Ethylene involvement in the cold storage disorder of 'Flavortop' nectarine

'Flavortop' nectarine was either held at 20 degreesC for ripening or stored at 0 degreesC for 30 days after treatment with 0.1 ppm 1-methylcyclopropen e (MCP) at harvest. Half of the untreated fruits were exposed to 15 ppm eth ylene during storage. Fruit softenin g was retarded by MCP both without sto rage or after storage but not affected by ethylene treatment during storage . Fruits treated with MCP developed severe flesh woolliness and reddening a nd had lower expressible juice compared to the ethylene treatment. Ethylene production of the fruits following treatment was not affected by MCP but w as inhibited after storage while it was enhanced by exogenous ethylene. mRN A abundance of ACC oxidase (ACO), polygalacturonase (PG) and pectin esteras e (PE) during storage was also inhibited by MCP, and ACO and PG expression was furthermore inhibited after post-storage ripening. Ethylene-treated fru its had higher message levels of ACC synthase (ACS) and PE than control fru it following storage while ACO levels were higher in control fruit and PG w as similar in both. The accumulation of endogluconase (EGase) mRNA was enha nced by MCP at all stages while inhibited by ethylene after post-storage ri pening. The data suggest that a certain level of ethylene production is ess ential for normal ripening of nectarines after cold storage. Exogenous ethy lene during storage enhanced ethylene production after storage, thereby pro moting the sequence of cell wall hydrolysis necessary for normal ripening. MCP blocked the ethylene action and inhibited its synthesis after cold stor age, subsequently leading to abnormal softening and the occurrence of sever e disorders. (C) 2001 Elsevier Science B.V. All rights reserved.