Postharvest Water Loss Research Articles

Osmolytes and CsAQP expression jointly influence water physiology in the peel and pulp of orange (Citrus sinensis (L.) Osbeck) fruit during postharvest water loss

Water loss is a serious issue affecting the quality of postharvest horticultural products. Aquaporins (AQPs) regulate the transport of water across biological membranes, along the gradient of water potential, and may play a role in water loss. In this study, matured orange fruits (Citrus sinensis) stored at ambinent temperature (RH 85-95%) for 105 d showed that the weight loss persistently increased, and its rate peaked at 45–60 d and 90–105 d. Both water content and potential were higher in the pulp than in the peel. Water content rose before 60 d, and peel water potential fell with an increased gradient after 60 d. Comparing with peel, osmolytes such as soluble sugar, sucrose, glucose, fructose, and organic acids showed higher accumulation, and their levels were the lowest around 60 d. In contrast, soluble protein and inorganic minerals showed low levels of accumulation in the pulp. In total, 31 CsAQP genes were expressed in the fruit, and most of them were down-regulated in the peel but up-regulated in the pulp during storage. These genes were subsequently classified into four clusters based on their expression patterns. Genes in Cluster I — including CsNIP1;1/2;1/2;2/2;3/3;1/4;1/6;1, CsTIP1;3/2;2/2;3/5;1/6;1, CsXIP1;1/1;2, CsSIP1;2, and CsPIP1;2 — were persistently up-regulated in the pulp for the 105 d of storage, especially at day 60, when some genes showed 103-fold higher expression. Pearson’s correlation and principal component analysis further revealed a significant positive correlation among weight loss rate, water content, and water potential gradient (R2 = 0.85). Indexes positively correlated with osmolyte content and Cluster I gene expression in pulp samples suggest that increased CsAQP gene expression in pulp is linked to faster water loss in oranges, particularly at 60 days postharvest.

Insect-derived chitosan, a biopolymer for the increased shelf life of white and red grapes

Post-harvest water loss and microbial infections are the root cause of the rapid deterioration of fresh fruit after the picking process, with both environmental and economic implications. Therefore, it is crucial to find solutions that can increase the shelf life of fresh fruits. For this purpose, edible coatings, naturally derived and non-synthetic, are acknowledged as a safe strategy. Among polymeric coatings, chitosan is one of the most effective. In this work, this biopolymer, produced from chitin extracted from Hermetia illucens, an alternative and more sustainable source than crustaceans (the commercial one), was exploited to extend the shelf life of white and red grapes. Chitosan from H. illucens pupal exuviae, at 0.5 % and 1 % concentrations, was applied on both grapes, which were then stored at room temperature or 4 °C. The study of chemical-physical parameters such as weight loss, Total Soluble Solids and pH, demonstrated the effectiveness of the biopolymer, even better than crustacean chitosan. Moreover, the analysis of nutraceutical properties has demonstrated that this natural edible coating improves the quality of grapes, with beneficial effects for human health. The obtained results, therefore, confirmed the viability of using insect-chitosan as an alternative to crustaceans for the preservation of fresh food.

Exploring Gene Action Underlying Post-Harvest Water Loss in Fresh Market Peppers

The objective of this study was to evaluate the genetic effects involved in post-harvest water loss of C. baccatum fruits and to correlate fruit morphological characteristics. Fruits of eight landraces of C. baccatum and their twenty-eight hybrids were evaluated in a randomized, complete block design. Analysis of variance, diallel analysis, phenotypic and genotypic correlation, and path analysis for eight fruit traits were performed. Fruit width, fruit length, dry matter content, and fruit wall thickness were determined by additive gene effects. On the other hand, the non-additive effects played more important role than additive ones, including water loss, cuticle thickness, exocarp thickness, and total soluble solids. The relationship of fruit traits suggested that indirect selection can be carried out from field experiments under different environmental conditions. Overall, genitors 4, 24, 50, and 56 should be selected to form new populations to improve these traits. The Brazilian pepper landraces of C. baccatum species are a source of genetic variability for plant breeders, and the new segregating populations emerging through the crossing of pepper lines with reduced water loss should be developed, opening new ways for conventional breeding.

Revealing the crucial role of cuticular wax components in postharvest water loss in passion fruit (Passiflora edulis Sims.)

Passion fruit (Passiflora edulis Sims.) is highly prone to water loss and shrinkage after harvesting. The fruit cuticle serves as a crucial barrier to prevent non-stomatal water loss. However, the impact of cuticle on water loss in passion fruit remains unclear. Therefore, the present study primarily focuses on the influence of the cuticle on postharvest water loss of passion fruit, specifically emphasizing the changes in cuticular wax components. Our results showed that both the thickness and content of cutin decreased during storage. The degradation of wax components exhibited a similar trend to fruit water loss. At the end of the storage, n-triacontane content was stored at 25 °C retained 2.8% of that at 7 °C. Follwed by stearic acid, palmitate, and so on, with amounts at 25 °C are 9.3% and 13.8% at 7 °C, respectively. Interestingly, the reduction of amides, erucamide and hexadecanamide lead to water loss in fruit. So far as we know, this is the first report demonstrating that cuticle amides influence water loss in fruit. This study provides new insights into the role of cuticle in the water loss of passion fruit.

Constitutive expression of apple endo-POLYGALACTURONASE1 in fruit induces early maturation, alters skin structure and accelerates softening.

During fruit ripening, polygalacturonases (PGs) are key contributors to the softening process in many species. Apple is a crisp fruit that normally exhibits only minor changes to cell walls and limited fruit softening. Here, we explore the effects of PG overexpression during fruit development using transgenic apple lines overexpressing the ripening-related endo-POLYGALACTURONASE1 gene. MdPG1-overexpressing (PGox) fruit displayed early maturation/ripening with black seeds, conversion of starch to sugars and ethylene production occurring by 80 days after pollination (DAP). PGox fruit exhibited a striking, white-skinned phenotype that was evident from 60 DAP and most likely resulted from increased air spaces and separation of cells in the hypodermis due to degradation of the middle lamellae. Irregularities in the integrity of the epidermis and cuticle were also observed. By 120 DAP, PGox fruit cracked and showed lenticel-associated russeting. Increased cuticular permeability was associated with microcracks in the cuticle around lenticels and was correlated with reduced cortical firmness at all time points and extensive post-harvest water loss from the fruit, resulting in premature shrivelling. Transcriptomic analysis suggested that early maturation was associated with upregulation of genes involved in stress responses, and overexpression of MdPG1 also altered the expression of genes involved in cell wall metabolism (e.g. β-galactosidase, MD15G1221000) and ethylene biosynthesis (e.g. ACC synthase, MD14G1111500). The results show that upregulation of PG not only has dramatic effects on the structure of the fruit outer cell layers, indirectly affecting water status and turgor, but also has unexpected consequences for fruit development.

SlCNR regulates postharvest water loss and wax accumulation in tomato fruit and directly represses the transcription of very-long-chain (VLC) alkane biosynthesis-related genes SlCER1-2 and SlCER6

Cuticular waxes play a crucial role in the control of quality and storability of fruit and many transcription factors (TFs) contribute to fruit wax accumulation and affect the postharvest water loss. The tomato SBP-box protein Colorless Non-Ripening (SlCNR) is commonly investigated as a TF regulating fruit ripening, and its regulation role in mediating postharvest water loss remains to be unknown. Here, we found that fruit of SlCNR knockout (KO) mutants (KO-SlCNR#16 and KO-SlCNR#23) generated by CRISPR/Cas9 editing system exhibited decreased postharvest water loss, while fruit of the SlCNR-overexpressing (OE-SlCNR#21 and OE-SlCNR#24) displayed increased water loss compared to the wild type (WT). The overall wax accumulation increased by 17–30% in fruit of SlCNR KO mutants and decreased by 26–42% in OE-SlCNR#21 and OE-SlCNR#24, accompanied by the change of major components of waxes, such as n-alkanes, triterpenoids, and primary alcohol. RNA-seq analysis showed that the expression of numerous genes involved in wax biosynthesis were up-regulated in fruit of KO-SlCNR#23, including SlCER1–2, which encodes one part of the VLC alkane formation complex, and SlCER6, which encodes a β-ketoacyl-coenzyme A synthase. Furthermore, we proved that SlCNR directly represses the transcription of wax biosynthetic genes SlCER1–2 and SlCER6 in vivo and in vitro, thereby negatively regulating wax accumulation. These findings expand our understanding in the genetic regulatory mechanisms governing ripe tomato fruit wax accumulation and present SlCNR as a novel target of wax accumulation and postharvest water loss.

1-Methylcyclopropene reduces postharvest water loss by modulating cuticle formation in tomato fruit

Water loss during fruit postharvest is influenced by both internal and external determinants. Although 1-MCP is extensively employed to prolong fruit storage life and retain quality by minimizing water loss, its influence on water loss rate remains underexplored. This research investigated the effect of 1-MCP on tomato fruit (Solanum lycopersicum cv. Micro-tom) at 5 days post-breaker stage with intact pedicels. The tomatoes were exposed to a 3-day fumigation with 1 μL L−1 1-MCP, followed by evaluations on fruit water loss, cuticle wax and cutin composition, and related gene expression. Our findings demonstrate that 1-MCP notably postponed fruit water loss and curbed ethylene production. It also modified cuticle wax biosynthesis by elevating specific alkanes (heptacosane, octacosane, nonacosane, triacontane, hentriacontane, dotriacontane, tritriacontane, tetratriacontane, and total alkanes), and 13-docosen-1-ol while diminishing triterpenoids and sterols. For cutin composition, 1-MCP increased the content of hexadecanedioic acid, 9,10-dihydroxyoctadecanoic acid, 9,10-dihydroxyoctadecanedioic acid, and 9,10,18-trihydroxyoctadecanoic acid. At the transcript level, 1-MCP upregulated the expression of SlCER2-Like1, SlCER3, SlCYP77A1, SlCYP77A2, and SlHTH, but downregulated the expression of SlLACS4. This study elucidates potential mechanisms underlying 1-MCP regulated water permeability during fruit postharvest.

Preharvest glycerol treatment enhances postharvest storability of orange fruit by affecting cuticle metabolism

Although cuticle is known to play an important role in the biotic and abiotic stress resistance of citrus fruit, there has been rare research on preharvest exogenous treatments to regulate cuticle metabolites and improve the postharvest storability of citrus fruit. In this study, the effect of spraying 10% glycerol 90 days before harvest on cutin, wax, fruit storability, and primary metabolites of citrus fruit was analyzed. The results demonstrated that exogenous glycerol could promote the biosynthesis of cutin at the early stage and delay the degradation of wax at the later stage of treatment, which could be attributed to the induction of genes associated with cuticle metabolism. Among them, the expression of CsLACS1, CsLACS2, CsCYP86A8, and CsMYB106 showed the highest correlation with cutin metabolism. Exogenous glycerol could further reduce postharvest water loss, decay, respiration rate, and accumulation off-flavor compounds such as acetaldehyde and ethanol, thereby improving fruit storability. Moreover, exogenous glycerol showed no effect on fruit quality before harvest, and the low levels of stress-response metabolites (such as γ-aminobutyric acid) suggested that glycerol-treated fruit were in a less stressful state compared to control fruit. In conclusion, preharvest glycerol treatment may be a safe and effective method to improve citrus fruit storability by regulating cuticle metabolism.

Desempenho de cultivares de pimenta, baseado em caracteres de frutos, para consumo in natura

ABSTRACT Different studies report that pepper fruit cuticle and pericarp thickness vary among marked cultivars and these variations likely influence many fruit quality traits, especially water loss rates. Thus, the objectives of this work was to evaluate the fresh market performance of pepper cultivars based on fruit traits, and indicate the cultivars of Capsicum spp. with less probability of post harvest water loss. Pepper fruits, belonging to C. chinense, C. frutescens and C. baccatum species, were collected in an experimental area at Bonfim’s settlement, Alagoinha, Paraíba, Brazil. After harvest, fruits were taken to the laboratory of biotechnology at Centro de Ciências Agrárias of the Universidade Federal da Paraíba. Fruits were characterized according to pericarp thickness, fruit weight, and fruit length, larger and smaller fruit diameter. The experimental design was completely randomized with eight treatments and four repetitions. Analysis of variance, mean test, heritability, and ratio of coefficient of genetic variation by coefficient of environmental variation, genotypic and environmental correlation, and Tocher’s grouping method were performed. The cultivar habanero vermelha had better performance for fruit weight and larger and smaller fruit diameter. On the other hand ‘dedo de moça’ presented the longest fruits and major pericarp thickness. These two cultivars also belonged to different groups based on Tocher’s method. The genetic correlation between pericarp thickness and fruit weight was high (0.70) and highly significant. Fruit wall thickness also presented highly significant genotypic correlation with larger fruit diameter (0.93) and small fruit diameter. (0.93). Those finds indicate that indirect selection for pericarp thickness could be done based on larger fruit diameter. These correlations are trustworthy and important due to the high heritability values presented for these traits. Some authors suggest selecting fruits with higher cuticle thickness and fruit width values due to lower water loss. Thus, we suggest that small farmers cultivate ‘habanero vermelha’ and ‘dedo de moça’ in order to produce fruits with extended shelf life.

Mineral Nutrients, Physiological Disorders, Postharvest Water Loss, and PR Gene Expression in Bell Pepper (Capsicum annuum L.) Fruit under Shade Nets

Abstract Shade nets can be an effective technology for producing bell pepper (Capsicum annuum L.) under hot climatic conditions. However, the effects of shading on fruit quality are still unclear. The objectives were to evaluate the effects of shade level on fruit mineral nutrient content, physiological disorders, and postharvest water loss. Trials were conducted in the spring–summer of 2016, 2017, and 2018 in Tifton, Georgia, USA, following a randomized complete block design with five shade levels: 0% (open field), 30%, 47%, 63%, and 80%. Shading increased the bell pepper fruit dimensions (length, diameter, and weight) in 2016 and mineral nutrient content in 2017. Fruit sunscald incidence decreased with increasing shade level, while blossom-end rot showed inconsistent responses. Postharvest fruit water loss and transpiration rates were highest in fruits from the unshaded treatment in 2016; there were no differences in fruit water loss among the shade levels. NONEXPRESSOR OF PATHOGENESIS-RELATED 1 (NPR1) and PATHOGENESIS-RELATED 1 (PR1) genes expressed more than 1.5-fold and 10-fold, respectively, at 47% shade level compared to 80%, though not significantly. Therefore, plants grown under shading had fruit with greater size, increased mineral nutrient content, and reduced sunscald incidence compared with the unshaded control.

QTL analysis reveals reduction of fruit water loss by NAC042 through regulation of cuticular wax synthesis in citrus fruit

Postharvest water loss is a critical factor that determines the quality and shelf life of fresh fruit. Cuticular wax constitutes a key barrier to reduce fruit water loss. Our previous study has shown that HJ (Citrus reticulata) has a significantly higher postharvest water loss rate than ZK (Poncirus trifoliata). Here, we investigated the fruit water loss rate of the HJ × ZK F1 pseudo-testcross population in 2016 and 2019. QTL mapping for fruit water loss rate was performed by high-density genetic map and bulk segregant analysis, and QTL9 was identified to be associated with fruit water loss. The expression of NAC042 from QTL9 in ZK was 170-fold that in HJ. Heterologous expression in Arabidopsis showed that NAC042 could reduce the water loss of leaves by increasing the cuticular wax content (especially alkanes). Further expression analysis revealed that NAC042 could enhance the expression of many wax-related genes in Arabidopsis leaves, including AtKCS1, AtKCS2, AtKCS9, AtKCS20, AtCER1 and AtCER3. Therefore, NAC042 might be involved in fruit cuticular wax synthesis to reduce fruit water loss. The findings provide new insights into the regulation of cuticular wax and fruit water loss as well as valuable information for breeding of citrus with better storability.

C24 and C26 aldehydes are potential natural additives of coating for citrus water retention

Water loss is a key factor for the postharvest senescence of fruit. It has been reported that natural cuticular wax at high concentrations has better performance than commercial coating in water retention of fruit, which can prevent postharvest water loss without the accumulation of off-flavor. Here, we analyzed the correlation between epicuticular wax and postharvest water loss with 75 citrus varieties from a natural population. The water loss rate of the fruit was little influenced by the wax microstructure (stomata and wax crystal morphology), but strongly affected by epicuticular wax components. Further, C24 and C26 aliphatic aldehydes showed the greatest impact on fruit water loss rate, whose correlation coefficients reached –0.63 and –0.67, respectively. These two substances could significantly reduce the fruit water loss rate, indicating that they are potential natural additives to be used in the coating for citrus fruit water retention.

Pathways of postharvest water loss from banana fruit

Transpiration affects the water balance of the skin of a banana. The objective was to monitor the skin permeance in ripening bananas and to identify the mechanism(s) and pathway(s) of water vapor movement from skin to atmosphere. Transpiration was quantified gravimetrically. Cumulative transpiration increased linearly with time. Inducing ripening using ethylene increased autocatalytic ethylene production, induced a change in skin color from green to yellow, but had no effect on the skin water vapor permeance. The permeance was highest at the calyx end of the fruit but there was no significant gradient of permeance along the remaining axis or among the three faces of the fruit. A banana fruit surface is stomatous. About 11% of the stomata were infiltrated by aqueous acridine orange; about 63% of stomata were infiltrated if a silicone surfactant was added. The skin permeance was closely related to the density of the stomata that were infiltrated with acridine orange without the surfactant. We calculate about 44% of total transpiration was stomatal, the remaining 56% was cuticular. The permeance of a hypothetical astomatous cuticle was estimated to be about 0.66 ( ± 0.06) × 10−4 m s−1. Along the cuticular pathway, the wax offered the largest resistance to transpiration, followed by the cutin matrix and, last, the cell wall. Transpiration rate was positively related to temperature, but negatively related to relative humidity. The results indicate transpiration is a physical process that occurs in ripening banana to about nearly equal extents via the stomata and via the cuticle.

Russeting of Fruits: Etiology and Management

The skin of a fruit protects the vulnerable, nutrient-rich flesh and seed(s) within from the hostile environment. It is also responsible for the fruit’s appearance. In many fruitcrop species, russeting compromises fruit appearance and thus commercial value. Here, we review the literature on fruit russeting, focusing on the factors and mechanisms that induce it and on the management and breeding strategies that may reduce it. Compared with a primary fruit skin, which is usually distinctively colored and shiny, a secondary fruit skin is reddish-brown, dull and slightly rough to the touch (i.e., russeted). This secondary skin (periderm) comprises phellem cells with suberized cell walls, a phellogen and a phelloderm. Russeted (secondary) fruit skins have similar mechanical properties to non-russeted (primary) ones but are more plastic. However, russeted fruit skins are more permeable to water vapor, so russeted fruits suffer higher postharvest water loss, reduced shine, increased shrivel and reduced packed weight (most fruit is sold per kg). Orchard factors that induce russeting include expansion-growth-induced strain, surface wetness, mechanical damage, freezing temperatures, some pests and diseases and some agrochemicals. All these probably act via an increased incidence of cuticular microcracking as a result of local concentrations of mechanical stress. Microcracking impairs the cuticle’s barrier properties. Potential triggers of russeting (the development of a periderm), consequent on cuticular microcracking, include locally high concentrations of O2, lower concentrations of CO2 and more negative water potentials. Horticulturists sometimes spray gibberellins, cytokinins or boron to reduce russeting. Bagging fruit (to exclude surface moisture) is also reportedly effective. From a breeding perspective, genotypes having small and more uniform-sized epidermal cells are judged less likely to be susceptible to russeting.

Morphological, physiochemical, and transcriptome analysis and CaEXP4 identification during pepper (Capsicum annuum L.) fruit cracking

In pepper (Capsicum annuum L.), fruit cracking is a common physical deformation that not only affects the fruit quality, but also increases the water loss rate during storage and reduces shelf-life and economic value. To comprehensively unravel the putative genes and mechanism underlying fruit cracking, the cracking-susceptible cultivar ‘L92’ was subjected to morphological, physiochemical and transcriptome analyses and an assay of postharvest water loss. The polygalacturonase, peroxidase, and cellulase activity levels and water-soluble pectin and lignin contents were significantly higher in FSC (fruit seriously cracking) fruits than in FNC (fruit without cracking) fruits. The hemicellulose and cellulose contents of FSC fruits were lower than those of FNC fruits; with non-significant differences in chelator trans-1,2-diaminocyclohexane-N,N,N0,N0-tetraacetic acid-soluble pectin and sodium carbonate-soluble pectin levels. By comparing the FSC with the FNC fruits and analyzing differentially expressed gene (DEG) profiles during the fruit cracking process, 1,574 DEGs were identified. Among them, 45 unigenes were significantly enriched in KEGG pathways related to cell wall metabolism and lignin biosynthesis. The silencing of CaEXP4 induced cells in the epidermal layer to be smaller and more neatly and tightly arranged, with a greater number of cell layers of the sub-epidermal layer compared with control fruit. Small structural modifications may lead to changes in cell wall structure and elasticity, which might have caused the fruit cracking. To the best of our knowledge, this is the first morphological, histological, physiochemical, and transcriptome analysis to show the role of CaEXP4 during cracking of pepper fruit.

Carboxymethyl cellulose-based water barrier coating regulated postharvest quality and ROS metabolism of pakchoi (Brassica chinensis L.)

The postharvest preservation of Brassica vegetables has received much attention for improving their nutritional and commercial value. In this study, carboxymethyl cellulose (CMC)-based cross-linking coating embedded with liquid paraffin was prepared to preserve fresh pakchoi (Brassica chinensis L.) and its effects on postharvest water loss, quality and reactive oxygen species (ROS) metabolism were evaluated. Results showed that ionic cross-linking and liquid paraffin reinforced the structure compactness and water barrier property of CMC coating by uniformly distributing liquid paraffin in cross-linking network. The novel CMC-based coating effectively reduced water loss and improved appearance and nutrition of fresh pakchoi stored at 25 °C and 60 % relative humidity for 48 h. Furthermore, the coating treatment enhanced ROS scavenging capacity and reduced lipid peroxidation, which was attributed to the improvement of antioxidant enzyme activities, ascorbate-glutathione cycle and phenylpropanoid metabolism. This work demonstrates that the novel CMC-based water barrier coating is promising to control the water loss of pakchoi and further maintain the whole quality by regulating ROS metabolism.

Variation in Petal and Leaf Wax Deposition Affects Cuticular Transpiration in Cut Lily Flowers

The vase life of cut flowers is largely affected by post-harvest water loss. Cuticular wax is the primary barrier to uncontrolled water loss for aerial plant organs. Studies on leaf cuticular transpiration have been widely conducted; however, little is known about cuticular transpiration in flowers. Here, the cuticular transpiration rate and wax composition of three lily cultivars were determined. The minimum water conductance of tepal cuticles was higher at the green bud than open flower stage. Lily cuticular transpiration exhibited cultivar- and organ-specific differences, where transpiration from the tepals was higher than leaves and was higher in the ‘Huang Tianba’ than ‘Tiber’ cultivar. The overall wax coverage of the tepals was higher compared to that of the leaves. Very-long-chain aliphatics were the main wax constituents and were dominated by n-alkanes with carbon (C) chain lengths of C27 and C29, and C29 and C31 in the tepal and leaf waxes, respectively. Primary alcohols and fatty acids as well as small amounts of alkyl esters, ketones, and branched or unsaturated n-alkanes were also detected in both tepal and leaf waxes, depending on the cultivar and organ. In addition, the chain-length distributions were similar between compound classes within cultivars, whereas the predominant C-chain lengths were substantially different between organs. This suggests that the less effective transpiration barrier provided by the tepal waxes may result from the shorter C-chain aliphatics in the tepal cuticle, compared to those in the leaf cuticle. These findings provide further insights to support the exploration of potential techniques for extending the shelf life of cut flowers based on cuticular transpiration barrier properties.

QTL analysis reveals the effect of CER1-1 and CER1-3 to reduce fruit water loss by increasing cuticular wax alkanes in citrus fruit

Postharvest water loss causes fruit softening, wilting, and a decline in quality and commodity value. Cuticular wax is a key barrier against non-stomatal water loss and plays a crucial role in fruit quality maintenance. However, there has been limited research on the genetic basis of fruit wax and postharvest water loss. Here, we found that HJ (Citrus reticulata) and ZK (Poncirus trifoliata) fruit had significant differences in postharvest water loss and cuticular wax. HJ fruit had a lower wax content and a faster water loss, and the main aliphatic wax components were alkanes and aldehydes. By contrast, ZK fruit had a higher wax content and a slower water loss, and the main aliphatic wax components were only alkanes. Correlation analysis revealed that fruit water loss seemed to be correlated with cuticular wax alkane in the F1 pseudo-testcross population of HJ and ZK. Furthermore, through high-density genetic map and bulk segregant analysis, alkanes and fruit water loss were co-localized to QTL3, resulting in the identification of CER1-1 and CER1-3 as the candidate genes. Heterologous overexpression in Arabidopsis revealed that they were involved in alkane synthesis and reduction of leaf water loss. In addition, coating with C28 alkane could reduce postharvest fruit water loss of six citrus varieties. Collectively, we speculated that cuticular wax alkanes might play an important role in limiting fruit water loss. The study provides new insights into the development of coating agents and breeding of citrus varieties with better storage performance.

Silicon leaf spraying increases biofortification production, ascorbate content and decreases water loss post-harvest from land cress and chicory leaves

Silicon (Si) leaf spraying can benefit the production and post-harvest quality of leafy vegetables, however the effect of Si application in land cress and chicory is unknown. This study aimed to verify Si supplementation by foliar spraying when using different sources and concentrations in content of Si and ascorbate in leaves, fresh and dry mass production, and water loss of chicory and land cress during storage. The experimental design was randomized in a 2 x 4 factorial scheme, with potassium silicate and sodium and potassium silicate stabilized with sorbitol, and four concentrations: 0 (control), 0.84, 1.68, and 2.52 g L −1 of Si. Tree foliar applications were carried out in four replications. Si foliar sprayings were applied every ten days; with the first application at 28 days after transplanting. It was determined that applying Si as a foliar spray was practical to increase the Si accumulation, plant growth, and biofortification as well as decrease the post-harvest water loss of land cress and chicory leaves. The Si concentration of 2.52 g L−1 as potassium silicate was recommended for foliar application in land cress and chicory.

Free and glycosylated green leaf volatiles, lipoxygenase and alcohol dehydrogenase in defoliated Nebbiolo grapes during postharvest dehydration

Background and Aims Nebbiolo grapes are used to produce Sfursat wine, following partial dehydration. This research aimed to clarify the influence of fruit exposure to light and postharvest water loss on the concentration of green leaf volatiles (GLVs) and lipoxygenase (LOX) and alcohol dehydrogenase (ADH) activity of grapes. Methods and Results Nebbiolo grapes from Control vines (no defoliation) (ND) and from vines defoliated at fruitset (DFS) or defoliated post-veraison (DPV) were harvested at about 23°Brix and dehydrated at 10 and 20°C, 60% RH and air flow of 1.5 m/s. Berries were sampled at 10 and 20% mass loss (ML). Significant differences in crop yield, bunch mass and berry mass were observed. As expected, the higher the dehydration temperature, the faster the dehydration process: 20% ML at 20°C occurred between 18 and 25 days, the shortest time corresponding to ND and the longest to DFS; at 10°C, the dehydration lasted between 27 and 32 days. At 10°C, the ADH activity was almost double that at 20°C, and in DFS was much higher than in other samples. At harvest, LOX did not show any difference among the samples, while at 10°C and 10% ML, the enzyme activity increased significantly and then declined at 20% ML, especially in defoliated samples. At harvest, the total free GLVs associated with the metabolism of lipid oxidation were 9434, 7212 and 11 656 μg/kg dry weight (DW) in ND, DFS and DPV samples, respectively; the total bound GLVs lipid-derived were 7599, 18 486 and 15 409 μg/kg DW in ND, DFS and DPV samples, respectively. During dehydration at 10°C, the ML induced ADH + LOX activity, especially in defoliated samples, but the bound GLVs, produced by defoliation, greatly decreased. Conclusions Defoliation affected the response of Nebbiolo grapes to dehydration temperature: postharvest cold stress (10°C) and ML induced glycosylation of GLVs, alcohol formation (via ADH) and membrane oxidation (via LOX); a further stress effect was observed with leaf removal, regardless of the time of application. Significance of the Study The timing of defoliation and postharvest dehydration temperature are significant factors to mitigate the postharvest stress response of Nebbiolo grapes.