Chilling Injury Symptoms Research Articles

Prevention of Chilling Injury in Pomegranates Revisited: Pre- and Post-Harvest Factors, Mode of Actions, and Technologies Involved.

The storage life of pomegranate fruit (Punica granatum L.) is limited by decay, chilling injury, weight loss, and husk scald. In particular, chilling injury (CI) limits pomegranate long-term storage at chilling temperatures. CI manifests as skin browning that expands randomly with surface spots, albedo brown discoloration, and changes in aril colors from red to brown discoloration during handling or storage (6-8 weeks) at <5-7 °C. Since CI symptoms affect external and internal appearance, it significantly reduces pomegranate fruit marketability. Several postharvest treatments have been proposed to prevent CI, including atmospheric modifications (MA), heat treatments (HT), coatings, use of polyamines (PAs), salicylic acid (SA), jasmonates (JA), melatonin and glycine betaine (GB), among others. There is no complete understanding of the etiology and biochemistry of CI, however, a hypothetical model proposed herein indicates that oxidative stress plays a key role, which alters cell membrane functionality and integrity and alters protein/enzyme biosynthesis associated with chilling injury symptoms. This review discusses the hypothesized mechanism of CI based on recent research, its association to postharvest treatments, and their possible targets. It also indicates that the proposed mode of action model can be used to combine treatments in a hurdle synergistic or additive approach or as the basis for novel technological developments.

N-α-Lauroyl-L-arginine ethyl ester hydrochloride combined with hot water treatment alleviates chilling injury of postharvest cucumber fruit

Postharvest cucumber fruit is prone to chilling injury (CI) under cold stress, leading to severe quality deterioration. In this study, the effects of N-α-Lauroyl-l-arginine ethyl ester hydrochloride (LAE), hot water (HW), and LAE combined with HW treatments on CI in cucumber fruit stored at 4 ± 1 ℃ were investigated. The response surface methodology (RSM) confirmed that the LAE concentration of 1.00 g L−1, HW temperature of 44 ℃, and immersion time of 10 min were the optimal condition for cucumber fruit preservation during cold storage. Further analysis revealed that LAE, HW, and LAE combined with HW treatments, all significantly mitigated chilling injury symptoms in cucumber fruit in comparison with the control, but the application of LAE combined with HW was the most effective method for enhancing cold tolerance in cucumber fruit. Moreover, LAE combined with HW treatment could reduce reactive oxygen species (ROS) accumulation, and enhance superoxide dismutase (SOD), catalase (CAT), peroxidase (POD), ascorbate peroxidase (APX) activities in cold-stored cucumber fruit. Meanwhile, the activities of arginine decarboxylase (ADC), ornithine decarboxylase (ODC), Δ1-pyrroline-5-carboxylate synthetase (P5CS), ornithine δ-aminotransferase (OAT), and glutamate decarboxylase (GAD) were also increased by LAE combined with HW treatment, while the activities of proline dehydrogenase (PDH) and γ-aminobutyric acid transaminase (GABA-T) were decreased by LAE combined with HW treatment, which contributed to maintaining higher polyamines, proline, and GABA contents. These findings suggested that LAE combined with HW treatment can reduce chilling injury in cucumber fruit via enhancing antioxidant enzymes activities, PA, proline, and GABA contents to maintain ROS homeostasis during cold storage.

Metabolite Profiling Reveals the Effect of Cold Storage on Primary Metabolism in Nectarine Varieties with Contrasting Mealiness

Chilling injury is a physiological disorder caused by cold storage in peaches and nectarines. The main symptom of chilling injury is mealiness/wooliness, described as a lack of juice in fruit flesh. In this work, we studied two nectarine varieties (Andes Nec-2 and Andes Nec-3) with contrasting susceptibility to mealiness after cold storage. A non-targeted metabolomic analysis was conducted by GC-MS to understand if changes in metabolite abundance are associated with nectarine mealiness induced by cold storage. Multivariate analyses indicated that in unripe nectarines, cold storage promoted a higher accumulation of amino acids in both varieties. Interestingly, for ripe nectarines, cold storage induced an accumulation of fewer amino acids in both varieties and showed an increased abundance of sugars and organic acids. A pathway reconstruction of primary metabolism revealed that in ripe nectarines, cold storage disrupted metabolite abundance in sugar metabolism and the TCA cycle, leading to a differential accumulation of amino acids, organic acids, and sugars in mealy and juicy nectarines.

Postharvest Treatment with Abscisic Acid Alleviates Chilling Injury in Zucchini Fruit by Regulating Phenolic Metabolism and Non-Enzymatic Antioxidant System.

Reports show that phytohormone abscisic acid (ABA) is involved in reducing zucchini postharvest chilling injury. During the storage of harvested fruit at low temperatures, chilling injury symptoms were associated with cell damage through the production of reactive oxygen species. In this work, we have studied the importance of different non-enzymatic antioxidants on tolerance to cold stress in zucchini fruit treated with ABA. The application of ABA increases the antioxidant capacity of zucchini fruit during storage through the accumulation of ascorbate, carotenoids and polyphenolic compounds. The quantification of specific phenols was performed by UPLC/MS-MS, observing that exogenous ABA mainly activated the production of flavonoids. The rise in all these non-enzymatic antioxidants due to ABA correlates with a reduction in oxidative stress in treated fruit during cold stress. The results showed that the ABA mainly induces antioxidant metabolism during the first day of exposure to low temperatures, and this response is key to avoiding the occurrence of chilling injury. This work suggests an important protective role of non-enzymatic antioxidants and polyphenolic metabolism in the prevention of chilling injury in zucchini fruit.

High-Relative-Humidity Storage Reduces the Chilling Injury Symptoms of Red Sweet Peppers in the Breaker Stage

Water loss, interwoven with other factors, is identified as the cause of chilling injury to sweet peppers. The breaker stage is the most vulnerable of all maturity stages. The purpose of this study was to see if increasing the storage relative humidity (RH) reduces the chilling injury and to compare its effect on breaker-stage fruits to red-ripe fruits at a normal RH. The fruits were stored at 5 °C with a RH of 98 ± 2% and 70 ± 6% for high and low RH, respectively. After 15 days of cold storage, the fruits were moved to ambient conditions for 3–5 days for chilling injury symptoms to appear. The results showed that high RH storage reduced fruit water loss by 4–4.5% compared to low RH storage, resulting in fewer chilling injury symptoms regardless of fruit maturity stage. Due to the increased RH, cell membrane damage indicators such as electrolyte leakage, MDA, respiration, and ethylene production rates were shown to be reduced, while brix and color were well maintained, indicating reduced or stopped senescence. Furthermore, DPPH antioxidant activity and vitamin C were retained and optimized. The microbiological analyses also showed that a high RH may not promote the growth of microorganisms as quickly as may have been thought. Finally, the findings of this study indicate that breaker-stage peppers stored at a high RH may be less susceptible to chilling injury than red-ripe peppers stored at a low RH.

Foliar Fertilization of Potassium Silicon Improved Postharvest Fruit Quality of Peach and Nectarine [Prunus persica (L.) Batsch] Cultivars

Peach fruit quality is dependent on preharvest treatments and orchard practices. The aim of this study is to evaluate the effects of preharvest potassium silicon fertilization on fruit postharvest quality. Two peach cultivars (“Early Bomba” and “Plagold 17”) were sprayed with three concentrations of potassium silicon (K-Si) at fruit set, stone hardening, and physiological maturity stages. The applied treatments corresponded to control (T0 = 0% K-Si) pulverized with distilled water and two K-Si treatments (T1 = 3% K-Si and T2 = 4.5% K-Si). The blooming and harvesting dates, vegetative growth and agronomical parameters were analyzed over two growing seasons (2021–2022). Peach fruits were stored at 5 °C and 95% RH during two cold storage periods (2 and 4 weeks) followed by 2 days at room temperatures. The fruit weights (FW), color, firmness, soluble solids content (SSC), titratable acidity (TA), pulp stone ratio (P/S) and fruit weight loss (FWL) were evaluated. The anthocyanins, flavonoids, total phenolics, carotenoids and antioxidant capacity (DPPH) were determined. Vitamin B5 and vitamin C were analyzed by HPLC. The ethylene rate and the chilling injury symptoms (CI) were analyzed after two cold storage periods (2 and 4 weeks). Results showed that the applied potassium silicon treatments (3% K-Si and 4.5% K-Si) enhanced the FW, SSC, TA, FWL, fruit composition and CI. Anthocyanins and total phenolics increased after cold storage period under K-Si treatments. The nectarine cultivar (cv) Early Bomba showed low sensibility to chilling injury symptoms as compared to the cv Plagold 17.

SlNPR1 modulates chilling stress resistance in tomato plant by alleviating oxidative damage and affecting the synthesis of ferulic acid

• NPR1 gene and protein content are dramatically induced by chilling stress. • CRISPR/Cas9-mediated SlNPR1 inhibition aggravated the symptoms of chilling injury. • SlNPR1 enhances tolerance to chilling stress by alleviating oxidative damage. • SlNPR1 enhances tolerance to chilling stress by affecting the synthesis of FA. Non-expresser of pathogenesis-related genes 1 (NPR1) has been demonstrated to be a master transcription factor during resistance against pathogens, the mechanisms by which regulates chilling stress, however, remain unclear. Our results revealed that the expression and protein content of SlNPR1 were dramatically induced by low temperature (4 °C). CRISPR/Cas9-mediated SlNPR1 mutagenesis aggravated the symptoms of chilling injury in tomato plant, which was accompanied with the accumulation of malonic dialdehyde (MDA), hydrogen peroxide (H 2 O 2 ) and superoxide anion (O 2 − ), and the decrease of soluble protein content, proline content as well as antioxidant enzymes activity. In addition, slnpr1 mutants showed lower expression of SlICE1 and SlCBF1 in contrast to wild type plants (WT) . PAL, C4H, C3H and COMT genes play important roles in the synthesis of ferulic acid (FA). We found that knockout of SlNPR1 reduced the expression of PAL, C4H, C3H and COMT induced by low temperature (4 °C) and inhibited the accumulation of FA content. Interestingly, FA-treated plants showed greater tolerance to chilling stress and displayed higher expression of SlICE1 and SlCBF1 , exhibited lower levels of MDA and H 2 O 2 , but higher antioxidant enzyme (APX, POD, SOD and CAT) activity than WT. These findings reveal a new regulatory pathway that SlNPR1 enhances tolerance to chilling stress in tomato plant by alleviating oxidative damage and affecting the synthesis of FA.

The Regulatory Mechanisms and Control Technologies of Chilling Injury and Fungal Diseases of Postharvest Loquat Fruit.

Loquat is a popular fruit widely cultivated all over the world. It is rich in minerals and carotenoids and has high commercial value. At room temperature, loquat fruit is impressionable to water and nutritional losses, physical damage, and microbial decay, resulting in a short postharvest life. Low-temperature storage is routinely used to prolong the shelf life of loquat fruit; however, cold storage can also lead to lignification of flesh tissue, which is one of the major symptoms of chilling injury (CI), reducing the quality and economic value of the fruit. In addition, fruit decay caused by microbial infection is another important reason for postharvest losses of loquat. To reduce quality deterioration and optimize the postharvest storage strategies of loquat fruit, considerable progress has been made in the physiological and molecular biological studies of CI, microbial decay, and preservation technologies of loquat fruit during the postharvest phase in recent decades. This review summarizes the current research progress and provides a reference for the improvement of loquat fruit quality.

Postharvest chitosan-arginine nanoparticles application ameliorates chilling injury in plum fruit during cold storage by enhancing ROS scavenging system activity

BackgroundPlum (Prunus domestica L.) has a short shelf-life period due to its high respiration rate and is sensitive to low storage temperatures, which can lead to the appearance of chilling injury symptoms. In this investigation, we applied new coating treatments based on chitosan (CTS) and arginine (Arg) to plum fruit (cv. ‘Stanley’).ResultsFruit were treated with distilled water (control), Arg at 0.25 and 0.5 mM, CTS at 1% (w/v) or Arg-coated CTS nanoparticles (CTS-Arg NPs) at 0.5 and 1% (w/v), and then stored at 1 °C for days. The application of CTS-Arg NPs at 0.5% attenuated chilling injury, which was accompanied by accumulation of proline, reduced levels of electrolyte leakage and malondialdehyde, as well as suppressed the activity of polyphenol oxidase. Plums coated with CTS-Arg NPs (0.5%) showed higher accumulation of phenols, flavonoids and anthocyanins, due to the higher activity of phenylalanine ammonia-lyase, which in turn resulted in higher DPPH scavenging capacity. In addition, CTS-Arg NPs (0.5%) treatment delayed plum weight loss and retained fruit firmness and ascorbic acid content in comparison to control fruit. Furthermore, plums treated with CTS-Arg NPs exhibited lower H2O2 accumulation than control fruit due to higher activity of antioxidant enzymes, including CAT, POD, APX and SOD.ConclusionsThe present findings show that CTS-Arg NPs (0.5%) were the most effective treatment in delaying chilling injury and prolonging the shelf life of plum fruit.

The influence of rootstocks on chilling injury symptoms of ‘Big Top’ nectarine fruits

The influence of rootstocks on chilling injury symptoms of ‘Big Top’ nectarine fruits

Comparative transcriptomic profiling of peach and nectarine cultivars reveals cultivar-specific responses to chilled postharvest storage.

Peach (Prunus persica (L.) Batsch,) and nectarine fruits (Prunus persica (L.) Batsch, var nectarine), are characterized by a rapid deterioration at room temperature. Therefore, cold storage is widely used to delay fruit post-harvest ripening and extend fruit commercial life. Physiological disorders, collectively known as chilling injury, can develop typically after 3 weeks of low-temperature storage and affect fruit quality. A comparative transcriptomic analysis was performed to identify regulatory pathways that develop before chilling injury symptoms are detectable using next generation sequencing on the fruits of two contrasting cultivars, one peach (Sagittaria) and one nectarine, (Big Top), over 14 days of postharvest cold storage. There was a progressive increase in the number of differentially expressed genes between time points (DEGs) in both cultivars. More (1264) time point DEGs were identified in 'Big Top' compared to 'Sagittaria' (746 DEGs). Both cultivars showed a downregulation of pathways related to photosynthesis, and an upregulation of pathways related to amino sugars, nucleotide sugar metabolism and plant hormone signal transduction with ethylene pathways being most affected. Expression patterns of ethylene related genes (including biosynthesis, signaling and ERF transcription factors) correlated with genes involved in cell wall modification, membrane composition, pathogen and stress response, which are all involved later during storage in development of chilling injury. Overall, the results show that common pathways are activated in the fruit of 'Big Top' nectarine and 'Sagittaria' peach in response to cold storage but include also differences that are cultivar-specific responses.

Peach for the future: A specialty crop revisited

• Current trends on peach cultivar and rootstock breeding initiatives are highlighted. • Efficient cropping system is linked to appropriate rootstock selection and canopy architecture. • Training system selection is of equal importance with rootstock selection. • High density plantation may result in reduced production cost and enhanced orchard sustainability. • Decision making in the orchard and packinghouse is critical for optimum fruit quality. • Peach industry needs to shift to a systems approach through a re-design of the whole supply chain. Peach is the most important temperate fruit crop worldwide in terms of production after apple. However, a descending trend has been registered over the recent years in several key producing peach countries, mainly due to the increased labor cost and the reduced revenue for the farmer. The present perspective review aims to shed light on the current trends on peach fruit production related to cultivar and rootstock breeding initiatives, appropriate training system selection and targeted integrated management of main diseases, most promptly Monilinia spp. Cultivar breeding programs should focus on the most relevant outcomes about the main drivers of consumer's acceptance. In the near future, a contribution from the breeding sector should be expected in the reduction of the trade-off between quality and yield, towards selection of elite cultivars with enhanced aroma (a pool of compounds still scarcely known), with appreciable nutritional properties and extended market life. Such cultivars need an appropriate rootstock and canopy architecture to facilitate efficient cropping systems. The training/cropping system selection is of equal importance with rootstock selection as it can also determine efficiency and potential for mechanization. A tendency for the future is that several semi- and dwarfing Prunus hybrid rootstocks aligned with the innovations on peach tree architecture will lead to higher planting densities, reduced tree height and thus enhanced peach production with reduced labor cost. With the aim to advance peach fruit production and consumption, there is an urgent need to dissect solutions to valorize on the market the exceptional peach diversity and flavor potential, already present in the varietal landscape. The development of sophisticated non-destructive tools that will allow in cost-effective manner to determine fruit quality and maturity stage is expected to facilitate consumer eating experience and storage requirements with minimum risk of chilling injury symptoms development. Lastly, the phytosanitary protocol of small-sized wall-grown plants would most likely be more effective and would require reduced quantities of pesticides while simultaneously responding to the needs of a market that is increasingly attentive to fruit healthiness and environment protection. Phytosanitary issues can be addressed by controlling diseases and/or by improving genetic resistance.

Delaying ripening using 1-MCP reveals chilling injury symptom development at the putative chilling threshold temperature for mature green banana.

Storage at the putative chilling threshold temperature (CTT) to avoid chilling injury still limits postharvest handling of tropical fruit like banana in that ripening may occur at the CTT. To determine whether chilling injury (CI) symptoms would develop in mature green (MG) banana fruit if the CTT exposure was extended by inhibiting ethylene action and thus ripening, 1-methylcyclopropene (1-MCP) was applied. Individual ‘fingers’ from multiple ‘clusters’ of MG bananas were either immersed in water or 50 μg L−1 1-MCP (a.i.) solution and each treatment was divided into three subgroups for storage at 5.0°C (severe CI), 13.0°C (mild CI), or 14.0°C (CTT) ± 0.1°C. 1-MCP delayed ripening in terms of color change for 10 days for fruit stored at the CTT. Ethylene production by fruit at 5.0°C remained around 0.04 ng kg−1 s−1 with no obvious increase during 31-day storage. Ethylene production at 14.0°C (−1-MCP/+1-MCP) increased on Day 33 while increasing on Day 38 for 13.0°C fruit without 1-MCP and on Day 39 for fruit with 1-MCP. Peak climacteric ethylene occurred on Days 44 and 39 for 13.0 and 14.0°C fruit without 1-MCP, respectively, and on Days 59 and 51 for 13.0°C and 14.0°C 1-MCP-treated fruit, respectively. As hypothesized, longer exposure of MG banana fruit to the CTT of 14.0°C without onset of ripening as was allowed by prior 1-MCP treatment allowed CI to develop at that normally non-chilling temperature. Vascular browning was the first visual and most sensitive CI symptom in the experiment and was observed on Day 4 at 5.0°C, Day 10 at 13.0°C, Day 19 at 14.0°C without 1-MCP, and on Day 28 at 14.0°C with 1-MCP. Using a 1-MCP pre-treatment to remove the influence of ethylene from bananas stored at 13°C or 14°C also resulted in slight reduction in vascular browning severity. In conclusion, a putative safe temperature may become a CI temperature if the shelf-life-limiting factor is removed, allowing longer exposure. Chilling at the CTT caused relatively mild injury on fruit, and vascular browning is a sensitive indicator of CI status, while the light-adapted quantum yield of photosystem II [Y(II)] could be a non-destructive indicator of early CI stress in MG banana. Fruit at 13.0/14.0°C developed CI symptoms slightly later with 1-MCP than without 1-MCP. This suggests that ethylene might be involved in early CI symptom development.

Lipid peroxidation and lipid-soluble antioxidants as quality control markers in cold-stored fruit for establishing commercial acceptability in Bacon avocados

Avocados are prone to chilling injury disorders when stored at low temperatures. Although most studies have been performed in the worldwide distributed ‘Hass’ variety, other less exploited commercial varieties such as ‘Bacon’ might be more cold-tolerant. Aiming at evaluating how cold storage influences chilling injury, the extent of lipid peroxidation and the contents of lipophilic antioxidants were measured in ‘Bacon’ avocados. Harvested fruit were divided into two groups: one stored for 6 weeks at 4 °C and sampled at various time intervals for 42 days, and the other maintained at low temperatures for 3 and 6 weeks and then exposed to room temperature for 5 days until ripened. Long-term cold storage negatively influenced tocochromanols and carotenoids composition in unripen fruit, decreasing progressively both vitamin E and plastochromanol-8 contents, and most particularly carotenoids; yet chilling injury was prevented during cold storage for 6 weeks. When these fruits were ripened at room temperature, chilling injury increased 20% in the peel but only 5% in the mesocarp (edible part). Enhanced chilling injury in the mesocarp was associated with a 2.3-fold increase in lipid hydroperoxides (a primary lipid peroxidation product) and a 2.5-fold increase in plastochromanol-8 content, while contents of other tocochromanols, carotenoids and malondialdehyde (a secondary product of lipid peroxidation) kept unaltered. Interestingly, medium-term cold storage (3 weeks at 4 °C) did not lead to chilling injury in ripe fruit, therefore cold storage for 3 weeks is considered optimal to prevent large antioxidant vitamin degradation and maintain fruit quality in ripen avocados. In conclusion, despite the high cold tolerance shown by ‘Bacon’ avocados, fruit showed a strong depletion (60%) in carotenoids content after 6 weeks of storage at 4 °C, negatively affecting their commercial acceptability. Aside from evaluating visual chilling injury symptoms, evaluation of lipid peroxidation markers and contents of lipid-soluble antioxidants are deemed to be essential to establish commercial acceptability in cold-stored fruit.

Melatonin Alleviates Chilling Injury Symptom Development in Mango Fruit by Maintaining Intracellular Energy and Cell Wall and Membrane Stability.

The efficacy of the signaling molecule melatonin for alleviating chilling injury (CI) in mango (Mangifera indica L.) fruit was studied to investigate the potential role of membrane integrity, energy charge, and ripening-related changes in the development of CI, and its management by melatonin. ‘Langra’ and ‘Gulab Jamun’ cultivar mango fruit was immersed in 100 μM of melatonin before storage for 28 days at 5°C with weekly transfers to shelf life at 25°C. CI symptom development was associated with compositional and enzymatic aspects of textural changes, cell membrane deterioration, and chemical energy status. Melatonin-treated ‘Langra’ fruit exhibited very low CI (5 vs. 21%) while ‘Gulab Jamun’ fruit exhibited higher CI (36 vs. 38%) during 28 days of storage at 5 ± 1°C. Higher chilling tolerance in melatonin-treated ‘Langra’ was associated with lower softening, ascribed to lower cell wall degrading exo- and endo-polygalacturonase, pectinesterase, and endo-1,4-β-D-glucanase. In addition, lower membrane deteriorating-phospholipase D and lipoxygenase activity in melatonin-treated ‘Langra’ corresponded to lower palmitic and stearic acids and higher oleic, linoleic, and linolenic acids accumulation, thus, higher unsaturated/saturated fatty acids ratio. Additionally, there was a higher intracellular energy supply with melatonin, represented by a higher adenylate energy charge (AEC) arising from higher ATP and ADP and lower AMP accumulation, related to higher H+-ATPase, Ca2+-ATPase, succinate dehydrogenase, and cytochrome c oxidase activities. This study for the first time provides evidence, suggesting that melatonin alleviation of CI is related to the preservation of membrane integrity, thereby protecting the intracellular energy supply, and preserving cell wall integrity via impeding cell wall degrading enzyme activities.

A combined technique of temperature preconditioning and modified atmosphere packaging to prolong the storage life of papaya

Papaya is a popular tropical fruit for human consumption over the world. However, it has a relatively short shelf life due to rapid ripening and anthracnose infection after harvest. Generally, papaya is stored at the optimum temperature of 12°C and can last only two weeks. After this period, the fruit will begin to ripen and spoil. Theoretically, fruit stored at lower temperatures will have a longer shelf life. However, papaya is prone to chilling injuries characterised by pitting and inability to ripen if stored at sub-optimum temperature, which may also cause secondary postharvest disease attacks if held for a longer period. The study aimed to evaluate the effectiveness of a combination of temperature preconditioning treatment and modified atmospheric packaging (MAP) in prolonging the storage life of papaya under sub-optimum temperature. In terms of visual appearance, no chilling injury symptoms were observed in samples stored at a suboptimum temperature of 7°C throughout the storage period. No significant differences were recorded in the parameters of total soluble solids (TSS), total titratable acidity (TTA) and TSS: TTA ratio. Relatively lower ascorbic acid content and higher firmness value were recorded in fruits subjected to the combined technique of temperature conditioning and MAP, which could be associated with delayed ripening. A combination of temperature preconditioning and MAP techniques maintains the papaya quality under storage at sub-optimum temperatures as low as 7°C without chilling injury problems, with a longer shelf life (4 weeks) than only 2 weeks for conventional handling techniques. The fruits can be ripened by being exposed to ethylene when they are ready to be marketed. The technology is helpful for the industry, farmers, wholesalers, and exporters, particularly for the delivery of more extended distribution and periods.

EjCaM7 and EjCAMTA3 synergistically alleviate chilling-induced lignification in loquat fruit by repressing the expression of lignin biosynthesis genes

Flesh lignification is a typical chilling injury (CI) symptom of loquat fruit during cold storage. Calcium chloride (CaCl2) could enhance chilling tolerance in loquat fruit, but the molecular mechanism is still not illuminated. In this study, CaCl2 treatment could decrease the activities and genes expression of peroxidase (POD) laccase (LAC), and inhibit the increase in firmness and lignin accumulation, thereby alleviating chilling-induced lignification in loquat fruit. Additionally, CaCl2 enhanced the calmodulin (CaM) content, free Ca2+ distribution, EjCaM7, and CaM binding transcription activator 3 (EjCAMTA3) expression in loquat fruit during cold storage, indicating Ca2+/CaM-CAMTA might be played a key role in response to cold stress. Moreover, the EjCAMTA3 and EjCaM7 proteins were identified and characterized from loquat fruit. EjCAMTA3 bound to the CG-box in EjPOD64 and EjLAC12-like promoters to repress their transcription. Further analysis revealed that EjCaM7 interacted with EjCAMTA3 in a Ca2+-dependent manner, and this interaction enhanced the EjCAMTA3-mediated transcriptional repression of EjPOD64 and EjLAC12-like genes. Taken together, these findings suggested that CaCl2 treatment alleviates chilling-induced lignification in loquat fruit, which probably via the synergistic role of EjCaM7 and EjCAMTA3 in the modulation of EjPOD64 and EjLAC12-like genes expression, leading to the repression of lignin polymerization.

Abnormal chilling injury of postharvest papaya is associated with the antioxidant response.

Generally, the lower the temperature and/or the longer the duration of low temperature, the more serious chilling injury (CI) symptom appears in fruit. However, our previous study showed that the higher storage temperature (6°C) resulted in a more serious CI in papaya fruit compared to that stored at 1°C, which could be viewed as an abnormal CI behavior. This study investigated the antioxidant responses that existed in abnormal CI behavior of papaya fruit. Compared to 6°C, antioxidant enzyme activities of papaya fruit which was stored at 1°C were maintained at a higher level while the circulatory metabolism of the ascorbate-glutathione cycle (AsA-GSH) was more vigorous in papaya fruit, as indicated by higher superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), ascorbate peroxidase (APX), dehydroascorbate reductase (DHAR), and monodehydroascorbate reductase (MDHAR) activities and higher AsA and GSH levels, which could reduce the superoxide anion (·O2 - ) production rate and the hydrogen peroxide (H2 O2 ) content. Suppressed reactive oxygen species (ROS) generation in papaya fruit at 1°C resulted in reduced membrane permeability and malondialdehyde (MDA) accumulation when compared to that at 6°C, thus the development of CI was restricted during storage at 1°C. This study deepened the understanding of differential antioxidant responses during cold storage at 1°C and 6°C in papaya fruit and provided a theoretical basis for further study on the mechanism of the abnormal CI behavior in papaya fruit. PRACTICAL APPLICATIONS: Low-temperature storage is one of the most effective methods to preserve fruit and vegetable products. While, inappropriate low temperature could induce CI, and the damage caused by CI is often more serious than estimated. Therefore, it is necessary to study the physiological and biochemical characteristics of different postharvest fruits and vegetables to prolong storage period, improve storage quality and reduce the loss of products. This study analyzed the antioxidant reaction in abnormal CI behavior of papaya, which could contribute to the further study on the mechanism of CI in papaya fruit and provide theoretical basis for the development of preservation technology of papaya fruit.

Detection of Chilling Injury Symptoms of Salak Pondoh Fruit during Cold Storage with Near Infrared Spectroscopy (NIRS)

One of the treatment methods that is suitable for maintaining the quality of salak pondoh fruit is cold storage. However, cold storage of salak pondoh fruit below its optimum storage temperature (15°C) can cause chilling injury/CI. This research aims to develop a non-destructive method of determining the CI symptoms of salak pondoh fruit during storage at 5°C with NIRS. Measurements were carried out for 14 days by measuring the CI parameters (pH and IL/ion leakage) and the NIR reflectance spectra. The best PLS method NIR calibration model for estimating pH was generated using the Savitzky-Golay Smoothing pretreatment with rk= 0.81, rv =0.76, SEC= 0.12%, SEP =0.12%, CV= 2.97%, RPD= 1.66, and consistency =100.06%. The IL slope of salak pondoh fruit correlated with the pH in a linear pattern relationship with the equation y = 0.1735x - 0.4305. The highest IL slope value was obtained on the 4th day of storage which means that IL has reached its peak, and CI was predicted to have occurred on the 4th day of storage.

Growth Temperature Influences Postharvest Quality and Cold Tolerance of Green Harvested Dwarf Tomatoes During Storage

Effect of cultivation temperature during the phase of flowering and fruit development on tomato quality was investigated. Plants of two dwarf tomato cultivars “Ponchi Re” and “Tarzan,” were subjected to three different growth temperatures: 16, 22, or 28°C, starting at the flowering phase. Mature green fruit was harvested and subjected to shelf life at 20°C for 20 days or first stored at 4°C for 15 days, and then placed under shelf life conditions. Fruit quality was determined through red color development, soluble solid content (SSC), softening, weight loss, and cold tolerance. Higher cultivation temperature increased development and production of fruit. Deviation from the 22°C growth temperature led to increased soluble solid content in both cultivars, and smaller fruit diameter in “Tarzan.” Fruit grown at lower temperature had delayed color development during shelf life, and this was further delayed by prior cold storage. “Tarzan” showed more chilling injury (CI) symptoms than “Ponchi Re.” In our experiment, SSC can be manipulated by modulating cultivation temperature, but that it is not associated with CI tolerance. Delayed color formation at the lowest growth temperature observed in “Ponchi Re” tomatoes could be resulted in lower lycopene levels leads to lower ROS scavenging capacity. For “Tarzan” tomatoes, higher firmness at harvest, less softening, and lower weight loss during cold storage in fruit from the lowest cultivation temperature might positively correlated with increased membrane integrity, resulting in increased CI tolerance. This indicates that CI incidence depends on growth temperature and is cultivar dependent in dwarf tomato fruit.