Effect of methyl salicylate in combination with 1-methylcyclopropene on postharvest quality and decay caused by Botrytis cinerea in tomato fruit

The Simultaneous Use of 1-Methylcyclopropene and Methyl Jasmonate Vapor as an Innovative Strategy for Reducing Chilling Injury and Maintaining Pomegranate Fruit Quality at Suboptimal Temperatures

Spain is one of the main contributors to global pomegranate production. Pomegranate presents a challenge for preservation at suboptimal temperatures. Preserving this fruit for an extended period is challenging due to its susceptibility to chilling injury (CI). For this reason, we have examined different postharvest treatments to extend the pomegranate shelf life and their potential impact on reducing CI. For this reason, two postharvest treatments have been applied: 1-Methylcyclopropene (1000 nL L-1 1-MCP) and methyl jasmonate vapors (0.01 mM MeJA), a natural elicitor found in many plant organs that induces a wide range of physiological processes, including the activation of defense mechanisms against stress. Following the application of these treatments and subsequent fruit storage at 2 °C for 90 days, maintenance of firmness and membrane integrity was observed. Additionally, a positive synergic effect was observed in these quality traits when combining both substances (1-MCP + MeJA), especially with regard to delaying weight loss, the external color evolution, and total polyphenol accumulation. On the other hand, MeJA treatment alone or in combination with 1-MCP also increased the anthocyanin content in arils, thereby enhancing the fruit quality. In general, the best results were observed when these two different technologies were applied as a combined treatment, especially in terms of maintaining quality traits such as fruit firmness and total acidity and reducing weight loss and CI. This is the first time that these two substances have been tested together in any fruit species, and their simultaneous application in the same container represents an innovative approach that could be an interesting tool for commercial purposes.

Structural variation underlies functional diversity at methyl salicylate loci in tomato

Methyl salicylate is an important inter- and intra-plant signaling molecule, but is deemed undesirable by humans when it accumulates to high levels in ripe fruits. Balancing the tradeoff between consumer satisfaction and overall plant health is challenging as the mechanisms regulating volatile levels have not yet been fully elucidated. In this study, we investigated the accumulation of methyl salicylate in ripe fruits of tomatoes that belong to the red-fruited clade. We determine the genetic diversity and the interaction of four known loci controlling methyl salicylate levels in ripe fruits. In addition to Non-Smoky Glucosyl Transferase 1 (NSGT1), we uncovered extensive genome structural variation (SV) at the Methylesterase (MES) locus. This locus contains four tandemly duplicated Methylesterase genes and genome sequence investigations at the locus identified nine distinct haplotypes. Based on gene expression and results from biparental crosses, functional and non-functional haplotypes for MES were identified. The combination of the non-functional MES haplotype 2 and the non-functional NSGT1 haplotype IV or V in a GWAS panel showed high methyl salicylate levels in ripe fruits, particularly in accessions from Ecuador, demonstrating a strong interaction between these two loci and suggesting an ecological advantage. The genetic variation at the other two known loci, Salicylic Acid Methyl Transferase 1 (SAMT1) and tomato UDP Glycosyl Transferase 5 (SlUGT5), did not explain volatile variation in the red-fruited tomato germplasm, suggesting a minor role in methyl salicylate production in red-fruited tomato. Lastly, we found that most heirloom and modern tomato accessions carried a functional MES and a non-functional NSGT1 haplotype, ensuring acceptable levels of methyl salicylate in fruits. Yet, future selection of the functional NSGT1 allele could potentially improve flavor in the modern germplasm.

A family of methyl esterases converts methyl salicylate to salicylic acid in ripening tomato fruit

Methyl salicylate imparts a potent flavor and aroma described as medicinal and wintergreen that is undesirable in tomato (Solanum lycopersicum) fruit. Plants control the quantities of methyl salicylate through a variety of biosynthetic pathways, including the methylation of salicylic acid to form methyl salicylate and subsequent glycosylation to prevent methyl salicylate emission. Here, we identified a subclade of tomato methyl esterases, SALICYLIC ACID METHYL ESTERASE1-4, responsible for demethylation of methyl salicylate to form salicylic acid in fruits. This family was identified by proximity to a highly significant methyl salicylate genome-wide association study locus on chromosome 2. Genetic mapping studies in a biparental population confirmed a major methyl salicylate locus on chromosome 2. Fruits from SlMES1 knockout lines emitted significantly (P < 0,05, t test) higher amounts of methyl salicylate than wild-type fruits. Double and triple mutants of SlMES2, SlMES3, and SlMES4 emitted even more methyl salicylate than SlMES1 single knockouts-but not at statistically distinguishable levels-compared to the single mutant. Heterologously expressed SlMES1 and SlMES3 acted on methyl salicylate in vitro, with SlMES1 having a higher affinity for methyl salicylate than SlMES3. The SlMES locus has undergone major rearrangement, as demonstrated by genome structure analysis in the parents of the biparental population. Analysis of accessions that produce high or low levels of methyl salicylate showed that SlMES1 and SlMES3 genes expressed the highest in the low methyl salicylate lines. None of the MES genes were appreciably expressed in the high methyl salicylate-producing lines. We concluded that the SlMES gene family encodes tomato methyl esterases that convert methyl salicylate to salicylic acid in ripe tomato fruit. Their ability to decrease methyl salicylate levels by conversion to salicylic acid is an attractive breeding target to lower the level of a negative contributor to flavor.

Effects of methyl salicylate pre-treatment on the volatile profiles and key gene expressions in tomatoes stored at low temperature

Tomato is one of the most widely cultivated horticultural plants in the world, while the key volatile compounds of tomato fruits generally derive from fatty acid, carotenoid, phenylalanine, and branched-chain amino acid pathways. As an important endogenous signal molecule, methyl salicylate (MeSA) plays a crucial role in the fruit ripening process of plant. Recently, it has been demonstrated that MeSA can maintain the flavor quality of full ripe tomatoes after cold-storage preservation. However, few research teams attempted to investigate the effects of MeSA plus low temperature treatment on the different volatile biosynthetic pathways of tomatoes previously. Therefore, in this study, the effects of methyl salicylate pre-treatment (0.05 mM MeSA, 24 h) on the volatile profile and flavor-related key gene expressions of tomato fruits stored at 10°C were evaluated for the first time. Our results showed that the loss of volatile compounds in low temperature-treated tomato fruits could be effectively alleviated by MeSA pre-treatment. Although MeSA had no remarkable effect on the formation of carotenoid pathway- and branched-chain amino acid pathway-related volatiles in tomatoes subjected to low temperature, the content of fatty acid pathway-related volatiles (including cis-3-hexenal, hexanal, and trans-2-hexenal) in full red fruits of 10°C MeSA group was remarkably higher than that of 10°C control group. Furthermore, MeSA pre-treatment significantly up-regulated the expression of LOXC or LOXD gene in low temperature-treated fruits at breaker or full red stage, respectively. In conclusion, pre-treatment with MeSA might avoid the loss of aromatic compounds in tomato fruits stored at low temperature by activating the fatty acid pathway.

The role of methyl salicylate in plant growth under stress conditions

Methyl salicylate is a volatile compound, the synthesis of which takes place via the salicylic acid pathway in plants. Both compounds can be involved in the development of systemic acquired resistance and they play their role partly independently. Salicylic acid transport has an important role in long-distance signalling, but methyl salicylate has also been suggested as a phloem-based mobile signal, which can be demethylated to form salicylic acid, inducing the de-novo synthesis of salicylic acid in distal tissue. Despite the fact that salicylic acid has a protective role in abiotic stress responses and tolerance, very few investigations have been reported on the similar effects of methyl salicylate. In addition, as salicylic acid and methyl salicylate are often treated simply as the volatile and non-volatile forms of the same compound, and in several cases they also act in the same way, it is hard to highlight the differences in their mode of action. The main aim of the present review is to reveal the individual role and action mechanism of methyl salicylate in systemic acquired resistance, plant-plant communication and various stress conditions in fruits and plants.

A Synergistic Effect Based on the Combination of Melatonin with 1-Methylcyclopropene as a New Strategy to Increase Chilling Tolerance and General Quality in Zucchini Fruit

Zucchini fruit are highly sensitive to low temperatures leading to significant peel depressions, increasing weight loss and making them impossible to be commercialized. In this study the effect on the reduction of chilling injury (CI) assaying different postharvest treatments to cv. Cronos was evaluated. We have compared the application of substances such as 1-methylcyclopropene (1-MCP) with the application of a natural origin compound as melatonin (MT), both with demonstrated activity against CI in different vegetal products. The effects of MT (1 mM) by dipping treatment of 1 h and 1-MCP (2400 ppb) have been evaluated on zucchini fruit during 15 days of storage at 4 °C plus 2 days at 20 °C. Treatments applied independently improved some fruit quality parameters in comparison with control fruit but were not able to manage CI even though they mitigated the impact on several parameters. However, when these two separated strategies were combined, zucchini cold tolerance increased with a synergic trend. This synergic effect affected in general all parameters but specially CI, being also the only lot in which zucchini fruit were most effectively preserved. This is the first evidence in which a clear positive effect on zucchini chilling tolerance has been obtained combining these two different strategies. In this sense, the combined effect of 1-MCP and MT could be a suitable tool to reach high quality standards and increasing shelf life under suboptimal temperatures.

Synergistic Effect of Melatonin and Selenium Improves Resistance to Postharvest Gray Mold Disease of Tomato Fruit

Melatonin (MT) is a ubiquitous hormone molecule that is commonly distributed in nature. MT not only plays an important role in animals and humans but also has extensive functions in plants. Selenium (Se) is an essential micronutrient for animals and humans, and is a beneficial element in higher plants at low concentrations. Postharvest diseases caused by fungal pathogens lead to huge economic losses worldwide. In this study, tomato fruits were treated with an optimal sodium selenite (20 mg/L) and melatonin (10 μmol/L) 2 h and were stored for 7 days at room temperature simulating shelf life, and the synergistic effects of Se and MT collectively called Se-Mel on gray mold decay in tomato fruits by Botrytis cinerea was investigated. MT did not have antifungal activity against B. cinerea in vitro, while Se significantly inhibited gray mold development caused by B. cinerea in tomatoes. However, the interaction of MT and Se showed significant inhibition of the spread and growth of the disease, showing the highest control effect of 74.05%. The combination of MT with Se treatment enhanced the disease resistance of fruits by improving the activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT), as well as increasing the gene expression level of pathogenesis-related (PR) proteins. Altogether, our results indicate that the combination of MT and Se would induce the activation of antioxidant enzymes and increase the expression of PR proteins genes that might directly enhance the resistance in tomato fruit against postharvest pathogenic fungus B. cinerea.

Transcriptomics and Metabolomics Reveal the Possible Mechanism by which 1-MCP Regulates the Postharvest Senescence of Zizania latifolia

To understand the mechanism governing the postharvest senescence of Zizania latifolia, and the regulatory mechanism induced by 1-methylcyclopropene (1-MCP) during storage at 25°C, physiobiochemical and conjoint analyses of the transcriptome and metabolome were performed. The results indicated that 1-MCP treatment engendered changes in the expression of genes and metabolites during the postharvest storage of Z. latifolia. The 1-MCP treatment maintained a good visual appearance, preserved the cell structure, and membrane integrity of Z. latifolia by keeping the expression of membranes-related lipolytic enzymes (and related genes) low and the amount of phosphatidylethanolamine high. Compared to the control group, 1-MCP treatment enhanced the activities of antioxidant enzymes, resulting in a decrease of reactive oxygen species (ROS) and malondialdehyde (MDA) contents, and thus inhibition of oxidative damage and loss of membrane integrity. In addition, 1-MCP treatment retarded the senescence of Z. latifolia by down-regulating the expression of ethylene biosynthesis-related genes and promoting up-regulation of brassinosteroid insensitive 1 (BRI1) kinase inhibitor 1, calmodulin (CaM), glutathione reductase, jasmonate amino acid synthase, and mitogen-activated protein kinase (MAPK)-related genes. Moreover, 1-MCP retarded Z. latifolia senescence by inducing the activity of ATP-biosynthesis related genes and metabolites. Our findings should facilitate future research on the postharvest storage of Z. latifolia, and could help delay senescence and prolong the storage time for commercial applications.

Dynamic Microbiome Changes Reveal the Effect of 1-Methylcyclopropene Treatment on Reducing Post-harvest Fruit Decay in "Doyenne du Comice" Pear

Pathogen-induced decay is one of the most common causes of fruit loss, resulting in substantial economic loss and posing a health risk to humans. As an ethylene action inhibitor, 1-methylcyclopropene (1-MCP) can significantly reduce fruit decay, but its effect on fruit pathogens remains unclear. Herein, the change in microbial community structure was analyzed using the high-throughput sequencing technology, and characteristics related to fruit quality were determined after 1-MCP (1.0 M l L-1) treatment in "Doyenne du Comiceis" pear fruit during storage at ambient temperature. Overall, 1-MCP was highly effective in reducing disease incidence and induced multiple changes of the fungal and bacterial microbiota. At day 15, the microbial diversity of fungi or bacteria was reduced significantly in the control fruit (non-treated with 1-MCP), which had the most severe decay incidence. For fungi, in addition to Alternaria being the most abundant in both 1-MCP treatment (59.89%) and control (40.18%), the abundances of Botryosphaeria (16.75%), Penicillium (8.81%), and Fusarium (6.47%) increased significantly with the extension of storage time. They became the primary pathogens to cause fruit decay in control, but they were markedly decreased in 1-MCP treatment, resulting in reduced disease incidence. For bacteria, the abundance of Gluconobacter (50.89%) increased dramatically at day 15 in the control fruit, showing that it also played a crucial role in fruit decay. In addition, Botryosphaeria, Fusarium fungi, and Massilia, Kineococcus bacteria were identified as biomarkers to distinguish 1-MCP treatment and control using Random Forest analysis. The redundancy analysis (RDA) result showed that the amount of Botryosphaeria, Penicillium, and Fusarium were positively correlated with disease incidence and respiration rate of pear fruits while negatively correlated with fruit firmness. This investigation is the first comprehensive analysis of the microbiome response to 1-MCP treatment in post-harvest pear fruit, and reveals the relationship between fruit decay and microbial composition in pear fruit.

Unraveling Interactions of the Necrotrophic Fungal Species Botrytis cinerea With 1-Methylcyclopropene or Ozone-Treated Apple Fruit Using Proteomic Analysis

Gray mold caused by the necrotrophic fungus Botrytis cinerea is one of the major postharvest diseases of apple fruit. The exogenous application of 1-methylcyclopropene (1-MCP) and gaseous ozone (O 3) is commonly used to ensure postharvest fruit quality. However, the effect of these treatments on the susceptibility of apple fruit to postharvest pathogens remains largely unknown. Herein, the effect of O 3 and 1-MCP treatments on the development of gray mold on apple fruit (cv. "Granny Smith") was investigated. Artificially inoculated apple fruits, treated or not with 1-MCP, were subjected for 2 months to cold storage [0°C, relative humidity (RH) 95%] either in an O3-enriched atmosphere or in a conventional cold chamber. Minor differences between 1-MCP-treated and control fruits were found in terms of disease expression; however, exposure to ozone resulted in a decrease of disease severity by more than 50% compared with 1-MCP-treated and untreated fruits. Proteomic analysis was conducted to determine proteome changes in the mesocarp tissue of control and 1-MCP- or O3-treated fruits in the absence or in the presence of inoculation with B. cinerea. In the non-inoculated fruits, 26 proteins were affected by 1-MCP, while 51 proteins were altered by ozone. Dynamic changes in fruit proteome were also observed in response to B. cinerea. In O3-treated fruits, a significant number of disease/defense-related proteins were increased in comparison with control fruit. Among these proteins, higher accumulation levels were observed for allergen, major allergen, ACC oxidase, putative NBS-LRR disease resistance protein, major latex protein (MLP)-like protein, or 2-Cys peroxiredoxin. In contrast, most of these proteins were down-accumulated in 1-MCP-treated fruits that were challenged with B. cinerea. These results suggest that ozone exposure may contribute to the reduction of gray mold in apple fruits, while 1-MCP was not effective in affecting this disease. This is the first study deciphering differential regulations of apple fruit proteome upon B. cinerea infection and postharvest storage treatments, underlying aspects of host response related to the gray mold disease.

Laminarin Induces Defense Responses and Efficiently Controls Olive Leaf Spot Disease in Olive

Olive leaf spot (OLS) caused by Fusicladiumoleagineum is mainly controlled using copper fungicides. However, the replacement of copper-based products with eco-friendly alternatives is a priority. The use of plant resistance-inducers (PRIs) or biological control agents (BCAs) could contribute in this direction. In this study we investigated the potential use of three PRIs (laminarin, acibenzolar-S-methyl, harpin) and a BCA (Bacillus amyloliquefaciens FZB24) for the management of OLS. The tested products provided control efficacy higher than 68%. In most cases, dual applications provided higher (p < 0.05) control efficacies compared to that achieved by single applications. The highest control efficacy of 100% was achieved by laminarin. Expression analysis of the selected genes by RT-qPCR revealed different kinetics of induction. In laminarin-treated plants, for most of the tested genes a higher induction rate (p < 0.05) was observed at 3 days post application. Pal, Lox, Cuao and Mpol were the genes with the higher inductions in laminarin-treated and artificially inoculated plants. The results of this study are expected to contribute towards a better understanding of PRIs in olive culture and the optimization of OLS control, while they provide evidence for potential contributions in the reduction of copper accumulation in the environment.

Preharvest application of methyl salicylate, acetyl salicylic acid and salicylic acid alleviated disease caused by Botrytis cinerea through stimulation of antioxidant system in table grapes

The main goal of this study was to describe impact of preharvest application of methyl salicylate (MeSA), acetyl salicylic acid (ASA) and salicylic acid (SA) on the reduction of disease caused by Botrytis cinerea in two table grape cultivars ('Crimson' and 'Magenta'). Based on previous studies, MeSA and SA were applied at 0.1 and 0.01 mM for both cultivars, while ASA was applied at 1 mM in 'Crimson' and 0.1 mM in 'Magenta'. At time of harvest, berry maturity-quality attributes, bioactive compounds and antioxidant enzymes were determined. In addition, grapes were artificially inoculated with B. cinerea spores, and the berries were ranked for visual decay incidence after 5 days of inoculation. Salicylates preharvest treatments led to higher total acidity, content of bioactive compounds and activity of antioxidant enzymes in treated than in control berries. The application of salicylate derivatives induced resistance to B. cinerea spoilage, since higher percentage of berries with no symptoms was observed and on the contrary, the highest percentages of berries were obtained in control grapes. All preharvest treatments with SA, ASA and MeSA alleviated postharvest disease caused by B. cinerea probably due to increasing levels of phenolic compounds and activity of antioxidant enzymes, although the best results were obtained with MeSA at 0.1 mM. Also, for this treatment and dose, higher quality properties, such as higher concentrations of ascorbic, succinic and fumaric acids, were observed compared with no treated-grapes.

The Co-regulation of Ethylene Biosynthesis and Ascorbate-Glutathione Cycle by Methy Jasmonate Contributes to Aroma Formation of Tomato Fruit during Postharvest Ripening

Currently, many fruits are always harvested at the early ripening stage to reduce postharvest losses followed by 1-methylcyclopropene (1-MCP) or ethephon treatment. However, harvesting at the early ripening stage adversely affects fruit quality, especially for the aroma. Methyl jasmonate (MeJA) treatment could induce the biosynthesis of bioactive compounds and maintain postharvest fruit quality. In the present work, the contributions of MeJA to tomato fruit quality during postharvest ripening were studied. The results showed that MeJA treatment significantly promoted the accumulation of volatile organic components (VOCs) by inducing the activities of enzymes related to lipoxygenase pathway and ethylene biosynthesis, whereas 1-MCP treatment largely inhibited the accumulation of VOCs by inhibiting activities of those enzymes. Although the application of ethephon also induced activities of the above enzymes in comparison with control, no significant differences were observed between the VOCs contents of the control and ethephon-treated fruit. Further study revealed that the ethephon treatment resulted in the enhancement of electrical conductivity and malondialdehyde content. Conversely, MeJA treatment inhibited the superoxide anion radical and hydrogen peroxide by regulating the ascorbate-glutathione cycle and further inhibited the enhancement of electrical conductivity and malondialdehyde content, which might be one of the most important reasons why the VOCs contents in fruit treated with ethephon were lower than those in MeJA-treated fruit. Thus, it is considered that MeJA treatment may be an effective and promising strategy to regulate postharvest tomato fruit quality, especially for the aroma, by regulating the ascorbate-glutathione cycle and ethylene biosynthesis.

SlARG2 contributes to MeJA-induced defense responses to Botrytis cinerea in tomato fruit

BACKGROUND

Arginase plays key roles in methyl jasmonate (MeJA)-mediated quality maintenance in vegetables and fruits. MeJA treatment induced the Arginase 2 (SlARG2) expression, which is one of the most important encoding genes of arginase. In addition, the treatment with MeJA induced resistance to pathogenic infection in many plants. However, the functions of SlARG2 in MeJA-induced defense to Botrytis cinerea are unclear. In our work, control and SlARG2-silenced tomato fruits (Solanum lycopersicum) were treated with 0.05 mmoL L^-1 MeJA before storage to assay the roles of SlARG2 in MeJA-induced defense responses to Botrytis cinerea.

RESULTS

Our results indicated that MeJA treatment induced both pathogenesis-related gene expression (PR1, PR2a, PR2b and PR3b), and the activity of defense-related enzymes, as well as upregulated arginine metabolism. Compared to control fruits, the treatment with MeJA also induced the activity of arginase, arginine decarboxylase (ADC) and ornithine aminotransferase (OAT), and expression of SlARG2, SlADC, ornithine decarboxylase (SlODC) and SlOAT, and consequently increased the accumulation of arginine, proline, glutamate, putrescine and spermine. However, the induction effects by MeJA were significantly reduced in fruits in which SlARG2 was silenced and severe disease symptoms were observed.

CONCLUSION

MeJA fumigation could inhibit disease development by inducing pathogenesis-related gene expression (PR1, PR2a, PR2b and PR3b) and defense-related enzymes activity, as well as upregulated arginine metabolism. In addition, SlARG2 silencing could inhibit the functions of MeJA in inducing the accumulation of the above substances. Overall, our study provided strong evidence that SlARG2 was essential for MeJA-induced tomato fruit defense responses to Botrytis cinerea. © 2020 Society of Chemical Industry.

Dynamic Changes of DNA Methylation Induced by Heat Treatment Were Involved in Ethylene Signal Transmission and Delayed the Postharvest Ripening of Tomato Fruit

Deoxyribonucleic acid (DNA) methylation plays an important role in fruit ripening and senescence. Here, the role of DNA methylation of the CpG island of SlACS10, LeCTR1, LeEIN3, LeERT10, and SlERF-A1 genes induced by heat treatment (37 °C) in postharvest ripening of tomato fruit was studied. After heat treatment, the firmness and vitamin C content showed higher levels, the loss of aldehydes in volatile components was delayed, and the activities of methylase and demethylase decreased in tomato fruit. Moreover, in heat-treated fruit, significant changes in DNA methylation of SlACS10, LeCTR1, LeEIN3, LeERT10, and SlERF-A1 were induced, the expression of LeERT10 and LeEIN3 was inhibited, the expression of SlERF-A1 was increased, by which ethylene signal transmission might be suppressed and the postharvest ripening of tomato fruit was delayed. The present study provided valuable information for understanding the essential role of DNA methylation in the postharvest ripening of tomato fruit.

Complexation of methyl salicylate with β-cyclodextrin and its release characteristics for active food packaging

A series of methyl salicylate (MeSA)/β-cyclodextrin (β-CD) inclusion complexes (ICs) were prepared at different MeSA concentrations by the co-precipitation method using methyl salicylate for maintaining the quality of fresh produce. The formation of IC was confirmed through FTIR, ¹H NMR, TGA, and SEM measurements. Among the grades applied, IC with 1:1 grade showed the highest MeSA entrapment efficiency (59%). The release rate of MeSA from an IC was greater at higher temperature and higher relative humidity. In addition, the MeSA release from ICs of all grades followed a diffusive nature and first-order kinetics at 25 °C under all RH conditions, except at 7 °C. These results indicate that the use of a MeSA/β-CD IC in active packaging applications can effective maintain the quality of fresh produce.

Methyl salicylate delays peel yellowing of 'Zaosu' pear (Pyrus bretschneideri) during storage by regulating chlorophyll metabolism and maintaining chloroplast ultrastructure

BACKGROUND

In some cultivars, yellowing resulting from chlorophyll breakdown has a direct and negative effect on food supply and health. The 'Zaosu' pear (Pyrus bretschneideri Rehd.), a commercial Asian pear cultivar in China, rapidly turns yellow when stored at room temperature after harvest. To develop techniques that delay or suppress chlorophyll degradation, the effects of methyl salicylate (MeSA) on yellowing in 'Zaosu' pear fruit during storage were evaluated.

RESULTS

Compared with the untreated fruit, the application of 0.05 mmol L^-1 MeSA delayed the decline of the total chlorophyll, chlorophyll a and chlorophyll b content, and maintained more intact chloroplasts with fewer and smaller plastoglobuli. Methyl salicylate suppressed enzyme activities, including chlorophyllase, chlorophyll-degrading peroxidase, Mg dechelatase, and pheophytinase, and the expression levels of NYC, NOL, CLH, SGR, PPH, PAO and RCCR in treated fruit.

CONCLUSION

Methyl salicylate could delay chlorophyll breakdown in the fruit. The results also suggested that the conversion from chlorophyll a to pheophorbide a could proceed via two pathways, and that alternative pathways for the breakdown of chlorophyll a exist in 'Zaosu' pears. © 2019 Society of Chemical Industry.

Ethanol treatment improves the sensory quality of cherry tomatoes stored at room temperature

The effects of ethanol treatment on quality characteristics of cherry tomatoes were investigated over 11 days of storage at room temperature (25 °C). Results showed that sensory quality was improved after ethanol treatment, with redder, softer fruits at the edible stage (11 days) compared with control fruit. In addition, the contents of ascorbic acid, sucrose and fructose were elevated after ethanol treatment as well as the concentration of 6-methyl-5-hepten-2-one. Conversely, decreased levels of methyl salicylate (MeSA), guaiacol, (Z)-3-hexenal and (E)-2-hexenal were observed. Selected consumers showed a preference for ethanol-treated cherry tomato fruits compared with controls. Taken together, 0.1% ethanol application has the potential to improve the quality characteristics of cherry tomatoes stored at room temperature.

Ethylene Perception Is Associated with Methyl-Jasmonate-Mediated Immune Response against Botrytis cinerea in Tomato Fruit

Jasmonic acid (JA)- and ethylene-mediated signaling pathways are reported to have synergistic effects on inhibiting gray mold. The present study aimed to explain the role of ethylene perception in methyl jasmonate (MeJA)-mediated immune responses. Results showed that exogenous MeJA enhanced disease resistance, accompanied by the induction of endogenous JA biosynthesis and ethylene production, which led to the activation of the phenolic metabolism pathway. Blocking ethylene perception using 1-methylcyclopropene (1-MCP) either before or after MeJA treatment could differently weaken the disease responses induced by MeJA, including suppressing the induction of ethylene production and JA contents and reducing activities of lipoxygenase and allene oxide synthase compared to MeJA treatment alone. Consequently, MeJA-induced elevations in the total phenolic content and the activities of phenylalanine ammonia-lyase, cinnamate 4-hydroxylase, 4-coumarate:coenzyme A ligase, and peroxidase were impaired by 1-MCP. These results suggested that ethylene perception participated in MeJA-mediated immune responses in tomato fruit.

Physiochemical properties of petunia edible flowers grown under saline conditions and their postharvest performance under modified atmosphere packaging and ethanol application

BACKGROUND

Edible flowers have both great nutritional value and sensory appeal; however, their shelf-life is limited to a few days because they are highly perishable.

RESULTS

The impact of postharvest ethanol (ET) treatment and modified atmosphere packaging (MAP) on the quality and storage of edible flowers collected from short-term salt-stressed plants was tested. Hydroponically grown petunia (Petunia x hybrita L.) plants were subjected to salinity (0-50-100 mmol L^-1 NaCl) and harvested flowers were stored for up to 14 days in MAP and/ET vapours. The salinity of 100 mmol L^-1 NaCl decreased plant biomass and negatively affected physiological processes as a result of stomata closure. Flower polyphenols, antioxidants, carotenoids and anthocyanins increased with 50 mmol L^-1 of NaCl, indicating a higher nutritional value. Short-term exposure of petunia to salinity decreased the flower N, K and Ca concentrations. During storage for 7 days, salinity lead to deteriorated flowers that showed browning as a result of tissue breakdown, whereas CO₂ production and weight loss were unaffected by salinity. After 14 days of storage, salinity decreased flower respiration and increased weight loss, whereas ET application completely destroyed the flowers. Carotenoids and anthocyanins were decreased by a combination of salinity and ET. Petunia flowers revealed the induction of both non-enzymatic (i.e. proline content) and enzymatic (catalase) mechanisms to overcome the stress caused by salinity at harvest stage and/or ethanol at storage.

CONCLUSION

The results of the present study demonstrate that a short-stress salinity of 50 mmol L^-1 NaCl can be used for petunia growth and also that flowers of nutritional value can be stored for up to 7 days, whereas ET application failed to preserve petunia flowers. © 2019 Society of Chemical Industry.

Defense Responses, Induced by p-Coumaric Acid and Methyl p-Coumarate, of Jujube ( Ziziphus jujuba Mill.) Fruit against Black Spot Rot Caused by Alternaria alternata

The esterified fraction of jujube ( Ziziphus jujuba Mill.) peel extract showed strong antifungal activity on Alternaria alternata. p-Coumaric acid (pCA) was found to be the most predominant individual phenolic acid that was correlated highly with the antifungal activity of the esterified fraction. Thus, effects of postharvest treatments with pCA and its simplest esterified derivative methyl p-coumarate (MeCA) against black spot rot on jujube fruit caused by A. alternata were investigated. pCA and MeCA strongly suppressed in vitro growth of the fungus and significantly reduced postharvest Alternaria rot on fresh jujubes. Biochemical and transcriptional analysis revealed that pCA and MeCA regulated the expression of some genes encoding antioxidant enzymes and their enzymatic activities, enhanced the phenylpropanoid pathway metabolism, and activated the expression of genes encoding pathogenesis-related proteins. These results suggested that, apart from its direct antifungal activity, pCA and MeCA induced defense responses in jujube fruit against postharvest Alternaria rot.

Cryptococcus laurentii controls gray mold of cherry tomato fruit via modulation of ethylene-associated immune responses

This research aimed to investigate the roles of phytohormone ethylene in cherry tomato fruit immune response against gray mold caused by Botrytis cinerea. Pretreatment with antagonistic yeast Cryptococcus laurentii resulted in a significantly decreased disease incidence of B. cinerea infection, and accompanied by a burst of ethylene production in the whole fruit. Blocking the ethylene perception by adding 1-MCP (5 μL L^-1 or greater) remarkably weaken the protection ability of fruit itself and suppressed the C. laurentii-stimulated host immune response. 5 μL L^-1 1-MCP prefumigation decreased the expression of ethylene biosynthesis and perception related genes SlACO1, SlACS2, SlERF1, SlPti5 and SlMPK3, and ethylene production in C. laurentii treated fruit. Consequently, the expressions of SlCHI9, SlGlub, SlPAL3, SlPR1 and SlPR5 up-regulated by the yeast were all impaired to different degrees by the 1-MCP prefumigation. These findings demonstrate that ethylene contributes to fruit immunity and C. laurentii-mediated immune responses of cherry tomato.

SlERF2 Is Associated with Methyl Jasmonate-Mediated Defense Response against Botrytis cinerea in Tomato Fruit

Methyl jasmonate (MeJA) and ethylene play important roles in mediating defense responses against Botrytis cinerea. Ethylene response factors (ERFs) are the final components of ethylene signal transduction; whether SlERF2 participates in disease resistance against Botrytis cinerea is unclear. The objective of this study was to investigate the role of SlERF2 in MeJA-mediated defense response by using both sense and antisense SlERF2 tomato fruit. Our results showed that both MeJA treatment and pathogen infection upregulated SlERF2 expression level. Overexpression of SlERF2 enhanced tomato fruit resistance against Botrytis cinerea. MeJA treatment increased ethylene production, promoted the activities of chitinase, β-1,3-glucanase, phenylalanine ammonia-lyase, and peroxidase, and elevated pathogenesis-related protein content and total phenolic content. Moreover, the effects of MeJA on disease response were reinforced in sense SlERF2 tomato fruit, while they were weakened in antisense SlERF2 tomato fruit. These results indicated that SlERF2 was involved in MeJA-mediated disease resistance against Botrytis cinerea in tomato fruit.