Quality of Japanese plums as influenced by time of harvest and rate of ethylene production

Time of harvest, within the commercial harvesting period, affects quality of plums. Four plum cultivars, 'Pioneer', 'Sapphire', 'Songold' and 'Angeleno' were harvested beginning prior to the commercial picking period and extending beyond it. Fruit was stored at -0.5degreesC for a total of 5 weeks and evaluated weekly after storage, and again after 1 week at 15degreesC. Maturity indices were measured on all four cultivars, but only 'Pioneer' and 'Songold' are discussed. Fruit harvested later in the season tended to be of better quality than fruit harvested earlier. Full colour development and reduction in firmness occurred in 'Pioneer' after 7 days at 15degreesC without the need of a cold storage period. In 'Songold', there was no change in colour or firmness without cold storage. Internal disorders increased with increasing storage time, but at the end of the storage period the incidence of disorders between fruit harvested at different times was not as great as expected. 'Pioneer' and 'Sapphire' were classified as climacteric and 'Songold' and 'Angeleno' as suppressed climacteric based on ethylene production. There was a correlation between the climacteric classification of a particular cultivar and its ripening response.