Chilling Injury In Fruit Research Articles

Exogenous arginine enhances the chilling tolerance in postharvest papaya fruit by regulating arginine and proline metabolism

Papaya fruit is easily affected by low temperature, causing chilling injury (CI). In this study, the exogenous arginine was applied in the storage of postharvest papaya fruit and it was found that 0.8 mM arginine treatment significantly alleviated CI of papaya fruit. Arginine treatment promoted the accumulation of polyamines (PAs), which might be ascribed to the increased activities of arginase, arginine decarboxylase (ADC), ornithine decarboxylase (ODC), and S-adenosylmethionine decarboxylase (SAMDC). A higher accumulation of proline was found in arginine-treated papaya fruit, which may be due to increased activity of ornithine-δ-aminotransferase (OAT) and Δ1-pyrroline-5-carboxylate acid synthase (P5CS) and inhibited activity of proline dehydrogenase (PDH). In addition, arginine treatment increased higher nitric oxide synthase (NOS) activity and promoted the generation of nitric oxide (NO). The results of this study indicate that exogenous arginine may improve the chilling tolerance of postharvest papaya fruit by regulating arginine and proline metabolism. Practical applications In recent years, chilling injury of tropical fruits is a significant problem, including papaya. Many studies on polyamine, proline, nitric oxide, and chilling injury of fruits, but arginine, as a common precursor of polyamine, proline, and nitric oxide, are rarely studied, especially in papaya fruit. Our findings demonstrated that the exogenous arginine can regulate endogenous arginine metabolism, induce polyamine, putrescine, and nitric oxide accumulation, and coordinate to alleviate chilling injury of papaya fruit.

Regulations of m6A methylation on tomato fruit chilling injury

Tomato fruit are sensitive to chilling injury (CI) during cold storage. Several factors have been discovered to be involved in chilling injury of tomato fruit. Plant hormones play an important regulatory role, however, the relationship between chilling injury and N6-methyladenosine (m6A) methylation of transcripts in plant hormone pathways has not been reported yet. In order to clarify the complex regulatory mechanism of m6A methylation on chilling injury in tomato fruit, Nanopore direct RNA sequencing was employed. A large number of enzymes and transcription factors were found to be involved in the regulation process of fruit chilling injury, which were associated with plant hormone, such as 1-aminocyclopropane 1-carboxylate synthase (ACS), aspartate aminotransferase (AST), auxin response factor (ARF2), ethylene response factor 2 (ERF2), gibberellin 20-oxidase-3 (GA20ox) and jasmonic acid (JA). By conjoint analysis of the differential expression transcripts related to chilling injury and m6A methylation differential expression transcripts 41 differential expression transcripts were identified involved in chilling injury including 1-aminocyclopropane-1-carboxylate oxidase (ACO) and pectinesterase (PE) were down-regulated and heat shock cognate 70 kD protein 2 (cpHSC70), HSP70-binding protein (HspBP) and salicylic acid-binding protein 2 (SABP2) were up-regulated. Our results will provide a deeper understanding for chilling injury regulatory mechanism and post-harvest cold storage of tomato fruit.

Exogenous melatonin alleviated chilling injury in harvested plum fruit via affecting the levels of polyamines conjugated to plasma membrane

Polyamines (PAs) are related closely with many abiotic stresses. However, conjugated PA functions are not clear in alleviating chilling injury in fruit. The contents of free PAs in plum flesh cell and conjugated PAs in plasma membrane (PM), the activities of S-adenosylmethionine decarboxylase (SAMDC) and transglutaminase (TGase), and the degree of chilling injury were investigated in harvested plum (Prunus salicina L.) fruit pre-treated with exogenous melatonin. Chilling treatment resulted in the injury of plasma membrane (PM), as judged by the increased PM permeability, chilling injury index and malondialdehyde (MDA) content, and the decreased sulfhydryl group contents. Exogenous melatonin alleviated chilling injury, in parallel with the increased levels of free spermidine (Spd) and spermine (Spm) in cell, conjugated non-covalently (CNC) Spd and Spm, and conjugated covalently (CC) Put and Spd in PM, resulting from the increased activities of SAMDC and TGase. The results of the additional experiments with two inhibitors, methylglyoxyl-bis (guanylhydrazone) (MGBG) and phenanthrolin, which inhibit the activities of SAMDC and TGase, respectively, were complementary evidences for our research. MGBG and TGase treatment decreased the level of CNC PAs (Spd and Spm) and CC PAs (Put and Spd), respectively, coupled with aggravating the chilling injury. From these above mentioned-results, it could be suggested that exogenous melatonin alleviated chilling injury by elevating the levels of CNC Spd, CNC Spm, CC Put and CC Spd in PM.

Reduction in chilling injury symptoms by hot electrolyzed functional water treatment may function by regulating ROS metabolism in Satsuma orange fruit

This study investigated the effects of electrolyzed functional water (EFW), hot water or hot electrolyzed functional water treatment on the quality of Satsuma orange (Citrus unshiu) during cold storage (2 °C) for 60 days, with untreated fruit as the control. In the study, the fruit chilling injury (CI) index, weight loss, total soluble solid, titratable acid, cell membrane permeability, the production of malondialdehyde and superoxide dismutase, peroxidase, catalase activities were assessed. The results showed that the CI index reduced to 37%, 32%, 25%, weight loss decreased 2.06, 2.98, 1.68 g and the fruit maturity decreased to 31.61, 28.57, 26.84 respectively on the 60 day after EFW, hot water, hot EFW treatment, these results were accompanied by the cell membrane permeability reduced to 34.15%, 32.86%, 30.25%, the content of malondialdehyde reduced to 1.37, 1.32, 1.22 μmol/g, at the same time, the activities of superoxide dismutase, peroxidase and catalase respectively increased to 6.21, 6.49, 7.16 U/mg, 2.92, 3.01, 3.52 U/mg and 82.44, 89.89, 90.88 U/mg. In conclusion, the three treatments played important roles in maintaining the fruit quality by regulating ROS metabolism during cold storage, and hot EFW treatment had the best effect.

Transcriptomic and Metabolic Analyses Provide New Insights into the Apple Fruit Quality Decline during Long-Term Cold Storage.

Long-term low-temperature conditioning (LT-LTC) decreases apple fruit quality, but the underlying physiological and molecular basis is relatively uncharacterized. We identified 12 clusters of differentially expressed genes (DEGs) involved in multiple biological processes (i.e., sugar, malic acid, fatty acid, lipid, complex phytohormone, and stress-response pathways). The expression levels of genes in sugar pathways were correlated with decreasing starch levels during LT-LTC. Specifically, starch-synthesis-related genes (e.g., BE, SBE, and GBSS genes) exhibited downregulated expression, whereas sucrose-metabolism-related gene expression levels were up- or downregulated. The expression levels of genes in the malic acid pathway (ALMT9, AATP1, and AHA2) were upregulated, as well as the content of malic acid in apple fruit during LT-LTC. A total of 151 metabolites, mainly related to amino acids and their isoforms, amines, organic acids, fatty acids, sugars, and polyols, were identified during LT-LTC. Additionally, 35 organic-acid-related metabolites grouped into three clusters, I (3), II (22), and III (10), increased in abundance during LT-LTC. Multiple phytohormones regulated the apple fruit chilling injury response. The ethylene (ET) and abscisic acid (ABA) levels increased at CS2 and CS3, and jasmonate (JA) levels also increased during LT-LTC. Furthermore, the expression levels of genes involved in ET, ABA, and JA synthesis and response pathways were upregulated. Finally, some key transcription factor genes (MYB, bHLH, ERF, NAC, and bZIP genes) related to the apple fruit cold acclimation response were differentially expressed. Our results suggest that the multilayered mechanism underlying apple fruit deterioration during LT-LTC is a complex, transcriptionally regulated process involving cell structures, sugars, lipids, hormones, and transcription factors.

Generation of fruit postharvest gene datasets and a novel motif analysis tool for functional studies: uncovering links between peach fruit heat treatment and cold storage responses

A survey of developed fruit gene-specific datasets and the implementation of a novel cis-element analysis tool indicate specific transcription factors as novel regulatory actors under HT response and CI protection. Heat treatment (HT) prior to cold storage (CS) has been successfully applied to ameliorate fruit chilling injury (CI) disorders. Molecular studies have identified several HT-driven benefits and putative CI-protective molecules and mechanisms. However, bioinformatic tools and analyses able to integrate fruit-specific information are necessary to begin functional studies and breeding projects. In this work, a HT-responsive gene dataset (HTds) and four fruit expression datasets (FEds), containing gene-specific information from several species and postharvest conditions, were developed and characterized. FEds provided information about HT-responsive genes, not only validating their sensitivity to HT in different systems but also revealing most of them as CS-responsive. A special focus was given to peach heat treatment-sensitive transcriptional regulation by the development of a novel Perl motif analysis software (cisAnalyzer) and a curated plant cis-elements dataset (PASPds). cisAnalyzer is able to assess sequence motifs presence, localization, enrichment and discovery on biological sequences. Its implementation for the enrichment analysis of PASPds motifs on the promoters of HTds genes rendered particular cis-elements that indicate certain transcription factor (TF) families as responsible of fruit HT-sensitive transcription regulation. Phylogenetic and postharvest expression data of these TFs showed a functional diversity of TF families, with members able to fulfil roles under HT, CS and/or both treatments. All integrated datasets and cisAnalyzer tool were deposited in FruitGeneDB (https://www.cefobi-conicet.gov.ar/FruitGeneDB/search1.php), a new available database with a great potential for fruit gene functional studies, including the markers of HT and CS responses whose study will contribute to unravel HT-driven CI-protection and select tolerant cultivars.

Determination of H+ and Ca2+ fluxes in cold-stored banana fruit using non-invasive micro-test technology

Ion concentration changes significantly under stress conditions such as chilling. Accurate assessment of the concentration, flow velocity and flow direction of ions is pivotal to understanding the mechanism of stress response of fruits and vegetables. Fibroin is a newly reported edible coating material effective in delaying fruit senescence and alleviating chilling injury. In the present study, banana fruit were fibroin-treated before cold-stored, and non-invasive micro-test technology (NMT) was employed to determine H+ and Ca2+ fluxes across the non-wound surfaces of pericarp cuboids of the fibroid-treated banana fruit. When the wound surfaces of banana pericarp cuboids were coated with food grease, H+ and Ca2+ fluxes across the wound surfaces fluctuated around 0 nmol m−2 s-1, indicating that ion flow across the wound surfaces of the pericarp cuboids had been completely prevented by food grease coating. This coating method was employed to coat the wound surfaces while H+ and Ca2+ fluxes across the normal surfaces of the pericarp cuboids of fibroin-treated cold-stored banana fruit were determined. The results suggested that fibroin treatment alleviated chilling injury by reducing H+ and Ca2+ effluxes. Utilization of food grease coating on wound surfaces will greatly improve our ability to reveal the mechanism of chilling injury in fruits and vegetables by learning ion fluxes in tissues and organs.

Hydrogen sulfide treatment confers chilling tolerance in hawthorn fruit during cold storage by triggering endogenous H 2 S accumulation, enhancing antioxidant enzymes activity and promoting phenols accumulation

Abstract Cold storage as the postharvest beneficial procedure has been used for retaining sensory and nutritional quality and extending postharvest life of hawthorn fruit. However, fruit chilling injury (CI) manifested by pitting is a dominant restriction for applying cold storage for hawthorn fruit. In this experiment, the impacts of postharvest hydrogen sulfide (H2S) fumigation releasing from 0, 0.5, 1 and 1.5 mM H2S donor NaHS on chilling injury manifesting by pitting and nutritional quality of hawthorn fruit during storage at 1 °C for 20 days was evaluated. Our results revealed that 1.5 mM H2S donor NaHS treatment remarkably ameliorated fruit chilling injury, which was accompanied by lower malondialdehyde (MDA) accumulation. Hawthorn fruit in response to H2S donor NaHS treatment showed remarkably higher endogenous H2S accumulation by triggering l -cysteine desulfhydrase (LCD) and d -cysteine desulfhydrase (DCD) enzymes activity, which coincided with higher reactive oxygen species (ROS) scavenging enzymes superoxide dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APX) activity give rise to lower H2O2 accumulation. In addition, hawthorn fruit treated with H2S showed remarkably higher phenols, flavonoids, and anthocyanins accumulation by triggering phenylalanine ammonia lyase (PAL) enzyme activity. Higher DPPH scavenging activity in hawthorn fruit treated with H2S donor NaHS arise from higher phenols, flavonoids, anthocyanins and ascorbic acid accumulation. According to our results, postharvest 1.5 mM H2S donor NaHS applying may be considered as a beneficial procedure not only for conferring chilling tolerance of hawthorn fruit by triggering endogenous H2S accumulation, enhancing ROS scavenging enzymes activity and promoting phenols accumulation which are crucial for maintaining membrane integrity, but also for preserving nutritional quality of hawthorn fruit during cold storage.

Selection of Spectral Resolution and Scanning Speed for Detecting Green Jujubes Chilling Injury Based on Hyperspectral Reflectance Imaging

Hyperspectral imaging is a non-destructive method for the detection of chilling injury in fruit. However, the limitation of this technique is the lacking of an appropriate working parameters and a feasible discriminating model for chilling on-line sorting. This research was aimed to select the optimal spectral resolution, scanning speed, and classification model for green jujube chilling injury detection based on hyperspectral reflectance imaging. Criminisi algorithm was firstly carried out to reconstruct the specular reflection region in spectral images before deriving mean spectra, and thus the optimal wavelengths were selected by random frog. Results showed that the Criminisi algorithm presented a desirable ability of spectral image inpainting. The linear discriminant analysis (LDA) achieved overall accuracies of 98.3% and 93.3% for two-class and three-class classification, respectively, at the speed of 20 mm/s with the spectral resolution of 5.03 nm based on selected spectral features. The results demonstrated that 20 mm/s with the spectral resolution of 5.03 nm was more feasible for the detection of green jujube chilling injury in hyperspectral imaging system due to a higher scanning efficiency, but a less data size.

Transcriptomic and metabolic analyses provide new insights into chilling injury in peach fruit.

Low temperature conditioning (LTC) alleviates peach fruit chilling injury but the underlying molecular basis is poorly understood. Here, changes in transcriptome, ethylene production, flesh softening, internal browning and membrane lipids were compared in fruit maintained in constant 0°C and LTC (pre-storage at 8°C for 5d before storage at 0°C). Low temperature conditioning resulted in a higher rate of ethylene production and a more rapid flesh softening as a result of higher expression of ethylene biosynthetic genes and a series of cell wall hydrolases. Reduced internal browning of fruit was observed in LTC, with lower transcript levels of polyphenol oxidase and peroxidase, but higher lipoxygenase. Low temperature conditioning fruit also showed enhanced fatty acid content, increased desaturation, higher levels of phospholipids and a preferential biosynthesis of glucosylceramide. Genes encoding cell wall hydrolases and lipid metabolism enzymes were coexpressed with differentially expressed ethylene response factors (ERFs) and contained ERF binding elements in their promoters. In conclusion, LTC is a special case of cold acclimation which increases ethylene production and, operating through ERFs, promotes both softening and changes in lipid composition and desaturation, which may modulate membrane stability, reducing browning and contributing to alleviation of peach fruit chilling injury.

Development of an improved postharvest cold treatment for Thaumatotibia leucotreta (Meyrick) (Lepidoptera: Tortricidae)

Some of South Africa’s fresh produce export markets require postharvest cold treatment of fruit as a phytosanitary risk mitigation treatment for Thaumatotibia leucotreta. Currently, the most widely used treatment entails a 22-d exposure to sub-zero temperatures. This treatment has been primarily based on studies conducted in the 1950s and 1960s. Given the age of the data and subsequent indications that a reduced duration treatment may be effective, a new set of cold treatment efficacy data was generated in this study. The treatments were tested at the probit 9 level, using fourth and fifth instar T. leucotreta, these instars having previously been shown to be the most cold-tolerant. Three time-temperature combinations using sub-zero temperatures were initially evaluated: 20 d, 18 d and 16 d at average temperatures in the range of −0.16°C to −0.44°C; and thereafter a time-temperature combination using an above-zero temperature was evaluated: 19 d at an average temperature of 1.05°C. All treatments were shown to cause mortality at or in excess of the probit 9 level (99.9968% efficacy at the 95% confidence level). These results demonstrate the efficacy of the following potential postharvest cold treatments for T. leucotreta for phytosanitary treatment purposes: 16 d at −0.2°C, 18d at −0.4°C, 20d at −0.4°C and 19d at 1.0°C, which are recommended for conversion into the following treatment protocols: 16d at or below −0.1°C, 18d at or below −0.3°C, 20d at or below −0.3°C and 19d at or below 1.2°C, commencing once all probe readings are at or below: −0.2°C, −0.4°C, −0.4°C and 1.0°C respectively. Relative to the cold treatments currently in use for T. leucotreta, the shorter duration and in some cases higher temperatures will be less costly and logistically easier to apply with reduced adverse effects in the form of fruit chilling injury and hence trade restriction.

Postharvest Quality of Two Pomegranate Genotypes as Influenced by Storage Temperature and Period = تأثير درجة حرارة التخزين والمدة التخزينية على نوعية ثمار صنفي الرمان شرمني وهبلري بعد الحصاد

The present investigation was carried out during 2011 season to study the effect of storage temperature and period on fruit storage behavior of local 'Sharmny' and 'Hablary' pomegranates. Fruits of both cultivars were stored at 2°C or 6°C with 85-90% RH for three storage periods; 1.5, 3 and 4.5 months. Results showed genotypic differences in total soluble solids (TSS), weight loss and titratable acidity. 'Sharmny' showed significantly higher TSS and lower fruit weight loss, while 'Hablary' recorded a significant increase in titratable acidity. Storing fruits of both cultivars at 6°C significantly reduced fruit chilling injury, titratable acidity but increased fruit weight loss in comparison with fruit stored at 2°C, while both storage temperatures didn't significantly affect the other parameters. Moreover, chemical characteristics of fruits were significantly decreased, while fruit weight loss and physiological disorders increased with prolonging of storage period.

Banana fruit VQ motif-containing protein5 represses cold-responsive transcription factor MaWRKY26 involved in the regulation of JA biosynthetic genes.

Most harvested fruits and vegetables are stored at low temperature but many of them are highly sensitive to chilling injury. Jasmonic acid (JA), a plant hormone associated with various stress responses, is known to reduce chilling injury in fruits. However, little is known about the transcriptional regulation of JA biosynthesis in relation to cold response of fruits. Here, we show the involvement of a Group I WRKY transcription factor (TF) from banana fruit, MaWRKY26, in regulating JA biosynthesis. MaWRKY26 was found to be nuclear-localized with transcriptional activation property. MaWRKY26 was induced by cold stress or by methyl jasmonate (MeJA), which enhances cold tolerance in banana fruit. More importantly, MaWRKY26 transactivated JA biosynthetic genes MaLOX2, MaAOS3 and MaOPR3 via binding to their promoters. Further, MaWRKY26 physically interacted with a VQ motif-containing protein MaVQ5, and the interaction attenuated MaWRKY26-induced transactivation of JA biosynthetic genes. These results strongly suggest that MaVQ5 might act as a repressor of MaWRKY26 in activating JA biosynthesis. Taken together, our findings provide new insights into the transcriptional regulation of JA biosynthesis in response to cold stress and a better understanding of the molecular aspects of chilling injury in banana fruit.

Preharvest foliar applications of glycine-betaine protects banana fruits from chilling injury during the postharvest stage

Banana plantations are affected by environmental factors such as chilling injury, which reduces the quality of fruits and causes losses of up to 50% in the yield of banana and it will be more important in terms of global climate change. Chilling injury of the fruits can also occur during transport and storage at low temperatures, particularly in tropical fruits. In banana, losses of up to 20% can occur during postharvest handling. Given this situation, it is necessary to explore alternatives that might reduce chilling injury, such as the use of compatible solutes including glycine-betaine (GB). In the present work, experiments were performed to analyze the possible role of preharvest foliar applications of GB, to prevent the subsequent development of chilling injury of banana fruits during the postharvest storage at low temperatures. After 3 days of the preharvest application of 100 mM GB over banana leaves (250 ml/plant), the fruits were harvested and first stored at 10°C for 6 h and then transferred to 23°C ± 1°C until they reached commercial ripening. A second group of plants were not treated with GB during the preharvest stage, but their fruits were exposed to 10°C for 6 h before transferring them to 23°C ± 1°C until they reached commercial ripening. A control group was untreated with GB during the preharvest stage, and fruits were not exposed to low temperatures but they were kept at 23°C until they reached commercial ripening. The results showed that the preharvest foliar application of GB (100 mM) to banana plants reduced the biochemical and physiological alterations caused by chilling injury on harvested fruits.

Involvement of lycopene in the induction of tolerance to chilling injury in grapefruit

Grapefruit are among the more sensitive Citrus varieties likely to develop chilling injury (CI) symptoms during postharvest storage at low temperatures. Comparative observations of the incidence of CI in fruit of white Marsh (MSH) and red Star Ruby (SR) grapefruit during postharvest storage at 2°C plus 7 days at 20°C to simulate shelf-life revealed that (1) the former was consistently more sensitive to CI, developing cold damage uniformly throughout the whole rind surface, and (2) more strikingly, CI symptoms in fruit of SR grapefruit were restricted to the yellow areas of the rind and the red-colored zones were almost absent of cold damage. This tolerance to CI in red flavedo was associated with high carotenoid (×2) and lycopene (×14) contents, as compared with yellow-colored flavedo. Absence of chilling damage in red areas of SR grapefruit rind was confirmed by cellular ultrastructure observations, in which these epidermal cells were intact, with a well-defined structure and compact vacuoles filled with content. Cells of yellow-colored tissue developing CI, were collapsed, with a contracted vacuole and shrinking organelles. To explore whether the tolerance to CI in red areas of grapefruit rind was due to an elevated lycopene concentration, chemical and environmental stimulation of this carotenoid was performed in fruit of both grapefruit varieties. Application of the inhibitor of the lycopene cyclase activity, CPTA (2-(4-chlorophenylthio) triethylamine hydrochloride) induced red coloration, increased lycopene accumulation (×32) and significantly delayed development of CI symptoms in the rind the CI-sensitive MSH. Bagging of SR grapefruit enhanced a homogenous red coloration and substantially induced lycopene accumulation (×75). CI symptoms in bagged fruit were notably delayed and reduced, as compared with non-bagged yellow fruit, upon subsequent storage at 2°C for up to 58 days and 7 days at 20°C. Analysis of the expression of ethylene biosynthetic genes (ACS1, ACS2 and ACO) revealed a significant induction in chilling-damaged tissue of both varieties that was almost absent in red chilling-tolerant tissue. Similarly, accumulation of transcripts of the ethylene receptors ETR1 and ETR3 were also associated with chilling damage, but a cold factor appears to also mediate the expression of these genes. Taken together, our results indicate that high lycopene concentration appears to be responsible for the induction of tolerance to chilling in the red-colored areas of the flavedo of grapefruit during postharvest storage at low temperatures.

Effect of exogenous γ-aminobutyric acid (GABA) treatment on chilling injury and antioxidant capacity in banana peel

In order to evaluate the effects of γ-aminobutyric acid (GABA) on chilling injury (CI) of banana fruit, CI index, malondialdehyde (MDA), total phenolics, proline, the activities of peroxidase (POD), phenylalanine ammonia-lyase (PAL), Δ1-pyrroline-5-carboxy-late synthetase (P5CS), proline dehydrogenase (PDH), ferric reducing antioxidant potential (FRAP) assay and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity were analyzed after pretreated 20mM GABA vacuum infiltration and stored at 7°C for 20 days. GABA treatment retarded the increase of CI index, electrolyte leakage and MDA content, while promoted the accumulation of total phenolics and proline. GABA treatment significantly enhanced the activities of P5CS, POD and PAL, while inhibited the activity of PDH. FRAP assay and DPPH radical scavenging activity of GABA-treated banana fruit were significantly higher than control fruit in the first 10 days. The results suggest that application of GABA plays an important role in alleviating banana fruit chilling injury through proline accumulation and enhancement of antioxidant defense system. GABA treatment may act as a promising approach in inhibiting chilling injury and maintaining quality of banana fruit.

Effect of low temperatures on pulp browning and endogenous abscisic acid and ethylene concentrations in peach (Prunus persica L.) fruit during post-harvest storage

SummaryChanges in the severity of pulp browning, endogenous abscisic acid (ABA) and ethylene concentrations, and related gene expression in peach (Prunus persica L. ‘Bayuecui’) fruit stored at the biological freezing-point temperature (BFT; 1ºC), at 4ºC, or at room temperature (20ºC; as a control) were investigated.The results showed that fruit stored at room temperature showed climacteric changes in ethylene and ABA concentrations and in levels of expression of the corresponding ethylene synthetase genes (PpACS1, PpACO1) and the gene for a key enzyme of ABA synthesis (PpNCED), concomitant with a significant decrease in fruit firmness and an increase in juice yield. Meanwhile, two sucrose synthase genes (PpSUS1 and PpSUS2) were expressed at relatively low levels. However, fruit firmness decreased slightly and chilling injury (CI) increased significantly 40 d after storage (DAS) at 4ºC, with a significant accumulation of proline [from 8.33 µg g–1 (at t = 0 d) to 9.125 µg g–1 (at t = 40 d)]. In contrast, fruit firmness decreased slowly and pulp browning increased slightly 80 DAS at the BFT ( 1ºC), with a lower accumulation of proline than in fruit stored at 4ºC. The concentrations of soluble sugars and titratable acidity decreased during storage at 1ºC, 4ºC, or 20ºC, but there was a peak of soluble sugars at a late stage of storage at the BFT ( 1ºC). The fruit browning index was significantly and positively correlated (R 2 = 0.967) with ABA concentration. The decrease in ABA concentration in cold-stored fruit (at both 1ºC and 4ºC) inhibited ethylene production. Moreover, there was no significant correlation between CI in fruit and ethylene production. In conclusion, the decrease in ABA concentration reduced ethylene concentrations and inhibited the development of pulp browning, which resulted in an improved taste, but crisper fruit, when fruit were stored at the BFT (–1ºC).

Hot air treatment‐induced arginine catabolism is associated with elevated polyamines and proline levels and alleviates chilling injury in postharvest tomato fruit

To understand whether arginine catabolism might be involved in hot air (HA)-induced chilling tolerance mechanism in tomato fruit, we investigated the effect of HA treatment on endogenous arginine catabolism in relation to chilling injury. Tomato fruit were harvested at mature green stage and treated with HA at 38°C for 12 h and then stored at 2°C for 21 days. The effects of HA treatment on fruit chilling injury and gene expression levels or enzyme activity, and metabolites related to arginine catabolism were evaluated. HA treatment reduced the chilling injury symptoms of tomato fruit and enhanced the accumulation of endogenous polyamines, especially putrescine and proline. This accumulation is associated with the increased transcript levels of genes encoding arginase (LeARG1 and LeARG2), arginine decarboxylase (LeADC), ornithine decarboxylase (LeODC) and ornithine aminotransferase (LeOAT) at most sampling times. However, HA treatment had little effect on nitric oxide synthase activity and nitric oxide concentration. These results revealed that the reduction in chilling injury by HA treatment may be due to the accumulation of putrescine and proline induced primarily by activating the catabolism of endogenous arginine.

Intermittent warming alleviated the loss of peach fruit aroma-related esters by regulation of AAT during cold storage

Low temperature storage slows ripening and reduces decay of peach fruit, although storage life is limited due to chilling injury. Intermittent warming (IW) can be used to alleviate fruit chilling injury, however, its effect on aroma remains unknown. Yellow-fleshed peach (Prunus persica L. Batsch cv. Jinxiu) fruit (melting type) was stored at 5°C or exposed to 20°C for 1d every week during storage. Changes in fruit esters, alcohol acyltransferase (AAT) activity and gene expression were investigated. Flesh browning (FB) was observed on the third day of shelf-life at 20°C after 21d of storage at 5°C, while no FB was found in IW-treated fruit for up to 28d. Significant lower ester contents were found in peach fruit with flesh browning. Expression profiles of PpAAT1 were similar to AAT activity profiles, both of which increased during shelf-life of fruit treated with IW. As precursors of esters, levels of linoleic and linolenic acids were high in IW-treated peach fruit. Treatment with IW effectively alleviated the loss of aroma-related esters associated with FB, and high levels of AAT activity and PpAAT1 expression in IW-treated peach fruit contributed to the formation of the esters.

MeJA induces chilling tolerance in loquat fruit by regulating proline and γ-aminobutyric acid contents

Abstract Loquat fruit were pretreated with 10 μmol l −1 methyl jasmonate (MeJA) for 24 h at 20 °C and then stored at 1 °C for 35 days to investigate the effect of MeJA treatment on chilling injury (CI) and changes in the contents of proline and γ-aminobutyric acid (GABA). The control fruit exhibited severe flesh leatheriness, a specific CI symptom, after 21 days of storage at 1 °C, but it was reduced in MeJA-treated fruit. During the development of CI in fruit, proline and GABA accumulated with the storage time, while MeJA treatment enhanced the increases in proline and GABA contents. The MeJA-treated fruit exhibited higher activities of Δ 1 -pyrroline-5-carboxylate synthetase (P5CS), ornithine δ-aminotransferase (OAT) and glutamate decarboxylase (GAD), and lower proline dehydrogenase (PDH) activity than control during storage. These results suggest that the reduction in CI in loquat fruit by MeJA may be due to the increased proline and GABA contents.