Ripening behavior and combined fungicide and prestorage heat effects on decay control of ‘Bosc’ pears in air or step-wise low oxygen storage

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Abstract ‘Bosc’ pears ( Pyrus communis , L.) harvested at commercial maturity with flesh firmness (FF) of 75 Newton (N) from the southern district of Oregon were stored in either air or step-wise low O 2 at −1 °C during the 1992–'93 and 1993–'94 seasons. The levels of O 2 in the step-wise low O 2 storage were maintained and increased from 0.5% for four months to 1.0% for two months, and finally to 1.5% for two months while the CO 2 concentration in the storage was kept below 0.05%. Air-stored fruit were capable of ripening normally with good dessert quality after one, two, and three months of storage. These fruit softened to between 9.7 N and 15.0 N and reached the ethylene climacteric peak on day 7 or 8 of ripening at 20 °C. The ripened fruit developed a buttery and juicy texture as indicated by an apparent reduction of extractable juice (EJ) from 67 ml juice per 100 g fresh weight (FW) of unripened pulp tissue to less than 45.0 ml juice per 100 g FW of ripened pulp tissue. Fruit in air storage for four and five months reached the ethylene climacteric peak on day 4 of ripening but did not soften properly. Fruit stored in step-wise low O 2 for six, seven and eight months reached the ethylene climacteric peak on day 6 of ripening. Step-wise low-O 2 -stored fruit softened properly to 12 N or lower and reduced EJ to 49 ml 100 g −1 FW (six and seven months of storage) or 59 ml 100 g −1 FW (eight months of storage) on day 8 of ripening. Based on the analyses of ethylene production, fruit softening and reduction of EJ during ripening, fruit stored in the step-wise low O 2 storage for six, seven and eight months maintained a physiological state similar to the fruit stored in air for one to three months. The combination of prestorage heat (28 °C for one day) and step-wise low oxygen storage effectively reduced side rot by 60 and 63% in 1993 and 1994, respectively. Even greater decay control was obtained with the fungicides imazalil and Exp10412A on inoculated fruit, and thiabendazole plus captan on non-inoculated fruit.