Ethylene Action Inhibitor 1-methylcyclopropene Research Articles

Difference of ethylene production and response to ethylene in cut flowers of dahlia (Dahlia variabilis) cultivars

Cut dahlia flowers have a short vase life of 3–7 days, and some cultivars exhibit petal abscission, even inside of cardboard boxes during transport. This petal abscission is induced by ethylene in many cases. In the present study, we investigated the role of ethylene in dahlia flower senescence by comparing the responses to ethylene, ethylene inhibitors, and ethylene production among cultivars. Exogenous ethylene significantly accelerated petal abscission in seven cultivars and petal wilting in other five cultivars out of 12 cultivars. Whole florets and detached receptacles (with bracts) produced different amounts of ethylene; ethylene production was higher in ‘Carnelian’ and ‘Port Light Pair Beauty’ than ‘Heavenly Peace’ and ‘Purple Stone’. Onset of senescence was delayed in detached petals compared with attached petals, suggesting that petal abscission was induced by ethylene produced by ovary and receptacles. The ethylene action inhibitor 1-methylcyclopropene inhibited petal abscission and delayed petal wilting in eight cultivars. Moreover, the silver thiosulfate complex delayed petal wilting of ‘Carnelian’. Together, our findings suggested that ethylene plays a role in senescence of cut dahlia flowers and ethylene inhibitors can extend their vase life.

Metabolic Profile of Strawberry Fruit Ripened on the Plant Following Treatment With an Ethylene Elicitor or Inhibitor.

Strawberry is the most studied nonclimacteric fruit for understanding the role ethylene has in ripening regulation. However, previous studies on the effects of ethylene on strawberry ripening were conducted with detached fruit. Thus, the aim of this work was to determine the effect of ethylene and the ethylene-action inhibitor 1-methylcyclopropene (1-MCP) applied at different developmental stages on important physical-chemical attributes of ripe ‘Albion’ strawberry. Fruit at four developmental stages that remained attached to the plant were dipped in one of three treatment solutions (Ethephon, 1-methylcyclopropene, and water), plus one absolute control that received no dip. Following treatment, when immature fruit were fully red or 24 h after treatment for red-treated fruit, strawberry fruit were assessed for physicochemical properties (mass, length, diameter, firmness, color, titratable acidity, soluble solids, pH, total phenolics, sugar, organic acid, amino acid, and volatile composition). The days following treatment required for fruit to ripen were also recorded. Treatments did not affect the rate of ripening nor fruit color, titratable acidity, pH, soluble solids, total phenolics, sugars, or organic acids of ripe fruit. Ethephon affected fruit mass, diameter, length, firmness, anthocyanins, amino acids, and volatiles, but these effects were dependent on fruit developmental stage at which the treatment was applied. When green fruit were treated with ethephon, ripe fruit had larger diameter and mass. Ethephon treatment of white fruit resulted in ripe fruit having greater anthocyanin content. Treatment of pink fruit resulted in ripe fruit having smaller diameter, length, and mass and greater firmness. Treatment of red fruit with ethephon altered fruit volatile composition, increasing concentrations of ethyl- and acetate-esters, which were reduced by the 1-MCP treatment. Ethephon treatment increased concentrations of 11 of the 19 free amino acids measured in ripe fruit with treatment of green and white fruit having the greatest effect. A total of 41 volatile compounds had significant correlations with 14 amino acids. While ethylene did not stimulate typical ripening of strawberry fruit, it does appear to alter fruit development and metabolism. The physiological effects of ethylene on strawberry fruit appear to depend on the developmental stage of the fruit.

Retardation of ‘Hayward’ kiwifruit tissue zone softening during storage by 1-methylcyclopropene

The use of the ethylene action inhibitor 1-methylcyclopropene (1-MCP) is becoming more common in the global kiwifruit industry as a tool for firmness management after harvest. The overall fruit firmness measured by penetrometer or compression is dependent on the relative changes in texture of the three main tissue zones: the outer pericarp, inner pericarp and core. This research has investigated the way in which 1-MCP affects the firmness of individual tissue zones during storage, and the changing response of 1-MCP treated fruit to ethylene. 1-MCP retarded fruit softening as measured by whole fruit compression or penetrometer. However, there was a long period in storage where the compression test did not show the same degree of softening as was detected by the penetrometer measurement. In addition, it was shown that 1-MCP retarded the softening of the three tissue zones investigated. The exposure of 1-MCP treated fruit to ethylene at intervals throughout storage demonstrated the long term nature of the anti-ethylene effect of a 1-MCP treatment at the start of storage; an effect that persisted in all three tissue zones. It is concluded that 1-MCP retards the overall softening of ‘Hayward’ kiwifruit, whether measured by compression or penetrometer. More specifically, the treatment affects the softening of the outer pericarp, inner pericarp and core tissues to a similar extent. The protective effect of a 1-MCP treatment at the start of storage against exogenous ethylene persists to some degree throughout storage.

Effects of 1-methylcyclopropene on surface wax and related gene expression in cold-stored 'Hongxiangsu' pears.

Surface wax protects fruit from dehydration and pathogen erosion during storage. The surface wax of pears changes greatly during storage. In this work, the effect of ethylene action inhibitor 1-methylcyclopropene on wax accumulation and related gene expression in 'Hongxiangsu' pears during cold storage was investigated. The alkanes, alkenes, fatty acids, esters, aldehydes and triterpenoids on the fruit surface accumulated and peaked at day 180, but fatty alcohols decreased before day 90 and then increased in the control. Treatment with 1-MCP (1.0 µL L-1 ) reduced surface wax at day 180 of storage. Compared with the control, the wax crystals became smaller in 1-MCP-treated fruit on days 90 and 270. The 1-MCP decreased the expression levels of ethylene synthesis, perception and signal genes ACS1, ACO1, ERS1, ETR2, ERF1 and wax-related genes (LACS1, LACS2, KCS2, KCS9, KCS20, FDH, CER6, CER10, LTPG1, LTP3, LTP4, ABCG11 and ABCG12). These results suggested that 1-MCP suppressed ethylene synthesis and signal-pathway and wax-related gene expression; it also reduced the wax and the size of crystals on the fruit surface in cold-stored 'Hongxiangsu' pears. © 2018 Society of Chemical Industry.

Effects of ethylene and 1-MCP on quality maintenance of fresh cut celery

Ethylene is accepted to be a key player in the regulation of climacteric fruit ripening and senescence of leafy vegetables. In contrast, there is still disparity in the literature on the role it may have on quality deterioration of edible petioles. In this work, we evaluated the influence of the ethylene generator 2-chloroethylphosphonic acid (Ethephon) and the ethylene action inhibitor 1-methylcyclopropene (1-MCP) on quality maintenance of fresh cut celery. Commercially mature stalks from self-blanching celery cv. Golden Clause were cut into 2 cm-long slices. Samples from the apical and basal petiole zones were segregated and treated with 2000 mg L−1 2-chloroethylphosphonic acid or with 1 μL L−1 1-MCP. Corresponding slices without any treatment were used as control. Samples were packed and stored for 0, 6, 13 and 20 d at 4 °C and during this period celery visual deterioration (VD), respiration, weight loss and aerobic mesophilic bacteria, yeasts and molds counts were determined. Carotenoids, chlorophylls, phenolics, ascorbic acid, polyphenol oxidase (PPO), sugars, acidity, cell wall content and consumer acceptability were also evaluated. Ethylene had no major effects on weight loss, PPO, phenolic, sugars, acidity, and ascorbic acid. Instead, it increased respiration and accelerated chlorophyll degradation and surface yellowing. These changes were delayed in 1-MCP treated celery, which also maintained lower mesophilic bacteria and yeast counts, showed lower incidence of soft rots. 1-MCP treated celery received higher consumer acceptability scores. The effects were more marked on the samples obtained from the apical region of the petioles. Overall, results reassess the role of ethylene on celery petiole metabolism and indicate that 1-MCP treatments may be useful to supplement the benefits of refrigeration and extend the shelf life of fresh cut self-blanching celery.

Pre-treatment with 1-methylcyclopropene alleviates methyl bromide-induced internal breakdown, softening and wall degradation in blueberry

Methyl bromide (MeBr) fumigation is the most common quarantine treatment used to control fruit flies in blueberry. Recent studies suggest that the treatments may increase decay and softening during transport, distribution and retail. We evaluated whether the ethylene action inhibitor 1-methylcyclopropene (1-MCP) could counteract the detrimental effects caused by MeBr. ‘Jewel’ and ‘Emerald’ blueberries with 100% surface blue color were harvested and treated with 1-MCP (1 μL L−1 12 h, 4 °C), MeBr (32 g m−3, 3 h, 21 °C), or 1-MCP followed by MeBr. Untreated berries were used as a control. Fruit was stored for 0, 7 or 14 d at 2 °C and internal breakdown, firmness, respiration, weight loss, color, soluble solids, acidity and the total ascorbic acid (AsA), anthocyanin and glutathione (GSH) concentrations were determined. We also assessed pectin solubility by sequential cell wall extraction and neutral sugar composition. MeBr exposure exacerbated internal breakdown and respiration after long-term storage. These effects were significantly reduced by pre-treatment with 1-MCP, indicating that MeBr-induced damage requires ethylene action. 1-MCP application prior to MeBr fumigation also prevented berry softening by delaying solubilization of cell wall uronic acids and galactose. The combination of 1-MCP followed by MeBr caused no detrimental effects on fruit surface color, anthocyanin, weight loss, soluble solids or acidity. MeBr fumigation reduced total GSH concentrations regardless of 1-MCP, indicating that the improved quality retention could not be attributed to the detoxification of the xenobiotic by this compound and was more likely due to inhibition of ethylene-dependent over-ripening and senescence symptoms. Pre-treatment with 1-MCP may be useful to alleviate MeBr-induced deterioration in blueberry.

Pre-harvest 1-methylcyclopropene application affects post-harvest physiology and storage life of the cut rose cv. Carola

We evaluated and optimized the effects of an alternative pre-harvest application of the non-toxic ethylene action inhibitor 1-methylcyclopropene (1-MCP)on the physiology and storage life of the cut rose (Rosa hybrida) cv. Carola. Cut rose was treated with a single pre-harvest liquid formula spray of 10 μL·L-11-MCP or a single treatment of a modified atmosphere packaging of 50-μm thick polyethylene film (PE50), or a combination of the two (1-MCP+PE50), and the effects on vase life, storage life, and cold storage senescence related physiological changes were evaluated. Cut rose subjected to the pre-harvest 1-MCP spray treatment had the longest storage life (26 days), while those subjected to PE50, 1-MCP+PE50, and the untreated control treatment had mean storage lives of 22, 19, and 16 days, respectively. Additionally, the pre-harvest 1-MCP spray treatment significantly extended the vase life of cold-stored flowers for zero or six days, by 27.08% and 42.55%, respectively. The pre-harvest spray treatment significantly suppressed respiration intensity, ethylene production, soluble protein degradation, 1-aminocyclopropane-1-carboxylic acid (ACC) production, and ACC oxidase activity. The 1-MCP+PE50 treatment compromised all the effects of the 1-MCP treatment except the effect on soluble protein content. We conclude that a pre-harvest 1-MCP spray treatment has positive effects on the vase life and storage longevity of cut rose, and that combining this treatment with a PE50 package diminishes these effects.

Effect of ethylene and 1-methylcyclopropene on the postharvest behavior of cape gooseberry fruits (Physalis peruviana L.).

Cape gooseberry (Physalis peruviana L.) fruits are highly perishable berries that exhibit a climacteric respiratory behavior. The objective of this study was to evaluate the effect of ethylene and the ethylene action inhibitor 1-methylcyclopropene on the postharvest behavior of cape gooseberry fruits (ecotype Colombia). Fruits were treated with ethylene, in an ethephon application (1000 µL L-1), and pretreated with 1-methylcyclopropene (1 µL L-1), 1-methylcyclopropene+ethylene, and results compared with a control without application. Subsequently, the fruits were maintained at room temperature (20 ℃, 75% RH) for up to 11 days. The pretreatment of the cape gooseberry fruits with 1-methylcyclopropene delayed most of the ripening-associated parameters, with a reduction in the respiration rate and ethylene production, skin color development, total soluble solids, total carotenoid content, loss of firmness, loss of total titratable acidity and emission of volatile compounds such as ethyl octanoate, ethyl butanoate, ethyl decanoate, and hexyl decanoate. Conversely, application of ethephon accelerated most of these physiological changes and also overcame most of the effects prevented by the ethylene action inhibitor. Altogether, the results supported the idea of a climacteric-like behavior for cape gooseberry fruits and pointing out that the pretreatment with 1-methylcyclopropene may be a promising and efficient postharvest treatment to delay maturity and extend the postharvest period.

Reduction of energy usage in postharvest horticulture through management of ethylene.

Cool chain management is the preferred technology to extend the postharvest life of horticultural produce, but with rising energy costs and community pressure to reduce greenhouse gas emissions, there is a need to use less energy-intensive technologies. Minimising the level of ethylene around horticultural produce inhibits ripening and senescence and therefore has the potential to reduce the use of refrigeration. The long-distance transport of bananas within Australia and from Central America to Europe is used as a case study to show that the need for refrigeration could be reduced if the appropriate concentrations of ethylene were maintained around fruit during transit. Data are also presented to show a similar benefit of ethylene control with green beans, as well as another study showing that apples treated with the ethylene action inhibitor 1-methylcyclopropene could be stored at a higher temperature without loss of quality to the consumer. The range of technologies available to manage ethylene levels is discussed.

1-Methylcyclopropene (1-MCP)-induced protein expression associated with changes in Tsai Tai (Brassica chinensis) leaves during low temperature storage

Leaf yellowing is an early symptom of senescence and greatly affects the commercial value of leafy vegetable products. The ethylene action inhibitor 1-methylcyclopropene (1-MCP) has been widely studied regarding its effects on senescence, but little is known on how it influences the protein expression profile of leafy vegetables in storage. In this study, by using a proteomic approach, changes in proteomic profile induced by 1-MCP in Tsai Tai (Brassica chinensis) leaves during storage under low but non-freezing temperature were investigated. Compared with the control, 1-MCP treatment inhibited leaf etiolation and reduced weight loss of Tsai Tai stored at 1°C, indicating that it delayed senescence. Two dimensional electrophoresis revealed 16 differentially accumulated protein spots, 12 of which were successfully identified by mass spectrometry. A comparison between the control and the 1-MCP-treated Tsai Tai showed that 1-MCP enhanced levels of four proteins involved in photosynthesis, i.e. photosystem II protein, oxygen-evolving enhancer protein 2, chloroplast ribulose 1,5-bisphosphate carboxylase/oxygenase activase and high molecular weight RuBisCO, inhibited malate dehydrogenase, a key enzyme involved in the tricarboxylic acid cycle, downregulated gibberellin 2-beta-dioxygenase expression, a key enzyme involved in biosynthesis of active gibberellins, and suppressed glutathione s-transferase, an important scavenger for reactive oxygen species. These results imply that 1-MCP could maintain leaf capacity for carbon assimilation, inhibit the tricarboxylic acid cycle, induce biosynthesis of GAs and reduce levels of reactive oxygen species, which together may have contributed to inhibition of leaf yellowing and delay of senescence.

EVALUATION OF SHELF LIFE AND RIPENING OF IMPORTED AVOCADO 'HASS' FRUIT FOLLOWING TREATMENT WITH E+® ETHYLENE REMOVER OR 1-METHYLCYCLOPROPENE (1-MCP) DURING MEDIUM-TERM COLD STORAGE

ISHS VI International Postharvest Symposium EVALUATION OF SHELF LIFE AND RIPENING OF IMPORTED AVOCADO 'HASS' FRUIT FOLLOWING TREATMENT WITH E+® ETHYLENE REMOVER OR 1-METHYLCYCLOPROPENE (1-MCP) DURING MEDIUM-TERM COLD STORAGE

1-Methylcyclopropene (1-MCP) application to Spadona pears at different stages of ripening to maximize fruit quality after storage

The ‘Spadona’ pear is a summer cultivar that ripens without chilling-induced ethylene production. To expand our understanding of ethylene involvement in the initiation and progress of ‘Spadona’ fruit ripening, and with the aim of improving fruit quality after storage, pears were treated with the ethylene action inhibitor 1-methylcyclopropene (1-MCP). Fruit were treated with 0.2 μL L −1 1-MCP for 20 h at 20 °C, at four stages of ripeness as determined by ethylene production: pre-climacteric fruit at early and late harvests (H1 and H2, respectively), and early harvested fruit after 7 and 12 d conditioning at 20 °C (C1 and C2, respectively), reflecting early and mid-climacteric fruit. The treatment effect was evaluated after 6 months’ storage in controlled atmosphere (−0.5 °C, 1.5% O 2, 5% CO 2) and subsequently during 2 weeks at 20 °C. 1-MCP treatment effectively inhibited pear ripening when applied immediately after both early (H1) and late (H2) harvests and improved the storage potential of the fruit. However, the effect of 1-MCP treatment on H2 pears was less pronounced, resulting in a more rapid recovery of sensory attributes after storage. 1-MCP application to C1 pears also effectively inhibited ethylene production after storage and delayed pear softening during the first week at 20 °C, but thereafter fruit quality deteriorated. Applying 1-MCP to C2 pears resulted in a transient inhibition of ethylene production, which was recovered at 20 °C, with little effect on the storage potential of the fruit. mRNA expression of ACC oxidase 1 (ACO1), ACC synthase 1b (ACS1b) and the ethylene response sensor 1 (ERS1) after storage was inhibited by 1-MCP treatment at all stages of ripening, but the extent of inhibition was affected by the stage of ripening at the time of application. ACO activity was inhibited in fruit of all stages of ripeness, apart from mid-climacteric fruit. Improved quality of ‘Spadona’ pears was achieved after 6 months controlled atmosphere (CA) storage and 2 weeks shelf-life by applying 1-MCP immediately after harvest and the later harvested fruit were larger and of superior sensory attributes. Thus, 1-MCP can serve as an important tool for the regulation of postharvest pear ripening with economic benefits.

Postharvest Longevity and Responsiveness of Guava Varieties with Distinctive Climacteric Behaviors to 1-Methylcyclopropene

The local guava (Psidium guajava) variety cultivated in Israel, named Ben Dov, emits a strong odor and suffers from a short postharvest life. To address these problems, we initiated a guava breeding program, and identified two new varieties, the pink-flesh King and the white/yellowish-flesh Omri, that have much better storage lives and emit fewer odors. Physiological characterization of their ripening process revealed that the traditional variety Ben Dov exhibited a classic climacteric behavior, whereas the new variety King had a suppressed-climacteric phenotype, and Omri was apparently nonclimacteric and did not exhibit any increases in respiration and ethylene production rates during ripening. Furthermore, differing concentrations of the ethylene action inhibitor 1-methylcyclopropene (1-MCP) were required to inhibit ripening in the various varieties: a high 1-MCP concentration of 500 nL·L−1 was required to delay ripening and to prolong postharvest storage life of the climacteric variety Ben Dov; a moderate concentration of 250 nL·L−1 inhibited ripening of the suppressed-climacteric variety King; and a low concentration of just 100 nL·L−1 was sufficient to inhibit ripening of the nonclimacteric variety Omri. The results of this study indicate that different guava varieties may pursue distinctive climacteric behaviors: the suppressed-climacteric variety and, to a greater extent, the nonclimacteric variety, have longer storage lives and are more sensitive to 1-MCP than the traditional variety.

Postharvest Longevity and Responsiveness of Guava Varieties with Distinctive Climacteric Behaviors to 1-Methylcyclopropene

The local guava (Psidium guajava) variety cultivated in Israel, named Ben Dov, emits a strong odor and suffers from a short postharvest life. To address these problems, we initiated a guava breeding program, and identified two new varieties, the pink-flesh King and the white/yellowish-flesh Omri, that have much better storage lives and emit fewer odors. Physiological characterization of their ripening process revealed that the traditional variety Ben Dov exhibited a classic climacteric behavior, whereas the new variety King had a suppressed-climacteric phenotype, and Omri was apparently nonclimacteric and did not exhibit any increases in respiration and ethylene production rates during ripening. Furthermore, differing concentrations of the ethylene action inhibitor 1-methylcyclopropene (1-MCP) were required to inhibit ripening in the various varieties: a high 1-MCP concentration of 500 nL·L−1 was required to delay ripening and to prolong postharvest storage life of the climacteric variety Ben Dov; a moderate concentration of 250 nL·L−1 inhibited ripening of the suppressed-climacteric variety King; and a low concentration of just 100 nL·L−1 was sufficient to inhibit ripening of the nonclimacteric variety Omri. The results of this study indicate that different guava varieties may pursue distinctive climacteric behaviors: the suppressed-climacteric variety and, to a greater extent, the nonclimacteric variety, have longer storage lives and are more sensitive to 1-MCP than the traditional variety.

Exogenous ethylene inhibits sprout growth in onion bulbs

Exogenous ethylene has recently gained commercial interest as a sprouting inhibitor of onion bulbs. The role of ethylene in dormancy and sprouting of onions, however, is not known. A cultivar (Allium cepa 'Copra') with a true period of dormancy was used. Dormant and sprouting states of onion bulbs were treated with supposedly saturating doses of ethylene or with the ethylene-action inhibitor 1-methylcyclopropene (1-MCP). Initial sprouting was determined during storage at 18 degrees C by monitoring leaf blade elongation in a specific size class of leaf sheaths. Changes in ATP content and sucrose synthase activity in the sprout leaves, indicators of the sprouting state, were determined. CO(2) and ethylene production of onion bulbs during storage were recorded. Exogenous ethylene suppressed sprout growth of both dormant and already sprouting onion bulbs by inhibiting leaf blade elongation. In contrast to this growth-inhibiting effect, ethylene stimulated CO(2) production by the bulbs about 2-fold. The duration of dormancy was not significantly affected by exogenous ethylene. However, treatment of dormant bulbs with 1-MCP caused premature sprouting. Exogenous ethylene proved to be a powerful inhibitor of sprout growth in onion bulbs. The dormancy breaking effect of 1-MCP indicates a regulatory role of endogenous ethylene in onion bulb dormancy.

Diphenylamine Metabolism in ‘Braeburn’ Apples Stored under Conditions Conducive to the Development of Internal Browning

Diphenylamine metabolism and ethylene action were evaluated as factors influencing the development of 'Braeburn' apple internal browning and cavitation during cold storage. Apples treated with the antioxidant diphenylamine (DPA) and/or the ethylene action inhibitor 1-methylcyclopropene (1-MCP) were held at 1 degrees C for up to 6 months in air or a controlled atmosphere (CA) containing 1 kPa of O2 and 3 kPa of CO2. Cortex tissues from fruit without disorders as well as from symptomatic and asymptomatic areas of fruit with disorders were analyzed for DPA and DPA derivative content. Internal browning and cavities developed in control and 1-MCP-treated fruit stored in CA, whereas air-stored and CA fruit treated with DPA or with DPA and 1-MCP prior to storage did not develop disorders. Depending on the storage regimen and duration, less DPA was detected in 1-MCP-treated fruit. The 4-hydroxydiphenylamine (4OHDPA) content of control fruit decreased during air storage duration but increased between 2 and 4 months in CA storage. 4OHDPA content in 1-MCP-treated fruit increased with storage duration in CA but not air. N-Nitrosodiphenylamine (NODPA) was detected after 2 months in control fruit stored in air or CA and in 1-MCP-treated fruit stored in CA, and NODPA content in control fruit was higher compared to that in 1-MCP-treated fruit. Accumulation of 4-methoxydiphenylamine (4MeODPA) in control fruit stored in air increased with storage duration, but 4MeODPA content did not change in 1-MCP-treated fruit stored in air or CA. 2-Nitrodiphenylamine content was reduced by prestorage treatment with 1-MCP, but storage environment and duration had no effect on its accumulation. The results indicate that CA storage increases the risk of disorder development in 'Braeburn' apples, that DPA can prevent disorder development, and that the content of DPA and DPA derivatives is influenced by storage environment and ethylene action. A clear relationship between DPA derivative formation and storage conditions that promote internal browning was not apparent.

Responses of ‘Golden Delicious’ Apples to 1-MCP Applied in Air or Water

The efficacy of the ethylene action inhibitor 1-methylcyclopropene (1-MCP) applied in water to slow ripening of ‘Golden Delicious’ [Malus sylvestris var. domestica (Borkh.) Mansf.] apples was evaluated in comparison with 1-MCP applied in air. The material was applied by dipping fruit in 1-MCP water solutions (0.03, 0.3, or 3 mmol·m−3) for 4 min or by exposing fruit to 1-MCP gas (0.42, 4.2, or 42 μmol·m−3) in air for 12 h. Fruit were held in air at 20 °C for 25 days after treatment or stored at 0.5 °C in air for up to 6 months followed by 7 days in air at 20 °C. Application of 1-MCP in water or air delayed the increase in respiration and ethylene production associated with fruit ripening and reduced the amount of fruit softening, loss of acidity, and change in peel color. Treatments applied in water required a 700-fold higher amount of active ingredient compared with treatments applied in air to induce similar physiological responses. Fruit responses to 1-MCP varied with treatment concentration, and the maximum effects were obtained at concentrations of 4.2 or 42 μmol·m−3 in air and 3 mmol·m−3 in water. Peel color change was impacted less than retention of firmness and titratable acidity for 1-MCP treatments applied at concentrations of 4.2 or 42 μmol·m−3 in air and 0.3 or 3 mmol·m−3 in water. Treatment with 1-MCP in air or water was less effective for slowing peel degreening when treated fruit were stored at 0.5 °C compared with storage at 20 °C. Fruit treated with 1-MCP and stored in air at 0.5 °C developed a peel disorder typified by a gray·brown discoloration that is unlike other disorders previously reported for this cultivar. Symptoms were present when fruit were removed from cold storage and no change in symptom appearance was observed during a 7-d holding period at 20 °C.

Ethylene and α-Farnesene Metabolism in Green and Red Skin of Three Apple Cultivars in Response to 1-Methylcyclopropene (1-MCP) Treatment

Relationships among alpha-farnesene synthesis and oxidation, ethylene production and perception, antioxidative enzyme activities, and superficial scald development in fruit of three commercial apple cultivars were investigated at the biochemical and gene transcriptional levels. Scald-susceptible Cortland and Law Rome and scald-resistant Idared apples were untreated or treated with the ethylene action inhibitor 1-methylcyclopropene (1-MCP) and stored for up to 25 weeks at 0.5 degrees C. Separate blushed (red) and unblushed (green) peel tissue samples were taken at harvest and after 2, 4, 6, 10, 15, 20, and 25 weeks of storage. Large increases in peel tissue concentrations of alpha-farnesene and its conjugated trienol (CTol) oxidation products occurred in untreated Cortland and Law Rome and were about 4-9-fold greater than those in Idared. In both Cortland and Law Rome, accumulation of CTols in green peel was nearly twice that in red peel. 1-MCP treatment delayed and attenuated alpha-farnesene and CTol accumulation in each cultivar. Activities of peroxidase (POX) and catalase (CAT) were lower in red peel than in green peel, with the exception of CAT in Law Rome, whereas no effects of 1-MCP on enzyme activities were detected except for Cortland. In control fruit, internal ethylene concentrations (IECs) increased during the first 4-6 weeks to reach highest levels in Cortland, intermediate levels in Law Rome, and low levels in Idared. In 1-MCP-treated fruit, IECs increased gradually to modest levels by 25 weeks in Cortland and Law Rome but were almost nil in Idared. Expression patterns of the alpha-farnesene synthase gene MdAFS1, the ethylene receptor gene MdERS1, and the ethylene biosynthetic genes MdACS1 and MdACO1 were generally in accord with the patterns of alpha-farnesene and ethylene production. In particular, MdAFS1 and MdACS1 showed similar patterns of expression in each cultivar. Among the controls, transcript levels increased more rapidly in Cortland and Law Rome than in Idared during the first few weeks of storage. In 1-MCP-treated fruit, transcript abundance in Cortland and Law Rome rose to untreated control levels after 10-15 weeks but remained low in Idared. Scald symptoms were restricted to unblushed skin, and the incidence in controls after 25 weeks was nearly 100% in Cortland and Law Rome compared with 1% in Idared. 1-MCP treatment reduced scald incidence to 14, 3, and 0% in Cortland, Law Rome, and Idared, respectively. Overall, the results support the proposed role of CTols in scald induction and indicate that alpha-farnesene synthesis is tightly regulated by ethylene. However, gene transcription alone does not account for the big differences in ethylene and alpha-farnesene production in Cortland, Law Rome, and Idared apples.

(203) Responses of `Golden Delicious' Apples to 1-MCP Applied in Air and Water

The efficacy of the ethylene action inhibitor 1-methylcyclopropene (1-MCP) applied in water to slow ripening of `Golden Delicious' [Malus sylvestris var. domestica (Borkh.) Mansf.] apples was evaluated in comparison with 1-MCP applied as a gas in air. The material was applied by dipping fruit in 1-MCP water solutions (0, 0.03, 0.3 or 3 μM) for 4 min, or by exposing fruit to 1-MCP gas (0, 0.01, 0.1 or 1 μL·L-1) in air for 12 h. Fruit were held in air at 20 °C for 25 days after treatment or stored at 0.5 °C in air for up to 6 months followed by 7 days in air at 20 °C. Application of 1-MCP in water or air delayed the increase in respiration and ethylene production associated with fruit ripening, and reduced the amount of fruit softening, loss of acidity and change in peel color. Treatments applied in water required a concentration 700-fold higher compared to those applied in air to induce similar physiological responses. Fruit responses to 1-MCP varied with treatment concentration, and the maximum effects were obtained at concentrations of 0.1 or 1 μL·L-1 in air and 3 μM in water. Peel color change was impacted less than retention of firmness and titratable acidity for some 1-MCP treatments. Treatment with 1-MCP was less effective for slowing peel degreening when treated fruit were stored at 0.5 °C compared to storage at 20 °C. In 1 of the 3 years of this study, fruit treated with 1-MCP and stored in air at 0.5 °C developed a peel disorder typified by a gray-brown discoloration that is unlike other disorders previously reported for this cultivar.

Influence of Ethylene Action, Storage Atmosphere, and Storage Duration on Diphenylamine and Diphenylamine Derivative Content of Granny Smith Apple Peel

The application of diphenylamine (DPA) to prevent the apple peel disorder superficial scald can result in accumulation of a number of DPA derivatives resulting from C-nitration, C-hydroxylation, O-methylation, and N-nitrosation during fruit storage. As the presence of these compounds may be indicative of metabolic processes leading to superficial scald development, the contents of DPA and DPA derivatives were determined in fruits treated at harvest with DPA or DPA plus the ethylene action inhibitor 1-methylcyclopropene (1-MCP), which also prevents scald development. Influences of fruit maturity, storage environment, storage duration, and a 14 day poststorage ripening period on accumulation of DPA metabolites were also assessed. Poststorage ripening, 1-MCP treatment, and controlled atmosphere storage had varied effects on DPA derivative contents suggesting that reactive oxygen and nitrogen species, such as *OH, *NO, and *NO2, or enzyme-catalyzed reactions may be present during certain ripening and senescence-related physiological processes. Definitive correlations between superficial scald incidence and contents of specific derivatives were not observed.