Melatonin treatment alleviates chilling injury in mango fruit 'Keitt' by modulating proline metabolism under chilling stress

Mangoes often suffer from low temperature-induced chilling injury (CI) during postharvest cold storage.Therefore,advanced techniques are crucial and in high demand to solve the chilling stress of mango fruit for a higher value.This study addresses chilling stress modulation by investigating the effects of melatonin treatment on CI,proline metabolism,and related gene expressions of ‘Keitt’ mango during cold storage after dipped in 0 (control),0.1 (MT1),and 0.2 mmol L^(-1)(MT2) melatonin solution for 30 min.The results revealed that melatonin treatment in MT1 significantly reduced CI development and increased proline content in mango fruit during cold storage compared to the control.These changes were along with increases in the activity of critical enzymes as well as the expression of encoding genes involved in proline biosynthesis,such as pyrroline-5-carboxylate synthetase (P5CS),pyrroline-5-carboxylate reductase (P5CR),ornithine D-aminotransferase (OAT),P5CS2,P5CR2,and OAT3.Additionally,proline dehydrogenase (PDH) activity and the expression of the PDH3 gene associated with proline dehydrogenation were lower in MT1-treated mangoes than the controlled group.Thus,melatonin treatment has regulated proline metabolism resulting in the accumulation of proline,subsequently contributing to enhancing the chilling tolerance of‘Keitt’mango fruit.

Research Progress and Outlook of Low Temperature Chilling Injury in Northeast China

Focused on the major agro-meteorological disaster in northeast China area—low temperature chilling injury,the research progresses of low temperature chilling injury in northeast China were reviewed systematically.The basic concepts which included the connotation and extension of chilling damage,the circulation characteristics and effect factors which formed summer low temperature in northeast China,the prediction,forecast and defense of low temperature chilling injury were summarized and done the outlook.

Methyl Jasmonate Reduces Chilling Injury and Maintains Postharvest Quality in Peaches

Zhaohui peaches(Prunus persica Batsch)were treated with 0(CK), 1, 10 or 100 μmol L-1 methyl jasmonate(MeJA)vapor at 20℃ for 24 h before stored at 0℃ for 35 d. The untreated fruits showed chilling injury(CD symptoms after 4 wk of storage, as indicated by increased fruit firmness and reduced ex-tractable juice, which is referred as leatheriness. Treatment with 1 and 10 μmol L-1 MeJA promoted normal ripening and softening, maintained higher levels of extractable juice, titratable acidity, pectinesterase(PE)and polygalacturonase(PC)activities, inhibited increases in fruit fresh weight loss, decay incidence, electrolyte leakage and MDA content, and improved color development, thereby preventing chilling injury symptoms development and maintaining edible quality. MeJA treatment also delayed the climacteric rise in respiratory rate, but promoted ethylene production during the later period of cold storage, suggesting that ethylene may involve in CI development of peaches. These results indicate that 1 and 10 μmol L-1 MeJA treatments could be used to reduce CI development and decay incidence in peaches.

Reduction of Chilling Injury and Ultrastructural Damage in Cherry Tomato Fruits After Hot Water Treatment

The effects of hot water treatment in alleviating chilling injury and reducing ultrastructural damage of mature-green cherry tomatoes （Lycopersicun esculentum cv. cerasiform Alef） were investigated. Mature-green cherry tomato fruits were treated in water at 40℃ or 45℃ for 5 min or 15 min, and then stored at 5℃ for 19 days followed by ripening at 20℃. Water treatment at 40℃ for 15 min increased tolerance of cherry tomato fruits to chilling stress, indicating as low outbreak of skin lesion, high color a＊ value, and low electrolyte leakage. Treated fruits showed typical climacteric respiration and developed normal red color with chlorophyll degradation and lycopene accumulation during ripening, while fruits without treatment failed to develop red color and suffered skin lesion. After 19 days of chilling, heated fruits showed the conversion of chloroplast to chromoplast with the disappearance of thylakoids. Mitochondria and other cell organelles were not adversely affected in treated fruits. However, ultrastructures in pericarp cells in control fruits severely damaged with extensive disorganization of cytoplasm, swelled chloroplasts, distorted and unstacked thylakoids. Chloroplast was the first and most severely impacted organelle by chilling stress. Hot water treatment （40℃ for 15 min） before storage alleviated chilling injury in cherry tomato fruits. The results suggest that chilling injury is related with the damage of cell structure under chilling stress.

Salicylic acid alleviates postharvest chilling injury of sponge gourd(Luffa cylindrica)

Effect of salicylic acid（SA）on chilling injury（CI）of sponge gourd during storage（9 days,9°C）plus shelf life（2 days,20°C）was evaluated in this study.SA treatment at the concentration of 1.5 mmol L^-1 significantly reduced postharvest CI of sponge gourds.Besides,the application of SA could effectively decrease the electrolyte leakage,reduce the accumulation of malondialdehyde（MDA）and total phenolics,enhance the activities of antioxidant enzymes such as superoxide dismutase（SOD）,catalase（CAT）and ascorbate peroxidase（APX）,and inhibit the activities of phenylalanine ammonia-lyase（PAL）and polyphenol oxidase（PPO）.The beneficial effects of SA could be attributed to preserved membrane integrity,inhibited membrane peroxidation,enhanced antioxidant system and suppressed activities of browning related enzymes.In a sense,SA as a postharvest tool may be commercially used in alleviating CI of sponge gourd.

Regulations of m^(6)A 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(m^(6)A)methylation of transcripts in plant hormone pathways has not been reported yet.In order to clarify the complex regulatory mechanism of m^(6)A 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 andm^(6)Amethylation 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.

Chilling Injury, Physicochemical Properties, and Antioxidant Enzyme Activities of Red Pitahaya (Hylocereus polyrhizus) Fruits under Cold Storage Stress

Low-temperature storage is extensively used to optimize the postharvest life of various fresh fruits.However,red pitahaya(Hylocereus polyrhizus)fruits are sensitive to chilling injury(CI),which leads to the limitation of low-temperature storage.In this study,red pitahaya fruits were stored at 2,4,6,8,and 10℃,respectively,for 27 days to determine the appropriate storage temperature.During the storage of red pitahaya fruits,storage at 8℃ was more effective in suppressing decay and maintaining quality than other low temperatures.Lowtemperature(2,4,and 6℃)storage decreased weight loss(WL)and maintained higher content of titratable acidity(TA),soluble sugars(SS),and total phenolics(TP)but different degrees of CI were detected.No CI was observed at 8℃ and 10℃.Red pitahay as stored at 8 and 10℃ were associated with better color evaluation,lower electrolyte leakage(EL),respiration rate,and lipoxygenase(LOX)activity,and higher fruit firmness,superoxide dismutase(SOD)activity,and catalase(CAT)activity.However,higher storage temperature(10℃)resulted in higher metabolic activity leading to lower quality and antioxidant capacities compared with 8℃.Therefore,our results demonstrated that red pitahaya stored at 8℃ exhibited a protective effect on fruit quality and resisted CI development during storage.

Effect of Exogenous Salicylic Acid on Physiological Parameters of Cucumber and Tomato Fruits During Chilling Injury Temperature Storage

Harvested tomato(Lycopersicum esculentum Mill)and cucumber (Cucumis Sativus L.)were immersed in 0, 0.01 g/L, 0.05 g/L, 0.1 g/L or 0 g/L, 0.001 g/L, 0.01 g/L, 0.05 g/L, 0.1 g/L salicylic acid solutions for 15 min, respectively. Some of physiological parameters of the fruits related to chilling injury were measured during cold storage (2℃±1℃ ). It showed that the cell membrane electrolyte leakage, MDA content and free proline content in tomato with 0.01 g/L and 0.1 g/L SA were lower than those of control to a various extent. The immersion in 0.001 g/L SA could significantly decrease the cell membrane electrolyte leakage and MDA content of cucumber stored at chilling injury temperature as well as decrease free proline content to some extent.

The location of 5′-nucleotidase in seedling cells in Yunnan rice varieties and the change of enzyme activity after chilling injury

The seedlings of three rice varieties (Damagu,Ligeng 2, and Xiuzinuo) were cultivated at 25 ±1℃. After chilling injury (at 2~C), blacksediments of lead phosphate appeared on plas-

Impact of chilling injury and global warming on rice yield in Heilongjiang Province

This study is focused on indexes for the rice chilling injury in Heilongjiang Province during 1960-2009. Firstly, we compared a new derived climate data weighted by rice planting density with the traditional method, and found that the new one is more reasonable to assess the impact of climate change on crop yields. Considering the frequency and intensity of rice chilling in the province, secondly, chilling indexes defined by meteorological, national and international levels were assessed. The result showed that the meteorological standards were suitable for the delayed-type injury, while the international one, so-called sum of Grow- ing Degree Day below threshold （GDDn.）, characterized best the sterile-type chilling injury for rice. The explanation ability of the rice yield time series model including both injury types as two independent variables reached approximately 92% （p 〈 0.05）. Finally, we concluded that the contribution rates of human and weather factors to rice yields are about 87.2% and 12.8% respectively, and as light increasing trend for sterile-type chilling injury was found during heading to flowing period in recent years, indicating a high chilling risk for rice planting in Heilongjiang Province in the future global warming.

Damage evaluation of soybean chilling injury based on Google Earth Engine(GEE)and crop modelling

Frequent chilling injury has serious impacts on national food security and in northeastern China heavily affects grain yields.Timely and accurate measures are desirable for assessing associated large-scale impacts and are prerequisites to disaster reduction.Therefore,we propose a novel means to efficiently assess the impacts of chilling injury on soybean.Specific chilling injury events were diagnosed in 1989,1995,2003,2009,and 2018 in Oroqen community.In total,512 combinations scenarios were established using the localized CROPGRO-Soybean model.Furthermore,we determined the maximum wide dynamic vegetation index(WDRVI)and corresponding date of critical windows of the early and late growing seasons using the GEE(Google Earth Engine)platform,then constructed 1600 cold vulnerability models on CDD(Cold Degree Days),the simulated LAI(Leaf Area Index)and yields from the CROPGRO-Soybean model.Finally,we calculated pixel yields losses according to the corresponding vulnerability models.The findings show that simulated historical yield losses in 1989,1995,2003 and 2009 were measured at 9.6%,29.8%,50.5%,and 15.7%,respectively,closely(all errors are within one standard deviation)reflecting actual losses(6.4%,39.2%,47.7%,and 13.2%,respectively).The above proposed method was applied to evaluate the yield loss for 2018 at the pixel scale.Specifically,a sentinel-2A image was used for 10-m high precision yield mapping,and the estimated losses were found to characterize the actual yield losses from 2018 cold events.The results highlight that the proposed method can efficiently and accurately assess the effects of chilling injury on soybean crops.

Cold shock treatment alleviates chilling injury in peach fruit by regulating antioxidant capacity and membrane lipid metabolism

Objectives The work intended to reveal the effect of cold shock(CS)treatment on chiling injury(CI),antioxidant capacity.and membrane fatty acid of peach fruit.Materials and methods Peaches were soaked in ice water(10℃)for 10 min and stored at 5℃ for 28 d for determination,except CI,and then stored for 3 dat 20℃,only CI was measured.The electrolyte leakage(EL)was measured by conductivity meter.The activities of antioxidant enzymes(superoxide dismutase,ascorbate peroxidase,catalase,and peroxidase)and key enzymes of membrane lipid metabolism(phospho-lipase D,lipase,and lipoxygenase)as well as reactive oxygen species(ROS,O_(2)^(-)and H_(2)O_(2))were measured with a spectrophotometer.An ELISA kit and gas chromatography were used to determine membrane lipids and membrane fatty acids.The relative gene expression was measured by real-time polymerase chain reaction analysis.Results The results showed that CS treatment effectively delayed CI,suppressed the increase of EL and malondialdehyde content.Meanwhile,CS-treated fruit exhibited lower level of ROS and higher activities of antioxidant enzymes.Furthermore,CS treatment inhibited the activities as well as the relative gene expression of key enzymes in membrane lipid metabolism.CS-treated fruits maintained higher membrane fatty acid unsaturation and lower phosphatidic acid content.Conclusions These results indicated that CS treatment effectively lleviated CI and maintained the integrity of cell membranes by inducing antioxidant-related enzyme activity and maintaining a higher ratio of unsaturated fatty acids to saturated fatty acids.

The membrane lipid metabolism in horticultural products suffering chilling injury

Horticultural commodities suffer chilling injury following exposure to extremely low temperatures,which results in visible symptoms and considerable quality loss.Therefore,it is of significance to understand the mechanism of this physiological disorder and to develop effective strategies to control it.Chilling stress causes alteration in structure and function of the plasma membrane,which is assumed to be the primary event in response to cold stress.During this process,the membrane lipid metabolism plays a pivotal role in membrane fluidity and stability.In this review,we summarized the possible roles of membrane lipid metabolism in the development of chilling injury,having the potential for developing effective strategies to alleviate chilling injury in horticultural products under refrigerated storage in practice.

Transcriptome and genome analysis to identify C2H2 genes participating in low-temperature conditioning-alleviated postharvest chilling injury of peach fruit

Objectives:This work intended to identify candidate C2H2 genes participating in low-temperature conditioning(LTC)-alleviated postharvest chilling injury of peach fruit.Materials and Methods:For LTC treatment,fruit were pre-stored at 10℃for 5 d and then transferred to 0℃storage.Fruit firmness was measured by a hardness tester.H_(2)O_(2)content was determined by luminosity measurement model using a multifunctional enzyme labeler.Identification of C2H2 family members was performed by HMMSCAN according to peach genome.The cis-acting element of gene promoters was analyzed using the Plant CARE website.Weighted gene coexpression network analysis(WGCNA)was performed by the WGCNA package in the BMK Cloud platform.Results:LTC treatment decreased flesh browning rate and H_(2)O_(2)production of‘Beijing No.9’peach.Transcription factor identification of differentially expressed genes in 0℃and the LTC treatment indicated that peach C2H2 participated in the regulation of chilling injury.A total of 47 C2H2 genes were identified based on peach genome.Real-time quantitative polymerase chain reaction(qRT-PCR),phylogenetic analysis and promoter cis-acting element analysis revealed that ZFP21 was involved in the regulation of LTC-alleviated chilling injury in peach.WGCNA and dual luciferase assay suggested that ZFP21 participated in LTC-alleviated chilling injury by downregulating the expression of reactive oxygen species-related genes Rboh.Conclusions:Our investigation,based on genome and RNA-seq,revealed that ZFP21 was involved in LTC treatment-alleviated chilling injury of peach fruit.This work is useful for the identification of peach cold tolerance-related genes and the study of C2H2 family in peach.

Melatonin treatment induces chilling tolerance by regulating the contents of polyamine,γ-aminobutyric acid,and proline in cucumber fruit

The mechanism of melatonin(MT)induced chilling tolerance in harvested cucumber fruit was investigated at commercial maturity.In this study,cucumber fruits were treated with 100μmol L^(-1) MT at 4℃ and 90% relative humidity for 15 d of storage.In comparison with the control,cucumber treatment with MT resulted in reduced chilling injury(CI),decreased electrolyte leakage and enhanced firmness.The fruits treated with MT showed higher chlorophyll contents in storage conditions with suppressed chlorophyllase enzyme activity.MT treatment increased arginine decarboxylase(ADC)and ornithine decarboxylase(ODC)enzyme activities.Moreover,enhanced expression of the Cucumis sativus ADC(CsADC)and C.sativus ODC(CsODC)genes resulted in the accumulation of polyamine contents.Similarly,proline levels exhibited higher levels among treated fruits.Meanwhile,the proline synthesizing enzymes △1-pyrroline-5-carboxylate syntheses(P5CS)and ornithine aminotransferase(OAT)were significantly increased,while a catabolic enzyme of proline dehydrogenase(PDH)activity was inhibited by treatment.In addition,MT induced expression of C.sativus OAT(CsOAT)and C.sativus P5CS(CsP5CS)genes.Cucumber fruits treated with MT also exhibited higher γ-aminobutyric acid(GABA)content by enhanced GABA transaminase(GABA-T)and glutamate decarboxylase(GAD)enzyme activities and a higher C.sativus GAD(CsGAD)gene expression.To sum up,the results show that MT treatment enhanced chilling tolerance,which was associated with the regulation of polyamines,as well as proline and γ-aminobutyric acid.

Effects of 1-MCP on proline,polyamine,and nitric oxide metabolism in postharvest peach fruit under chilling stress

Peach(Prunus persica Batsch‘Yuhualu’)fruit are sensitive to chilling injury(CI).Proline,polyamine(PA),and nitric oxide(NO)are important small regulators of various metabolic pathways under chilling stress that mitigate CI.Ethylene is known to promote senescence and CI,while 1-methylcyclopropene(1-MCP)is an antagonist that inhibits the effects of ethylene.However,how1-MCP and ethylene affect proline,PA,and NO levels under chilling stress remains unclear.To address these questions,1-MCP(1μL·L^(−1))and ethylene(1μL·L^(−1))treatments were applied to peach fruit.Fruit were stored at 4°C for 28 d,then moved to 25°C for 3 d immediately after cold storage.Peach fruit exhibited CI symptoms after 7 d of cold storage with enhanced electrolyte leakage and malondialdehyde contents.The 1-MCP treatment significantly(P<0.05)restrained peach CI,and fruit did not exhibit CI symptoms until 14 d of cold storage.Proline and PAs in peach under chilling stress weremostly synthesized from glutamate and arginine,which were catalyzed by1-pyrroline-5-carboxylate synthetase and arginine decarboxylase,respectively.1-MCPtreated fruit exhibited higher proline and PA contents and enhanced chilling tolerance compared to the control,while ethylene-treated fruit had lower proline and PA contents and reduced chilling tolerance.Ethylene-treated fruit,which exhibited more severe CI symptoms compared to the control,had significantly(P<0.05)lower NO contents and NO synthase activities.However,NOmay not be a direct acting factor in 1-MCPinduced chilling tolerance,as 1-MCP-treated fruit had lower NO contents and NO synthase activities compared to the control.In conclusion,proline and PA clearly played direct and important roles in 1-MCP-induced peach chilling tolerance,while NO may not be actively involved.

Effect of Maturity Stage on the Gene Expression of Antioxidative Enzymes in Cucumber (Cucumis sativus L.) Fruits Under Chilling Stress

The gene expression pattems of antioxidative enzymes in cucumber （Cucumis sativus L.） fruits at four different maturity stages, immature （3-8 d after anthesis （DAA）, mature （9-16 DAA）, breaker （17-22 DAA）, and yellow （35-40 DAA）, were determined before and after cold storage at 2℃ for 9 d and after subsequent rewarming at 20℃ for 2 d. The electrolyte leakage and malondialdehyde content in cucumber fruits were increased after cold storage and subsequent rewarming. Increased expressions of peroxidase, ascorbate peroxidase （APX）, and monodehydroascorbate reductase after cold storage played an important role in cucumber fruits to cope with chilling injury. The elevated cyt-superoxide dismutase, catalase, APX and dehydroascorbate reductase after subsequent rewarming in cucumber fruits facilitated the recovery from chilling stress. The highest expression levels of all the seven antioxidative enzyme genes in yellow fruits might be responsible for the enhanced chilling tolerance. Cucumber fruits at earlier developmental stages was more susceptible to chilling stress than those at later stages. The relative higher gene expressions of antioxidative enzymes genes at earlier developmental stages may be the responses to the sever oxidative stress caused by chilling injury.

Postharvest physiological responses of pomegranate fruit (cv. Wonderful) to exogenous putrescine treatment and effects on physico-chemical and phytochemical properties

Pomegranate fruit(cv.Wonderful)were treated with putrescine(1,2 and 3 mmol/L)before storage for 4 months at 5℃ and 95%RH and the effects on postharvest life and quality attributes were studied.Results showed that incidence of physiological disorders such as external decay,husk scald,chilling injury and aril browning increased with progressive storage but treating pomegranate fruit with putrescine reduced incidence of most disorders.Control fruit had higher levels of external decay(1.72%–33.26%),chilling injury(10.53%–38.77%)and scalding(15.04%–100%)with less attractive color during 4 month storage.Variations were observed on other fruit quality parameters although treatment with putrescine at 2 and 3 mmol/L concentration reduced changes in color,total soluble solid,Titratable acidity and ascorbic acid.Sensory parameters were best preserved in fruit treated with 2 mmol/L concentration of putrescine with respect to juiciness and crispness.Treatment of pomegranate fruit with putrescine resulted in improved storability and fruit quality during storage.Therefore,for short term storage,2 mmol/L concentration of putrescine could be recommended for maintaining fruit quality especially in the first two months of storage.However,for longer storage period,a higher concentration is recommended,as 3 mmol/L concentration was the most effective in alleviating disorders and maintaining physico-chemical parameters and sensory attributes during storage in this study.

Distribution Characteristics of Winter Continuous Extreme Low Temperature in China

[Objective] The research aimed to study the distribution characteristics of winter continuous extreme low temperature in China. [Method] Based on the daily minimum temperature data in winter during 1961-2008 in 195 observatories, the continuous extreme low temperature event (cold night) which happened in winter in China and the distribution characteristics of accumulated temperature anomaly in 48 years were analyzed by using the actual probability distribution threshold method. [Result] Besides in Northeast China, Northwest China and Qinghai-Tibet Plateau where the geographical position was northerly, and the altitude was high, the long-time (above 5 d) extreme low temperature event was also easy to happen in the south of Yangtze River, especially in Guizhou, Guangxi, Hunan and so on. The continuous extreme low temperature event in the middle and lower reaches of Yellow River was the least. Started from the metaphase of the 1980s, the frequency trend of continuous extreme low temperature event decreased. But in 1992, 2000 and 2007, the low temperature event which continued above 7 d was more than the average. The accumulated cold in January in 48 years was the strongest. The second one was in February, and the smallest was in December. The accumulated cold in Northeast China and the north of Inner Mongolia was the biggest in December and January. The accumulated cold in the north of Xinjiang was the biggest in February. In the whole winter, the accumulated cold in Qinghai-Tibet Plateau was the smallest. The chilling injury was easier to happen in Guizhou, Guangxi and Hunan than other south areas in December and February. The occurrence probability of chilling injury in most areas of Szechwan Basin, Yunnan and Qinling Mountains in central China was smaller than that in other areas. [Conclusion] The research provided the reference basis for analyzing the influence of chilling injury on the agriculture in China.

Chill injury in the eggs of the migratory locust, Locusta migratoria （Orthoptera： Acrididae）： the time-temperature relationship with high-temperature interruption

Mortality of the overwintering egg of the migratory locust, Locustamigratoria L., was attributed to chill injury because of its occurrence well above the egg' ssupercooling point. In this study, two parameters, upper limit of chill injury zone (ULCIZ) and sumof the injurious temperature (SIT), were used to examine the locust egg's cold hardiness. The valueof ULCIZ for the locust egg is 1.06 ± 0.54℃, and the SIT is -329.7 (hour ? degree). Thesuperoxide dismutase (SOD) and catalase (CAT) activities changed dramatically after cold stress,indicating that oxygen and hydroxide free radicals are probably efficiently detoxified at lowtemperatures. It was suggested that the nature of chill injury in locust egg might be a complex ofmetabolic disorder and a non-proportional decrease in enzymatic reaction and transports, because theLDH activity at low temperature increased significantly and the ATPase activity decreased withprolonged duration of exposure to low temperatures. The results from high temperature interruptionrevealed that the high temperature intervals significantly increased the survival of locust eggs.