Postharvest Fruit Research Articles

Methyl jasmonate suppressed the pericarp browning in postharvest longan fruit by modulating membrane lipid and energy metabolisms

Methyl jasmonate (MeJA) is an important bioactive metabolite in fruits and vegetables that regulates various physiological processes. The effects of MeJA on pericarp browning in longan fruit and its underlying mechanism were investigated. Results showed that treatment with 100 μM MeJA substantially suppressed the development of pericarp browning in harvested longan fruit. Compared to untreated fruit, MeJA-treated fruit exhibited reduced cell membrane permeability during storage. Meanwhile, MeJA-treated fruit displayed lower levels of phosphatidic acid and higher content of phosphatidylcholine, phosphatidylinositol, phosphatidylglycerol, and phosphatidylethanolamine through suppressing the activities of key enzymes involved in membrane lipids metabolism, such as phospholipases, lipase and lipoxygenase. Furthermore, MeJA treatment enhances the energy status of the fruit, evidenced by elevated the levels of adenosine triphosphate and energy charge. This effect could be attributed to the enhanced activities of various energy metabolism enzymes. Overall, all results suggest that MeJA is a promising agent for inhibiting pericarp browning in longan fruit through modulation of membrane lipid and energy metabolisms.

Construction of photocatalytic coating for alleviating the shriveling of postharvest fruit cucumber after simulated transportation

The shriveling of fruit cucumber was commonly occurred during supply chain, photocatalyst exposed to UV light can endow the coatings with ethylene removal capacity to reduce the respiration of fruit and water loss. The study developed a novel photodynamic technology responsive photocatalytic coating with exceptional ultraviolet (UV) photocatalytic degradation of ethylene ability to decay the shriveling of postharvest fruit cucumber during supply chain. This coating involved the integration of Carbon dots (CDs)-loaded nano ZnO and the skillful selection of pullulan (Pul) and apple pectin (AP) matrix. The CDs/ZnO coatings boasted an impressive array of photocatalytic degradation of ethylene and adhesion properties, including high ethylene removal rates of 32.04 % in 60 min UV light stimulation. The decrease of cell-wall strength, degradation of the cell wall polysaccharides and water loss resulted in cucumber shriveling. Compared with CK sample, after UV-CDs/ZnO coating treatment, the higher firmness and cell wall polysaccharides were found in cucumbers with lower cell wall degrading enzymes activities, weight loss and water movement, which was associated with the decrease of respiration and ethylene accumulation. The UV-CDs/ZnO coatings possessed promising potential for alleviating the shriveling of postharvest fruit cucumber and applications in fruits preservation in the future.

Exploring the function of MaPHO1 in starch degradation and its protein interactions in postharvest banana fruits

Banana is a quintessential fruit known for its starch conversion process. During development, substantial starch accumulates in banana fruit and subsequently undergoes rapid degradation, contributing to flavor development during postharvest ripening. However, the genes orchestrating this crucial starch degradation process have not been comprehensively studied thus far. Through temporal transcriptomic analysis, we screened 63 active genes that were actively expressed in association with starch degradation during the ripening of banana fruits. The results found that phosphorolytic enzymes primarily regulate starch degradation at the early to middle stages of fruit ripening and that hydrolytic enzymes significantly contribute to starch degradation at the later stage. The expression of Musa acuminata starch phosphorylase 1 (MaPHO1) was the highest at the early to middle stages of banana ripening, characterized by the insertion of an L80 domain. While MaPHO1 was predominately found in the chloroplast, MaPHO2 was localized to the cell membrane. Starch accumulation was significantly increased by transient attenuation of MaPHO1 expression, whereas a drastic reduction in starch content was triggered by transient overexpression of MaPHO1, affirming its functional role in banana fruit ripening. By constructing a co-expression network, 29 categories, including 74 proteins interacting with MaPHO1 were identified. Tripartite interactions between MaPHO1 and both glucan, water dikinase 1 (GWD1) and enolase 1 (ENO1) were revealed by further validation through yeast two-hybrid and glutathione-S-transferase pull-down analyses.

Management Of Pre And Post Harvest Fruit Rot Diseases Of Ber

The main focus of this research is to produce the good quality and disease free fruits. In this aspect, the investigation was carried out to reduce or control the pre and post-harvest fungal fruit rot. The study on pre and post-harvest management of fruit rot diseases of ber caused by Alternaria and Colletotrichum was carried out and the results showed that two pre-harvest sprays of Thiophanate Methyl (0.1 %) at 15 day intervals during the marble stage of ber fruit was found effective against Alternaria fruit rot recorded 6.8 PDI compared to untreated control recorded 43.6 PDI. Two pre-harvest sprays of 0.1 per-cent carbendazim at 15 day intervals was found effective against Colletotrichum fruit rot during the pea fruit stage of ber recorded 6.6 PDI compared to untreated control recorded 44.2 PDI. The post-harvest studies revealed that dipping of ber fruits in 2 per cent sodium chloride solution for 10 min. recorded the lowest PDI of 5.27 against post-harvest fungal rot as compared to untreated control recorded 25.27 PDI.

Physical and physiological characteristics, as well as miRNA concentrations, are affected by the storage time of tomatoes.

This study aims to investigate the potential of miRNA measurements in indicating tomato quality during transportation and storage. The impact of storage temperature, duration, and mechanical loading on tomato senescence, carotenoid content, total soluble solids, fruit firmness, and relevant miRNA concentrations were examined. Significant two-way or three-way interactions were observed between storage conditions and physical/physiological characteristics (excluding carotenoids). Remarkably, significant three-way interactions were found between storage conditions and miRNA concentrations. Strong correlations were observed between the physiological characteristics of the tomatoes and their miRNA concentrations. These findings suggest that measuring miRNAs could serve as a convenient and portable method for evaluating postharvest fruit quality, reducing reliance on labor-intensive laboratory techniques.

Pest categorisation of Pestalotiopsis disseminata.

Following the commodity risk assessments of bonsai plants from China consisting of Pinus parviflora grafted on P. thunbergii performed by EFSA, the EFSA Plant Health Panel performed a pest categorisation of Pestalotiopsis disseminata, a clearly defined plant pathogenic fungus of the family Pestalotiopsidaceae. The pathogen has been reported on herbaceous, woody and ornamental plants causing symptoms such as leaf blight, shoot blight, seedling blight, pod canker, pre- and post-harvest fruit rot, and gummosis. Moreover, the fungus was reported as an endophyte on a wide range of asymptomatic hosts. The pathogen is present in Africa, North and South America, Asia, Europe and Oceania. It has been reported from the EU, with a restricted distribution (Portugal). There is a key uncertainty on the geographical distribution of P. disseminata in the EU and worldwide, because of the endophytic nature of the fungus, the lack of surveys and since the pathogen might have been misidentified based only on morphology and pathogenicity tests. The pathogen is not included in Commission Implementing Regulation (EU) 2019/2072. This pest categorisation focuses on those hosts that are relevant for the EU and for which there is robust evidence that the pathogen was formally identified by a combination of morphology, pathogenicity and multilocus sequence analysis. Plants for planting, fresh fruits, bark and wood of host plants as well as soil and other plant growing media are the main pathways for the entry of the pathogen into the EU. Host availability and climate suitability factors occurring in parts of the EU are favourable for the establishment of the pathogen. Despite the low aggressiveness observed in most reported hosts, and the fact that P. disseminata may colonise plants as an endophyte, its introduction and spread in the EU may have an economic and environmental impact (with a key uncertainty) where susceptible hosts are grown. Phytosanitary measures are available to prevent the introduction and spread of the pathogen. The Panel cannot conclude on whether P. disseminata satisfies all the criteria that are within the remit of EFSA to assess for this species to be regarded as potential Union quarantine pest, because of the key uncertainties on the restricted distribution in the EU and the magnitude of the impact.

Shelf life enhancement technique of Musa acuminata in a controlled environment and optimization of process parameters affecting shelf life using genetic algorithm.

An economical and effective storage solution has been designed in this work for the storage of postharvest fruits and vegetables. Musa acuminata or banana has a shelf life of 5-6 days in open uncontrolled environment. This article reports a storage solution of M. acuminata in a controlled enclosure containing titanium oxide (TiO2 )-coated inner walls and irradiated with ultraviolet ray of band "C," an air filtration unit, 5% by volume potassium permanganate (KMnO4 ) solution in a clay pot, grow lights, and activated charcoal granules. The same fruit was kept in an uncontrolled environment too. The percentages of dark spots on banana (M. acuminata) upon storage in controlled and uncontrolled environments have been estimated using an image-processing algorithm. The prediction of dark spots was conducted using multi-linear and multivariate polynomial regression. Experimentation with optimum process parameters obtained with genetic algorithm resulted in a shelf life extension of 6 days as compared to its storage in an uncontrolled environment. The setup can be used in vegetable and fruit markets for the extension of shelf life of postharvest perishable items in a compact and cost-effective manner. The setup does not use any refrigeration process thereby decreasing energy requirement.

Melatonin treatment induces DNA methylation to alleviate chilling induced-browning in cold stored peach fruit

Chilling injury (CI) often occurs in postharvest peach fruit during low-temperature storage, and exogenous melatonin (MT) treatment has been demonstrated to alleviate CI in cold-stored peach fruit. In this study, we further investigated the effect of MT treatment on DNA methylation in relation to the chilling-induced browning in cold stored peaches. The results revealed that MT treatment upregulated PpPAL expression while simultaneously suppressing the transcripts of PpPPO and PpPOD. This dual effect resulted in the increased accumulation of phenolics, effectively reducing the incidence of browning in peaches stored at 4 °C. In addition, MT treatment increased the activities of methylesterase and demethylase, affecting significant changes in the DNA methylation levels of the local genes PpPPO, PpPOD and PpPAL, which suggested that MT treatment could mediate DNA methylation of the browning-related genes such as PpPPO, PpPOD and PpPAL, and consequently increased the phenolic contents and alleviated browning symptoms in cold-stored peaches.

Alternative splicing of the PECTINESTERASE gene encoding a cell wall-degrading enzyme affects postharvest softening in grape

The firmness of table grape berries is a crucial quality parameter. Despite extensive research on postharvest fruit softening, its precise molecular mechanisms remain elusive. To enhance our comprehension of the underlying molecular factors, we initially identified differentially expressed genes (DEGs) by comparing the transcriptomes of folic acid (FA)-treated and water-treated (CK) berries at different time points. We then analyzed the sequences to detect alternatively spliced (AS) genes associated with postharvest softening. A total of 2,559 DEGs were identified and categorized into four subclusters based on their expression patterns, with subcluster-4 genes exhibiting higher expression in the CK group compared with the FA treatment group. There were 1,045 AS-associated genes specific to FA-treated berries and 1,042 in the CK-treated berries, respectively. Gene Ontology (GO) annotation indicated that the AS-associated genes in CK-treated berries were predominantly enriched in cell wall metabolic processes, particularly cell wall degradation processes. Through a comparison between treatment-associated AS genes and subcluster-4 DEGs, we identified eight genes, including Pectinesterase 2 (VvPE2, Vitvi15g00704), which encodes a cell wall-degrading enzyme and was predicted to undergo an A3SS event. The reverse transcription polymerase chain reaction further confirmed the presence of a truncated transcript variant of VvPE2 in the FA-treated berries. Our study provides a comprehensive analysis of AS events in postharvest grape berries using transcriptome sequencing and underscores the pivotal role of VvPE2 during the postharvest storage of grape berries.

Effect of lactic acid bacteria and Bacillus on anthracnose disease in postharvest papaya fruit

Abstract. Thi QVC, Dung TQ, Huynh NTN, Truc NT, Thuy NP. 2023. Effect of lactic acid bacteria and Bacillus on anthracnose disease in postharvest papaya fruit. Biodiversitas 24: 5883-5894. Anthracnose disease of papaya fruit caused by Colletotrichum (isolate TD1), identified by 5.8S rRNA sequence homology, is a main obstacle in papaya fruit, influencing fruit quality and minimizing shelf life. Therefore, to diminish the disease and sustain the fruit quality, the impact of Lactic Acid Bacteria (LAB) and Bacillus on the growth of anthracnose disease and fruit quality was investigated in vitro and in vivo. Furthermore, 13 LAB and 12 Bacillus isolates were collected from traditional fermented vegetables and papaya rhizospheric soils. The results showed that 13 LAB isolates and 6 isolates of Bacillus were inhibitory against Colletotrichum in an in vitro test. Two isolates of LDC11 and BHL21 with the highest antifungal activity were selected to evaluate their effect on Colletotrichum growth and papaya fruit quality under in vivo conditions. These findings indicated that the isolates LDC11 and BHL21 at a density of 106 CFU/mL reduced the disease incidence and severity. The LAB and Bacillus treated papaya fruit increased a number of parameters, such as weight loss, TSS, and L*, a*, and b* values. However, vitamin C content, TA, and fruit firmness were reduced compared to the control. The research shows a potential applications of LAB and Bacillus in the postharvest preservation of papaya fruit. To our knowledge, this is the first study to apply Bacillus and LAB bacteria to control diseases in postharvest papaya in Vietnam.

Carboxymethyl chitosan and polycaprolactone-based rapid in-situ packaging for fruit preservation by solution blow spinning

Nanofiber packaging has not yet gained practical application in fruit preservation because of some limitations, such as low production rate and utilization, and failure due to poor adhesion to the fruit. Herein, to solve this issue, a novel fruit packaging method based on solution blow spinning (SBS), called in-situ packaging, was pioneered. Specifically, carboxymethyl chitosan (CMCH) and polycaprolactone (PCL) were chosen as substrate materials and cherry tomatoes were selected as demonstration subjects. CMCH/PCL nanofibers were deposited directly onto the surface of cherry tomatoes by SBS, forming a tightly adherent and stable fiber coating in 8 min. Also, this in-situ packaging could be easily peeled off by hand. The in-situ packaging was an excellent carrier for active substances and was effective in inhibiting gray mold on cherry tomatoes. The in-situ packaging film formed a barrier on the surface of cherry tomatoes to limit moisture penetration, resulting in reduced respiration of fruits, which led to reduced weight and firmness loss. In addition, metabolomics and color analysis revealed that the in-situ packaging delayed ripening of cherry tomatoes after harvest. Overall, the in-situ packaging method developed in the present work provides a new solution for post-harvest fruit preservation.

Biological control of fruit rot of postharvest orange (Citrus aurantium) by aqueous plant extracts

Post-harvest rot symptoms caused by complex airborne fungi are nowadays the most serious threatening disease affecting orange fruits in Nigeria and presumably in many African countries. Experimental trials were conducted at the Department of Biological Sciences (Akwa Ibom State, Nigeria) from January to December 2022 to ascertain the pathogens associated with postharvest fruit rot of oranges (Citrus aurantium L.). Results of the pathogenic test revealed that Fusarium sp. and Penicillium sp. are pathogenic and produced the highest lesion diameter (38.67 and 40.33 mm, respectively) and disease severity index (88.67 and 94.33%, respectively). The frequency occurrence of Fusarium sp. (69.14%) and Penicillium sp. (50.62%) was the highest. Two aqueous extracts of Azadirachta indica Juss. leaves and Zingiber officinale Roscoe rhizomes (at 80% concentration) were evaluated for their antifungal activities against the pathogenic isolates under in vitro and in vivo conditions. The results revealed that A. indica and Z. officinale aqueous extracts exhibited the highest mycelial growth inhibition (>90%) of Fusarium sp. and Penicillium sp. Similarly, under in vivo assay minimum lesion diameter (≤ 6.37 mm) and disease severity index (≤11.13%) were recorded in these aqueous extracts. In conclusion, the application of A. indica and Z. officinale can provide an alternative to fungicides against Penicillium sp. + Fusarium sp.

Attenuation of prochloraz phytotoxicity to postharvest mango fruit by melatonin is associated with the regulation of detoxification capacity

Excessive fungicide residues in crops threaten food safety, and may initiate oxidative stress and cause phytotoxicity to products. Melatonin (Mel), a pleiotropic bioactive molecule, plays multiple physiological functions in plants. In this study, utilizing postharvest dipping with Mel and fungicide prochloraz (Pcz) as the model, we explored the effect of Mel on Pcz-triggered toxification and its underlying physiological mechanism in ‘Guifei’ mango fruit during storage at 25 °C. Results showed that pretreatment with 1 mmol L−1 Mel before exposure to 1.2 g L−1 Pcz (Mel + Pcz) reduced Pcz residues by 15.1% and 30.7% in mango fruit at 4 and 8 d, respectively, while ameliorating phytotoxicity to a greater extent than Pcz treatment alone. Microscopic observation revealed that Mel alleviated Pcz-triggered damage to lenticels on fruit exocarp tissue. Mel appreciably repressed Pcz-induced oxidative stress, as indicated by lower levels of reactive oxygen species, malondialdehyde, damaged DNA and carbonylated proteins and good maintenance of membrane integrity and mitochondrial membrane potential in Mel + Pcz fruit. Moreover, Pcz-induced increases in activities of antioxidant enzymes (superoxide dismutase, catalase and peroxidase), levels of ascorbate-glutathione cycle components and activities of pesticide degradative enzymes (cytochrome P450, glutathione S-transferase and glycosyltransferase) were further amplified after treatment with Mel + Pcz, which contributed to a stronger detoxification capacity in mango fruit. The study might provide a strategy for diminishing fungicide residues and attenuating phytotoxicity in postharvest fruits.

Early bruising detection of 'Korla' pears by low-cost visible-LED structured-illumination reflectance imaging and feature-based classification models.

Nondestructive detection of thin-skinned fruit bruising is one of the main challenges in the automated grading of post-harvest fruit. The structured-illumination reflectance imaging (SIRI) is an emerging optical technique with the potential for detection of bruises. This study presented the pioneering application of low-cost visible-LED SIRI for detecting early subcutaneous bruises in 'Korla' pears. Three types of bruising degrees (mild, moderate and severe) and ten sets of spatial frequencies (50, 100, 150, 200, 250, 300, 350, 400, 450 and 500 cycles m-1) were analyzed. By evaluation of contrast index (CI) values, 150 cycles m-1 was determined as the optimal spatial frequency. The sinusoidal pattern images were demodulated to get the DC, AC, and RT images without any stripe information. Based on AC and RT images, texture features were extracted and the LS-SVM, PLS-DA and KNN classification models combined the optimized features were developed for the detection of 'Korla' pears with varying degrees of bruising. It was found that RT images consistently outperformed AC images regardless of type of model, and LS-SVM model exhibited the highest detection accuracy and stability. Across mild, moderate, severe and mixed bruises, the LS-SVM model with RT images achieved classification accuracies of 98.6%, 98.9%, 98.5%, and 98.8%, respectively. This study showed that visible-LED SIRI technique could effectively detect early bruising of 'Korla' pears, providing a valuable reference for using low-cost visible LED SIRI to detect fruit damage.

Glycine Enhances Oxidative Stress Tolerance and Biocontrol Efficacy of Sporidiobolus pararoseus against Aspergillus niger Decay of Apples.

Apples are deeply loved by people because of their rich nutritional value, but they are susceptible to rotting. The use of antagonistic yeast is a promising method for controlling postharvest fruit diseases, but biocontrol efficacy of yeast will be weakened in environmental stress. In this study, the effects of glycine (Gly) on the oxidative stress tolerance and the biocontrol efficacy of Sporidiobolus pararoseus (S. pararoseus) against Aspergillus niger (A. niger) are discussed. Under the stimulation of H2O2, the yeast cells treated with Gly (1 mM) showed lower ROS content, less mitochondrial impairment and cellular oxidative damage, and the cell survival rate was significantly higher than Gly-untreated yeast. The yeast cells exposed to Gly significantly increased the activities of antioxidant enzymes superoxide dismutase (SOD), catalase (CAT), and the content of glutathione (GSH). Notably, Gly-treated yeast cells had better biocontrol efficacy against A. niger in postharvest apples. The lesion diameter and decay incidence were reduced by 17.67 mm and 79.63% compared to the control, respectively, when S. pararoseus was treated with 1 mM Gly. Moreover, Gly-treated yeast increased the antioxidant enzymes activities and their gene expression were up-regulated in apples. These results indicated that 1 mM Gly not only reduced the oxidative damage of yeast, but also induced resistance-related enzymes of apples under oxidative stress, which contributed to enhancing the biocontrol efficacy of S. pararoseus against A. niger in apples.

The role of the auxin-response genes MdGH3.1 and MdSAUR36 in bitter pit formation in apple

Apples often exhibit bitter pits in response to metabolic disorders during ripening and storage; however, the mechanisms underlying the bitter pit (BP) development remain unclear. Here, metabolome and transcriptome analyses were performed to investigate BP pulp of ‘Fuji’. Two auxin-response genes, MdGH3.1 and MdSAUR36, were screened. Their expression as well as the auxin content in BP pulp were found to be higher than those in healthy pulp (P < 0.01). In the field, excess CO(NH2)2 increased the incidence of BP. Moreover, the auxin content and MdGH3.1 expression increased in apples after nitrogen fertilization. On Day 30 before harvest, the two genes were transiently transferred to the fruit, and 20.69% and 23.21% of BP fruits were harvested. After 10 μmol·L−1 auxin was infiltrated at low pressure into postharvest fruit, the increase in MdGH3.1 expression occurred earlier than that in MdSAUR36. MdGH3.1 increased the expression of MdSAUR36, but MdSAUR36 did not increase expression of MdGH3.1. Therefore, we suggest that MdGH3.1 acts upstream of MdSAUR36 during BP formation and that these genes induce BP formation by regulating auxin and phenylpropanoid biosynthesis.

Elucidating Softening Mechanism of Honey Peach (Prunus persica L.) Stored at Ambient Temperature Using Untargeted Metabolomics Based on Liquid Chromatography-Mass Spectrometry

Peach fruit softening is the result of a series of complex physiological and biochemical reactions that influence shelf life and consumer acceptance; however, the precise mechanisms underlying softening remain unclear. We conducted a metabolomic study of the flesh and peel of the honey peach (Prunus persica L.) to identify critical metabolites before and after fruit softening. Compared to the pre-softening profiles, 155 peel metabolites and 91 flesh metabolites exhibited significant changes after softening (|log2(FC)| &gt; 1; p &lt; 0.05). These metabolites were mainly associated with carbohydrate metabolism, respiratory chain and energy metabolism (citrate cycle, pantothenate and CoA biosynthesis, nicotinate and nicotinamide metabolism, and pentose and glucuronate interconversions), reactive oxygen species (ROS) metabolism, amino acid metabolism, and pyrimidine metabolism. During peach fruit softening, energy supply, carbohydrate and amino acid metabolism, oxidative damage, and plant hormone metabolism were enhanced, whereas amino acid biosynthesis and cell growth declined. These findings contribute to our understanding of the complex mechanisms of postharvest fruit softening, and may assist breeding programs in improving peach fruit quality during storage.

Formulation of selective hydrophobic deep eutectic oil-in-water nanoemulsion as green fungicides for mitigating anthracnose fungus Colletotrichum gloeosporioides

Hydrophobic deep eutectic nanoemulsions derived from fatty acids and terpenes (referred to as HyDEN) were introduced as potential nano-coating to effectively combat anthracnose during the postharvest preservation of fruits. Anthracnose primarily caused by the Colletotrichum gloeosporioides species is known for causing substantial damage to fruits. Synthetic fungicides have proven to be effective but come with environmental, health, and safety concerns. In this study, hydrophobic deep eutectic solvents (HDESs) were evaluated for their physical properties to identify the most suitable HDES for the formulation of HyDEN. Menthol-Thymol (MT) at 1:1 and 2:1 ratio met the criteria and was chosen for the formulation of HyDEN. HyDEN (MT-N 1:1) displayed a higher zeta potential value and smaller mean droplet diameter and then tested for its antifungal properties against C. gloeosporioides compared with selected antifungal agents. HyDEN (MT-N 1:1) exhibited strong antifungal activity against C. gloeosporioides and was attributed to its potent mode of action, binding affinity, and rapid onset compared to HDES and fungicide (Globus 5.5). This study also investigated how HyDEN (MT-N 1:1) affects mycelial growth, cell membrane permeability, and cellular leakage of C. gloeosporioides, highlighting its superior disruption of cell membranes compared to HDES and Globus 5.5. This research presents an eco-friendly alternative to the use of toxic chemicals and showcases an innovative and sustainable approach to controlling anthracnose in postharvest fruit preservation.

Bordeaux mixture accelerates ripening, delays senescence, and promotes metabolite accumulation in jujube fruit

Abstract The old, but eco-friendly pesticide, Bordeaux mixture (Bm), is widely used in agriculture. Here, the effects of Bm on preharvest fruit ripening, and postharvest senescence of fruit and the accumulation of antioxidants were studied in Ziziphus jujuba. A 200× dilution of Bm enhanced preharvest ripening and retarded jujube fruit postharvest senescence. Treatment with Bm increased the reddening index and promoted the accumulation of total phenolics (TP) and the total antioxidant capacity (TAC) in preharvest fruit. However, this Bm-accelerated ripening could be partly reversed using dimethylthiourea (DMTU), a specific scavenger of reactive oxygen species. Compared with preharvest fruit, Bm treatment decreased weight loss and decay and increased firmness in postharvest fruit. Similarly, Bm-delayed senescence was partly reversed using dimethylthiourea. Moreover, the decrease in TP and TAC during storage was partly impeded by Bm. A higher H2O2 content was detected in preharvest fruit than in postharvest fruit. Moreover, this Bm-induced H2O2 accumulation was significantly mitigated using dimethylthiourea. Interestingly, both preharvest and postharvest spraying with Bm significantly enhance copper and calcium accumulation in fruit. Thus, Bm can be widely used before or after harvest to improve fruit quality.

Integrative metabolome and transcriptome analyses reveal the mechanism by which white light increases apple phenolics

Apple is a photophilic fruit and the nutrients content such as phenolics loss is a major problem during fruit storage. Light can affect the yield, appearance and quality of apples. However, the molecular mechanism behind how white light induces phenolics accumulation to improve quality in fruits remains unclear. In this study, we discovered that white light with an intensity of 4 w/m2 can enhance the total phenolic and flavonoid content in postharvest apple fruits. To investigate the specific phenolics that undergo changes during this process, we analyzed the metabolomes of apples exposed to white light for 5 days after harvesting. We identified a total of 97 differentially accumulated metabolites (DAMs), including 15 phenolics. Isorhamnetin-O-hexos, tangereti, phloretin, cis-p-coumaroyltartaric acid and cis-p-coumaroyltartaric acid contents decreased in white light. While myricetin 3-O-galactoside, astilbin, sieboldin 2′-hydroxygenistein, syringaresinol, pinoresino, maleoyl-caffeoylquinic acid, rosmarinyl glucosid, coniferyl alcohol, p-coumaryl alcoho, and feruloylferuloyltartaric acid contents increased in white light. Additionally, RNA-seq analysis allowed us to identify 1988 differentially expressed genes (DEGs), which included three key enzymes (phenylalanine ammonia-lyase [MdPAL-1], chalcone isomerase [MdCHI-like], and 4-coumarate: -CoA ligase [Md4CL-1]) involved in the phenolic synthesis pathway, as well as a basic leucine zipper domain (bZIP) transcription factor known as MdbZIP67. Further investigations revealed that white light can regulate the transcription of MdPAL-1, Md4CL-1, and MdCHI-like genes through MdbZIP67, resulting in an increase in phenolic content during fruit storage. Here, we have identified a new method to enhance the phenolic content in apple fruits with characteristics of easy to use and low cost. And we have elucidated the mechanism by which white light affects phenolic content during the fruit's shelf life.