Fruit Cuticle Research Articles

SlMYB72 interacts with SlTAGL1 to regulate the cuticle formation in tomato fruit.

The cuticle is the first physical barrier covering the surface of tomatoes and plays an important role in multiple stress responses. But the molecular regulatory networks of cuticle formation are not fully understood. In this study, we found that SlMYB72 can interact with SlTAGL1 to regulate the formation of fruit cuticle in tomato. Downregulating the expression of SlMYB72 inhibits the formation of fruit cuticle, resulting in a reduced fruit cuticle thickness, accelerated postharvest water loss, and increased susceptibility to Botrytis cinerea. RNA sequencing analysis showed that downregulation of the SlMYB72 gene decreased the expression levels of genes related to fatty acid and cuticle metabolism. SlMYB72 regulates the cuticle formation by directly binding to the promoter of long-chain acyl-coA synthetases (SlLACS1) and medium-chain alkane hydroxylase (SlMAH1). Moreover, SlMYB72 interacts with SlTAGL1, which can enhance the transcriptional activation of SlMYB72 on the SlMAH1 promoter. Overall, our study expands our understanding of the regulation of cuticle formation by SlMYB72 and provides new insights into fruit shelf life extension via manipulation of cuticle content.

Genome-Wide Association Study of Cuticle and Lipid Droplet Properties of Cucumber (Cucumis sativus L.) Fruit.

The fruit surface is a critical first line of defense against environmental stress. Overlaying the fruit epidermis is the cuticle, comprising a matrix of cutin monomers and waxes that provides protection and mechanical support throughout development. The epidermal layer of the cucumber (Cucumis sativus L.) fruit also contains prominent lipid droplets, which have recently been recognized as dynamic organelles involved in lipid storage and metabolism, stress response, and the accumulation of specialized metabolites. Our objective was to genetically characterize natural variations for traits associated with the cuticle and lipid droplets in cucumber fruit. Phenotypic characterization and genome-wide association studies (GWAS) were performed using a resequenced cucumber core collection accounting for >96% of the allelic diversity present in the U.S. National Plant Germplasm System collection. The collection was grown in the field, and fruit were harvested at 16-20 days post-anthesis, an age when the cuticle thickness and the number and size of lipid droplets have stabilized. Fresh fruit tissue sections were prepared to measure cuticle thickness and lipid droplet size and number. The collection showed extensive variation for the measured traits. GWAS identified several QTLs corresponding with genes previously implicated in cuticle or lipid biosynthesis, including the transcription factor SHINE1/WIN1, as well as suggesting new candidate genes, including a potential lipid-transfer domain containing protein found in association with isolated lipid droplets.

Identification of long-chain acyl-CoA synthetase gene family reveals that SlLACS1 is essential for cuticular wax biosynthesis in tomato

Long-chain acyl-CoA synthetases (LACSs), belonging to the acyl-activating enzyme superfamily, play crucial roles in lipid biosynthesis and fatty acid catabolism. Here, we identified 11 LACS genes in the tomato reference genome, and these genes were clustered into six subfamilies. Gene structure and conserved motif analyses indicated that LACSs from the same subfamily shared conserved gene and protein structures. Expression analysis revealed that SlLACS1 was highly expressed in the outer epidermis of tomato fruits and leaves. Subcellular localization assay results showed that SlLACS1 was located in the endoplasmic reticulum. Compared with wild-type plants, the wax content on leaves and fruits decreased by 22.5–34.2 % in SlLACS1 knockout lines, confirming that SlLACS1 was involved in wax biosynthesis in both leaves and fruits. Water loss, chlorophyll extraction, water-deficit, and toluidine blue assays suggested that cuticle permeability was elevated in SlLACS1 knockout lines, resulting in reduction in both drought stress resistance and fruit shelf-life. Overall, our analysis of the LACSs in tomato, coupled with investigations of SlLACS1 function, yielded a deeper understanding of the evolutionary patterns of LACS members and revealed the involvement of SlLACS1 in wax accumulation contribute to drought resistance and extended fruit shelf-life in tomato.

Metabolic and gene-expression analyses reveal developmental dynamics of cutin deposition in pomegranate fruit grown under different environmental conditions

The chemical and transcriptional changes in the cuticle of pomegranate (Punica granatum L.) fruit grown under different environmental conditions were studied. We collected fruit from three orchards located in different regions in Israel, each with a distinct microclimate. Fruit were collected at six phenological stages, and cutin monomers in the fruit cuticle were profiled by gas chromatography-mass spectrometry (GC–MS), along with qPCR transcript-expression analyses of selected cutin-related genes. While fruit phenotypes were comparable along development in all three orchards, principal component analyses of cutin monomer profiles suggested clear separation between cuticle samples of young green fruit to those of maturing fruit. Moreover, total cutin contents in green fruit were lower in the orchard characterized by a hot and dry climate compared to orchards with moderate temperatures. The variances detected in total cutin contents between orchards corresponded well with the expression patterns of BODYGUARD, a key biosynthetic gene operating in the cutin biosynthetic pathway. Based on our extraction protocols, we found that the cutin polyester that builds the pomegranate fruit cuticle accumulates some levels of gallic acid—the precursor of punicalagin, a well-known potent antioxidant metabolite in pomegranate fruit. The gallic acid was also one of the predominant metabolites contributing to the variability between developmental stages and orchards, and its accumulation levels were opposite to the expression patterns of the UGT73AL1 gene which glycosylates gallic acid to synthesize punicalagin. To the best of our knowledge, this is the first detailed composition of the cutin polyester that forms the pomegranate fruit cuticle.

Physiological characterization of the tomato cutin mutant cd1 under salinity and nitrogen stress.

We identified tomato leaf cuticle and root suberin monomers that play a role in the response to nitrogen deficiency and salinity stress and discuss their potential agronomic value for breeding. The plant cuticle plays a key role in plant-water relations, and cuticle's agronomic value in plant breeding programs is currently under investigation. In this study, the tomato cutin mutant cd1, with altered fruit cuticle, was physiologically characterized under two nitrogen treatments and three salinity levels. We evaluated leaf wax and cutin load and composition, root suberin, stomatal conductance, photosynthetic rate, partial factor productivity from applied N, flower and fruit number, fruit size and cuticular transpiration, and shoot and root biomass. Both nitrogen and salinity treatments altered leaf cuticle and root suberin composition, regardless of genotype (cd1 or M82). Compared with M82, the cd1 mutant showed lower shoot biomass and reduced partial factor productivity from applied N under all treatments. Under N depletion, cd1 showed altered leaf wax composition, but was comparable to the WT under sufficient N. Under salt treatment, cd1 showed an increase in leaf wax and cutin monomers. Root suberin content of cd1 was lower than M82 under control conditions but comparable under higher salinity levels. The tomato mutant cd1 had a higher fruit cuticular transpiration rate, and lower fruit surface area compared to M82. These results show that the cd1 mutation has complex effects on plant physiology, and growth and development beyond cutin deficiency, and offer new insights on the potential agronomic value of leaf cuticle and root suberin for tomato breeding.

Ripening and rot: How ripening processes influence disease susceptibility in fleshy fruits.

Fleshy fruits become more susceptible to pathogen infection when they ripen; for example, changes in cell wall properties related to softening make it easier for pathogens to infect fruits. The need for high-quality fruit has driven extensive research on improving pathogen resistance in important fruit crops such as tomato (Solanum lycopersicum). In this review, we summarize current progress in understanding how changes in fruit properties during ripening affect infection by pathogens. These changes affect physical barriers that limit pathogen entry, such as the fruit epidermis and its cuticle, along with other defenses that limit pathogen growth, such as preformed and induced defense compounds. The plant immune system also protects ripening fruit by recognizing pathogens and initiating defense responses involving reactive oxygen species production, mitogen-activated protein kinase signaling cascades, and jasmonic acid, salicylic acid, ethylene, and abscisic acid signaling. These phytohormones regulate an intricate web of transcription factors (TFs) that activate resistance mechanisms, including the expression of pathogenesis-related genes. In tomato, ripening regulators, such as RIPENING INHIBITOR and NON_RIPENING, not only regulate ripening but also influence fruit defenses against pathogens. Moreover, members of the ETHYLENE RESPONSE FACTOR (ERF) family play pivotal and distinct roles in ripening and defense, with different members being regulated by different phytohormones. We also discuss the interaction of ripening-related and defense-related TFs with the Mediator transcription complex. As the ripening processes in climacteric and non-climacteric fruits share many similarities, these processes have broad applications across fruiting crops. Further research on the individual contributions of ERFs and other TFs will inform efforts to diminish disease susceptibility in ripe fruit, satisfy the growing demand for high-quality fruit and decrease food waste and related economic losses.

Diffusion in biological media: a comprehensive numerical-analytical study via surface analysis and diffusivities calculation

The study of diffusion in biological materials is crucial for fields like food science, engineering, and pharmaceuticals. Research that combines numerical and analytical methods is needed to better understand diffusive phenomena across various dimensions and under variable boundary conditions within food matrices. This study aims to bridge this gap by examining the diffusion of substances through biological materials analytically and numerically, calculating diffusivity and conducting surface analysis. The research proposes a process for sweetening Bing-type cherries (Prunus avium) using sucrose/xylitol solutions and a staining technique utilising erythrosine and red gardenia at varying concentrations (119, 238 and 357 ppm) and temperatures (40, 50 and 60 °C). Given the fruit's epidermis resistance, the effective diffusivities of skin were inferior to those in flesh. Temperature and concentration synergise in enhancing diffusion coefficients and dye penetration within the food matrix (357 ppm and 60 °C). Red gardenia displayed significant temperature-dependent variation (p = 0.001), whereas erythrosine dye remained stable by temperature changes (p > 0.05). Gardenia's effective diffusivities in cherry flesh and skin, at 357 ppm and 60 °C, 3.89E−08 and 6.61E−09 m2/s, respectively, significantly differed from those obtained at lower temperatures and concentrations. The results highlight the temperature-concentration impacts on mass transfer calculations for food colouring processes and preservation methodologies.

Microplastics supply contaminants in food chain: non-negligible threat to health safety.

The occurrence of microplastics (MPs) and organic pollutants (OPs) residues is commonly observed in diverse environmental settings, where their interactions can potentially alter the behavior, availability, and toxicity of OPs, thereby posing risks to ecosystems. Herein, we particularly emphasize the potential for bioaccumulation and the biomagnification effect of MPs in the presence of OPs within the food chain. Despite the ongoing influx of novel information, there exists a dearth of data concerning the destiny and consequences of MPs in the context of food pollution. Further endeavors are imperative to unravel the destiny and repercussions of MPs/OPs within food ecosystems and processing procedures, aiming to gain a deeper understanding of the joint effect on human health and food quality. Nevertheless, the adsorption and desorption behavior of coexisting pollutants can be significantly influenced by MPs forming biofilms within real-world environments, including temperature, pH, and food constituents. A considerable portion of MPs tend to accumulate in the epidermis of vegetables and fruits, thus necessitating further research to comprehend the potential ramifications of MPs on the infiltration behavior of OPs on agricultural product surfaces.

Preparation of Cellulose Fiber Loaded with CuO Nanoparticles for Enhanced Shelf Life and Quality of Tomato Fruit

The present study reports on the preparation of a cellulose fiber (CF) composite from D. lutescens, combined with copper oxide nanoparticles (DL@CF/CuO), to prolong the shelf life of tomatoes after harvest. The isolated cellulose fiber material was comprehensively characterized using XRD, FTIR, and FE-SEM analyses. The DLCF and DL@CF/CuO nanoparticles exhibited crystalline cellulose, as indicated by the XRD investigation. Both DLCF and DL@CF/CuO showed O-H and C-H FTIR spectra with identifiable vibrational peaks. The FE-SEM images depicted the dispersion of DL@CF/CuO-based fibers in a cellulose fiber matrix containing CuO nanoparticles. A 0.3% (wt/wt), a solution of DL@CF/CuO was coated onto the surface of early ripening tomato fruits. After a 25-day storage period at 25–29 °C and 85% RH, the results showed a significant extension in the shelf life of the tomato fruits, in line with changes in physiological properties and fruit quality. The extension of shelf life in tomato fruit epidermis treated with DL@CF/CuO was confirmed through FE-SEM analysis. L929 fibroblast cells were treated with the developed DL@CF/CuO nanocomposite, and no signs of toxicity were detected up to 75 µg/mL. Additionally, the DL@CF/CuO nanocomposite exhibited significant antifungal activity against Aspergillus flavus. In conclusion, this study provides novel insights for sustainable food security and waste control in the agricultural and food industries.

The adsorption-desorption behavior of chlorothalonil in the cuticles of apple and red jujube

The distribution fate of chlorothalonil (CHT) in the environment (soil and water) and fruits is controlled by the capacity of cuticles to adsorb and desorb CHT, which directly affects the safety of both the environment and fruits. Batch experiments were conducted to reveal the adsorption-desorption behaviors of CHT in the cuticles of apple and red jujube. The adsorption kinetics showed that both physisorption and chemisorption occurred during the adsorption process. Furthermore, the isothermal adsorption of CHT in the fruit cuticles followed the Freundlich model. The thermodynamic parameters (ΔG ≤ −26.16 kJ/mol, ΔH ≥ 31.05 kJ/mol, ΔS ≥ 0.20 kJ/(mol K) showed that the whole CHT adsorption process was spontaneous, and the hydrophobic interaction was predominant. The CHT adsorption capacity of the apple cuticle was higher than that of the red jujube cuticle, potentially due to the significantly higher alkanes content of apples than that of red jujubes. An appropriate ionic strength (0.01 moL/L) could induce a higher adsorption capacity. In addition, the desorption kinetics were shown to conform to a Quasi-first-order model, meaning that not all the adsorbed CHT could be easily desorbed. The desorption ratios in apple and red jujube cuticles were 41.38% and 35.64%, respectively. The results of Fourier-transformed infrared spectroscopy and X-ray photoelectron spectroscopy further confirmed that CHT could be adsorbed and retained in the fruit cuticles. Investigating the adsorption-desorption behavior of CHT in the apple and red jujube cuticles allowed to determine the ratio of its final distribution in the fruits and environment, providing a theoretical basis to evaluate the risk of residue pesticide.

Preharvest Applications of Aminoethoxivinylglycine in Mangifera indica L. “Ataulfo” Variety in Two Contrasting Environments

Mangifera indica var Ataulfo is the main variety grown in the Soconusco region of Chiapas, Mexico and faces a decrease in firmness and weight loss due to hydrothermal treatment, in addition to non-uniform ripening and consequently a decrease in price as the harvest period lengthens. In order to improve the postharvest quality of the “Ataulfo” mango fruit, preharvest applications of aminoethoxyvinylglycine (AVG; ReTain®, a.i. 15%) were carried out in “La Norteña” with Phaeozem soil, 1500 mm of annual precipitation, and applications of agrochemicals, and in “Santa Cecilia” with Acrisol soil, 2500 mm of annual precipitation, and without agrochemicals. The treatments were: (1) Control, (2) One application 7 days before harvest (0.1 g L−1), (3) Two applications (14 days and 7 days before harvest, 0.2 g L−1) and (4) Three applications (21, 14 and 7 days before harvest, in total 0.3 g L−1), with completely randomized design in the laboratory. The results show contrasting differences between the evaluation sites, with lower weight loss (18.4%) and 3.1% more firmness in a drier climate and higher soil calcium content. The average firmness (N) on day 14 was 18.3 and with three applications of AVG it was 22.0. The °Brix at the end of the study in the control was 11.3 and on average with AVG applications it was 14.4. Three-time applications of AVG in preharvest delayed the weight loss with an increase in the maintenance of the firmness of the fruits. The weight of the fruit epidermis was lower with AVG applications, and increased with the number of applications.

Tomato pomace food waste from different variants as a high antioxidant potential resource

Pomaces obtained from three San Marzano tomato genotypes including the wild type (WT), Sun Black (SB), and colorless fruit epidermis (CL) were dried at 50 °C and analyzed for nutritional composition, total polyphenol (TPC), flavonoid (TFC) content, polyphenol qualitative profile, total antioxidant capacity (TAC), and antimicrobial activity. Commercial dried tomato powder (CTRP) was included as a control. No differences were detected nutritionally, in TPC and antimicrobial activity, but significant changes were observed for TFC and TAC, underlying variation in the phenolic profile. SB pomace (SBP) had the highest TFC and TAC. LC-HRMS analysis showed a flavonoid-enriched profile in SBP besides the exclusive presence of anthocyanins, with petanin and negretein as the most abundant. Among flavonoids, quercetin-hexose-deoxyhexose-pentose, naringenin, and rutin were the major. Overall, we showed the potential of dried tomato pomace, especially SBP, as an extremely valuable waste product to be transformed into a functional ingredient, reducing the food industry waste.

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.

The Biophysical Properties of the Fruit Cuticles of Six Pear Cultivars during Postharvest Ripening

Pears are abundant in bioactive compounds, which exert favorable effects on human health. The biophysical attributes of fruit cuticles are pivotal in determining fruit quality, storability, and susceptibility to mold growth. This study aimed to elucidate the biophysical properties of six pear cultivars, ‘Conference’, ‘Celina’, ‘Abate Fetel’, ‘Packham’s Triumph’, ‘Sweet Sensation’, and ‘Williams’. Two maturity stages, unripe and fully ripened, were investigated. Furthermore, the efficacy of trimethyl-chitosan-coated pear surfaces in preventing Penicillium expansum (P. expansum) growth was assessed. Basic maturity indices (CIE color, ethylene evolution, firmness, soluble solids), cuticle contact angle, roughness, and zeta potential were analyzed. Surface roughness was measured using an optical profilometer, hydrophobicity was measured via profilometry, and zeta potential was quantified using an electrokinetic analyzer. The ‘Celina’ cultivar exhibited the highest roughness, whereas ‘Williams’ had the lowest roughness. All the cultivars’ cuticles demonstrated hydrophilic characteristics, with contact angles ranging between 65° and 90°. For pH values exceeding 3.5, all pear surfaces exhibited a negative zeta potential. P. expansum growth was the slowest on the ‘Packham’s Triumph’ and ‘Conference’ cultivars. Treatment with trimethyl chitosan effectively inhibited P. expansum growth in the initial hours of incubation. In conclusion, diverse pear cultivars manifest distinct biophysical surface properties and varying susceptibility to P. expansum growth. The growth of P. expansum correlates positively with roughness, contact angle, and zeta potential. These differences can significantly impact shelf life potential and the overall postharvest quality of pears.

La2O3 Nanoparticles Can Cause Cracking of Tomato Fruit through Genetic Reconstruction.

La2O3 nanoparticles (NPs) have shown great potential in agriculture, but cracking of plant sensitive tissue could occur during application, resulting in a poor appearance, facilitating entry for insects and fungi, and increasing economic losses. Herein, exocarp cracking mechanisms of tomato (Solanum lycopersicum L.) fruit in response to La2O3 NPs were investigated. Tomato plants were exposed to La2O3 NPs (0-40 mg/L, 90 days) by a split-root system under greenhouse condition. La2O3 NPs with high concentrations (25 and 40 mg/L) increased the obvious cracking of the fruit exocarp by 20.0 and 22.7%, respectively. After exposure to 25 mg/L La2O3 NPs, decreased thickness of the cuticle and cell wall and lower wax crystallization patterns of tomato fruit exocarp were observed. Biomechanical properties (e.g., firmness and stiffness) of fruit exocarp were decreased by 34.7 and 25.9%, respectively. RNA-sequencing revealed that the thinner cuticle was caused by the downregulation of cuticle biosynthesis related genes; pectin remodeling, including the reduction in homogalacturonan (e.g., LOC101264880) and rhamnose (e.g., LOC101248505), was responsible for the thinner cell wall. Additionally, genes related to water and abscisic acid homeostasis were significantly upregulated, causing the increases of water and soluble solid content of fruit and elevated fruit inner pressure. Therefore, the thinner fruit cuticle and cell wall combined with the higher inner pressure caused fruit cracking. This study improves our understanding of nanomaterials on important agricultural crops, including the structural reconstruction of fruit exocarp contributing to NPs-induced cracking at the molecular level.

MdDEWAX decreases plant drought resistance by regulating wax biosynthesis

Apple epidermal wax protects plants from environmental stresses, determines fruit gloss and improves postharvest storage quality. However, the molecular mechanisms underlying the biosynthesis and regulation of apple epidermal waxes are not fully understood. In this study, we isolated a MdDEWAX gene from apple, which localized in the nucleus, expressed mainly in apple fruit, and induced by drought. We transformed the MdDEWAX gene into Arabidopsis, and found that heterologous expression of MdDEWAX reduced the accumulation of cuticular waxes in leaves and stems, increased epidermal permeability, the rate of water loss, and the rate of chlorophyll extraction of leaves and stems, altered the sensitivity to ABA, and reduced drought tolerance. Meanwhile, overexpression or silencing of the gene in the epidermis of apple fruits decreased or increased wax content, respectively. This study provides candidate genes for breeding apple cultivars and rootstocks with better drought tolerance.

Carotenoid retention during post-harvest storage of Capsicum annuum: the role of the fruit surface structure.

In this study, a chilli pepper (Capsicum annuum) panel for post-harvest carotenoid retention was studied to elucidate underlying mechanisms associated with this commercial trait of interest. Following drying and storage, some lines within the panel had an increase in carotenoids approaching 50% compared with the initial content at the fresh fruit stage. Other lines displayed a 25% loss of carotenoids. The quantitative determination of carotenoid pigments with concurrent cellular analysis indicated that in most cases, pepper fruit with thicker (up to 4-fold) lipid exocarp layers and smooth surfaces exhibit improved carotenoid retention properties. Total cutin monomer content increased in medium/high carotenoid retention fruits and subepidermal cutin deposits were responsible for the difference in exocarp thickness. Cutin biosynthesis and cuticle precursor transport genes were differentially expressed between medium/high and low carotenoid retention genotypes, and this supports the hypothesis that the fruit cuticle can contribute to carotenoid retention. Enzymatic degradation of the cuticle and cell wall suggests that in Capsicum the carotenoids (capsanthin and its esters) are embedded in the lipidic exocarp layer. This was not the case in tomato. Collectively, the data suggest that the fruit cuticle could provide an exploitable resource for the enhancement of fruit quality.

Characterization of Fungal Communities Associated with the Lenticel-Like Damage of ‘Hass’ Avocados in Two Geographical Locations in Colombia

Different postharvest diseases and disorders affect ‘Hass’ avocado fruits. Among them, lenticel-like damages, which compromise the fruit epidermis without affecting the mesocarp, are important causes of fruit rejection worldwide. However, lenticel-like damage etiology is still unclear. To better comprehend this disorder, we evaluated the level of the lenticel-like damage from Hass avocado fruits from two different growing regions in Colombia at different harvest seasons. We also characterized the fungal microbial communities associated with these fruits by Illumina MiSeq. We found that the level of lenticel-like damage varies with the farm and with the harvest season, and increases during cold storage. Fungal communities associated with Hass avocado fruits were influenced by the farm and the lenticel-like damage level. Regardless of the farm, Ascomycetes were increased four-fold compared with Basidiomycetes in severely damaged fruits, while in mildly damaged fruits the ratio was equal. In particular, severely damaged fruits from the more affected farm (El Sinaí) were enriched in Colletotrichum and Pseudocercospora, while fungi in mildly damaged fruits from the less affected farm (La Escondida) include Cladosporium, Vishniacozyma, Meira, and Symmetrospora. Altogether, our results suggests that fungal communities of Hass avocado exocarps influence the lenticel-like damage development and might be responsible for the damage differences between farms.

Microcracking of strawberry fruit cuticles: mechanism and factors

Microscopic cracks in the cuticle (microcracks) are the first symptom of the strawberry fruit disorder ‘water soaking’ in which the fruit surface appears watery, translucent, and pale. Water soaking severely impacts fruit quality. The objective was to investigate the factors and mechanisms of cuticular microcracking in strawberry. Fluorescence microscopy revealed numerous microcracks in the achene depressions, on the rims between depressions and at the bases of trichomes. Microcracks in the achene depressions and on the rims were either parallel or transversely oriented relative to a radius drawn from the rim to the point of attachment of the achene. In the achene depression, the frequency of microcracks with parallel orientation decreased from the calyx end of the fruit, towards the fruit tip, while the frequency of those with transverse orientation remained constant. Most microcracks occurred above the periclinal cell walls of the epidermal cells. The long axes of the epidermal cells were primarily parallel-oriented. Microcracking increased during fruit development. Cuticle mass per fruit remained constant as fruit surface area increased but cuticle thickness decreased. When fruit developed under high relative humidity (RH) conditions, the cuticle had more microcracks than under low RH conditions. Exposing the fruit surface to increasing RHs, increased microcracking, especially above 75% RH. Liquid-phase water on the fruit surface was markedly more effective in inducing microcracking than high vapor-phase water (high RH). The results demonstrate that a combination of surface area growth strain and water exposure is causal in inducing microcracking of the strawberry cuticle.

Effect of Foliar Calcium Fertilization on Fruit Quality, Cell Wall Enzyme Activity and Expression of Key Genes in Chinese Cherry

ABSTRACT Chinese cherries are early flowering and early fruiting, with both edible and ornamental values. This study aims to explore the effects of pre-harvest spraying with different concentrations of CaCl2, amino acid calcium, and sugar alcohol calcium on the quality of Chinese cherry and the expression of genes related to cell wall softening. The goal is to identify suitable calcium-based agents for pre-harvest spraying on Chinese cherry. The results of the study demonstrated that all three exogenous calcium treatments significantly increased the mineral content compared to the control group. Moreover, these treatments also led to a significant increase in various fruit quality parameters such as hundred fruit weight, firmness, soluble solid, soluble sugar, titratable, vitamin C, soluble protein, β-Carotene content and superoxide dismutase, peroxidase activities. Additionally, they were found to effectively reduce rot rate, polyphenol oxidase activity, malondialdehyde content and relative conductivity. The activity of pectin methylesterase, polygalacturonase, cellulase and β-galactose was reduced by amino acid calcium and sugar alcohol calcium. All three types of exogenous calcium down-regulated the expression of PME and ChCaBP1. Additionally, amino acid calcium and sugar alcohol calcium decreased the expression of PG, Cx, and BGal. Exogenous calcium reduces the size of stomata in the fruit epidermis, leading to a decrease in both fruit respiration rate and transpiration. Of the three calcium preparations, amino acid calcium and sugar alcohol calcium were more effective than CaCl2, with 0.12 g·L−1sugar alcohol calcium and 0.06 g·L−1 amino acid calcium being the most effective.