Rapid fruit softening, weight loss and pathogen infection induced by mechanical wound are major factors causing postharvest losses in muskmelon. As a secondary messenger, calcium can enhance plant resistance to various stresses. However, it remains unknown whether exogenous calcium affects wound healing and softening in wounded muskmelon fruit. In this study, calcium chloride (CaCl2) and ethylene glycol tetraacetic acid (EGTA) were applied to wounded muskmelon fruit, respectively. After that, all fruit were stored in darkness at 20 ± 1 °C and 85% relative humidity. The results showed that CaCl2 treatment activated phenylpropanoid metabolism related enzymes at the wound sites and promoted the accumulation of phenolic acid monomers and lignin precursors, thereby accelerating the deposition of suberin polyphenolic periderm (SPP) and lignin during wound healing. Meanwhile, CaCl2 treatment suppressed respiration rate and ethylene production, and reduced the content of total soluble solids during storage. By inhibiting the activities of cell wall-degrading enzymes, it further inhibited the degradation of cell wall components such as pectin, cellulose and hemicellulose, consequently delaying fruit softening. In contrast, EGTA treatment inhibited the deposition of SPP and lignin at the wound sites, and promoted wound ethylene production and respiration rate, and accelerated the degradation of cell wall components, thus accelerating fruit softening. In conclusion, exogenous CaCl2 treatment can effectively reduce quality deterioration during storage by accelerating the formation of wound healing structures and delaying softening in wounded muskmelon fruit. These findings offer potential application value for reducing postharvest losses of muskmelon caused by mechanical wound.

Ochratoxin A (OTA), a planar small molecule mycotoxin prevalent in agricultural products, poses significant food safety concerns. Aptamers serve as ideal recognition elements for OTA sensors due to their high specificity and stability. However, research on the interaction mechanism between aptamers and OTA remains incomplete. In this study, fluorescence spectroscopy, circular dichroism (CD) spectroscopy, nuclear magnetic resonance (NMR) spectroscopy and molecular docking were utilized to analyze the recognition and binding mechanism of aptamer H8-OTA under different pH values and different cations (Ca2*, Mg2*, Na*, K*). It was found that OTA interacts with the aptamer through intercalation, where OTA binds to the edge of the quadruplex groove through hydrogen bonding, and divalent cations is benefit for the recognition of OTA by the aptamer. Compared with monovalent ions (Na*, K*), divalent cations (Ca2*, Mg2*) can improve the stability of OTA-aptamer complex. Moreover, OTA disrupted the parallel G-quadruplex structure of the aptamer in the presence of Ca2*, while higher Ca2* concentrations restored the parallel conformation and stabilized the OTA-aptamer complex (Kd = 0.162 mu m). The mechanistic insights into OTA-aptamer recognition provides a theoretical foundation for further development and utilization of OTA detection technologies.

Trichothecium roseum is an important postharvest pathogenic fungus, which can cause postharvest disease of diverse fruit. In addition to causing decay and quality deterioration, T. roseum infection can also metabolize trichothecenes that pose potential health risks to consumers. Calcium propionate (CP) is widely recognized as a food-grade antifungal agent. However, limited information is available regarding its antifungal mechanism against T. roseum and its potential application in controlling postharvest diseases of fruit. In this study, the antifungal efficacy of CP. against T. roseum was systematically evaluated both in vivo and in vitro, and its potential mechanism of action was further explored. The results demonstrated that CP inhibited spore germination and mycelial growth of T. roseum in a concentration-dependent manner, and effectively controlled the development of core rot of apple fruit, and powdery mildew of apricot and peach fruit. The antifungal mechanism is mainly that CP treatment targets the cell membrane, resulting in damage to cell membrane integrity and subsequent induction of oxidative stress, destruction of redox homeostasis, and inhibition of Ca2+/Mg2+-ATPase activity, resulting in disturbed calcium ion homeostasis and elevated intracellular Ca2+ levels. The reactive oxygen species (ROS) and calcium overload further contribute to a decline in mitochondrial membrane potential (ΔΨm), impair the function of key enzymes involved in energy metabolism (including hexokinase, malate dehydrogenase, succinate dehydrogenase, and ATP synthase), and ultimately block ATP synthesis. These events collectively lead to mitochondrial dysfunction and the suppression of energy metabolism. In vivo experiments demonstrated that treatment with CP inhibited the development of disease caused by T. roseum in fruit such as apple, peach, and apricot, and effectively maintained key quality parameters of apple fruit during postharvest storage, including weight loss rate, firmness, total soluble solids (TSS), reducing sugar content, vitamin C (Vc), and titratable acidity (TA).

As a vital part of the Rho GTPase family, Cdc42 is essential for fungal growth and its ability to cause disease, however, its function in Penicillium expansum, a major postharvest pathogen, remains unexplored. In this study, we characterized the biological function of PeCdc42 through gene deletion. Deletion of PeCdc42 disrupted MAPK and cAMP signaling by downregulating core regulatory genes. Pecdc42 deletion reduces colony growth, biomass, and spore formation, and alters the morphology of mycelium and spores. Furthermore, PeCdc42 deletion led to reduced patulin biosynthesis. Pathogenicity assays revealed diminished virulence of the pathogen on apple and pear fruit, with reduced lesion formation and depth, lower expression of genes encoding extracellular enzymes, and lower levels of reactive oxygen species (ROS). Collectively, our findings demonstrate that PeCdc42 is a central regulator of growth, secondary metabolism, and pathogenicity in P. expansum, offering new perspectives on fungal disease mechanisms and possible targets for controlling postharvest diseases.

Calcium ion (Ca2+) signalling is crucial for multiple biological processes in fungi, including growth, stress adaptation and pathogenic behaviour. The vacuolar Ca2+/H+ exchanger (VCX) is vital for maintaining calcium homeostasis within fungal cells, yet its specific biological functions in phytopathogenic fungi remain poorly understood. This study focused on the role and transcriptional regulation of AaVCX in Alternaria alternata, the organism responsible for pear black spot disease. By employing a split-marker strategy, we generated AaVCX knockout (ΔAaVCX) and complemented (ΔAaVCX-C) strains. Phenotypic assessments revealed that ΔAaVCX exhibited reduced mycelial growth, abnormal accumulation of intracellular Ca2+ and heightened sensitivity to various stressors. Deletion of AaVCX severely hindered spore germination, differentiation of appressoria and invasive hyphae in A. alternata triggered by pear peel wax. The ΔAaVCX nearly lost its ability to penetrate cellophane, and its virulence on pear fruits and leaves was markedly diminished. Molecular docking analysis indicated that AaCrz1, a key transcription factor in the calcium signalling pathway, can bind to the promoter of AaVCX. Dual-luciferase and yeast one-hybrid assays demonstrated that AaCrz1 binds to the AaVCX promoter in vitro and positively regulates its expression, with a predicted GCC-core motif identified in the promoter region. Furthermore, transcript levels of AaVCX were significantly reduced in the ΔAaCrz1 background, indicating that AaVCX is positioned downstream of AaCrz1 in a regulatory cascade. Our findings enhance the understanding of calcium signalling networks in phytopathogenic fungi and propose that components involved in vacuolar calcium storage may serve as potential targets for disease management.

Objective:To investigate the storage characteristics and quality evolution of fresh Radix Astragali under low-temperature of 4 ℃and dark storage conditions.Methods:The storage characteristics and quality changes of fresh Radix Astragali at 4 ℃were analyzed by monitoring its physiological parameters and storage quality during storage.Results:The moisture content of fresh Radix Astragali decreased from 57.92%to 48.19%,accompanied by a steady increase in weight loss,which reached 9.76%at 60 days.Respiration intensity showed a rise-then-fall trend,peaking at 15 days(15.17 CO2 mg·kg-1·h-1),indicating active metabolism in the early storage stage.In the initial 30 days,overall quality remained stable;however,in the later period,sensory quality and b* value declined significantly(P<0.05),with surface browning and texture softening.The b* value of the cross-section decreased by 33.07%at 60 days compared to 0 day.Total flavonoid content slightly increased initially,peaking at 0.56 mg/g at 15 days,then declined markedly to 0.34 mg/g by 60 days(P<0.05).Calycosin content continuously decreased,reaching 0.0175 mg/g at 60 days.Antioxidant capacities(DPPH,ABTS+,and hydroxyl radical scavenging)also peaked at 15 days,but dropped by 54.81%,17.5%,and 23.40%,respectively,at 60 days.Superoxide anion content increased significantly(P<0.05),reaching 3.92 μmol/g by 60 days.Both acid value and peroxide value increased over time,reaching 39.36 mg/g and 4.86%at 60 days,reflecting severe oxidative deterioration.With prolonged storage,decay rate and disease index increased notably.Mold appeared after 30 days,with decay rates of 8.83%and 12.57%,and disease indices of 7.34%and 10.59%at 45 and 60 days,respectively.Conclusion:A storage duration of up to 30 days at 4 ℃under dark conditions was found to effectively preserve the sensory quality and biological activity of fresh Radix Astragali,with flavonoid levels,antioxidant capacity,and metabolic status remaining relatively stable.Beyond this period,decay became progressively severe,accompanied by a rapid decline in overall quality and antioxidant function.This study provides a theoretical foundation for optimizing postharvest storage strategies and quality control of fresh Radix Astragali.

This study developed an antimicrobial composite film with dual functions of antibacterial activity and freshness preservation. Carvacrol-loaded microcapsules were embedded into a linear low-density polyethylene (LLDPE) matrix using the melt extrusion process. Compared to the pure LLDPE film, the composite films containing 0.5

The fabrication of natural, biodegradable, and food-grade particles as Pickering emulsions stabilizers has attracted considerable attention. This work involved the fabrication of Pickering emulsions stabilized by zein/ lecithin/pectin complex particles (Z/P/Lec) and the exploration of their application in the delivery of hyperoside (Hyp). The results showed that as the mass ratio of zein to lecithin (Lec) reached 4:1, the three-phase contact angle of Z/P/Lec was 83.07 degrees, which is close to neutral wettability, indicating that Z/P/Lec possess the potential to function as a stabilizer for Pickering emulsions. The droplet size of Pickering emulsion was decreased from 33.22 mu m to 10.99 mu m with the rise in Z/P/Lec concentration from 1.25% to 6.25%. Meanwhile, CLSM and CyroSEM imaging indicated that Z/P/Lec formed a tightly interfacial layer on the droplet surface, effectively providing protective barriers against droplet coalescence, thereby endowing it with long-term storage stability. Furthermore, the Pickering emulsions stabilized by Z/P/Lec provided sustained release of Hyp under simulated gastrointestinal conditions. Overall, this study indicates that Z/P/Lec is a novel and effective stabilizer for Pickering emulsions and offers a strategy for designing emulsion based sustained delivery systems for hydrophobic bioactive compounds.

BACKGROUND:Ca2+ acts as a pivotal second messenger in plants, activating downstream signaling components that enhance resistance to both abiotic and biotic stresses. Suberin polyaliphatic (SPA) is a major component of the protective barriers in wounded fruit. However, it is unknown whether exogenous calcium treatment can reduce postharvest losses by promoting SPA deposition. This study investigated how calcium treatment promotes the accumulation of SPA in postharvest muskmelon. RESULTS:Treatment with 1 mm CaCl2 enhanced the activity and gene expression of succinate dehydrogenase and malate dehydrogenase, raising ATP and energy charge, and providing energy for fatty acid synthesis. It also increased peroxidase and superoxide dismutase activity and gene expression, at the same time as upregulating calcium-dependent protein kinase (CmCDPK) and NADPH oxidase (CmNOX). This resulted in elevated O2•- and H2O2, serving as an oxidant for the cross-linking of suberin. Furthermore, calcium upregulated genes for fatty acid synthesis, boosting production of primary alcohols, α,ω-dicarboxylic acids, ω-hydroxy acids, fatty acids and glycerides. These responses accelerated SPA accumulation at wound sites, improving tissue texture, as well as reducing weight loss and disease index. By contrast, ethylene glycol tetraacetic acid, a specific Ca2+ chelator, sequestered endogenous Ca2+ in the wound tissues, thereby blocking calcium signaling and exerting inhibitory effects diametrically opposite to those of CaCl2 treatment on healing processes, including energy metabolism, reactive oxygen species metabolism and SPA synthesis. CONCLUSLON:Collectively, CaCl2 treatment accelerates fruit wound healing by increasing the accumulation of SPA at the wound site, thereby maintaining the quality of the fruit. EGTA treatment delayed wound healing by chelating Ca2+. © 2026 Society of Chemical Industry.

Fresh-cut muskmelons have garnered significant attention due to the consumption trend of convenience and health, but they are prone to softening, browning and flavor deterioration, which limits their commercial value. L-Phenylalanine (L-Phe), the initial substrate for phenylpropane biosynthesis, is fundamentally important for plant stress resistance. This research investigated the impact of four consecutive (young fruit stage, early expansion stage, late expansion stage and mature stage) L-Phe spray throughout the melon fruit development phase on the postharvest quality of fresh-cut melons. The results indicated that L-Phe significantly increased the activities of NADPH oxidase (NOX), superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), enzymes related to the ascorbate-glutathione (AsA-GSH) cycle and the gene expression levels of aquaporins, it also promoted the accumulation of ascorbic acid (AsA), glutathione (GSH), total phenolics and flavonoids. This effectively eliminates excessive reactive oxygen species (ROS), reduces the O2 & sdot;- production rate and hydrogen peroxide (H2O2) levels. Meanwhile, L-Phe treatment enhanced the scavenging activity against DPPH, ABTS+ and FRAP free radicals, suppressed the accumulation of malondialdehyde (MDA), reduced cell membrane permeability, ultimately delayed the decline in hardness and total soluble solids (TSS) content, stabilized color and mitigated quality deterioration during storage. In conclusion, preharvest spraying of L-Phe can effectively improve the quality of fresh-cut melons by maintaining the ROS homeostasis of fruit and enhancing their antioxidant capacity. This study presents a safe, low-cost and feasible new strategy for preserving the quality of fresh-cut fruit and vegetables.

Autophagy is a conserved intracellular degradation and recycling pathway that plays essential roles in fungal growth, development, and virulence. However, its function in the postharvest pathogen Penicillium expansum remains largely unexplored. In this study, we constructed a PeAtg2 deletion mutant (Delta PeAtg2) and a complementation strain (Delta PeAtg2-C) to elucidate the role of PeAtg2. Loss of PeAtg2 disrupted autophagosome formation and altered the expression of multiple autophagy-related genes. Delta PeAtg2 exhibited abnormal hyphal branching, markedly reduced conidiation and germination, and defective spore morphology. Under different nutritional conditions, Delta PeAtg2 displayed impaired vegetative growth and heightened sensitivity to osmotic stress, while showing enhanced tolerance to cell wall and oxidative stresses. Moreover, PeAtg2 deletion significantly suppressed patulin and pigment biosynthesis and attenuated pathogenicity on apple and pear fruit. These findings demonstrate that PeAtg2-mediated autophagy is central to fungal development, secondary metabolism, and virulence in P. expansum.

alpha-L-Arabinofuranosidase (alpha-AFase) and beta-D-xylosidase (beta-Xyl) are cell wall-modifying enzymes that often exhibit overlapping substrate specificity and are involved in the coordinated disassembly of pectin and hemicellulose networks during fruit softening. A genome-wide analysis of this functionally linked gene family in apple is lacking. Here, we identified 13 alpha-AFase/beta-Xyl genes in the apple genome. Phylogenetic, structural, and promoter analyses revealed their evolutionary relationships and potential for complex regulation. Expression profiling via reverse transcription quantitative polymerase chain reaction (RT-qPCR) demonstrated that three genes were detectable in flesh tissue of 'Oregon Spur II' fruit during ambient storage, with MdAF3 showing the strongest induction. Functional characterization through transient transformation indicated that MdAF3, a cell wall-localized protein, positively regulates fruit softening by modulating the activities of multiple cell wall-degrading enzymes and accelerating the solubilization and degradation of cell wall polysaccharides. Our work provides an integrated analysis of the alpha-AFase/beta-Xyl family in apple and establishes MdAF3 as a key regulator of fruit texture, offering a potential target for improving postharvest quality in apple.

Mefentrifluconazole, a novel isopropanol triazole fungicide belonging to the demethylation inhibitor (DMI) fungicides, has shown strong antifungal activity against Colletotrichum fructicola, the causal pathogen of strawberry anthracnose. However, the resistance risk and mechanisms of mefentrifluconazole in C. fructicola remain unclear. In this study, the sensitivity of 80 C. fructicola isolates to mefentrifluconazole was determined. The EC50 values ranged from 0.20 to 2.59 mg L−1, with a mean of 0.97 ± 0.38 mg L−1, and the unimodal sensitivity distribution indicated the absence of resistant subpopulations in field isolates. Seven laboratory-induced resistant mutants were obtained at a low mutation frequency (1.43 × 10-4). Most mutants exhibited reduced fitness relative to their parental isolates. Resistance was unstable during successive subcultures, suggesting a limited likelihood of field persistence. Correlation analysis indicated that mefentrifluconazole generally showed no strong cross-resistance relationship with the six tested fungicides, although difenoconazole exhibited the highest but still moderate-to-low correlation with mefentrifluconazol. Sequence analysis of CYP51A and CYP51B revealed nucleotide substitutions without corresponding amino acid changes, indicating that target-site mutations were not responsible for resistance. Quantitative PCR analysis demonstrated significant upregulation of CYP51A, and to a lesser extent CYP51B, particularly after fungicide exposure. These results indicate that inducible overexpression of CYP51A is a major contributor to low-level resistance in C. fructicola. Overall, the resistance risk of C. fructicola to mefentrifluconazol appears low, although resistance management strategies should still be implemented to maintain long-term fungicide efficacy.

Peroxisomes are essential organelles that facilitate various metabolic processes in eukaryotic cells. PEX5 and PEX7 function as key receptors for the targeted transport of peroxisomal matrix proteins, making them critical for peroxisome biogenesis. However, their functions in the postharvest pathogenic fungus Alternaria alternata remain unclear. In this study, we identified the AaPex5 and AaPex7 genes from A. alternata JT-03. Bioinformatics analysis revealed that AaPex5 and AaPex7 contain characteristic TPR and WD40 domains, respectively. Fluorescence localization demonstrated that AaPex5 acted as a specific receptor for the PTS1 pathway, while AaPex7 specifically regulates the PTS2 pathway. Deletion of either gene disrupted the transcriptional levels of PEX genes, with AaPex5 deletion leading to more extensive global transcriptional reprogramming. Phenotypic analysis indicated that the deletion of AaPex5 significantly impaired vegetative growth, hyphal development, and stress tolerance. Furthermore, the Delta AaPex5 mutant showed reduced melanin content and diminished virulence. At 6 days post-inoculation, the lesion diameter was reduced by 77.78% in Zaosu pear, 91.63% in Huangguan pear, and 89.59% in tomato, compared to the wild-type. Conversely, the Delta AaPex7 mutant displayed only minor effects. Transcriptomic analysis revealed that AaPex5 deletion resulted in significant enrichment of differentially expressed genes associated with peroxisomes, fatty acid beta-oxidation, and energy metabolism pathways. Furthermore, Nile red staining revealed significant accumulation of lipid droplets in the Delta AaPex5 mutant, while metabolic analysis demonstrated increased levels of medium to long-chain fatty acids. Although the activities of beta-oxidation enzymes were compensatorily increased, both NADH and ATP levels were significantly reduced. These findings indicate that AaPex5-mediated peroxisome biogenesis is essential for beta-oxidation and energy homeostasis, which in turn supports growth, development, and virulence in A. alternata. This study offers new insights into the role of peroxisomes in postharvest fungal pathogenesis.

BACKGROUND:Isorhamnetin-3-O-glucoside-7-O-rhamnoside (IGRh) is a characteristic flavonoid in sea buckthorn leaves, yet its anti-aging potential and underlying mechanisms remain largely unexplored. PURPOSE:This study aimed to systematically evaluate the anti-aging effects of IGRh and elucidate its mechanistic basis using Caenorhabditis elegans. METHODS:Lifespan, healthspan, stress resistance, and metabolic phenotypes were assessed in wild-type, mutant, and transgenic C. elegans strains. IGRh metabolites were profiled in vivo using UHPLC-QTOF-MS, and their interactions with SIR-2.1 were analyzed through molecular docking and molecular dynamics simulations. RESULTS:IGRh significantly extended lifespan and improved key aging-related phenotypes, including motility, intestinal barrier integrity, muscle structure, and lipid homeostasis, without impairing reproduction. IGRh also enhanced tolerance to heat and oxidative stress by elevating superoxide dismutase (SOD) and catalase (CAT) activities and reducing reactive oxygen species (ROS) and malondialdehyde (MDA) levels. Mechanistically, IGRh upregulated SIR-2.1 expression and promoted nuclear translocation of the transcription factors DAF-16 and HSF-1, thereby upregulating antioxidant and proteostasis-related genes. IGRh further stimulated the autophagy-lysosomal system and mitochondrial quality control, and its longevity-promoting effects were abolished in sir-2.1, daf-16, hlh-30, bec-1, clk-1, and mev-1 mutants. Metabolomic profiling revealed that IGRh was rapidly transformed into bioactive metabolites, including isorhamnetin, isorhamnetin-3-O-glucoside (I3G), quercetin-3-O-glucoside (Q3G), protocatechuic acid, and vanillic acid, several of which persisted in vivo. Q3G showed the most favorable docking score and the highest structural stability within the SIR-2.1 binding pocket. Functional assays further demonstrated that Q3G significantly delayed aging and enhanced stress resistance in C. elegans in a sir-2.1-dependent manner. Together with the CETSA results, these findings support Q3G as a key candidate bioactive metabolite contributing to the SIR-2.1-dependent anti-aging effects of IGRh. CONCLUSION:IGRh and its metabolites delay aging in C. elegans by mediating SIR-2.1/DAF-16 signaling and modulating downstream IIS and autophagy-lysosomal pathways. These findings provide mechanistic insight into sea buckthorn leaf flavonoids and support their potential development as natural anti-aging interventions.

Previous studies have shown that Alternaria alternata can utilize media supplemented with exogenous phenolic acid monomers at concentrations comparable to those found in pear peel as its sole carbon source, degrading these compounds in a species-specific and concentration-dependent manner. However, the detailed molecular mechanisms underlying the degradation of phenolic acids in pear peel remain incompletely understood. Transcriptome analysis indicated that genes associated with aromatic compound metabolism in A. alternata were significantly up-regulated following exposure to 1 mM exogenous chlorogenic and ferulic acids. Catechol 1,2dioxygenase (AaCHD), a key enzyme involved in phenolic metabolism, was selected for further investigation using targeted gene knockout techniques. Although no significant differences in growth, spore germination, or pathogenicity were observed between the AaCHD mutants and the WT strain, the deletion of AaCHD1 and AaCHD2 resulted in increased sensitivity to exogenous phenolic acids and osmotic stress. Moreover, quaternary ultra-fast liquid chromatography analysis revealed that, after 48 h of incubation with exogenous phenolic acids, the Delta AaCHD1 mutant still maintained higher levels of chlorogenic acid, while both Delta AaCHD1 and Delta AaCHD2 mutants exhibited elevated residual p-coumaric acid compared to the WT. These findings suggest that AaCHD enzyme may play a critical role in the degradation of chlorogenic acid and p-coumaric acid in pear peel by A. alternata, even though they are not essential for the fungus's growth and development.

The cell wall integrity (CWI) MAPK signal pathway is crucial for the assembly of fungal cell walls and their associated virulence, as it activates the expression of the downstream transcription factors Mbp1, Swi6, and RlmA. However, the transcription factors directly regulated by this pathway in Alternaria alternata have yet to be identified. In this study, we delineated the functional roles of two transcription factors, AaSwi6 and AaMbp1, through targeted gene deletion. Disruption of either gene resulted in impaired hyphal extension, reduced mycelial accumulation, decreased conidiation, altered differentiation of infection structures, and impaired melanin synthesis. Furthermore, when compared to the WT, the levels of alternariol (AOH), alternariol monomethyl ether (AME), and tenuazonic acid (TeA) toxins in the two ΔAaSwi6 and ΔAaMbp1 mutants decreased by 63.98% and 86.32%, 36.71% and 82.85 %, and 33.28% and 33%, respectively. These defects were correlated with diminished virulence on tomato and pear fruit. Compositional analysis of the cell wall composition indicated that the deletion of AaSwi6 resulted in decreased levels of chitin, glucan, and mannan, whereas the deletion of AaMbp1 led to reduced levels of chitin and mannan. Yeast two-hybrid experiments further demonstrated that the MAPK kinase AaSlt2 physically interacted with downstream partners AaSwi6 and AaRlmA, and that AaSwi6 also interacted with AaMbp1 and AaRlmA. In conclusion, our study identifies a physical interaction between AaSlt2 and Swi6/RlmA, suggesting that these components are critical for cell wall synthesis. The finding advances our understanding the pathogenic mechanisms of A. alternata and proposes potential strategies for controlling postharvest diseases.

Broccoli (Brassica oleracea L. var. italica) is a highly perishable vegetable that undergoes rapid postharvest senescence and yellowing, resulting in the loss of nutritional and bioactive compounds. To address this issue, the present study investigated the effects of preharvest salicylic acid (SA) spraying on the quality of broccoli after 25 d of storage at 4 degrees C. Compared with the control group, preharvest SA treatment, particularly at a concentration of 0.5 mmol/L (SA0.5), effectively maintained phenotypic appearance, suppressed changes in color parameters (L*, a*, b*, and H*), reduced weight loss, retained higher stem hardness, and increased soluble solids content. The application of SA also preserved the contents of total chlorophyll and chlorophyll b by inhibiting the activities and gene expression of key chlorophyll-degrading enzymes, including chlorophyllase, Mg-dechelatase, pheophytinase, and pheophorbide a oxygenase, thereby delaying yellowing. Additionally, SA treatment elevated hydrogen peroxide (H2O2) levels while decreasing superoxide anion (O2-& centerdot;) accumulation. It increased superoxide dismutase activity while decreasing the activities of peroxidase and catalase, and enhanced the contents of non-enzymatic antioxidants such as vitamin C, total phenolics, and flavonoids. These results indicate that preharvest SA application contributes to delayed senescence in broccoli by modulating chlorophyll degradation and reactive oxygen species metabolism.

Wound healing is essential for maintaining postharvest quality in potato tubers, and phenylpropanoid metabolism plays an important role in forming protective aromatic barriers at wound sites. This study investigated whether exogenous L-phenylalanine (L-Phe) could enhance wound responses associated with phenylpropanoids in wounded potato tubers. Treatment with 0.05 mmol L-1 L-Phe increased the activity of phenylpropanoid-related enzymes, including phenylalanine ammonia-lyase (PAL), cinnamate 4-hydroxylase (C4H), 4-coumarate: CoA ligase (4CL), cinnamyl alcohol dehydrogenase (CAD), and peroxidase (POD). This was associated with higher accumulation of selected phenylpropanoid-related acids, soluble monolignols, total phenolics, and lignin-associated aromatic wall material at wounds. Microscopy further showed enhanced deposition of suberin polyphenolic (SPP) material and expansion of the wound-associated lignified zone in L-Phe-treated tubers. These structural and biochemical responses were accompanied by reduced weight loss and a modest reduction in disease severity during healing. Collectively, these results suggest that exogenous L-Phe enhances phenylpropanoid-associated aromatic wound-barrier development in potato tubers.