Influence of 1-methylcyclopropene on pectic enzyme activities,gene expression,and cell wall modification in papaya (Carica papaya cv. ‘Sunrise’) fruit

SUMMARY

‘Sunrise’ papaya fruit harvested at two stages of maturity [colour break (< 10% yellow peel colour) and 25% yellow peel colour] were treated with 100 nl l^–1 1-methylcyclopropene (1-MCP) to determine its effects on ripening, on the activities and levels of gene expression of polygalacturonase (PG), pectin methyl esterase (PME), and βgalactosidase ( βGal), and on the degradation of cell wall components. 1-MCP delayed ripening and the onset of the climacteric, although the peak in the respiration rate was almost the same as that in untreated control fruit. Colour-break fruit treated with 1-MCP exhibited a continuous increase in ethylene production, but at a lower rate than in control fruit. Consequently, 1-MCP-treated fruit ripened with a concomitant reduction in firmness, which was accompanied by an increase in PG and βGal enzyme activities and gene expression. On the other hand, fruit treated with 1-MCP at the 25% yellow stage exhibited lower levels of ethylene production and developed pulp with a rubbery texture at the ripe stage which was attributed to reduced PG, βGal, and PME enzyme activities and gene expression. This was consistent with the higher level of cell wall polysaccharides measured in 1-MCP-treated fruit. The above results indicated that ‘Sunrise’ papaya fruit can be treated with 1-MCP at the colour break stage since they have a greater capacity to recover from the effects of 1-MCP than fruit treated at the 25% yellow stage.     

Responses of banana fruit to pro-long coating at different times relative to the initiation of ripening

Coating banana fruit with Pro-long 24 h after initiation of ripening decreased their skin permeability to gases and depressed their O₂ content. Coating the fruit immediately before ripening initiation delayed the onset of rapid ethylene production, which normally begins as the fruit start to ripen. Coating slightly suppressed rapid C₂H₄ production when applied immediately after ripening initiation, and exerted a strong, temporary inhibition of C₂H₄ production when applied 24 h later. A climacteric rise in respiration was absent from fruit coated with Pro-long immediately before or after ripening initiation; delaying coating by a further 24 h arrested development of the climacteric in mid-rise. In mid-climacteric fruit, inhibition of C₂H₄ production by coating occurred more rapidly than inhibition of respiration. Coating the fruit delayed the chlorophyll loss which normally accompanies ripening, but the magnitude of this effect declined as the coating treatment was delayed relative to ripening initiation. The effects of coating on skin colour change and on respiration appeared to be largely independent of its effect on the fruit's C₂H₄ content.     

1-MCP处理对新高梨冷藏后常温货架寿命的影响

以新高梨为试材,果实经1-MCP(1-甲基环丙烯)处理再冷藏一定时间后,研究常温货架期间1-MCP对果实贮藏效果的影响.结果表明:1-MCP能明显抑制果实呼吸强度、乙烯释放量的升高,推迟呼吸高峰和乙烯高峰出现的时间;抑制了果实丙二醛(MDA)和果皮相对膜透性的升高;延缓了果实硬度、可滴定酸含量的下降,阻碍了可溶性固形物的上升,使果实的货架期明显延长,延缓了果心褐变,但却加速了果实的果皮褐变.     

1-MCP处理对采后‘澳洲青苹’苹果叶绿素降解的影响

【目的】以‘澳洲青苹’苹果为试材,研究1-甲基环丙烯(1-MCP)对果实采后叶绿素降解代谢的影响,为果实采后贮藏、保鲜及保绿技术提供新的理论基础。【方法】采用1μL·L^-11-MCP处理‘澳洲青苹’苹果果实,定期测定果实色泽、乙烯释放量和呼吸强度,通过高效液相色谱法(HPLC)对果皮中的叶绿素及其降解代谢产物进行定性定量分析,并采用实时荧光定量PCR技术检测叶绿素降解途径中关键基因的表达水平。【结果】1-MCP处理显著延缓‘澳洲青苹’果皮颜色转变,降低乙烯释放量和呼吸强度。1-MCP处理能保持果皮叶绿素a、b含量处于较高水平,并抑制脱镁叶绿素a和脱镁叶绿酸a的生成。叶绿素降解相关基因MdSGR、MdHCAR、MdPPH和MdNYC1的表达量受到1-MCP的调控,1-MCP抑制基因MdPAO和MdRCCR的表达,推迟叶绿素降解代谢的下游反应;MdPAO表达量与果皮色泽和叶绿素含量显著相关。【结论】1-MCP可调节叶绿素降解途径相关基因表达水平来控制代谢产物的降解和生成,从而延缓果皮叶绿素降解,其中,MdPAO是调控叶绿素降解的关键基因。     

Effects of 1-methylcyclopropene (1-MCP) on ripening of apple fruit without cold storage

Summary

The objectives of this study were to determine the efficacy of 1-methylcyclopropene (1-MCP) treatment on ripening of ‘Tsugaru’ fruit at different stages of maturity (early, mid-, and late harvest) and the responses of the early- to late-maturing apple cultivars,‘Tsugaru’,‘Hongro’ and ‘Fuji’, respectively, during storage at ambient temperature (20º ± 2ºC). Fruit at different stages of ripening were treated with 0.5, 1.0, or 2.0 µl l^–1 1-MCP for different durations (e.g., 1.0 µl l^–1 1-MCP for 8 h, 16 h, or 24 h) or with various delays before treatment (e.g., 1.0 µl l^–1 1-MCP on the day of harvest, or 1 d, or 2 d later). Application of 1-MCP to unripe fruit inhibited ethylene production, lowered the rate of respiration and maintained titratable acidity (TA) more effectively than when more mature fruit was treated. However, the effects of 1-MCP on flesh firmness were similar for apples at mid- or late harvests. 1-MCP treatment of early-harvested fruit of the early-maturing ‘Tsugaru’, which had the highest level of ethylene production and respiration rate, inhibited softening and loss of TA to a greater extent than for late harvested fruit. The same pattern of softening was found for ‘Hongro’ and ‘Fuji’. Firmness of ‘Tsugaru’ and ‘Fuji’ apples was maintained after 8 h treatment with 1.0 µl l^–1 1-MCP, while a 16 h treatment was required for ‘Hongro’. Treatment delays of ≤ 2 d before the application of 1-MCP had no negative impact on fruit firmness. Overall, these results indicate that 1-MCP can be used to maintain the quality of non-refrigerated apples.     

The post-harvest ripening of water stressed banana fruits

SUMMARY

Maintaining banana fruit in a low humidity environment accelerated fruit ripening. This was reflected in an earlier increase in respiration and ethylene production and more advanced peel colour and pulp sugars. At the end of the trial the fruit kept in low humidity were yellow with green tips (stage 5) whereas those kept at high humidity were still green (stage 1-2). Fruit kept at low humidity did not show a large increase in pulp ethylene production compared with the fruits stored at high humidity. This difference occurred despite a large increase in the 1-aminocyclopropane-l-carboxylic acid (ACC) content of both samples, with the low humidity fruit preceding the high by two days. The peel ethylene production of the low humidity stored fruit increased dramatically as the fruit ripened, coinciding with an increase in ACC. The ACC oxidase activity of the peel reflected the ethylene production with a large increase in the low humidity stored fruit and a later, smaller increase in the high humidity stored fruit. The ACC oxidase activity of the pulp of both low and high humidity stored fruit increased gradually during storage. The changes in ethylene production are discussed with reference to banana ripening being regarded as co-ordinated by pulp ethylene production while the peel is passive, depending on pulp ethylene production for degreening.     

‘乔纳金’苹果采后1-MCP 处理对常温贮藏效果的影响

 试验结果表明, 1-MCP (1 - 甲基环丙烯) 处理可以明显降低‘乔纳金’苹果果实的呼吸强度,延迟呼吸高峰的出现, 明显减缓硬度和酸度的下降, 减少叶绿素的分解, 但低浓度的1-MCP 处理增加了苦痘病的发生率。     

Strawberry Yellows in the Variety Auchincruive Climax

Summary

Fresh ‘Mavra Markopoulou’ fig fruits, harvested close to a fully ripe state in October, were stored at ?1?C in either air or 2% O₂ (balance N₂) for 29.d. During storage in air the rates of O₂ uptake and ethylene production declined substantially and fruit weight loss increased up to 2.1%. Storage in 2% O₂ resulted in further reduction of O₂ uptake and ethylene production rates. The effects of storage conditions on ripening indices at 20?C in air were also investigated. Fruit stored in air showed decreased firmness, ethylene production rate and flesh colour lightness, but no significant or consistent changes in respiratory quotient, O₂ uptake and CO₂ production rates, soluble solids content, titratable acidity and other colour changes in peel or flesh were observed. In contrast, storage in 2% O₂ resulted in decreased respiratory quotient (although values remained above 1), O₂ uptake and CO₂ production rates and prevented fruit softening, loss of green peel colour and decrease in flesh lightness during post-storage at 20?C. All fruit were stored successfully under the above conditions, but 2% O₂ is recommended for better firmness retention during storage for longer than 8.d.     

Postharvest UV-C treatment combined with 1-methylcyclopropene (1-MCP), followed by storage in continuous low-level ethylene atmosphere,improves the quality of tomatoes

Mature green tomatoes (Solanum lycopersicum L. cv Neang Pich) were exposed to 13.6 kJ m^?2 UV-C or 0.5 μL L^?1 1-MCP or combination of 13.6 kJ m^?2 UV-C and 0.5 μL L^?1 1-MCP, with appropriate untreated controls. After treatment, tomatoes were stored in air containing 0.1 μL L^?1 ethylene at 20°C and 100% RH. The untreated fruit ripened significantly faster than those of all other treatments. UV-C treatment alone was able to delay fruit ripening by up to 5 days longer compared to untreated fruits whilst the additional of 1-MCP further delayed fruit ripening. UV-C and 1-MCP treatments alone or in combination had significantly slower ethylene production rates throughout the storage period. The fruit treated with the combination of 1-MCP and UV-C was significantly firmer and had higher total phenolic content compared to that of the other treatments. However, there was no difference between treatments in soluble solids content/titratable acids ratio, chlorophyll content, lycopene content and total antioxidant activity. These results show that UV-C and 1-MCP treatment delay ripening and improve the quality of tomatoes in the presence of low-level ethylene during storage. This new treatment could be used to extend the shelf-life of mature green tomatoes through the supply chain without the use of refrigeration.     

Chilling induced ethylene biosynthesis in ‘Hayward’ kiwifruit following storage

‘Hayward’ kiwifruit were stored at 0, 5, 10, 15 and 20°C for 5, 12 and 17 days before rewarming to 20°C for 10 more days. Ethylene and CO₂ production, ACC, ACC synthase (ACS) and ACC oxidase (ACO) activities, flesh and core firmness, soluble solids content (SSC) and flesh colour were measured. Kiwifruit stored at 0, 5, 10 and 15°C did not ripen, produce ethylene or show increases in ACS or ACO activity. Fruit stored for 5 days at the above temperatures, then rewarmed to 20°C, did not show any change during the following 10 days. Rewarmed fruit, pre-stored at 0–10°C for 12 days, started autocatalytic ethylene production within 24 h, followed by fruit ripening. Fruit stored at 15°C for 12 days needed 72 h to start ethylene autocatalyse and did not fully ripen during 10 days at 20°C. After 17 days storage at 0–15°C kiwifruit started autocatalytic ethylene production with no delay upon exposure to 20°C. Autocatalytic ethylene production correlated with increased ACC content, and increased activities of ACS and ACO. Fruit held continuously at 20°C started autocatalytic ethylene production after 19 days, with concomitant increases in ACC content, ACS and ACO activities and ripening. Respiration increased after rewarming, concomitantly with the increase in ethylene production.We concluded that exposing kiwifruit to chilling temperatures (0–10°C) for 12 days advanced ethylene biosynthesis and ripening when compared with fruit held continuously at 20°C. The advanced ethylene biosynthesis was due to increase ACS and ACO activities immediately upon rewarming of the fruit.     

Biochemical and physiological changes during chlorophyll degradation in lime (Citrus aurantifolia Swingle cv. ‘Paan’)

Summary

Lime (Citrus aurantifolia Swingle cv. ‘Paan’) native to South East Asia, has a distinct flavour and quality characteristics. Maintenance of the green colour in the peel of lime is a desirable quality attribute during storage. Post-harvest chlorophyll degradation in lime was studied in fruit stored at room temperature (30°C) at a relative humidity (RH) of 70 – 85%. Within 7 d of storage, the total chlorophyll content decreased to 53.9% of its initial level. The highest chlorophyllase activity (1.68 units mg^–1 protein) was observed after 4 d of storage and declined thereafter. Peroxidase activity differed from chlorophyllase activity and increased significantly to 6.25 units mg^–1 protein after 9 d of storage, (i.e., at the late maturity stage). Respiration rate and 1-aminocyclopropene-1-carboxylic acid (ACC) oxidase activity did not significantly affect the chlorophyll degradation process in lime.The total nitrogen content of lime peel was inversely correlated with its chlorophyll content. A higher soluble protein content was observed in yellow peel than in mature green peel. A colour index chart was developed for maturity stages 1–4 in lime based on peel colour changes from mature green to full-yellow, and its correlation with chlorophyll content and fruit quality attributes.     

采后1-MCP和热处理对红富士苹果生理变化和贮藏品质的影响

采用1-MCP(浓度为1μL/L,18h)、热空气(HA)38℃-96h及2者结合对富士苹果进行处理,处理后的果实置于(0±0.5)℃条件冷藏4个月,然后置于20℃条件下7d(模拟货架期)。试验发现在整个贮藏过程中所有处理组均能抑制果实的乙烯释放速率和呼吸强度,减缓果实硬度的降低。热处理组对固酸比的上升有显著作用,保持了较高的非水溶性果胶含量和较低的水溶性果胶含量。热处理在贮藏过程中对于果实硬度的保持与对照组相比起到一定的作用,但加速了果皮中叶绿素含量的降解。1-MCP处理组能够较好地抑制果实果皮的褪绿,保持果皮中较高的叶绿素含量,初期抑制细胞膜透性的上升,延缓果实的后熟衰老。结合处理组较好地保持果实膜的完整性,减缓了由热处理所引起的果皮叶绿素的降解,并保持较高的含酸量,保持了较好的风味品质。     

Response of kiwifruit (Actinidia deliciosa cv. Allison) to post-harvest treatment with 1-methylcyclopropene

Summary

Experiments were conducted to observe the effect of different concentrations of 1-methylcyclopropene (1-MCP) on the post-harvest life and quality of ‘Allison’ kiwifruit (Actinidia deliciosa). Fruit were treated with 1-MCP at 0.5 µl l^–1, 1.0 µl l^–1, or 2.0 µl l^–1, un-treated fruit served as controls. Each 1-MCP treatment was applied for 24 h at 20°C. After treatment, fruit were transferred to ambient temperature storage (22º ± 4ºC; 65 – 70% relative humidity) for 18 d, during which time observations on various physical, physiological, and biochemical parameters were recorded at 3 d intervals. Our results indicated that 2.0 µl l^–1 1-MCP was the most effective treatment to delay softening and ripening in ‘Allison’ kiwifruit, as such fruit showed the lowest mean weight loss (9.8 ± 0.2%), the highest mean fruit firmness value (32.7 ± 0.2 N), and began to ripen only after 12 d in storage, whereas untreated fruit started ripening on day-6 of storage. The activities of fruit softening enzymes such as polygalacturonase (PG; 58.5 ± 0.3 µg galacturonic acid g^–1 FW h^–1), and lipoxygenase (LOX; 3.96 ± 1.3 µmoles linoleic acid oxidised min^–1 g^–1 FW h^–1) were lower, and total phenolics (TP) contents (24.3 ± 0.3 mg 100 g^–1) and anti-oxidant (AOX) activities (12.5 ± 0.03 µmol Trolox g^–1 FW h^–1) were higher in 1-MCP-treated fruit than in untreated fruit (PG, 98.3 ± 0.5 µg galacturonic acid g^–1 FW h^–1; LOX, 4.39 ± 1.0 µmoles min^–1 g^–1 FW h^–1; TP, 5.3 ± 0.6 mg 100 g^–1; AOX, 4.7 ± 0.02 µmol Trolox g^–1 FW h^–1, respectively). In addition, 1-MCP-treated fruit exhibited lower rates of respiration (48.3 ± 0.4 ml CO₂ kg^–1 h^–1) and ethylene production (30.2 ± 0.02 µl kg^–1 FW h^–1) than untreated fruit (58.9 ± 0.6 ml CO₂ kg^–1 h^–1; 38.7 ± 0.04 µl kg^–1 FW h^–1, respectively). Similarly, 1-MCP-treated fruit had higher titratable acidity (TA; 1.33 ± 0.3%) and ascorbic acid (AA) contents (115.9 ± 2.6 mg 100 g^–1 pulp) and lower soluble solids contents (SSC; 8.33º ± 0.2º Brix) than untreated kiwifruit (TA, 1.0 ± 0.2 %; AA, 105.3 ± 2.2 mg 100 g^–1 pulp; SSC, 13.7º ± 0.3º Brix, respectively). Thus, 2.0 µl l^–1 1-MCP can be used for the post-harvest treatment of ‘Allison’ kiwifruit to enhance its shelf-life and marketability by approx. 6 d.     

1-甲基环丙烯对‘富有’甜柿采后主要生理指标及细胞超微结构的影响

 以完全甜柿‘富有’ (Diospyros kaki L.‘Fuyu’) 为试材, 研究了在室温(20 ±2) ℃贮藏条件下1 - 甲基环丙烯(1-MCP) 0.50 μL·L^-1处理对果实的影响。结果表明: 1-MCP处理可显著抑制其呼吸速率、乙烯释放速率和衰老软化进程; 12MCP处理通过抑制果实中LOX活性的升高和MDA含量的积累,一定程度上维持了果肉细胞器和膜系统的完整性, 延缓甜柿果实的软化衰老进程。     

青梅果实的采后成熟特性和肉质变化

研究了２０℃，相对湿度９３％条件下青梅果实的采后成熟特性和肉质变化，结果表明，青梅果实采后呼吸活性和乙烯生成量随着成熟作用的进展而加大，乙烯生成量极高，在呼吸类型上属于跃变型果实；果皮急速黄化，果肉急速软化，主要原因在于多聚半乳糖醛酸酶，果胶甲酯酶活性的增大，导致水溶性果胶含量上升和盐酸可溶性果胶含量的下降。     

Effects of water deficit during stage II of peach fruit development and postharvest on fruit quality and ethylene production

Summary

This study examined the hypothesis that enhancement of peach quality resulting from Regulated Deficit Irrigation (RDI) is caused primarily by changes in fruit physiology during development. Water deficit was applied during either stage II of fruit development (RDI-SII) or during stage II and postharvest (RDI-SII-PH), as compared with non-droughted (control) and postharvest (RDI-PH) treatments. Fruit from the various RDI treatments had significantly higher soluble solids concentrations and red colour at harvest than control fruit. While fruit respiration was not altered by any RDI treatment, ethylene production indicated sooner the onset of climacteric phase for fruit from RDI-SII and RDI-SII-PH than for control or RDI-PH fruit. Accordingly, greater ethylene production in detached fruit was related to their having experienced water stress during development. Ethylene production by RDI-PH fruit did not change, but their quality did in terms of increased soluble solids concentration and improved skin colour similar to the RDI-SII treatment. This observation suggests that water-stress related changes occurring during fruit development are not the only factors involved in enhancing quality in RDI fruit.     

Slowing the deterioration of mango fruit during cold storage by pre-storage application of oxalic acid

Summary

The effects of pre-storage application of oxalic acid (OA) on the incidence of decay and ripening in mango fruit, and its physiological effects on the peel and flesh of mango were investigated after mango fruit (Mangifera indica L. cv. Zill) were dipped in 5 mM OA for 10 min at 25ºC then stored at 14º ± 1ºC for 5 weeks. In addition, spore germination and mycelium growth of Colletotrichum gloeosporioides Penz. on potato dextrose agar (PDA) media containing different concentrations of OA were measured. Application of OA decreased the incidence of decay and delayed the ripening process in mango fruit during cold storage. However, there was no reduction in fruit quality, as judged by the soluble solids content (SSC) and titratable acidity (TA) of fruit ripened at 25ºC for 3 d, following 3 weeks of cold storage. Oxalic acid-treatment resulted in decreased lipoxygenase (LOX) activity and increased superoxide dismutase (SOD) activity in the peel, and increased ascorbate peroxidase (APX) activity in both the peel and the flesh, coincident with a decrease in reactive oxygen species (ROS).At or above 5 mM, OA with unaltered (natural) pH or after neutralisation, also inhibited C. gloeosporioides development in vitro. It is suggested that the physiological effects of OA, in decreasing LOX activity and enhancing defense against oxidation damage, contributed to delaying the ripening process in mango fruit during cold storage. Thus, pre-storage application of OA could be a promising method to suppress post-harvest deterioration and extend the shelf-life of refrigerated mango fruit, possibly due to a combination of its physiological effect in delaying the ripening process, coupled with an inhibition of the development of pathogens such as C. gloeosporioides.     

Ethylene-enhanced chlorophyllase activity during degreening of Citrus unshiu Marc.

Ethylene induces the degreening of the peel of Citrus unshiu Marc. and simultaneously the increase of chlorophyllase activity, indicating that ethylene accelerates the chlorophyll destruction through the enhancement of chlorophyllase activity. Cycloheximide inhibited the ethylene-enhanced chlorophyll degradation and repressed the enhancement of the chlorophyllase activity, while chloramphenicol did not affect the chlorophyll degradation nor the chlorophyllase activity. Based on these results, the role of ethylene in the chlorophyllase activation and the chloroplast senescence is discussed.