Nitric oxide participates in the regulation of LeCBF1 gene expression and improves cold tolerance in harvested tomato fruit

Nitric oxide (NO) is an important signal molecule involved in numerous plant responses to biotic and abiotic stress. C-repeat/dehydration-responsive element (CRT/DRE)-binding factors (CBFs) play a prominent role in cold response regulation. To investigate the relationship between NO and the CBF pathway during cold stress, tomato (Solanum lycopersicum cv. Lichun) fruit were treated with the NO donor (sodium nitroprusside, SNP) and nitric oxide synthase (NOS) inhibitor (N (omega)-nitro-l-arginine, l-NNA) before storage at 2 °C. Treatment with 0.02 mM SNP decreased the chilling injury (CI) index, whereas l-NNA treatment increased the appearance of chilling symptoms. NO content in fruit following SNP treatment was higher, while malondialdehyde (MDA) content and ion leakage were lower than that in water- and l-NNA-treated fruit. The relative expression of LeCBF1, measured by q-RTPCR, in SNP-treated fruit was higher than that in l-NNA-treated and control fruit after cold storage for 0.5 and 4 h. These results suggest that SNP treatment protects tomatoes from cold injury by inducing NO accumulation and expression of LeCBF1. NOS activity may play a role in NO accumulation associated with cold tolerance.     

Postharvest application of gum arabic and essential oils for controlling anthracnose and quality of banana and papaya during cold storage

Management of anthracnose caused by Colletotrichum spp. is the most important issue for the tropical fruit industry because of resulting financial losses. Antifungal effects of gum arabic (GA) (10%), lemongrass oil (LG) (0.05%), cinnamon oil (CM) (0.4%), and their combinations were investigated in vitro and in vivo for controlling postharvest anthracnose of banana and papaya. LG at 0.05% and 0.4% CM showed fungicidal effects against Colletotrichum musae and Colletotrichum gloeosporioides, causal organisms of banana and papaya anthracnose, respectively. GA alone did not show any fungicidal effects while the combination of 0.05% LG and 0.4% CM with Ten percent GA alone showed more fungicidal effects. However, potato dextrose agar (PDA) medium modified with 10% GA combined with 0.4% CM showed the most promising results among all treatments against C. musae and C. gloeosporioides in suppressing the mycelial growth (73.4%) and (70.0%) and spore germination inhibition (88%) and (85%), respectively. In vivo studies also revealed that 10% GA combined with 0.4% CM was the optimal concentration in controlling decay (80%) and (71%), showing a synergistic effect in the reduction of C. musae and C. gloeosporioides, respectively, in artificially inoculated bananas and papayas. The results regarding quality evaluation also confirmed the efficacy of 10% GA combined with 0.4% CM coatings since ripening was significantly delayed, in terms of percentage weight loss, fruit firmness, soluble solids concentration and titratable acidity. The results suggest the possibility of using 10% gum arabic combined with 0.4% cinnamon oil as a biofungicide for controlling postharvest anthracnose in major tropical fruit such as banana and papaya.     

A review on adaptation of banana (Musa spp.) to cold in subtropics

Global production of bananais adversely affected by abiotic stresses, namely, drought, salinity and low temperature which cause changes in morphology, anatomy, physiology and biochemical metabolism in plant. Different banana cultivars respond differently when grown in subtropical regions due to changes in temperature mainly at the time of flowering and fruiting. The subtropical regions persist cold in winter which become a major constraint for proper growth and development of banana. Only few cultivars are identified for cold tolerance. The cold tolerance is a complex phenomenon, involving numbers of interrelated metabolic pathways. With the onset of cold, growth decrease through alteration in the synthesis of metabolites which are regulated by expression of genes and their interactions. Recently, complete genome sequencing, mutation and transgenesis provided deep insight into the complex mechanism of cold tolerance in banana. In this review, efforts are made to compile the findings and to interpret the better application of technologies in understanding the cold tolerance which may assist in banana breeding.     

Effects of cinnamon extract,chitosan coating,hot water treatment and their combinations on crown rot disease and quality of banana fruit

The antifungal activities of cinnamon extract (CE), piper extract (PE) and garlic extract (GE) were evaluated on banana crown rot fungi (Colletotrichum musae, Fusarium spp. and Lasiodiplodia theobromae) in vitro. The assay was conducted with extracts of CE, PE and GE with concentrations of 0, 0.1, 0.5, 1.0, 5.0, 10.0 and 0.75 g L⁻¹ of carbendazim (CBZ) on potato dextrose agar at room temperature. CE completely inhibited conidial germination and mycelial growth of all fungi at 5.0 g L⁻¹. PE totally suppressed mycelial growth of all fungi at 5.0 g L⁻¹ and conidial germination at 10.0 g L⁻¹ except for Fusarium spp. GE had no significant effects but low concentrations (0.1 and 0.5 g L⁻¹) enhanced germ tube elongation of the three fungi. The ED₅₀ values were higher for mycelial growth than for conidia except for Fusarium spp. Combined treatments were investigated on crown rot development in banana fruit (Musa AAA group ‘Kluai Hom thong’). Treatments included 5.0 g L⁻¹ CE, 1% (w/v) chitosan solution, hot water treatment (HWT, 45 °C for 20 min), CE plus chitosan, CE plus HWT and 0.75 g L⁻¹ of CBZ, applied before and after inoculation of the fruit. Crown rot development was assessed during storage at 13 °C for 7 weeks. Disease development was least (25%) on CE treated fruit after inoculation compared to CBZ but was higher when CE was applied before inoculation. Chitosan significantly delayed ripening as in terms of peel color, firmness, soluble solids and disease severity. CE showed no negative effects on quality of fruit. CE plus HWT caused unacceptable peel browning.     

Effect of oxalic acid on ripening attributes of banana fruit during storage

The effect of exogenous oxalic acid treatment on ripening attributes of banana fruit during storage was investigated. Banana fruit were dipped into solutions of 0 (control) or 20 mM oxalic acid for 10 min and then stored at room temperature (23 ± 2 °C) and 75–90% relative humidity. The application of oxalic acid reduced fruit deterioration during storage. The oxalic acid treatment also reduced the rates of respiration and ethylene production, and delayed the decreases in firmness, hue angle, and maximal chlorophyll fluorescence (Fv/Fm) of banana fruit during storage. Furthermore, fruit treated with oxalic acid exhibited higher superoxide dismutase activity and antioxidant capability with a lower production of reactive oxygen species at the late storage period compared with non-oxalic acid-treated fruit. Overall, the oxalic acid treatment was effective in inhibiting postharvest ripening of banana fruit and exhibited the potential for commercial application to store the bananas at room temperature. It can be concluded that the delay in banana fruit ripening associated with oxalic acid treatment could be due to inhibition of respiration and ethylene production rates, and reduction of oxidative injury caused by reactive oxygen species through increased antioxidant activity.     

Molecular characterization of two banana ethylene signaling component MaEBFs during fruit ripening

EIN3 Binding F-box protein (EBF) is an essential signaling component necessary for ethylene response. However, little information is available on EBF genes during banana fruit ripening. Two EBF genes designated MaEBF1 and MaEBF2 were isolated and characterized from banana fruit. Subcellular localization analysis showed that MaEBF1 and MaEBF2 were both nuclear proteins. Expression of MaEBF1 and MaEBF2 in fruit with four ripening characteristics revealed that MaEBF2 was enhanced by ethylene during fruit ripening, while MaEBF1 changed only slightly. Moreover, the MaEBF2 promoter was activated after ethylene treatment, further supporting its involvement in fruit ripening. More importantly, MaEBF2 was shown to physically interact with MaEIL5, using yeast two-hybrid (Y2H) and bimolecular fluorescence complementation (BiFC) assays. Together, these results suggest that MaEBF may be involved in banana fruit ripening, at least partly via interaction with MaEIL5. Our findings expand our understanding of the regulatory network of ethylene signaling cascade in banana fruit ripening.     

Low temperature induced changes in activity and protein levels of the enzymes associated to conversion of starch to sucrose in banana fruit

Storage at low temperature is the most frequently used method to extend the shelf life of banana fruit, and is fundamental for extended storage and transport over long distances. However, storage and transport conditions must be carefully controlled because of the high susceptibility of many commercial cultivars to chilling injury. The physiological behavior of bananas at low temperatures has been studied to identify possible mechanisms of resistance to chilling injury. The aim of this work was to evaluate differences in the starch-to-sucrose metabolism of a less tolerant and susceptible (Musa acuminata, AAA cv. Nanicão) and a more tolerant (M. acuminata × Musa balbusiana, AAB, cv. Prata) banana cultivar to chilling injury. Fruits of these cultivars were stored in chambers at 13 °C for 15 d, at which point they were transferred to 19 °C, where they were left until complete ripening. The low temperature induced significant changes in the metabolism of starch and sucrose in comparison to fruit ripened only at 19 °C. The sucrose accumulation was slightly higher in cv. Prata, and different patterns of starch degradation, sucrose synthesis, activity and protein levels of the α- and β-amylases, starch phosphorylase, sucrose synthase and sucrose phosphate synthase were detected between the cultivars. Our results suggest that starch-to-sucrose metabolism is likely part of the mechanism for cold acclimation in banana fruit, and the cultivar-dependent differences contribute to their ability to tolerate cold temperatures.     

The role of active oxygen metabolism in hydrogen peroxide-induced pericarp browning of harvested longan fruit

Effects of hydrogen peroxide (H₂O₂), as exogenous reactive oxygen, on browning and active oxygen metabolism in pericarp of harvested ‘Fuyan’ longan fruit were investigated. The results showed that as compared with the control fruit, there was a higher browning index in pericarp of H₂O₂-treated fruit. The fruit treated with H₂O₂ resulted in increased rate of superoxide anion (O₂⁻) production, reduced activities of superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (APX), decreased amounts of ascorbic acid (AsA), glutathione (GSH) and carotenoid, and increased malondialdehyde (MDA) content. These results indicated that H₂O₂-induced browning in pericarp of harvested longan fruit might be due to a reducing capacity of active oxygen scavenging and an increase of accumulation of O₂⁻, which might stimulate membrane lipid peroxidation, disrupt cellular membrane structure, and cause the loss of cellular compartmentalization, in turn, resulting in the contact of polyphenol oxidase (PPO) and peroxidase (POD) with phenolic substrates and subsequently oxidation phenolics to form brown polymers.     

Phomopsis longanae Chi-induced pericarp browning and disease development of harvested longan fruit in association with energy status

The effects of Phomopsis longanae Chi infection on browning development and disease incidence in relation to energy status in pericarp of harvested longan fruit were investigated. Longan fruit were inoculated for 5 min with P. longanae at 10⁴ spores mL⁻¹, while fruit dipped in sterile deionized water were used as control. These fruits were stored at (28 ± 1) °C and 90% relative humidity for up to five days. The results showed that the browning index, disease incidence, cellular membrane permeability and AMP content increased but the contents of ATP and ADP, and energy charge decreased in pericarp of longan fruit infected by P. longanae. It was suggested that P. longanae infection caused energy deficiency in longan fruit, possibly resulting in accelerated senescence and decreased resistance to pathogen, and thus promoted browning development and disease occurrence.     

A novel technique using 1-MCP microbubbles for delaying postharvest ripening of banana fruit

This study aimed to investigate the application of microbubble technology for delaying banana ripening. A preparation of 1-MCP designed for use as a form of aqueous micro bubble (MBs) solutions was formulated. Banana fruit were immersed in 500 nL L⁻¹ of aqueous 1-MCP microbubbles (1-MCP-MBs) or fumigated with 500 nL L⁻¹ 1-MCP, then stored at 25 °C for 8 days. 1-MCP-MBs were more effective in delaying postharvest ripening than conventional 1-MCP fumigation. 1-MCP-MBs reduced the respiration rate and ethylene production compared to the control and 1-MCP fumigated fruit. Moreover, 1-MCP-MBs delayed yellowing and maintained firmness of banana fruit during storage. These results indicate that 1-MCP-MBs can be used as an alternative method for delaying the postharvest ripening of banana fruit, and its application for other commodities needs to be further elucidated.     

Effect of adenosine triphosphate on changes of fatty acids in harvested litchi fruit infected by Peronophythora litchii

Recent investigations have shown that disease development of harvested horticultural crops may be attributed to a limited availability of energy or low energy production. In this study, litchi fruit were treated with 1.0 mM adenosine triphosphate (ATP) or 0.5 mM 2,4-dinitrophenol (DNP) and then half of the ATP-treated fruit were inoculated with Peronophythora litchii. The composition and contents of fatty acids (FAs) and esterase activity in litchi fruit during storage were investigated. Free fatty acids (FFAs) in all fruit increased over storage, especially in the P. litchii-inoculated fruit. In particular, the content of saturated FAs increased faster than unsaturated FAs. In polar lipids (PL), a decrease in the amount of C18:3 and an increase in the amount of C16:0 or C18:0 was found during storage, while the proportions of C16:0, C18:0 and C18:1 in neutral lipid (NL) gradually increased but the proportions of C18:3 decreased during storage. The proportion of C18:2 increased within the first four days and then decreased. Exogenous ATP treatment suppressed the release of FFAs and increased the contents of each FA in PL, indicating a slower hydrolysis of lipids. ATP treatment also delayed the increase in the proportion of C18:0 in NL. Further analysis showed that the double bond index (DBI) of litchi fruit decreased in all fractions of FAs and ATP treatment can slow the decrease in DBI. In addition, lower esterase enzyme activity was detected in all ATP-treated fruit. Treatment with DNP (a respiration uncoupler) increased esterase activity. P. litchii-inoculated fruit after ATP treatment also exhibited similar trends in delaying the release of FFAs. Enhanced disease resistance of litchi fruit by ATP could involve the levels of FAs and esterase activity.     

不同浓度臭氧对皖翠猕猴桃冷藏过程中品质和生理的影响

采用不同浓度的臭氧(10.7、42.8、171.2 mg/m3)定期处理皖翠猕猴桃果实,研究在冷藏(2±1℃)条件下其品质和后熟生理生化的变化。结果表明:较低浓度的臭氧(10.7 mg/m3)处理能显著抑制猕猴桃果实的呼吸强度,降低腐烂率,延缓丙二醛(MDA)含量和相对电导率的上升,维持较高的超氧化物歧化酶(SOD)和过氧化物酶(POD)活性,保持良好的贮藏品质,皖翠猕猴桃冷藏140 d时的好果率可达95%。较高浓度的臭氧(171.2 mg/m3)处理则加速猕猴桃果实呼吸高峰出现的时间,贮藏中后期果实腐烂率、MDA含量和相对电导率快速上升,SOD和POD活性下降,从而加快果实的衰老进程。臭氧处理浓度越高对猕猴桃的贮藏品质和后熟生理损害越大。     

The effect of dialkylamine compounds and related derivatives of 1-methylcyclopropene in counteracting ethylene responses in banana fruit

Compounds that can block the ethylene receptor and be applied either as a gas or as a salt by spray or dip have been prepared and tested. Cyclopropenes with a methyl group in the 1-position, on which was attached a substituted amine, were allowed to evaporate in the presence of bananas that were treated with the gas. The minimum amount of a given compound required to inhibit chlorophyll degradation in the banana peel (an indicator of protective effect of the compound against ethylene action) that was subsequently exposed to ethylene, varied considerably depending on the compound, but N,N-dipropyl-(1-cyclopropenylmethyl)amine and N,N-di-(1-cyclopropenylmethyl)amine were the most effective. The degree of response to the ethylene inhibitory effect was similar for all of the compounds tested (32–34 d). The amount of cyclopropene compound required for inhibiting ethylene action following a 24 h exposure of bananas to the salt followed by a 15 h exposure to ethylene was higher than that required by the gas form used under the same conditions for the same effect. However, time of exposure could be much longer than 24 h with the salt than with the gas. The bananas treated with the salt do not need to be in an air-tight container, but could be used in open spaces. Only the banana peel appeared to be protected against ethylene during the 24 h interval when the salt was used. The pulp ripened upon exposure to ethylene.     

Apparent synergism between the positive effects of 1-MCP and modified atmosphere on storage life of banana fruit

Fruit of cv. Gros Michel banana were treated with 1-MCP (1000 nL L⁻¹ for 4 h at 25 °C) and then packed in non-perforated polyethylene (PE) bags for modified atmosphere storage (MAP). The bags were placed in corrugated cardboard boxes and stored at 14 °C. Fruit were removed from cool storage and ripened at room temperature using ethephon. The length of storage life was determined by the change in peel color to yellow, after this ethephon treatment. Fruit treated with 1-MCP + MAP had a storage life of 100 days. The storage life of control fruit (no 1-MCP and no MAP) was 20 days. Fruit held in PE bags without 1-MCP treatment had a 40 day storage life, and the same was found in fruit treated with 1-MCP but without PE bags. 1-MCP is an inhibitor of ethylene action, but also inhibited ethylene production, mainly through inhibition of ACC oxidase activity in the peel. MAP inhibited ethylene production mainly through inhibition of ACC oxidase, both in the peel and pulp. The combination of 1-MCP treatment and MAP storage resulted in much lower ethylene production due to inhibition of both ACC synthase and ACC oxidase activity.     

Respiration and quality responses of sweet cherry to different atmospheres during cold storage and shipping

Most sweet cherries produced in the US Pacific Northwest and shipped to distant markets are often in storage and transit for over 3 weeks. The objectives of this research were to study the effects of sweet cherry storage O₂ and CO₂ concentrations on the respiratory physiology and the efficacy of modified atmosphere packaging (MAP) on extending shelf life. Oxygen depletion and CO₂ formation by ‘Bing’ and ‘Sweetheart’ cherry fruit were measured. While respiration rate was inhibited linearly by reduced O₂ concentration from 21% to 3–4% at 20 °C, it was affected very little from 21% to ∼10% but declined logarithmically from ∼10% to ∼1% at 0 °C. Estimated fermentation induction points determined by a specific increased respiratory quotient were less than 1% and 3–4% O₂ for both cultivars at 0 and 20 °C, respectively. ‘Bing’ and ‘Sweetheart’ cherry fruits were packaged (∼8 kg/box) in 5 different commercial MAP box liners and a standard macro-perforated polyethylene box liner (as control) and stored at 0 °C for 6 weeks. MAP liners that equilibrated with atmospheres of 1.8–8.0% O₂ + 7.3–10.3% CO₂ reduced fruit respiration rate, maintained higher titratable acidity (TA) and flavor compared to control fruit after 4 and 6 weeks of cold storage. In contrast, MAP liners that equilibrated with atmospheres of 9.9–14.4% O₂ + 5.7–12.9% CO₂ had little effect on inhibiting respiration rate and TA loss and maintaining flavor during cold storage. All five MAP liners maintained higher fruit firmness (FF) compared to control fruit after 6 weeks of cold storage. In conclusion, storage atmospheres of 1.8–14.4% O₂ + 5.7–12.9% CO₂ generated by commercial MAP, maintained higher FF, but only the MAP with lower O₂ permeability (i.e., equilibrated at 1.8–8.0% O₂) maintained flavor of sweet cherries compared to the standard macro-perforated liners at 0 °C. MAP with appropriate gas permeability (i.e., equilibrated at 5–8% O₂ at 0 °C) may be suitable for commercial application to maintain flavor without damaging the fruit through fermentation, even if temperature fluctuations, common in commercial storage and shipping, do occur.     

Effect of atmospheric modification, 1-MCP and chemicals on quality of fresh-cut banana

Fresh-cut banana slices have a short shelf-life due to fast browning and softening after processing. The effects of atmospheric modification, exposure to 1-MCP, and chemical dips on the quality of fresh-cut bananas were determined. Low levels of O₂ (2 and 4 kPa) and high levels of CO₂ (5 and 10 kPa), alone or in combination, did not prevent browning and softening of fresh-cut banana slices. Softening and respiration rates were decreased in response to 1-MCP treatment (1 μL L⁻¹ for 6 h at 14 °C) of fresh-cut banana slices (after processing), but their ethylene production and browning rates were not influenced. A 2-min dip in a mixture of 1% (w/v) CaCl₂ + 1% (w/v) ascorbic acid + 0.5% (w/v) cysteine effectively prevented browning and softening of the slices for 6 days at 5 °C. Dips in less than 0.5% cysteine promoted pinking of fresh-cut banana slices, while concentrations between 0.5 and 1.0% cysteine delayed browning and softening and extended the post-cutting life to 7 days at 5 °C.