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-methylcyclopropene (MCP) at harvest. Half of the untreated fruits were exposed to 15 ppm ethylene during storage. Fruit softenin g was retarded by MCP both without storage or after storage but not affected by ethylene treatment during storage. Fruits treated with MCP developed severe flesh woolliness and reddening and had lower expressible juice compared to the ethylene treatment. Ethylene production of the fruits following treatment was not affected by MCP but was inhibited after storage while it was enhanced by exogenous ethylene. mRNA abundance of ACC oxidase (ACO), polygalacturonase (PG) and pectin esterase (PE) during storage was also inhibited by MCP, and ACO and PG expression was furthermore inhibited after post-storage ripening. Ethylene-treated fruits had higher message levels of ACC synthase (ACS) and PE than control fruit following storage while ACO levels were higher in control fruit and PG was similar in both. The accumulation of endogluconase (EGase) mRNA was enhanced by MCP at all stages while inhibited by ethylene after post-storage ripening. The data suggest that a certain level of ethylene production is essential for normal ripening of nectarines after cold storage. Exogenous ethylene during storage enhanced ethylene production after storage, thereby promoting the sequence of cell wall hydrolysis necessary for normal ripening. MCP blocked the ethylene action and inhibited its synthesis after cold storage, subsequently leading to abnormal softening and the occurrence of severe disorders. (C) 2001 Elsevier Science B.V. All rights reserved.