Pre-harvest UV-C irradiation triggers VOCs accumulation with alteration of antioxidant enzymes and phytohormones in strawberry leaves

Dose-dependent physiological effects of UV-C radiation on seashore paspalum

Positive effects of ultraviolet-C (UV-C) radiation on plants have been documented in previous literature with a focus on extending shelf life and reducing disease development. However, its effect on plant growth habits has been scarcely explored, especially in turfgrass where a compact shoot growth is a desirable trait. Seashore paspalum (Paspalum vaginatum) is a warm-season perennial turfgrass requiring low fertilizer and pesticide inputs. This project aimed to test the effects of different doses of UV-C radiation on growth and performance of seashore paspalum cv. Seastar. Here, we provide evidence of dose-dependent effects. Lower UV-C doses (6 s and 1 min daily) improved the performance of seashore paspalum, as manifested by higher tiller density, reduced clipping yields, increased chlorophyll level on selected dates as well as enhanced photosynthetic efficiency compared to control. Contrastingly, higher doses (6 min and 30 min daily) resulted in severe damage with 30-min treatment being lethal to seashore paspalum, causing marked declines in all measured parameters. This is the first time that UV-C-induced growth response was reported in turf. Conclusions drawn from this study would shed light into the effects of UV-C radiation on the growth and performance of seashore paspalum and offer exciting potential for the utilization of UV-C at non-lethal dosage in turfgrass management.

Effect of drainage ratio during strawberry cultivation:The volatilomics-based shelf-life indicators for strawberry fruit

The metabolome of strawberries at harvest determines their storage capacity. Therefore, dynamics of volatile production during storage of strawberry cultivated under diverse drainage ratios, T1 (12.0%), T2 (25.3%), T3 (36.4%), and T4 (56.5%), were evaluated. Among the various non-target VOCs analysis, there were some groups including aldehydes, esters, and furans occupied over 5% with exhibiting high coefficient of determination (R² ) following the days after storage (DAS). Aldehydes content decreased over the storage period, while the esters (methyl butanoate, methyl hexanoate, ethyl hexanoate, and benzyl acetate) and furanones (furaneol and mesifuran) were increased as representing aroma compounds in strawberry ripening. Even on the same day, it was investigated that the release of VOCs linked to fruit decay was delayed in the groups (T1 and T2) that were given relatively little water compared to T3 and T4. The hexanal and ethyl hexanoate as an over-ripened signal showed a rapid increase from 4 DAS to 5 DAS in T3 and T4, respectively, while T1 and T2 showed significant increase from 5 DAS to 6 DAS. Relatively slower over-ripening tendency of T1 and T2 was supported by changes of firmness, total soluble solid content, anthocyanin content, and antioxidant activity during storage. T1 and T2 showed higher antioxidant activity at the harvest time and lower anthocyanin accumulation than T3 and T4. The present study elucidated that the preharvest drainage changes during cultivation was involved in fruit quality during strawberry storage. Besides, volatilomics analysis depicted that T2 as an optimal ratio, could delay the occurrence of stress and senescence, and guaranteed the strawberry yield. In conclusion, this study provided evidence that the practical application of drainage ratios could improve horticultural product quality even with low water use and VOCs might be considered an early indicator for strawberry fruit shelf-life.

Prediction of banana quality during storage by brown area

To study the feasibility of evaluating the quality characteristics of banana based on the browning area. The texture characteristics, total soluble solids (TSS), ascorbic acid, malondialdehyde (MDA) concentrations, relative conductivity, polyphenol oxidase, peroxidase, and phenylalanine ammonia-lyase (PAL) activities in banana peels were detected during storage. A linear model was made by principal component analysis and multiple linear regression between the banana browning area and characteristic indices. The results showed that the changes in the physiological characteristics of bananas were significantly different during different storage periods. The main factors that affected the banana browning area were relative conductivity, PAL, TSS, and MDA, indicating that lipid peroxidation, respiration, and metabolism of phenylpropanoids had significant influence on the banana browning area during storage. Thus, it is feasible to predict banana quality based on changes in browning area, which could be a rapid and non-destructive detection of banana quality during storage.

Effect of processing and storage on the volatile profile of sugarcane honey: A four-year study

Sugarcane honey (SCH) is a syrup from Madeira Island recognized by its unique and excellent aroma, associated to volatile organic compounds (VOCs) generated during the well-defined five stages of its traditional making process. The establishment of volatile profile throughout all SCH-making stages during four years, allowed the evaluation of the influence of each stage in the typical characterisitcs of SCH. One hundred eighthy seven VOCs were identified, being associated to several origins and formation pathways. VOCs formed during stage 1 and 2 were originate from raw material, and its oxidation (i.e. enzymatic browning) and thermal degradation (i.e. lipid oxidation, Maillard reactions, Strecker degradation). In stage 3 and 4, the caramelization and melanoidin degradation also occurred, while in stage 5, the thermal degradation continues, followed by microbial activity. Chemometric analysis allowed to identify 35 VOCs as potential markers for processing control by the producers and as guarantee of the typicality and authenticity of SCH. Based on the obtained results, we propose for the first time an innovative schematic diagram explaining the potential reactions and pathways for VOCs formation during the different steps of the SCH production.

Impact of UV-C Radiation Applied during Plant Growth on Pre- and Postharvest Disease Sensitivity and Fruit Quality of Strawberry

Ultraviolet-C (UV-C) radiation is efficient in reducing the development of diseases in many species, including strawberry (Fragaria × ananassa). Several studies suggest that UV-C radiation is effective not only because of its disinfecting effect but also because it may stimulate plant defenses. In this study, the effect of preharvest UV-C radiation applied during strawberry cultivation on plant growth, fruit quality, and susceptibility to major fungal diseases such as gray mold, powdery mildew, and soft rot was evaluated. UV-C treatments had an impact on flowering initiation and fruit development. Flowering occurred earlier for UV-C-treated plants than for nontreated plants. At harvest, a larger amount of fruit was produced by treated plants despite their slight decrease in leaf area. UV-C treatment did not improve strawberry shelf life but did not alter the physical integrity of strawberry fruit. Natural infection of leaves to powdery mildew and of fruit to Rhizopus spp. strongly decreased in response to UV-C treatment.

Ultraviolet-C priming of strawberry leaves against subsequent Mycosphaerella fragariae infection involves the action of reactive oxygen species, plant hormones, and terpenes

Ultraviolet-C (UV-C) radiation has been reported to induce defence responses to pathogens in growing crops and described as a new environmentally friendly method for disease control. However, whether the effect of the induced defence mechanisms will persist after the stress imposed by UV-C is alleviated and how these mechanisms interact with pathogen elicitors upon infection have not yet been investigated. Thus, we inoculated strawberry plants with Mycosphaerella fragariae, the causal agent of leaf spot disease, after 5 weeks of repeated UV-C irradiation treatment (cumulative dose of 10.2 kJ m^-2 ) and investigated the alteration of gene expression and biochemical phenotypes. The results revealed that UV-C treatment had a significant impact on gene expression in strawberry leaves and led to the overexpression of a set of genes involved in plant-pathogen interaction. UV-C-treated leaves displayed a stronger response to infection after inoculation, with reduced symptoms and increases in accumulation of total phenolics and volatile terpenes, higher expression of pathogenesis-related proteins and the activity of several defence enzymes. This study presumptively describe, for the first time, the involvement of terpenes, reactive oxygen species, and abscisic acid, salicylic acid, jasmonic acid, and their transduction factors, in the network underpinning UV-C priming of growing crops for improved protection against pathogens.

Exogenous progesterone treatment alleviates chilling injury in postharvest banana fruit associated with induction of alternative oxidase and antioxidant defense

The effects of exogenous progesterone (PROG) on chilling injury (CI) in postharvest banana fruit were investigated. Concentration screening tests showed that 10^-5 mol/l PROG was most effective in reducing CI in banana fruit stored for 25 d at 5 ± 1 °C, but did not markly increase PROG content of pulps. This PROG treatment significantly reduced the electrolyte leakage, levels of malondialdehyde, O₂^- production rate and H₂O₂ contents in banana compared with control fruit. The PROG treatment caused an early induction of alternative oxidase (AOX) at the transcript and protein level to reduce the generation of O₂^- and H₂O₂. PROG treatment also enhanced the transcript levels and activities of antioxidant enzymes and maintained higher levels of reduced glutathione and ascorbic acid than the control fruit. These results suggested that PROG attenuating CI in banana fruit may be attributed to the induction of AOX and the improvement of enzyme and non-enzymatic antioxidant defenses.

Preharvest Ultraviolet C Treatment Affected Senescence of Stored Strawberry Fruit with a Potential Role of MicroRNAs in the Activation of the Antioxidant System

Recent studies presented preharvest ultraviolet C (UV-C) as an environmentally friendly approach for the management of horticultural crop diseases. The effect of this approach on quality preservation during postharvest storage has not yet been investigated. Strawberry fruit harvested from plants grown with supplemental UV-C were stored at room temperature for 72 h, and their postharvest shelf-life biochemical indicators were evaluated. The involvement of microRNAs (miRNAs) in the activation of UV-C-induced antioxidant systems was investigated. Preharvest UV-C contributed to the preservation of sugar and organic acid and reduced overall lipid peroxidation in strawberry fruit during storage. We found that miR159 and miR398 were downregulated by preharvest UV-C and that their respective targets were upregulated at the early stage of storage with enhancement of the activity of antioxidant enzymes. The initial burst of H₂O₂ and O₂^• - suggested that preharvest UV-C primed the fruit in an antioxidative activated state via reactive-oxygen-species-mediated feedback control with post-transcriptional involvement of miRNAs.

Phomopsis longanae Chi-Induced Change in ROS Metabolism and Its Relation to Pericarp Browning and Disease Development of Harvested Longan Fruit

Phomopsis longanae Chi is a major pathogenic fungus that infects harvested longan fruit. This study aimed to investigate the effects of P. longanae on reactive oxygen species (ROS) metabolism and its relation to the pericarp browning and disease development of harvested longan fruit during storage at 28°C and 90% relative humidity. Results showed that compared to the control longans, P. longanae-inoculated longans displayed higher indexes of pericarp browning and fruit disease, higher O2 -. generation rate, higher accumulation of malondialdehyde (MDA), lower contents of glutathione (GSH) and ascorbic acid (AsA), lower 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging ability and reducing power in pericarp. In addition, P. longanae-infected longans exhibited higher activities of superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APX) in the first 2 days of storage, and lower activities of SOD, CAT, and APX during storage day 2-5 than those in the control longans. These findings indicated that pericarp browning and disease development of P. longanae-infected longan fruit might be the result of the reducing ROS scavenging ability and the increasing O2 -. generation rate, which might lead to the peroxidation of membrane lipid, the loss of compartmentalization in longan pericarp cells, and subsequently cause polyphenol oxidase (PPO) and peroxidase (POD) to contact with phenolic substrates which result in enzymatic browning of longan pericarp, as well as cause the decrease of disease resistance to P. longanae and stimulate disease development of harvested longan fruit.

Modulation of Enhanced Antioxidant Activity by Hydrogen Sulfide Antagonization of Ethylene in Tomato Fruit Ripening

Ethylene (C₂H₄) and hydrogen sulfide (H₂S) play important physiological roles in regulating fruit ripening and senescence. The mechanism of H₂S in ethylene-induced tomato fruit ripening and senescence is still unknown. Here, we show that exogenous H₂S reduced the production of superoxide anion (·O₂^-), malondialdehyde (MDA), and H₂O₂ in tomato fruit. Further, additional H₂S was found to induce the activities of guaiacol peroxidase, catalase, ascorbate peroxidase, and superoxide dismutase compared with C₂H₄ treatment alone, whereas the activities of lipoxygenase, polyphenol oxidase, and phenylalanine ammonia lyase were adversely affected. Moreover, the expression of the antioxidant-encoding genes SlAPX2, SlCAT1, SlPOD12, and SlCuZnSOD was generally up-regulated with C₂H₄-H₂S cotreatment, compared with their expression after ethylene treatment. Thus, the present results suggest that exogenous H₂S acts as a fruit-ripening regulator by antagonizing the effect of ethylene, thereby providing a potential application for H₂S in the postharvest storage of fruit.