Nengguo Tao

BACKGROUND: trans ‐2‐Hexenal (TH) is a promising alternative to chemical fungicide in controlling postharvest disease in fruits. This research sought to disclose how TH controls citrus green mold and induces fruit resistance through RNA‐Seq, physiochemical and natural decay. RESULTS: TH effectively delayed green mold incidence in citrus fruits. RNA‐Seq showed that multiple genes involved in the redox balance, ascorbic acid and aldehyde acid, and phenylpropanoid pathways were greatly influenced. In particular, the expression levels of genes involved in lignin and flavonoid biosynthesis – namely phenylalanine ammonia‐lyase , cinnamate‐4‐hydroxylase , 4‐coumarate‐CoA ligase , peroxidase 31 , cinnamoyl‐CoA reductase 1 , cinnamyl‐alcohol dehydrogenase1 , chalcone synthase2 , flavanone 3‐ hydroxylase , and flavonol synthase – were increased by TH treatment, which thereby promoted flavonoids and lignin accumulation. Meanwhile, the antioxidant capacity of TH‐treated citrus fruit was improved, as demonstrated by elevated levels of ascorbic acid and glutathione, and increased activities of enzymes and gene expression pertaining to the AsA‐GSH cycle, including ascorbate peroxidase 2 , glutathione reductases , monodehydroascorbate reductase 4 , dehydroascorbate reductase 2 , and glutathione s‐transferase , resulting in reduction of H ₂ O ₂ . Correspondingly, the protective effects of TH on citrus fruits decreased its susceptibility to Penicillium digitatum . CONCLUSION: TH exposure at 5 μL L ⁻¹ induces disease resistance against P. digitatum by stimulating the biosynthesis of lignin and flavonoid, along with the AsA‐GSH cycle in the peel of citrus fruit, thus improving antioxidant capacity and maintaining redox balance in the citrus fruit. These findings suggest that TH has potential for use as a protective measure against P. digitatum in citrus fruit. © 2026 Society of Chemical Industry.

Fruit rot caused by Alternaria alternata infection is one of the primary diseases responsible for postharvest losses in blueberries. Litsea cubeba essential oil (LCEO) exhibits potent control efficacy against A. alternata , but its antifungal mechanisms and effects on the postharvest quality of blueberries remain unclear. In vitro text showed that LCEO treatment induced severe developmental and hyphal morphology impairments of A. alternata . Treatment with 2×MFC LCEO notably reduced blueberry fruit rot incidence while decreasing fruit respiration rate and maintaining fruit quality such as higher fruit weight, firmness, total soluble solids, total acidity, total phenolic, and flavonoid. Mechanistic studies revealed that LCEO treatment severely impaired the cell membrane integrity of A. alternata mycelium, manifesting as markedly increased intracellular propidium iodide (PI) fluorescence intensity, pronounced intracellular solute leakage, and increased extracellular electrical conductivity. However, LCEO treatment did not alter cell wall calcofluor white (CFW) fluorescence intensity and alkaline phosphatase activity. Additionally, LCEO application triggered a sharp and sustained increase in ROS accumulation and consequent lipid peroxidation, while leading to a progressive decline in mitochondrial membrane potential. Therefore, LCEO exerts its antifungal activity by impairing the normal growth and development of A. alternata through multi‐target damage, thereby reducing postharvest rot losses in blueberries.

Botrytis cinerea poses a major threat to postharvest strawberries, causing significant losses due to gray mold. As a plant-derived antifungal agent, Rhodiola rosea L. essential oil (REO) possesses considerable healthcare benefits. However, its effectiveness and underlying mechanisms in the maintenance of postharvest products remain poorly understood. This study demonstrated that REO at 0.5 µL/mL completely inhibited the growth of B. cinerea under in vitro conditions. In vivo fumigation treatment with REO alleviated the severity of gray mold in strawberry fruit. Additionally, REO decreased natural decay and positively impacted marketability, as evidenced by higher firmness, total soluble solids, and ascorbic acid contents, as well as more favorable color attributes. Further investigations involving scanning electron microscopy, calcofluor white (CFW) staining, propidium iodide (PI) staining, 2′,7′-dichlorodihydrofluorescein diacetate assay, and cellular leakage tests were conducted to investigate the effects of REO treatment on gray mold mycelium. Results showed that REO treatment induced severe morphological distortions and collapse of mycelium. Within 30 min of exposure, REO triggered a sharp increase in PI fluorescence accompanied by a decrease in CFW fluorescence, without inducing an elevation in intracellular reactive oxygen species levels. The elevated leakage of nucleic acids and soluble proteins further confirmed that REO compromised the integrity of the cell barrier in B. cinerea. Collectively, these findings indicate that REO exerts potent antifungal activity by disrupting the integrity and functionality of B. cinerea cellular barriers, thereby reducing postharvest decay and positively impacting the marketability of strawberry fruit. Taken together, our findings suggest that REO represents a promising natural alternative for environmentally sustainable postharvest protection of strawberries.

Sour rot is a significant postharvest disease affecting citrus fruit, causing sourness and decay in various cultivars, particularly lemons. How the pathogen, Geotrichum citri-aurantii, adapts to the highly acidic environment of citrus fruit remains inadequately understood. In this study, the growth characteristics, morphological and structural changes, gene expression profiles, and adaptive mechanisms of G. citri-aurantii under highly acidic conditions were elucidated. The findings indicated that G. citri-aurantii modified the environmental pH by either alkalizing (pH < 3.00) or acidifying (pH > 3.00) the host tissue. It exhibited strong adaptability at pH 2.2, showing shortened and aggregated hyphae, delayed spore germination, and increased vacuoles. Transcriptomic analysis and qRT-PCR identified the significant regulation of key differentially expressed genes involved in cell wall remodeling, cell membrane component synthesis, carbon metabolism, and signal transduction. These regulatory changes enable the pathogen to prevent an influx of external acids and maintain the energy supply under acid stress conditions. Additionally, the Pal/Rim pH signaling pathway genes exhibit distinct response patterns in citrus cultivars with different acidities. These findings enrich the comprehension of the pathogenic process of G. citri-aurantii and offer a theoretical foundation for preventing and managing citrus sour rot.

Green mold formed by Penicillium digitatum is a major disease that limits the yield and overall value of postharvest citrus fruits. The antifungal activity of sodium cuminate (SC) against P. digitatum and the corresponding mechanism were explored in this research. The minimal inhibitory concentration (MIC) and minimal fungicidal concentration (MFC) of SC against P. digitatum were 0.4 and 0.8 g L⁻¹, respectively. SC (8× MFC) reduced the incidence of disease in Ponkan fruits without compromising their quality. The results of CFW staining and extracellular alkaline phosphatase assays revealed that 1/2MIC SC for 30 min had no impact on the cell wall integrity of P. digitatum. In contrast, 1/2MIC SC apparently destroyed cell membrane integrity, as shown by the increase in the content of reactive oxygen species (ROS), malondialdehyde, and H₂O₂. The addition of exogenous cysteine (Cys) or diphenyleneiodonium chloride (DPI) significantly mitigated the cytotoxic effects of SC. At the same time, mitochondrial membrane potential was significantly decreased by 1/2MIC SC, and the addition of exogenous Cys or DPI restored it to normal levels. In summary, the antifungal capacity of SC might be attributable to membrane damage in P. digitatum caused by oxidative stress.