Inhibited Ethylene Production Research Articles

Effects of 1-MCP on postharvest physiology and quality of bitter melon (Momordica charantia L.)

Young immature bitter melons were fumigated with 1-MCP at different concentrations (0.5, 5.0 or 50.0μll−1) for 12h, then stored at 20°C and 85–90% relative humidity (RH) to investigate postharvest quality and physiology. According to the visual appearance of bitter melon, we determined the effective concentration of 1-MCP was 5.0μll−1. Furthermore, we demonstrated that the application of 1-MCP inhibited ethylene production and thereby improved fruit quality of bitter melon as reflected from ascorbic acid (AsA) and soluble protein content. In addition, 1-MCP maintained antioxidant enzymes activities such as superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD) of bitter melon at initial stage but suppressed at the subsequent shelf life. Our results suggested that the use of 1-MCP was an effective method to retain postharvest physiology and quality of bitter melon.

Role of putrescine in regulating fruit softening and antioxidative enzyme systems in ‘Samar Bahisht Chaunsa’ mango

The role of putrescine (PUT) in regulating fruit softening, antioxidative enzymes and biochemical changes in fruit quality was investigated during ripening and cold storage of mango (Mangifera indica cv. Samar Bahisht Chaunsa). Fruit were treated with various PUT concentrations (0.0, 0.1, 1.0 and 2.0mM) and were allowed to ripen at 32±2°C for 7 days, or stored at 11±1°C for up to 28 days. Respiration rate and ethylene production were measured daily during ripening and cold storage. Cell wall degrading enzymes such as exo-polygalacturonase (exo-PG), endo-polygalacturonase (endo-PG), pectin esterase (PE), endo-1,4-β-d-glucanase (EGase), antioxidative enzymes including superoxide dismutase (SOD), peroxidase (POX), and catalase (CAT), fruit firmness as well as biochemical fruit quality characteristics were estimated during ripening and cold storage at 2 and 7 day intervals, respectively. PUT treatments reduced respiration rate, ethylene production and maintained higher fruit firmness during ripening as well as cold storage. PUT-treated fruit exhibited significantly suppressed activities of cell wall enzymes (exo-, endo-PG and EGase), but retained higher PE activity during ripening and cold storage. Total phenolic and antioxidant contents were significantly higher in PUT-treated fruit during ripening as well in the cold storage period than in the controls. Activities of antioxidative enzymes (CAT, POX and SOD) were also significantly higher in PUT-treated fruit during ripening as well as cold storage. SSC and SSC:TA were lower in PUT-treated fruit, while TA and ascorbic acid content showed the reverse trend. In conclusion, pre-storage 2.0mM PUT treatment inhibited ethylene production and suppressed the activities of cell wall enzymes, while resulting in higher activities of antioxidative enzymes and maintaining better fruit quality during ripening and cold storage.

Quality deterioration of cut carnation flowers involves in antioxidant systems and energy status

Adenosine triphosphate (ATP) has played an important role in regulating senescence of horticultural crops. The physiological mechanism of exogenous ATP to affect the senescence of cut carnation during vase life was investigated. Fresh cut carnation flowers were treated with distilled water (control), 0.1mM adenosine triphosphate (ATP) or 0.5mM 2,4-dinitrophenol (DNP, an agent for uncoupling oxidative phosphorylation) and then held at 25°C up to nine days. Exogenous ATP supply increased flower size, maintained fresh weight, extended vase life, reduced ethylene production rate and maintained membrane integrity. ATP treatment also reduced activities of phospholipase D (LD) and lipoxygenase (LOX), enhanced activities of superoxide dismutase (SOD) and catalase (CAT) and increased endogenous contents of ATP and adenosine diphosphate (ADP) and energy charge level at the later vase life. In comparison to control, exogenous application of DNP accelerated ethylene production and reduced vase life, increased membrane permeability, MDA content and activities of PLD and LOX and reduced activities of SOD and CAT. Furthermore, contents of ATP and ADP and energy charge level decreased in the DNP-treated flowers during vase life. Thus, exogenous ATP supply could maintain membrane integrity, increase antioxidant system and improve endogenous energy level, thereby suppressing ethylene production and retarding the senescence of cut carnation flower during vase life.

Simultaneous application of ethylene and 1-MCP affects banana ripening features during storage

In order to avoid the ripening blocking effect of 1-MCP (1-methylcyclopropene) on bananas when applied before ethylene commercial treatment, 1-MCP in combination with 'CD ethylene' (ethylene-cyclodextrin complex) was used in gas formulations: 300 nmol mol(-1) 1-MCP + 1200, 2400 or 4800 nmol mol(-1) ethylene (ETH). Control bananas received 1-MCP alone or 4800 nmol mol(-1) ethylene alone or no treatment. Treatments were done on overseas shipped bananas, at 14 °C, 90% relative humidity (RH), for 16 h; the bananas were stored under the same atmospheric conditions. After 4 or 12 days the bananas were commercially treated with 500 µmol mol(-1) ethylene. A 300 nmol mol(-1) 1-MCP treatment significantly blocked banana ripening in terms of physiological and technological parameters, inhibiting ethylene production and respiration, despite the commercial ethylene treatment. The application of 300 nmol mol(-1) 1-MCP + 1200 or 2400 nmol mol(-1) ethylene delayed ripening but with a regular pattern. A 300 nmol mol(-1) 1-MCP + 4800 nmol mol(-1) ethylene application did not delay ripening as did 4800 nmol mol(-1) ethylene treatment. The development of black spots was closely associated with advanced ripening/senescence of fruits. The combined 300 nmol mol(-1) 1-MCP + 1200 or 2400 nmol mol(-1) ethylene treatment appears to be a promising treatment to extend banana storage, following overseas shipping.

Involvement of ethylene in alleviation of Cd toxicity by NaCl in tobacco plants

The possible involvement of ethylene in alleviating cadmium (Cd) toxicity by NaCl was investigated because our previous experiments showed that a low concentration of NaCl could alleviate Cd toxicity of tobacco plants. Tobacco plants exposed to the treatment of a combination of Cd–NaCl exhibited more vigorous growth than did those exposed to the treatment of Cd stress alone, as reflected by greater biomass, longer roots, taller shoots, larger SPAD values and higher photosynthetic rates. The results also indicated that it is Na+, rather than Cl−, that alleviates Cd toxicity. Cd–NaCl treatments enhanced and inhibited ethylene production in roots and in leaves, respectively, in comparison with the plants exposed to Cd alone. However, the exogenous application of ethylene did not improve root growth under Cd exposure, indicating that ethylene is not directly involved in the rooting process. It may be assumed that the addition of NaCl into the solution containing Cd regulates root growth by mediating ethylene synthesis.

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).

Involvement of ethylene biosynthesis and signalling in fruit set and early fruit development in zucchini squash (Cucurbita pepoL.)

BackgroundWe have identified a kind of parthenocarpy in zucchini squash which is associated with an incomplete andromonoecy, i.e. a partial conversion of female into bisexual flowers. Given that andromonoecy in this and other cucurbit species is caused by a reduction of ethylene production in the female flower, the associated parthenocarpic development of the fruit suggested the involvement of ethylene in fruit set and early fruit development.ResultsWe have compared the production of ethylene as well as the expression of 13 ethylene biosynthesis and signalling genes in pollinated and unpollinated ovaries/fruits of two cultivars, one of which is parthenocarpic (Cavili), while the other is non-parthenocarpic (Tosca). In the latter, unpollinated ovaries show an induction of ethylene biosynthesis and ethylene signal transduction pathway genes three days after anthesis, which is concomitant with the initiation of fruit abortion and senescence. Fruit set and early fruit development in pollinated flowers of both cultivars and unpollinated flowers of Cavili is coupled with low ethylene biosynthesis and signalling, which would also explain the partial andromonoecy in the parthenocarpic genotype. The reduction of ethylene production in the ovary cosegregates with parthenocarpy and partial andromonoecy in the selfing progeny of Cavili. Moreover, the induction of ethylene in anthesis (by ethephon treatments) reduced the percentage of bisexual parthenocarpic flowers in Cavili, while the inhibition of ethylene biosynthesis or response (by AVG and STS treatments) induces not only andromonoecy but also the parthenocarpic development of the fruit in both cultivars.ConclusionsResults demonstrate that a reduction of ethylene production or signalling in the zucchini flower is able to induce fruit set and early fruit development, and therefore that ethylene is actively involved in fruit set and early fruit development. Auxin and TIBA treatments, inducing fruit set and early fruit development in this species, also inhibit ethylene production and the expression of ethylene biosynthesis and response genes. A model is presented that discusses the crosstalk between ethylene and auxin in the control of fruit set and early fruit development in zucchini squash.

Postharvest UV-C irradiation inhibits the production of ethylene and the activity of cell wall-degrading enzymes during softening of tomato (Lycopersicon esculentum L.) fruit

Mature green cherry tomato fruit were harvested and treated with ultraviolet-C (UV-C) irradiation at a predetermined dose of 4.2kJm−2 and stored at 18°C for 35 days. The effects of UV-C treatment on firmness, cell wall compositions (pectin and cellulose), cell wall ultra-structure, levels of ethylene production, and activities of cell wall degrading enzymes in the fruit were investigated during storage. Major genes involved in cell wall degradation (PME 2.1, Cel 1, PG cat and Exp 1) were also checked. Fruit firmness was better maintained in UV-C treated fruit corresponding with higher contents of cellulose and acid-soluble pectin. Transmission electron microscopy indicated that UV-C irradiation retarded cell wall disassembly in the pericarp. Ethylene production was significantly inhibited by UV-C treatment. The UV-C treatment also suppressed the transcriptional expression of PME2.1, Cel1, PGcat and Exp1 genes, and inhibited pectin methylesterase (PME; EC 3.1.1.11), polygalacturonase (PG; EC3.2.1.15) and cellulase (EC3.2.1.4) activities during storage. These results suggested that the inhibition of ethylene production, which in turn down-regulated expression of genes encoding cell wall degrading enzymes, might be one of the possible mechanisms of UV-C delaying tomato fruit softening.

UV-C effect on ethylene, polyamines and the regulation of tomato fruit ripening

Molecular responses of tomato fruit harvested at the breaker ripening stage treated with UV-C (3.7kJ/m2) and 1-methylcyclopropene (1-MCP; 2μL/L) both separately and in combination, were evaluated postharvest until fruit reached fully ripe stage. Metabolite content and transcript accumulation of selected genes were examined in both the exocarp and mesocarp tissues of tomato fruit. UV-C radiation induced ethylene production but delayed red color development. As expected, 1-MCP inhibited ethylene production, color development and loss of flesh firmness. UV-C treatment delayed degreening and carotenoid accumulation when compared to control fruit. In addition, polyamine content of UV-C treated fruit was higher than in untreated tomatoes. In general, the studied genes had increased transcript accumulation one day after UV-C treatment and the mesocarp showed higher gene expression than the exocarp. 1-MCP prevented transcript accumulation of almost all genes on either the exocarp or mesocarp one day after treatments. The 1-MCP+UV-C induction of total carotenoid accumulation suggested that UV-C induction of total carotenoid accumulation is a partially ethylene dependent event, since 1-MCP alone inhibited accumulation and UV-C alone induced accumulation. Chlorophyll degradation was also partially ethylene dependent. 1-MCP prevented degradation, but control and UV-C treated fruit had high chlorophyll degradation while 1-MCP+UV-C treated fruit showed chlorophyll degradation higher than in 1-MCP alone and lower than in UV-C alone. The results suggest that UV-C slows down ripening, despite ethylene production stimulation, with molecular changes more pronounced in the mesocarp than the exocarp, and changes limited to phytochemical content, which may be influenced by the increased polyamine content.

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 (1000nLL−1 for 4h 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.

Hydrogen sulfide alleviates hypoxia-induced root tip death in Pisum sativum.

Flooding of soils often results in hypoxic conditions surrounding plant roots, which is a harmful abiotic stress to crops. Hydrogen sulfide (H2S) is a highly diffusible, gaseous molecule that modulates cell signaling and is involved in hypoxia signaling in animal cells. However, there have been no previous studies of H2S in plant cells in response to hypoxia. The effects of H2S on hypoxia-induced root tip death were studied in pea (Pisum sativum) via analysis of endogenous H2S and reactive oxygen species (ROS) levels. The activities of key enzymes involved in antioxidative and H2S metabolic pathways were determined using spectrophotometric assays. Ethylene was measured by gas chromatography. We found that exogenous H2S pretreatment dramatically alleviated hypoxia-induced root tip death by protecting root tip cell membranes from ROS damage induced by hypoxia and by stimulating a quiescence strategy through inhibiting ethylene production. Conversely, root tip death induced by hypoxia was strongly enhanced by inhibition of the key enzymes responsible for endogenous H2S biosynthesis. Our results demonstrated that exogenous H2S pretreatment significantly alleviates hypoxia-induced root tip death in pea seedlings and, therefore, enhances the tolerance of the plant to hypoxic stress.

Effect of One-methylcyclopropene (1-MCP) and chlorine dioxide (ClO2) on preservation of green walnut fruit and kernel traits.

The effect of the ethylene receptor competitor 1-methylcyclopropene (1-MCP) and the legally approved disinfectant chlorine dioxide (ClO2) on preservation of the green walnut fruit during storage was investigated. Green Chinese walnut fruit cv. Xilin No.2 was harvested on commercial maturity and stored at 0-1°C after the fruit was treated by water (control), 80mgL(-1)ClO2 (ClO2), 0.5μL L(-1)1-MCP (1-MCP), or combination treatment of 80mgL(-1) ClO2 with either 0.1μL L(-1) 1-MCP (0.1 1-MCP+ ClO2) or 0.5μL L(-1) 1-MCP (0.5 1-MCP+ ClO2). During storage, respiration, ethylene production, phenolics content, antioxidative activity, weight changes, decay of the fruit and kernel traits of acid value, peroxide value,free fatty were measured. All treatments decreased postharvest respiration intensity in different degrees and inhibited ethylene production peak. ClO2 increased the total phenol and flavonoid content of the green fruit compared with other treatments and the control (P < 0.05), but not did the total antioxidant activity for this treatment. After 42-day storage, ClO2 remained higher fresh weight and lower decay index than control, while 1-MCP increased the fruit decay index. Final acid values of kernel from ClO2, control and 0.1 1-MCP+ ClO2 were not different from their initial values, which from 0.5 1-MCP increased. Final peroxide value for kernel from ClO2 showed no change during storage but increased at least 1.0-fold for other treatments. ClO2 preserved 99.9% of initial free fatty acid, similar to that for the control (99.8%), whereas 0.5 1-MCP preserved only 95.7%. ClO2 is of potential in decay retardation and kernel traits maintenance of green walnut fruit, whereas the 1-MCP has a negative effect for decay control on walnut.

NITRIC OXIDE FUMIGATION DELAYS MANGO FRUIT RIPENING

Hard mature green ‘Kensington Pride’ mango fruit were fumigated with 0, 5, 10, 20 and 40 µL.L−1 NO gas for 2 h and allowed to ripen at ambient temperature (21±1°C) to evaluate its effects on fruit ripening. NO-fumigation treatments significantly (P ≤ 0.05) suppressed ethylene production and respiration rates during fruit ripening. NO treatments (20 and 40 µL.L−1) retarded fruit softening (hand firmness) and delayed fruit ripening by 2-days as compared to all other treatments. NO-fumigated (40 µL.L−1) ripe fruit exhibited significantly higher pulp cohesiveness, springiness and chewiness as compared to all other treatments. NO fumigation retarded fruit color development (visual colour, L*, a*, b*, C*) and delayed the reduction of h° during fruit ripening. The concentrations of SSC, total sugars, glucose and fructose in the ripe fruit were significantly reduced in response to NO treatments. In conclusion, the postharvest fumigation of NO (20 µL.L−1) suppressed climacteric ethylene production, respiration rate, retarded colour development, softening consequently delayed mango fruit ripening.

Effects of acetylsalicylic acid on kiwifruit ethylene biosynthesis and signaling components

The effects of acetylsalicylic acid (ASA) on kiwifruit (Actinidia deliciosa cvs Bruno and Hayward) ethylene biosynthesis and signaling were investigated. Exogenous application of ASA inhibited ethylene production in both whole fruit, and in vitro with flesh discs, and enzymes associated with ethylene biosynthesis (ACS and ACO). The effect of ASA treatment on kiwifruit softening was relatively weak. Combination treatments also had inhibitory effects on fruit ripening, with ASA+C2H4 more effective than C2H4+ASA. In order to evaluate the effects of ASA on ethylene signaling, twenty-four ethylene signaling components (five ethylene receptors, two CTR1 like genes, four EIN3-like genes and thirteen ERF genes) were analyzed at the transcriptional level. The results indicated that ASA treatment generally inhibited ethylene-induced modulation of ethylene receptor genes, and had little effect on softening-related ethylene signaling components, which suggested that ASA inhibits fruit ripening mainly by interfering directly with ethylene biosynthesis and perception. In addition, the ethylene response factors AdERF1, AdERF3 and AdERF12 were characterized as ASA-responsive genes, and their roles in fruit stress response are also discussed.

Ripening behavior and quality of modified atmosphere packed ‘Doyenne du Comice’ pears during cold storage and simulated transit

The effect of MAP on extending storage life and maintaining fruit quality was studied in ‘Doyenne du Comice’ (Pyrus communis L.) pears at Hood River and Medford, Oregon. Control fruit packed in standard perforated polyethylene liners started to show senescent core breakdown and lost the capacity to ripen at 20°C after 4–5 months of cold storage in Hood River and after 5.25–6 months in Medford. LifeSpan® L257 MAP achieved steady-state atmospheres of 15.8% O2+3.7% CO2 in Hood River and 15.7–17.5% O2+3.8–5.7% CO2 in Medford. MAP inhibited ethylene production, ascorbic acid degradation and malondialdehyde accumulation, and extended storage life for up to 6 months with maintenance of fruit flesh firmness (FF) and skin color without commercially unacceptable level of physiological disorders. After 4, 5 and 6 months at −1°C, MAP fruit exhibited climacteric-like patterns of ethylene production and softened to proper texture with desirable eating quality on day 5 during ripening at 20°C. After 6 months at −1°C plus 2 weeks of simulated transit conditions, MAP fruit maintained FF and skin color and had good eating quality at transit temperatures of 2 and 4.5°C (10.1–11.5% O2+4.8–5.2% CO2), but reduced FF substantially and developed internal browning disorder at 7.5 and 20°C (3.2–7.2% O2+7.9–9.5% CO2). The storage life of ‘Doyenne du Comice’ pears with high eating quality could be increased by up to 2 months when packed in MAP as compared with fruit packed in standard perforated polyethylene liners.

Exogenous Spermidine Inhibits Ethylene Production in Leaves of Cucumber Seedlings under NaCl Stress

To examine whether 1 mm of spermidine (Spd) modifies plant ethylene production in response to short-term salt stress, cucumber (Cucumis sativus) seedlings were grown in nutrient solution with or without 75 mm NaCl stress for 3 days, and the leaves were sprayed with 1 mm Spd or water (control). We investigate the effects of the treatments on ethylene production, 1-aminocyclopropane-1-carboxylate (ACC) content, 1-(malonylamino) cycolpvopane-1-carboxylic acid (MACC) content, activities of 1-aminocyclopropane-1-carboxylate synthase (ACS), and 1-aminocyclopropane-1-carboxylate oxidase (ACO) and gene expression of acs2, aco1, and aco2 in the cucumber leaves. The results indicate that ethylene production was increased significantly under salt stress as did ACC and MACC content, the activities of ACS and ACO, and the transcriptional level of acs2, whereas the gene expression of aco1 and aco2 was somewhat decreased. However, exogenous Spd treatment depressed the content of ACC and MACC, ACS activity, and the level of acs2 transcripts in the leaves of salt-stressed cucumber. Although the activity of ACO and gene expressions of aco1 and aco2 increased by Spd, ethylene emission was inhibited. Our results suggest that application of exogenous Spd could reverse salinity-induced ethylene production by inhibiting the transcription and activity of ACS under salt stress. We conclude that exogenous Spd could modify the biosynthesis of ethylene to enhance the tolerance of cucumber seedlings to salt stress.

Xanthomonas Type III Effector XopD Desumoylates Tomato Transcription Factor SlERF4 to Suppress Ethylene Responses and Promote Pathogen Growth

XopD, a type III secretion effector from Xanthomonas euvesicatoria (Xcv), the causal agent of bacterial spot of tomato, is required for pathogen growth and delay of host symptom development. XopD carries a C-terminal SUMO protease domain, a host range determining nonspecific DNA-binding domain and two EAR motifs typically found in repressors of stress-induced transcription. The precise target(s) and mechanism(s) of XopD are obscure. We report that XopD directly targets the tomato ethylene responsive transcription factor SlERF4 to suppress ethylene production, which is required for anti-Xcv immunity and symptom development. SlERF4 expression was required for Xcv ΔxopD-induced ethylene production and ethylene-stimulated immunity. XopD colocalized with SlERF4 in subnuclear foci and catalyzed SUMO1 hydrolysis from lysine 53 of SlERF4, causing SlERF4 destabilization. Mutation of lysine 53 prevented SlERF4 sumoylation, decreased SlERF4 levels, and reduced SlERF4 transcription. These data suggest that XopD desumoylates SlERF4 to repress ethylene-induced transcription required for anti-Xcv immunity.

The Accumulation of Rare Earth Elements Fertilizer and its Subsequent Effects on Apple Fruit Quality at Harvest and During Storage

Rare earth elements fertilizer and Ca were sprayed on eight-year-old ‘Fuji’/M.9 apple trees during two consecutive seasons, and fruit quality was quantified at harvest and 5-month long storing in a commercial cooling house at 4℃ and 80~85% RH. In the first season, single-sprayed of rare earth elements fertilizer showed appreciable accumulations of its elements (La, Pr, Gd, and Nd) in the fruit. In the following season, application of higher doses accumulated higher amount, indicating that the accumulation of rare earth elements was dose-dependent. However, rare earth elements did not affect the accumulations of Ca, Mg, and K in ‘Fuji’ apple fruit showed that there was no interaction between rare earth elements and these macronutrients. Double-spray of 0.2% rare earth elements increased fruit redness at harvest and had exhibited better color. Although at harvest it did not show significant effects on fruit weight, pulp firmness and titratable acidity (TA), but had pronounced effects on inhibiting fruit softness and retarded decrease of TA during storing. Furthermore, it reduced respiration rate and inhibited ethylene production during storing indicated that rare earth elements may be an alternative for prolonging the shelf life of ‘Fuji’/M.9 apple fruit.

Effects of alginate edible coating on preserving fruit quality in four plum cultivars during postharvest storage

Four plum (Prunus salicina Lindl.) cultivars (“Blackamber”, “Larry Ann”, “Golden Globe” and “Songold”), were treated with 1 or 3% alginate as an edible coating before storage. Analytical determinations were made after 7, 14, 21, 28 and 35 days at 2°C and after a 3 day period at 20°C (shelf-life). Both treatments were effective in inhibiting ethylene production for all cultivars, especially when 3% alginate was used. The changes in fruit quality parameters related to plum postharvest ripening, such as weight and acidity losses, softening and colour changes, were significantly delayed by the use of both edible coatings. The delay of the ripening process was also related to lower anthocyanin and carotenoid accumulation. Overall results suggest that these treatments could increase the plum storage period with optimum quality, 2 weeks for “Larry Ann” and “Songold” and 3 weeks for “Blackamber” and “Golden Globe” more than controls.

Pyridine 2,4-Dicarboxylate Downregulates Ethylene Production in Response to Mechanical Wounding in Excised Mature Green Tomato Pericarp Discs

Pyridine 2,4-dicarboxylate (PDCA) is a structural analog of 2-oxoglutarate and a potent inhibitor of 2-oxoacid-dependent dioxygenases (2-ODDs), such as prolyl 4-hydroxylases (P4Hs). It has been reported that PDCA inhibited the in vitro activity of P4Hs in cut carnation flowers and delayed petal senescence due to suppression of climacteric ethylene production. In this study, the effect of PDCA on ethylene evolution in response to mechanical wounding due to excision of mature green tomato pericarp discs was investigated. Ethylene evolution was induced within 1 h of mechanical wounding in control discs and gradually increased throughout 24 h, whereas it was partially suppressed in PDCA-treated discs during the first 12 h of a 24-h experimental period. This transient, partial suppression of ethylene production can be attributed to the lack of induction and the downregulation of ethylene biosynthetic genes within 1 h and after 12 h of wounding, respectively. However, it cannot be attributed to the suppression of ACC oxidase, a well-known 2-ODD, because no significant change in enzymatic activity was observed in PDCA-treated discs. In addition, the transcript abundance of wound-induced and ethylene-regulated PIN1, PIN2, and E4 genes was also partially suppressed in PDCA-treated discs. PDCA was also shown to be involved in ethylene evolution and color development of mature green and turning fruit discs. Overall, these results indicate that PDCA downregulates ethylene production in response to mechanical wounding and during ripening of preclimacteric and climacteric tomato fruit discs.