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  • Author or Editor: Ryohei Nakano x
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`La France' pear (Pyrus communis L.) fruit were exposed to chilling temperature (-1 °C) for a week to induce ethylene biosynthesis before they were transferred to 20 °C to allow ripening. On 1, 4, or 7 days after the transfer to room temperature, fruit were treated with 20 μL·L-1 1-MCP for 12 hours. The 1-MCP treatments suppressed ethylene and carbon dioxide production significantly and slowed fruit softening. The shelf life period of fruit with desirable firmness treated with 1-MCP on day 4 was twice that of untreated fruit, with firmness of 1-MCP treated fruit on day 1 being higher than desirable while that of fruit treated on day 7 was lower than desirable. To determine the optimum 1-MCP concentration for treatment, fruit were exposed to 0.01 to 100 μL·L-1 1-MCP 3 days after the transfer to 20 °C. The fruit treated with 1 μL·L-1 1-MCP and less ripened similarly to untreated fruit, having a shelf life of a week. 1-MCP treatments of 10 and 100 μL·L-1 inhibited ethylene and carbon dioxide production, and delayed fruit softening and occurrence of senescent break down. The flesh firmness of these fruit maintained suitable eating quality for more than 3 weeks. Our results indicate that 1-MCP treatment of 10 μL·L-1 at 20 °C 3 to 4 days after initiation of ripening can extend the shelf life of `La France' pear fruit. Chemical name used: 1-methylcyclopropene (1-MCP).

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We investigated the differential regulation of two 1-aminocyclopropane-1-carboxylate synthase (ACS) genes, one 1-aminocyclopropane-1-carboxylate oxidase (ACO) gene and one ethylene response sensor (ERS1) ortholog during ripening and in response to wounding in avocados (Persea americana Mill. `Bacon'). The 1-aminocyclopropane-1-carboxylate (ACC) content, ACS activity and detectable expression of PA-ACS1 mRNA increased and reached a maximum prior to the climacteric peak, whereas ACO activity and the PA-ACO mRNA levels increased markedly only at the upsurge of ripening ethylene. A basal level of PA-ERS1 transcript was detected as from harvest, however, PA-ERS1 transcript was hyper-induced at the climacteric peak of ethylene production. 1-Methylcyclopropene (1-MCP) application at thepreclimacteric and the onset of climacteric stages inhibited the ACS and ACO activities, the transcription of PA-ACS1 and suppressed PA-ACO and PA-ERS1 mRNAs to trace levels. Discontinuation of 1-MCP treatment led to super-induction of PA-ACS1, PA-ACO, and PA-ERS1 transcripts. Wound induced ethylene biosynthesis and wound-induced PA-ACS2 mRNA accumulation were enhanced by 1-MCP, whereas wound-induced PA-ACO mRNA accumulation was unaffected by 1-MCP. These results indicate positive feedback regulation of the PA-ACS1 gene and negative feedback regulation of the PA-ACS2 gene by ethylene, while PA-ACO exhibits positive feedback regulation by ethylene and is also induced by wounding. The hyper-induction of PA-ERS1 mRNA at relatively high concentrations of ethylene may be a mechanism of avocados to regulate the ethylene responsiveness of the tissues by dissipation of the gas.

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