fruit sampling was carried out in the middle of the crop cycle, coinciding with the peak of yield; then, the fruits were divided into two groups: one group was inoculated with Rhizopus in order to assess the effectiveness of washing, whilst the other was treated with sterile water. The fruits of each group were divided into lots to be treated with six washing treatments: dipping in hot water at 20, 40 and 60 °C for 20 s; the fruits were then sprayed with the following solutions: 0.6% of Hydrogen Peroxide 23% + Peracetic acid 15%; commercial bleach at 0.5% and 2% of Hydrogen Peroxide 50%. The control sample was not washed. The results show that there was an influence of cultivar on fruit cracking, which was strongly related with Rhizopus infection. Three cultivars were not susceptible to cracking, and therefore, were not sensitive to Rhizopus infection. The effectiveness of different washing treatments of tomato fruits depends on several factors; nonetheless, hot water treatment has been shown to be more effective than the use of chemical products such as commercial bleach or hydrogen peroxide. Another factor, the susceptibility of cultivars to cracking, determines the effectiveness of the washing treatment. The results provide an important basis for making decisions about the washing management of tomato fruits in packaging houses.

The sex-determining gene CitACS4 is a pleiotropic regulator of flower and fruit development in watermelon (Citrullus lanatus).

In the species of the Cucurbitaceae family, the occurrence of separate male and female flowers in the same plant (monoecy) is controlled by an ethylene biosynthesis ACS gene, which specifically suppresses the development of stamen in the female flower. In watermelon, a mutation of loss of function in CitACS4 promotes the conversion of female into hermaphrodite flowers, and of monoecious into andromonoecious plants. We have studied whether the ethylene produced by CitACS4 enzyme could also be involved in other ethylene-regulated traits, including pistillate flowering transition and the number of female flowers per plant, the development of floral organs other than stamens, as well as fruit and seed set, and fruit development. A linkage analysis approach was performed in three independent F2 populations segregating for the two alleles of the gene (M, monoecious; m, andromonoecious), and the different traits under study. The CitACS4m allele not only cosegregated with andromonoecy, but also with earlier pistillate transition, an increased number of pistillate flowers per plant, and a slower growth and maturation of petals and carpels, which delayed anthesis time in hermaphrodite flowers. The m allele was also found to be linked to a reduced fruit set, which was not caused by a deficiency in pollination or fertilization. The gene also affected the longitudinal and transverse growth rates of the ovary and fruit, which means that fruits from andromonoecious plants (mm) were rounder than those from monoecious (MM) ones. Taken together, these data indicate that the locus defined by the ethylene biosynthesis and sex-determining gene CitACS4 acts as a pleiotropic regulator of the complete development of the pistillate flower and the earlier development of the fruit.

Individual Shrink Wrapping of Zucchini Fruit Improves Postharvest Chilling Tolerance Associated with a Reduction in Ethylene Production and Oxidative Stress Metabolites.

We have studied the effect of individual shrink wrapping (ISW) on the postharvest performance of refrigerated fruit from two zucchini cultivars that differ in their sensitivity to cold storage: Sinatra (more sensitive) and Natura (more tolerant). The fruit was individually shrink wrapped before storing at 4°C for 0, 7 and 14 days. Quality parameters, ethylene and CO2 productions, ethylene gene expression, and oxidative stress metabolites were assessed in shrink wrapped and non-wrapped fruit after conditioning the fruit for 6 hours at 20°C. ISW decreased significantly the postharvest deterioration of chilled zucchini in both cultivars. Weight loss was reduced to less than 1%, pitting symptoms were completely absent in ISW fruit at 7 days, and were less than 25% those of control fruits at 14 days of cold storage, and firmness loss was significantly reduced in the cultivar Sinatra. These enhancements in quality of ISW fruit were associated with a significant reduction in cold-induced ethylene production, in the respiration rate, and in the level of oxidative stress metabolites such as hydrogen peroxide and malonyldialdehyde (MDA). A detailed expression analysis of ethylene biosynthesis, perception and signaling genes demonstrated a downregulation of CpACS1 and CpACO1 genes in response to ISW, two genes that are upregulated by cold storage. However, the expression patterns of six other ethylene biosynthesis genes (CpACS2 to CpACS7) and five ethylene signal transduction pathway genes (CpCTR1, CpETR1, CpERS1, CpEIN3.1 and CpEN3.2), suggest that they do not play a major role in response to cold storage and ISW packaging. In conclusion, ISW zucchini packaging resulted in improved tolerance to chilling concomitantly with a reduction in oxidative stress, respiration rate and ethylene production, as well as in the expression of ethylene biosynthesis genes, but not of those involved in ethylene perception and sensitivity.