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1.
In this work, Metschnikowia pulcherrima Disva 267, Wickerhamomyces anomalus Disva 2, and Saccharomyces cerevisiae Disva 599 yeast strains were evaluated for their biocontrol activity on postharvest decay brown rot, mainly caused by Monilinia laxa on sweet cherries, using three increasing concentrations (106, 107 and 108 CFU/mL). M. pulcherrima significantly reduced brown rot incidence, severity and McKinney index at all three concentrations, W. anomalus was effective at the concentration of 107 CFU/mL, and S. cerevisiae reduced brown rot only at 108 CFU/mL. M. pulcherrima and W. anomalus survived on the surface of sweet cherries during 2 weeks cold storage. When the three yeasts were sprayed on the canopy of sweet cherry trees at 107 CFU/mL, M. pulcherrima and W. anomalus showed good survival and colonization. In contrast, under the same conditions, S. cerevisiae strain did not survive. None of the yeasts produced phytotoxic substances, both on intact and on wound-inoculated fruit. Therefore, M. pulcherrima Disva 267 and W. anomalus Disva 2 could be promising biocontrol agents, able to survive in field and storage environments, providing a clear decrease in postharvest decay. However, further investigations with large scale trials are needed to lead to a possible formulation and commercial use.  相似文献   

2.
The immersion of sweet cherry fruit in Pichia membranefaciens at a concentration of 5 × 107 cells ml−1 or in salicyclic acid (SA) at 0.5 mM for 10 min reduced the incidence of decay and lesion size caused by Penicillium expansum. Without pathogen inoculation, peroxidase (POD) activity was enhanced in yeast-treated fruit, but activities of catalase (CAT) and superoxide dismutase (SOD) showed a decrease in the same fruit. SA-treatment significantly inhibited CAT activity, but stimulated SOD and POD activities. After inoculation with P. expansum, CAT activity decreased and SOD activity increased in both yeast- and SA-treated fruit. No obvious difference was found in POD activity between treatments and water control. Treatments with yeast and SA changed the expression of POD isozymes. In addition, yeast and SA treatment increased total protein content of sweet cherry and up-regulated 33 and 47 kDa protein bands shown by SDS-PAGE. These results indicated that yeast- and SA-treatments induced synthesis of anti-oxidant enzymes and specific proteins, which may play a role in the resistance against postharvest blue mold.  相似文献   

3.
The effect of ultraviolet-B (UV-B) light treatment on total soluble phenolic (TSP) contents of various whole and fresh-cut specialty crops was evaluated. Whole fruits (strawberries, blueberries, grapes), vegetables (cherry tomatoes, white sweet corn) and root crops (sweet potatoes, colored potatoes), and fresh-cut fruit, vegetables and root crops (apple wedge, iceberg lettuce, broccoli floret and stem, and sliced radish, daikon, and parsnip) were treated with increasing UV-B dose levels (1.3–5.9 kJ m−2) and followed by incubation to allow for the samples to respond. TSP levels were measured. The changes in TSP were species-dependent. Whole grapes, blueberries, pink and red cherry tomatoes, white sweet corn, colored potatoes and sweet potatoes did not benefit from UV-B exposure. Strawberries showed a slight, but significant increase in TSP at the highest UV-B dose. UV-B exposure did not affect TSP of apple wedge, broccoli floret and stem, sliced radish and daikon after incubation. Fresh-cut lettuce and parsnip showed significant 1.2 and 2.3 times increase, respectively, in TSP mostly due to the combination effect of wounding and UV-B light exposure after 3 d of incubation. UV-B light exposure (1.3–5.9 kJ m−2) can be used as an additional processing step on selected specialty crops to enhance their soluble phenolic contents.  相似文献   

4.
Control of primary postharvest diseases caused by Rhizopus stolonifer, Botrytis cinerea, and Penicillium expansum on a variety of fresh fruit was evaluated with an invert emulsion formulation of Trichoderma harzianum. Diseases evaluated were quantified by the period of protection conferred by the antagonist and the diameter of decay lesions. Treatment of the various fruit species with formulated T. harzianum conidia in an invert emulsion significantly (P ≤ 0.05) reduced the mean lesion diameters of R. stolonifer on apple, pear, peach and strawberry, B. cinerea on grape, pear, strawberry, and kiwifruit, and P. expansum on grape, pear, and kiwifruit in comparison with the control treatment. Significant differences (P ≤ 0.05) were obtained in the mean percent reduction in lesion diameter caused by the same postharvest pathogens on the same fruit species due to the treatment with the formulated T. harzianum conidia relative to control treatment. The greatest mean percent reduction (86.7%) was obtained on apple fruit for the infection with R. stolonifer. Significant differences (P ≤ 0.05) were also obtained in the mean durations of the minimum protection period due to treatment with the formulated T. harzianum against the infection with the same postharvest pathogens on the same fruit species. The longest mean duration of the minimum protection period (up to 59 days) was obtained for unwounded apple fruit against the infection with R. stolonifer. Overall, the results indicate that the treatment with the invert emulsion formulation of T. harzianum protected fruit from infection by the primary postharvest pathogens of the fruit tested for up to 2 months and reduced the diameters of decay lesion up to 86% and is a promising treatment to prolong the postharvest shelf-life of fresh fruit.  相似文献   

5.
UV-C inactivation kinetic data of Penicillium expansum on intact and wounded pear disks were determined. P. expansum conidia (0.5 mL, 1.6 × 107 CFU/mL) were spot inoculated onto intact and wounded pear tissue with skin (excised disks), treated with UV-C doses ranging 0.101–3.06 kJ/m2 at 23 °C and surviving conidia were enumerated. Changes in selected physicochemical parameters and sensory quality following UV-C treatment of whole pears were determined immediately after treatment, and 4 and 8 weeks of storage at 4 °C. A greater UV-C intensity was required for similar inactivation levels of P. expansum populations on wounded pear disks (3.1 kJ/m2 for 2.7 log reduction) compared to intact pear disks (1.7 kJ/m2 for 2.8 log reduction). No significant difference in % weight loss, or soluble solids content and texture was observed between UV-C treated and untreated pears. However, browning was observed on UV-C treated pear surfaces after 4 and 8 weeks along with changes in flavor and texture. An increase in consumer preference was noticed for the untreated control pears after 4 weeks storage.  相似文献   

6.
The feasibility of non-destructive estimation of internal ethylene concentration (IEC) in apple fruit via fruit reflectance using recently developed approaches and a fiber-optics reflectometer was investigated. The relationships between IEC and fruit reflectance in the 400–800 nm range were studied in stored apple (Malus × domestica Borkh., cv. Antonovka) fruit. A strong correlation between IEC and optical reflectance spectra taken from sunlit surfaces of the fruit was detected whereas reflectance of the shaded fruit surface showed a weak correlation with IEC. The increase of the reflectance in the red occurred along with IEC build-up during ripening resulting a strong (r2 > 0.80) correlation. By contrast, reflectance in the blue-green part of the spectrum remained low and was negatively (r2 ≈ 0.65) correlated with IEC. These observations are consistent with the phenomenon of degradation of chlorophylls which often occurs in parallel with the retention of carotenoids in ripening apple skin. As a result, IEC showed a significant correlation (r2 > 0.69; P < 0.001) with the index based on reflectances in the red and blue-green regions of the spectrum (R678 ? R480)/R800. The effects of strong solar light on the relationships between IEC and fruit reflectance are considered. The possibilities and limitations of a non-destructive reflectance-based assay of IEC in apple fruit are discussed.  相似文献   

7.
A UV-C treatment system (two treatment chambers connected by an inclined belt to rotate apricots between chambers) was tested in a commercial setting. Escherichia coli ATCC 25922, used as a surrogate for E. coli O157:H7 to determine the system's antimicrobial efficacy, was inoculated onto fruit surfaces at a population of 6.8 log CFU/fruit. UV-C dosage was evaluated by attaching film dosimeters to six fixed locations on each apricot. Results suggested that reduction of inoculated E. coli ATCC 25922 populations on the apricot fruit by UV-C treatment was small (only 0.5–0.7 logs). There were large variations in UV-C doses among varying apricot surface locations. Approximately 1/3 of apricots had individual surfaces receiving less than 0.2 kJ m−2 UV-C exposure, even though fruit received, on average, more than 1 kJ m−2. Low reductions of E. coli may be attributed, in part, to non-uniform UV-C exposure. This study demonstrates the need to use a fruit rotation device more capable of delivering uniform UV-C dosage to the surface of apricots for inactivating bacteria in a commercial setting.  相似文献   

8.
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9.
The development of red color in the peel of red Chinese sand pears (Pyrus pyrifolia Nakai) is influenced by temperature and light; however, the response patterns vary among different cultivars. In this study, we systematically investigated the influence of postharvest treatment with various temperatures (low, high, variant and constant) on detached mature fruit of red Chinese sand pear ‘Mantianhong’ and ‘Meirensu’. Fruit of red apple (Malus domestica Borkh.) ‘Royal Gala’ and red European pear (P. communis L.) ‘Cascade’ received the same treatments for comparison. Furthermore, the effects of light quality and irradiance level on ‘Mantianhong’ pears were evaluated at the optimum temperature for anthocyanin accumulation. Fruit firmness and concentrations of total soluble sugars and organic acids were measured to determine fruit quality. The effect of temperature on red Chinese sand pear fruit color was similar to that of apples, but not European pear. Moreover, low temperature more effectively induced red coloration in ‘Mantianhong’ and ‘Meirensu’ pears than high temperature; anthocyanin levels increased with increasing irradiance level from 0 to 532 μmol m−2 s−1, and UV-B and visible light synergistically improved the red color of the fruit. Therefore, a combination of low temperature and high intensity of UV-B/visible light could improve the postharvest coloration of red sand pear fruit. The results will contribute to an improved understanding of the mechanism responsible for the coloration of red Chinese sand pears and will aid development of new techniques to improve color in postharvest fruit.  相似文献   

10.
Aureobasidium pullulans strains Ach 1-1 and 1113-5 are two effective biocontrol agents against Botrytis cinerea and Penicillium expansum on stored apples. In the present work, a monitoring system allowing their identification and quantification was developed. The methodology used consisted of the development of both molecular markers and a semi-selective medium. The random amplified polymorphic DNA (RAPD) technique was applied to a collection of 15 strains of A. pullulans, including Ach 1-1 and 1113-5. Five specific RAPD fragments were amplified for strain Ach 1-1 and three others for strain 1113-5. Among them, a fragment of 528 bp specific to strain Ach 1-1 (generated with the OPR-13 RAPD primer) and another one of 431 bp specific to strain 1113-5 (amplified with the OPQ-03 RAPD primer) were selected, cloned, sequenced, and used to design sequence-characterized amplified region (SCAR) primers. Three different SCAR markers were amplified: two specific to strain Ach 1-1 (189 bp and 387 bp) and one specific to strain 1113-5 (431 bp). These SCAR primers can clearly identify strains Ach 1-1 and 1113-5 among 14 strains of A. pullulans and among eight yeast strains commonly present on apple fruit surfaces. Their selectivity was also tested using DNA extracted from epiphytic microflora of the apple surface. As a semi-selective medium, PDA medium supplemented with 0.5 mg L−1 euparen, 1 mg L−1 sumico, 2.5 mg L−1 hygromycin B, 30 mg L−1 streptomycin sulphate, and 1 mg L−1 cycloheximide was selected. It inhibited the development of the air microflora and appeared highly toxic for the epiphytic microflora of apple surface without altering the growth of the targeted strains Ach 1-1 and 1113-5. The combination of the semi-selective medium and SCAR markers provides a valuable monitoring tool to specifically identify and quantify A. pullulans strain Ach 1-1 and strain 1113-5 and could be used in future studies to evaluate their population dynamics under various laboratory and practical conditions.  相似文献   

11.
The effectiveness of alternatives to synthetic fungicides for the control of pathogens causing postharvest diseases of sweet cherry was tested in vitro and in vivo. When amended to potato dextrose-agar, oligosaccharides, benzothiadiazole, chitosan, calcium plus organic acids, and nettle macerate reduced the growth of Monilinia laxa, Botrytis cinerea and Rhizopus stolonifer. Treatment of sweet cherries three days before harvest or soon after harvest with oligosaccharides, benzothiadiazole, chitosan, calcium plus organic acids, nettle extract, fir extract, laminarin, or potassium bicarbonate reduced brown rot, gray mold, Rhizopus rot, Alternaria rot, blue mold and green rot of cherries kept 10 d at 20 ± 1 °C, or 14 d at 0.5 ± 1 °C and then exposed to 7 d of shelf-life at 20 ± 1 °C. Among these resistance inducers, when applied either preharvest or postharvest, chitosan was one of the most effective in reducing storage decay of sweet cherry, and its antimicrobial activity in vitro and in field trials was comparable to that of the fungicide fenhexamid. Benzothiadiazole was more effective when applied postharvest than with preharvest spraying. These resistance inducers could represent good options for organic growers and food companies, or they can complement the use of synthetic fungicides in an integrated disease management strategy.  相似文献   

12.
Green mould (caused by Penicillium digitatum) is a major cause of postharvest losses in citrus. Residue loading of thiabendazole (TBZ) with application methods typically used in South African packhouses and green mould control was studied. TBZ was applied curatively and protectively in dip, drench and wax coating treatments and fruit were inoculated with a TBZ-sensitive or a TBZ-resistant isolate of P. digitatum. The dip treatments consisted of TBZ concentrations of 0–2000 μg mL−1; fruit were dipped for 60 s at 22 °C at a pH of 7. Residues differed between fruit batches and ranged from 0.5 to 1.7 μg g−1 at 1000 μg mL−1 TBZ. Curative dip treatments almost completely controlled green mould (>96% at 1000 μg mL−1 TBZ). The residue level needed for 75% curative control ranged from 0.06 to 0.22 μg g−1, depending on citrus type. Protective treatments were unreliable and control varied from 17% to 97.9% at 1000 μg mL−1 TBZ between fruit batches. Drench treatments consisted of exposure times of 30, 60 and 90 s with 1000 or 2000 μg mL−1 TBZ. Average TBZ residues were 2.14 μg g−1 for Clementine mandarin fruit and 3.50 μg g−1 for navel orange fruit. Green mould control on navel orange fruit resulted in 66–92%, 34–90% and 9–38% control for curative treatments after 6 and 24 h and protective treatments, respectively, depending on fruit batch. Wax with 4000 μg mL−1 TBZ was applied at 0.6, 1.2 and 1.8 L wax ton−1 fruit. Chilling injury was evaluated after fruit storage at −0.5 °C for 40 days. Average TBZ residues loaded was 1.3, 1.3 and 2.7 μg g−1 at the recommended 1.2 L ton−1 for Satsuma mandarin, Clementine mandarin and Valencia orange fruit, respectively. Protective treatments showed lower infection levels (14–20%) than curative treatments (27–40%) for Valencia orange fruit. The same trend was observed with Satsuma (92–95% curative; 87–90% protective) and Clementine mandarin fruit (82–90% curative; 59–88% protective), but control was relatively poor. TBZ application in wax exceeded 5 μg g−1 at higher wax loads (1.2 and 1.8 L ton−1). Wax treatments showed a significant reduction in chilling injury; TBZ had an additive effect. TBZ resistant isolates could not be controlled.  相似文献   

13.
The effectiveness of short hyperbaric treatments to control postharvest decay of sweet cherries (Prunus avium L., cv Ferrovia) and table grapes (Vitis vinifera L., cv Italia) was investigated. Sweet cherries and table grape berries were exposed to the pressure of 1140 mmHg (1.5 atm) for 4 and 24 h, respectively, in 64 L gas-proof tanks. Fruit kept at ambient pressure (near 760 mmHg, 1.0 atm) served as a control. Postharvest rots of sweet cherries arose from naturally occurring infections, whereas table grape berries were artificially wounded, exposed to the hyperbaric treatment, then the wounds inoculated with 20 μL of a Botrytis cinerea conidial suspension (5 × 104 spores mL−1). Sweet cherries were stored at 0 ± 1 °C for 14 d, followed by 7 d at 20 ± 1 °C. Table grapes berries were kept at 20 ± 1 °C for 3 d. On sweet cherries, hyperbaric treatment reduced the incidence of brown rot, grey mould, and blue mould, with respect to the control. Similarly, on treated table grapes a significant reduction of lesion diameter and percentage of B. cinerea infected berries was observed. Induced resistance was likely to be responsible for the observed decay reduction. To our knowledge, this is the first report on the effectiveness of short hyperbaric treatments in controlling postharvest decay of sweet cherries and table grapes.  相似文献   

14.
In Israel, black spot caused by Alternaria alternata is the main postharvest factor that impairs the quality and reduces the storability of persimmon fruit (Diospyros kaki cv. Triumph). The fungus infects the fruit in the orchard and remains quiescent until harvest. After harvest, the pathogen slowly colonizes the fruit during storage at 0 °C, which elicits black spot symptom development 2–3 months after storage entry. A commercial postharvest dip treatment in chlorine at 500 mg L?1, released from sodium troclosene tablets, effectively controlled black spot in fruit stored for up to 2 months. However, decay incidence increased as the length of storage was extended beyond 2.5 months. The long incubation period that precedes black spot symptom development after harvest enabled the development of a series of integrative approaches for application at the pre- and postharvest stages, in combination with the commercial chlorine dip treatment, to improve the control of black spot disease. Preharvest treatments included treatment with the cytokinin-like N1-(2-chloro-4-pyridyl)-N3-phenylurea (CPPU) 30 d after fruit set, or a single spray with the curative fungicide polyoxin B 14 d before harvest, and when one of these was applied in combination with the postharvest chlorine dip treatment, the black spot infected area was reduced by 3 and 60%, respectively, compared with the chlorine dip alone. At the postharvest stage, fogging during storage, or post-storage on-line spraying with sodium troclosene, when applied in combination with the postharvest chlorine dip, improved the percentage of marketable fruit by 2 or 10%, respectively, compared with the chlorine dip alone. The results indicate that postharvest pathogens that show a slow colonization pattern might enable the integration of pre- and postharvest disease control methods to improve quality and reduce postharvest disease development.  相似文献   

15.
The objective of this work was to preserve the postharvest quality of litchi cv Brewster by the application of Lactobacillus plantarum. A suspension of 1 × 109 CFU/mL of the bacteria was sprayed on ripe litchis and then stored at 10 °C with 75% of relative humidity. Treated fruit exhibited a significantly higher Gram positive bacteria growth on the rind (4–5 log CFU/g) than that detected in control fruit (2.5–3.75 log CFU/g). This result was corroborated by observing a high population of lactobacilli in scanning electron micrographs and by measurement of the content of lactic acid produced. Treated fruit displayed significantly (α ≤ 0.05) reduced color losses as indicated by the higher L* and C* values in comparison with the untreated ones. Additionally, cyanidin-3-rutinoside and total anthocyanin contents supported the measured color retention, since the pericarp of fruit treated with Lb. plantarum showed a significantly higher concentration of pigments than those used as control. In addition, a high concentration of phenolic compounds was found in the rind of treated fruit.  相似文献   

16.
Pantoea agglomerans CPA-2 is an effective biocontrol agent of postharvest diseases of citrus and pome fruit. A monitoring technique was developed for its identification and to quantify its populations. The methodology used consisted of (i) searching for a semi-selective medium, (ii) identification of molecular markers and (iii) monitoring population dynamics in a commercial trial. As a semi-selective medium, Malonate Broth Agar supplemented with tetracycline hydroxychloride and incubation at high temperature (max. of 40 °C) facilitated the selective recovery of P. agglomerans CPA-2 colonies. The RAPD technique was applied to a collection of 13 strains of P. agglomerans, including CPA-2. Among the 12 primers tested, OPL-11 amplified a fragment (about 720 bp) specific to strain CPA-2. On the basis of this fragment, two SCAR markers were amplified using a primer pair derived from OPL-11 elongation. A first SCAR marker of 720 bp was specifically amplified for the strain CPA-2 and a second one of 270 bp was obtained for all P. agglomerans strains tested, including CPA-2. Commercial trials demonstrated a significant reduction of decay with the treatment of formulated cells of P. agglomerans CPA-2. Population dynamics of CPA-2 in commercial trials were determined on fruit surfaces and in the environment using both the classical plating technique and PCR with SCAR primers. In general, no significant differences were observed between results obtained from the two methods. On fruit surfaces, 1 day after CPA-2 applied its population by classical methods was 4.37 × 106 cfu wound−1 and at the end of the experiment the population increased to 5.8 × 105 cfu wound−1. The percentages of colonies identified as P. agglomerans CPA-2 at these sampling times using SCAR primers were 90 and 95%, respectively. Population dynamics in the environment to evaluate the environmental fate of P. agglomerans CPA-2 showed that it has a limited persistence and limited capacity for dispersion.  相似文献   

17.
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.  相似文献   

18.
Common food additives (sodium bicarbonate (SB), sodium carbonate (SC), and potassium sorbate (PS)) were compared to the fungicide fludioxonil for the control of gray mold on California-grown ‘Wonderful’ pomegranates artificially inoculated with Botrytis cinerea and stored at 7.2 °C in either air or controlled atmosphere (CA, 5 kPa O2 + 15 kPa CO2) conditions. Fludioxonil was superior to other treatments. PS was the most effective additive. Synergistic effects between antifungal treatments and CA storage were observed. After 15 weeks of storage at 7.2 °C, the combination of PS treatment (3 min dip in 3% solution at 21 °C) and CA storage was as effective as the combination of heated fludioxonil (30 s dip in 0.6 g L−1 of active ingredient at 49 °C) and air storage. Mixtures of PS with SB or SC did not improve the efficacy of either treatment alone. In tests conducted in commercial facilities, decay development and external and internal fruit quality were assessed on naturally infected pomegranates stored in either air or CA after application of a selected postharvest antifungal combined treatment (CTrt) integrating PS, SB + chlorine, and fludioxonil. CTrt was effective in controlling natural gray mold after 6 weeks of storage at 8.9 °C, but lacked persistence and it was not effective after 14 weeks. CA storage greatly enhanced decay control ability of CTrt. Skin red color was better maintained in CA-stored than in air-stored fruit. Juice color and properties (SSC, TA, and pH) were not practically affected by either postharvest treatment or storage condition. The integration of PS treatments with CA storage could provide an alternative to synthetic fungicides for the management of pomegranate postharvest decay.  相似文献   

19.
γ-Aminobutyrate (GABA) accumulates in apple fruit during controlled atmosphere storage. Here, we demonstrated that GABA levels declined markedly in apples (Malus × domestica Borkh. cv. Empire) within 3 h after transfer from controlled atmosphere storage (3 °C, 2.5 kPa O2, 2.5 kPa CO2) to ambient conditions. Also, we identified two genes encoding apple fruit GABA transaminase (GABA-T), the enzyme responsible for the catabolism of GABA to succinic semialdehyde. The deduced amino acid sequences of the two MdGABA-T enzymes were 93% identical to each other, and 74–83% identical to known Arabidopsis and tomato GABA-Ts. Transient expression of the individual full-length proteins fused to the green fluorescent protein in tobacco suspension-cultured cells revealed that MdGABA-T1 and MdGABA-T2 were localized to mitochondria. Removal of the N-terminal targeting presequences yielded good recovery of the soluble recombinant proteins in Escherichia coli when they were co-expressed with the GroES/EL molecular chaperone complex. Continuous monitoring of recombinant GABA-T activity via a bacterial NADP+-dependent succinic semialdehyde dehydrogenase-linked assay established that the two GABA-Ts in apple fruit, like the mitochondrial GABA-T in Arabidopsis and the mitochondrial, plastidial and cytosolic GABA-Ts in tomato, utilized pyruvate and glyoxylate, but not 2-oxoglutarate. Thus, the substrate specificity of the two apple fruit GABA-Ts was similar to that for the GABA-Ts in Arabidopsis and tomato. However, the existence of two GABA-Ts in the mitochondria of apple fruit differed from the scenarios found in the other two species, providing yet another variation on the subcellular distribution of GABA-Ts in plant cells.  相似文献   

20.
A continuing challenge for commercializing 1-methylcyclopropene (1-MCP) to extend the storage life and control superficial scald of ‘d’Anjou’ pear (Pyrus communis L.) is how to initiate ripening in 1-MCP treated fruit. ‘D’Anjou’ pears harvested at commercial and late maturity were treated with 1-MCP at 0.15 μL L−1 and stored either at the commercial storage temperature −1.1 °C (1-MCP@−1.1 °C), or at 1.1 °C (1-MCP@1.1 °C) or 2.2 °C (1-MCP@2.2 °C) for 8 months. Control fruit stored at −1.1 °C ripened and developed significant scald within 7 d at 20 °C following 3–5 months of storage. While 1-MCP@−1.1 °C fruit did not develop ripening capacity due to extremely low internal ethylene concentration (IEC) and ethylene production rate for 8 months, 1-MCP@1.1 °C fruit produced significant amounts of IEC during storage and developed ripening capacity with relatively low levels of scald within 7 d at 20 °C following 6–8 months of storage. 1-MCP@2.2 °C fruit lost quality quickly during storage. Compared to the control, the expression of ethylene synthesis (PcACS1, PcACO1) and signal (PcETR1, PcETR2) genes was stable at extremely low levels in 1-MCP@−1.1 °C fruit. In contrast, they increased expression after 4 or 5 months of storage in 1-MCP@1.1 °C fruit. Other genes (PcCTR1, PcACS2, PcACS4 and PcACS5) remained at very low expression regardless of fruit capacity to ripen. A storage temperature of 1.1 °C can facilitate initiation of ripening capacity in 1-MCP treated ‘d’Anjou’ pears with relatively low scald incidence following 6–8 months storage through recovering the expression of certain ethylene synthesis and signal genes.  相似文献   

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