Satoru Kondo

The ability of salicylic acid (SA) to control post-harvest fungal disease mango anthracnose caused by plant pathogen Colletotrichum gloeosporioides and the accompanying biochemical and metabolomic changes were studied. In vitro, C. gloeosporioides mycelial growth at 25 °C for 7 days was inhibited by SA at 2 and 5 mM concentrations. In vivo, mango fruits were treated with 2 mM SA for 10 min, then inoculated with C. gloeosporioides. The fruits were then stored at 25 °C and sampled every 2 days after inoculation. The anthracnose severity, infection index, malondialdehyde (MDA), antioxidant capacity (DPPH and FRAP), total phenolics (TPC), total flavonoids (TFC), ascorbic acid, and metabolomic changes in the peel were studied. Six days post inoculation, the SA-treated fruits showed reduced anthracnose severity, and the infection index was significantly reduced by SA (57%) compared to the control (67%). The SA-treated fruits exhibited decreased MDA, enhanced antioxidant capacity, and increased levels of TPC, TFC, and vitamin C in the peel. Compared with the control, SA treatment reduced MDA content by approximately 50% and increased TPC, TFC, and FRAP antioxidant capacity by 77%, 31%, and 29%, respectively. Vitamin C content and DPPH antioxidant activity were also significantly higher in SA-treated fruits. Untargeted metabolomics and a principal component analysis revealed a separation group between the SA-treated and control fruit. The SA treatment induced D-amino acids, phenylalanine pathways, and the biosynthesis of secondary metabolites such as phenolic acid. Together, these findings demonstrate that SA enhances mangoes’ resistance to post-harvest anthracnose through direct antifungal action and the activation of host defense by improving the antioxidant systems and stimulating the accumulation of secondary defense metabolites in mango fruit.

BACKGROUND: High‐voltage electrostatic field (HVEF) is a physical postharvest handling technique, which is clean and safe technology for consumers and the environment and can be used to extend the postharvest shelf life of avocados. Therefore, the effects of a HVEF on cell wall modification related to mesocarp softening in avocados during storage were investigated, as well as physiological changes. Avocados were treated with 1 kV cm ⁻¹ for 120 min and then packed into carton boxes. Fruit without an HVEF served as the untreated control. The fruit were subsequently stored at room temperature (25 ± 2 °C) and 75 ± 5% relative humidity for 7 days. RESULTS: The results revealed that the HVEF had physiological affects by significantly delaying respiration rate and ethylene production. HVEF‐treated fruit maintained fruit firmness (15.34 N), representing a 3.5‐fold (approximately 352%) increase compared with control samples (3.39 N), and exhibited approximately 30% lower water‐soluble pectin (WSP) content (0.41 vs. 0.56 g L ⁻¹ ) at 3 days after treatment. These changes were correlated with a negative relationship between firmness and WSP content. Additionally, the HVEF treatment significantly repressed the activities of key cell wall‐degrading enzymes: pectin methyl esterase, polygalacturonase, and pectate lyase. Fourier transform infrared spectroscopy – a molecular analysis technique – and principal component analysis – a statistical method for data interpretation – confirmed structural changes in the pectin. Furthermore, compared with the untreated control treatment, HVEF significantly maintained peel color and delayed a decrease in hue° value. CONCLUSION: These results indicated that HVEF could be an effective method for extending avocado shelf life by approximately 2 days compared with the control, based on the delay in reaching the edible‐ripening stage (firmness < 10 N and hue° < 90°). Overall, HVEF treatment provides a non‐destructive and environmentally friendly approach to delay ripening and extend the postharvest shelf life of avocados under ambient conditions. © 2025 Society of Chemical Industry.

Background and Aims: Color, a key determinant of grape berry quality, is influenced by light, temperature, and plant hormones during development. We investigated the effects of red‐, blue‐, and combined red‐and‐blue‐light irradiations on photoreceptors, abscisic acid (ABA) signaling, and anthocyanin biosynthesis in order to clarify their mutual relationships. Methods and Results: The experiment was conducted over two consecutive years (2023–2024) using the same nine “Kyoho” grapevines, which were eight years old at the start of the study. In 2023, treatments consisted of irradiating grape clusters with either red‐light‐emitting diodes (LEDs) or blue LEDs. In 2024, the treatments were modified to irradiation with blue LEDs or a combination of red and blue LEDs. Compared to an untreated control group, the irradiation of grape clusters with red or blue LEDs at 240 μmol m ⁻² s ⁻¹ both significantly increased the expressions of the photoreceptor genes VvPHYa (phytochromes) , VvPHYb , VvCRYa (cryptochromes), and VvPHOT2 (phototropins), those of genes VvSnRK2.6 (an SNF 1‐related protein kinase) and VvABF2 (an ABA‐responsive element‐binding transcription factor) involved in the activation of ABA signaling, and those of genes VvMYBa1 and VvUFGT involved in anthocyanin synthesis, as well as anthocyanin synthesis. The expression of VvPP2C9 (protein phosphatase 2C9), which is negatively related to ABA signaling, was decreased. There were no significant differences in these factors between the red‐ and blue‐irradiated sections. The combined treatment with red and blue light, as well as blue‐light exposure alone, upregulated photoreceptor genes’ expression, ABA signaling, anthocyanin synthesis enzyme genes’ expression, and anthocyanin synthesis compared to the untreated control, whereas no difference was observed between the combined treatment and the blue‐light treatment. Conclusions: These results suggest that both red‐ and blue‐light exposure stimulate ABA signaling in grape skins and that the activation of either the red‐ or blue‐light receptors promotes anthocyanin synthesis.

Various attempts have been made to use abscisic acid (ABA) as a plant bioregulator (PBR). Recently, a new ABA formulation, produced through microbial fermentation, has been commercialized in Japan as a PBR for improving grape peel color. Nonetheless, the horticultural application of ABA remains limited compared to other plant hormones. Generally, the vital functions of ABA include the regulation of abiotic stress tolerance and plant dormancy via metabolic changes associated with the antioxidant system and the modulation of sugar biosynthesis/translocation, respectively. These metabolic changes are crucial for the quality of fruit, suggesting the potential of ABA for promoting the production of high-quality fruit. In non-climacteric fruit, ABA plays a pivotal role in anthocyanin pigmentation, a significant component of the antioxidant machinery. Studies in grapes and strawberries have shown that the responses to ABA differ depending on the type of ABA agonist used and the specific organs to which it is applied. Herein, the influence of ABA on climacteric fruit exhibiting ethylene-regulated ripening is discussed. ABA-mediated ethylene induction followed by ripening suggests a shared regulatory mechanism that underlies ripening in both climacteric and non-climacteric fruits that involves crosstalk between ABA and ethylene. This review firstly summarizes the historical challenges with ABA and its agonist for application as PBRs and discusses the role of ABA in the ripening of non-climacteric fruit, particularly grapes. Subsequently, the molecular background of ABA in both climacteric and non-climacteric fruit ripening is explained, with a focus on peel coloration, sugar synthesis, and aroma volatile synthesis.

ISHS IV Asian Horticultural Congress ? AHC2023 Isoprothiolane regulates endogenous abscisic acid and indole-3-acetic acid during grape berry maturation

The effects of blue-light irradiation on abscisic acid (ABA) signaling, sugar metabolism and translocation, and photoreceptors and gene expressions were investigated to clarify the mechanism by which blue-LED irradiation increases sugar concentrations in grape berries (Vitis labruscana L.). Blue light-emitting diode (LED) irradiation increased the portion of ¹³C-photosynthates in the grapevine clusters that were fed ¹³CO₂; compared to the portion in the cluster in the untreated control. Fructose and glucose concentrations and the expressions of VvSWEET10, VvSUC11, and VvSUS4 in blue LED-irradiated berries were increased. The blue LED-irradiated berries’ sucrose concentrations were significantly lower than the untreated control at 14 days after treatment. We speculated that the blue LED-treated berries’ decreased sucrose was associated with the increased Sugars Will Eventually be Exported Transporter (VvSWEET10), sucrose transporter (VvSUC11), and sucrose synthase (VvSUS4) expressions and promoted the translocation of ¹³C-photosynthates from the leaves that were fed ¹³CO₂. Blue-LED irradiation increased the expressions of SNF1-related protein kinases (VvSnRK2.6) and ABA responding element binding transcription factor (VvABF1), while decreasing the expression of protein phosphateses 2C9 (VvPP2C9) genes, which are related to ABA signaling. Blue-LED irradiation increased the expressions of cryptochrome (VvCRYa) and phototropin (VvPHOT2), which are photoreceptor genes. The application of the pyrabactin resistance-like (PYL)-PP2C ABA receptor interaction antagonist AS6 did not affect endogenous ABA concentrations in the grape berries, but it decreased sucrose concentrations at harvest. The application of ABA did not affect sucrose, glucose, or fructose concentrations or the expressions of VvSnRK2.6 and VvPP2C9. The application of nordihydroguaiaretic acid (NDGA, an inhibitor of 9-cis-epoxycarotenoid dioxygenase activity in ABA biosynthesis) did not affect sugar concentrations at harvest. These results suggest that upregulation of photoreceptor gene expressions and ABA signaling are associated with sugar concentrations in grape berries.

Epigenetic changes serve as a cellular memory for cumulative cold recognition in both herbaceous and tree species, including bud dormancy. However, most studies have discussed predicted chromatin structure with respect to histone marks. In the present study, we investigated the structural dynamics of bona fide chromatin to determine how plants recognize prolonged chilling during the initial stage of bud dormancy. The vegetative axillary buds of the ‘Fuji’ apple, which shows typical low temperature-dependent, but not photoperiod, dormancy induction, were used for the chromatin structure and transcriptional change analyses. The results were integrated using a deep-learning model and interpreted using statistical models, including Bayesian estimation. Although our model was constructed using a small dataset of two time points, chromatin remodelling due to random changes was excluded. The involvement of most nucleosome structural changes in transcriptional changes and the pivotal contribution of cold-driven circadian rhythm-dependent pathways regulated by the mobility of cis-regulatory elements were predicted. These findings may help to develop potential genetic targets for breeding species with less bud dormancy to overcome the effects of short winters during global warming. Our artificial intelligence concept can improve epigenetic analysis using a small dataset, especially in non-model plants with immature genome databases.