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Chris B. Watkins, Jacqueline F. Nock, and Tarek Wardeh

A sprayable formulation of 1-MCP (250 μL·L-1) and 1% oil adjuvant was applied to `McIntosh' and `Empire' apple trees 24, 14, and 7 days prior to anticipated optimum harvest dates (early, mid-, and late-spray timings, respectively), and fruit harvested sequentially over 2 to 3 weeks from this date. At harvest, internal ethylene concentrations (IEC), percentage of blush, starch indices, firmness, and soluble solids concentration (SSC) were measured, as well as ethylene production of fruit maintained for 7 days at 20 °C. Additional fruit were stored in air (0.5 °C) with or without postharvest 1-MCP treatment. Preharvest drop of `McIntosh' apples was also measured. Quality of these fruit was assessed at intervals for up to 4.5 months (`McIntosh') or 6 months (`Empire'). All spray timing resulted in marked delays of preharvest drop. For both cultivars, increases of IEC were inhibited or delayed by sprayable 1-MCP treatment, but effects on other maturity and quality factors were small. Ethylene production of treated fruit was lower than that of untreated fruit. The effects of sprayable 1-MCP on IEC and firmness were maintained during storage, but the longetivity of these effects was affected by cultivar, spray timing, and storage period. Postharvest application of 1-MCP further inhibited IEC and maintained firmness of the fruit during storage. These experiments show that sprayable 1-MCP may be a valuable tool to manipulate both pre- and postharvest responses of apple fruit. However, with the formulation used in these experiments, phytotoxicity, primarily as damage around lenticel areas, was observed at harvest indicating that further development of the formulation is necessary for industry use.

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Polyxeni M. Filios and William B. Miller

ethylene contamination. As it is unlikely to completely remove ethylene from the postproduction chain, a significant effort has been placed into technologies to reduce the effect of ethylene on floriculture crops. 1-MCP binds to ethylene receptor sites on

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Narendra Sankhla, Wayne Mackay*, and Tim Davis

Low concentration fumigation with nitric oxide (NO*) has been shown to extend the postharvest life of a range of flowers, fruits and vegetables by down-regulating ethylene production. Since ethylene is involved in flower abscission and leaf senescence of `John Fanick' phlox cut flower heads, a superior selection of perennial phlox (Phlox paniculata L.) bearing attractive long-lasting flowers, we have evaluated the effect of NO* delivered in vivo using sodium nitroprusside (SNP) as the source of NO* donor, on postharvest performance of `John Fanick' phlox flower heads. Although the presence of SNP (10-200 μmol·L-1) in the vase solution promoted the abscission of the open flowers, the young flower buds continued to open even in the presence of high SNP concentrations. On the other hand, at high SNP concentrations, the leaves became either yellow, or more frequently turned progressively black and senesced. Inclusion of sucrose in the vase solution, or pretreatment of flower heads with either 1-MCP or STS, significantly delayed the abscission of flowers and blackening of leaves. The pretreatment of flower heads with either 1-MCP or STS, or the presence of sucrose in the vase, together with SNP, greatly reduced the toxicity of the latter chemical resulting in improved postharvest display life. These results indicate that in `John Fanick' the leaves are relatively more susceptible to NO*-induced toxicity than the flowers. However, both sucrose and ethylene perception inhibitors are able to minimize the toxicity of high concentrations of NO* delivered in vivo via SNP.

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Toshikazu Matsumoto, Hajime Matsuzaki, Kou Takata, Yoko Tsurunaga, Hiroyasu Takahashi, Takao Kurahashi, Shinya Maki, and Kazushi Fujiwara

material fruit storage of semidried fruit of ‘Saijo’ persimmon using this approach is needed. Recently, a new technology based on 1-methylcyclopropene (1-MCP), an inhibitor of ethylene perception, has become available to horticultural industries around the

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Jinhe Bai*, Paul Chen, Elizabeth Baldwin, and James Mattheis

`Bartlett' pears were treated with 300 nL·L-1 1-MCP at 20°C for 24 h shortly after harvest, and were stored at -1 °C in either regular atmosphere (RA) or controlled atmosphere (CA: 1.5 kPa O2 / 0.5 kPa CO2). After 2 and 4 months of RA storage, or 4 months of CA storage, fruit were pre-conditioned at 10 °C, 15 °C or 20 °C for 5, 10, or 20 days, respectively. Pre-conditioned fruit were then held at 20 °C for 14 days to simulate marketing conditions. Flesh firmness (FF) and extractable juice (EJ) were monitored during the marketing period. The optimal stage of ripeness for `Bartlett' pears was defined to be when FF decreases to 27 N and EJ decreases to 55 mL/100 g. The proper pre-conditioning combinations of temperature and duration were 15 °C or 20 °C for 10 d or 10 °C for 20 d if the fruit had been stored in RA for 2 months, 10 °C or 15 °C for 5 d if the fruit had been in RA for 4 months, and 20 °C for 10 d or 10°C for 20 d if the fruit had been in CA for 4 months, for which combinations the fruit ripened within a week and maintained quality for 14 days at 20 °C. The treatment combinations of lower temperature and/or shorter duration times in pre-conditioning delayed the ripening response of the fruit, and combinations of higher temperature and/or longer duration times in pre-conditioning resulted in a shorter marketing life because of senescence breakdown, in comparison the optimal combinations mentioned above. These results indicate that pre-conditioning regimes for 1-MCP treated `Bartlett' pears are storage atmosphere and time dependent. Generally, CA stored fruit needed more preconditioning (in terms of higher temperature and/or longer duration) than did RA stored fruit.

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Jennifer DeEll and Behrouz Ehsani-Moghaddam

1-MCP is an inhibitor of ethylene perception that can delay fruit ripening and extend storage life. 1-MCP is marketed as SmartFresh™ for postharvest treatment and its use has become common practice in many apple-growing regions. 1-MCP reduces

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Jiwon Jeong and Donald J. Huber

Pre-ripe `Booth 7' avocado (Persea americana Mill.) fruit, a cross of West Indian and Guatemalan strains, were treated with 0.9 μL·L-1 1-methylcyclopropene (1-MCP) for 12 hours at 20 °C. After storage for 18 days in air at 13 °C, at which time whole fruit firmness values averaged about 83 N, half of the 1-MCP-treated fruit were treated with 100 μL·L-1 ethylene for 12 hours and then transferred to 20 °C. 1-MCP delayed softening, and fruit treated with 1-MCP retained more green color than air-treated fruit when full ripe (firmness 10 to 15 N). 1-MCP affected the activities of pectinmethylesterase (EC 3.2.1.11), α-(EC 3.2.1.22) and β-galactosidases (EC 3.2.1.23), and endo-β-1,4-glucanase (EC 3.2.1.4). The appearance of polygalacturonase (EC 3.2.1.15) activity was completely suppressed in 1-MCP-treated fruit for up to 24 days, at which time the firmness of 1-MCP-treated fruit had declined nearly 80% compared with initial values. The effect of exogenous ethylene applied to partially ripened 1-MCP-treated fruit differed for different ripening parameters. Ethylene applied to mid-ripe avocado exerted no effect on the on-going rate or final extent of softening of 1-MCP-treated fruit, even though polygalacturonase and endo-1,4-β-glucanase activities increased in response to ethylene. β-galactosidase decreased in 1-MCP-treated fruit in response to ethylene treatment. 1-MCP delayed the increase in solubility and depolymerization of water- and CDTA (1,2-cyclohexylenedinitrilotetraacetic acid)-soluble polyuronides, likely due to reduced polygalacturonase activity. At the full-ripe stage, the levels of arabinose, galactose, glucose, mannose, rhamnose, and xylose associated with the CDTA-soluble polyuronide fraction were similar among all treatments. In contrast, the galactose levels of water-soluble polyuronides declined 40% and 17% in control and 1-MCP treated fruit, respectively. Hemicellulose neutral sugar composition was unaffected by 1-MCP or ethylene treatment. The data indicate that the capacity of avocado fruit to recover from 1-MCP-mediated suppression of ripening can be only partially amended through short-term ethylene application and differs significantly for different ripening parameters.

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Daniel K. MacKinnon, Dale Shaner, Scott Nissen, and Phil Westra

Ethylene, a gaseous plant hormone, regulates many of the plant processes associated with senescence, fruit ripening, and abscission. 1-Methylcyclopropene (1-MCP) blocks ethylene from binding to receptors in plant cells, preventing ethylene

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Jiwon Jeong and Donald Huber

The present study was performed to characterize the physiological responses of cantaloupe [Cucumismelo (L.) var. reticulates`Athena'] fruit harvested at preripe (1/4 slip), half-slip, and full-slip stages of development and treated with 1-methylcyclopropene (1-MCP) prior to storage at 13 or 15 °C. Cantaloupe fruit (1/4 to full-slip stage) were treated with 1-MCP (0.01 and 1 μL·L-1) for 18 hours at 20 °C and then stored at 15 °C (pre-ripe fruit) or 13 °C (half- and full-slip fruit). The firmness of pre-ripe `Athena' fruit was significantly retained in response to 1 μL·L-1 1-MCP, but did not differ greatly from control fruit in response to 0.01 μL·L-1 1-MCP. Control fruit reached an edible condition (≈70 N) after 6 days of storage at 15 °C and persisted until day 12 (50 N), whereas 1 μL·L-1 1-MCP-treated fruit reached an edible stage after 17 days and persisted through 21 days (over 60 N). Fruit treated with 1-MCP exhibited slightly (0.01 μL·L-1) or dramatically (1 μL·L-1) lower electrolyte leakage throughout storage. 1-MCP (1 μL·L-1) significantly suppressed ethylene production and respiratory rates of pre-ripe cantaloupe during storage at 15 °C. Firmness retention was also highly significant for cantaloupe harvested and treated with 1-MCP (1 μL·L-1) at the half-slip and full-slip stages of development. 1-MCP treatment had a significant effect at reducing decay incidence and the occurrence of depressed or sunken regions of the fruit surface.

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Jorge A. Osuna-Garcia, Jeffrey K. Brecht, Donald J. Huber, and Yolanda Nolasco-Gonzalez

(with 31% of the total) and some countries of the European Union, which accounts for 19%. With very few exceptions, the United States requires QHWT for the entire volume of mangoes imported, although the European Union does not. 1-MCP is a potent