The effects of 1-methylcyclopropene on chilling and cell wall metabolism in loquat fruit

Loquat (Eriobotrya japonica L.) fruit were pre-treated with 0 (control) or 50 nl l(-1) 1-methylcyclopropene (1-MCP) for 24 h at 20 degrees C, then stored at 1 degrees C for 35 d to investigate the relationship between chilling injury and cell wall metabolism. Chilling increased fruit firmness and browning, and decreased the extractable juice content, with fewer symptoms of chilling injury in treated fruit. 1-MCP inhibited the activities of phenylalanine ammonia-lyase, cinnamyl alcohol dehydrogenase, 4-coumarate:coenzyme-A ligase, peroxidase, polyphenol oxidase, and slowed lignification. Treated fruit had a higher polygalacturonase activity, higher contents of water-soluble pectins, and lower contents of water-insoluble pectins compared with values in control fruit. These results suggest that the reduction in chilling injury in loquat caused by 1-MCP was primarily due to inhibition of lignin accumulation, a higher PG:PME ratio, and enhanced solubilisation of pectin in the cell walls.