A study to compare the response to postharvest chilling (4 °C) for up to 3 weeks of melting-flesh (MF)—FL 90-20, FL 90-21W, and FL 91-16—and nonmelting-flesh (NMF)—`Oro A', FL 90-35C, and FL 90-47C—peach (Prunus persica L.) genotypes revealed that MF fruit were notably more susceptible to the development of mealiness than NMF types. Cell separation in mealy fruit was demonstrated by the release of mesocarp cells to an aqueous medium, allowing determination of mealiness severity. At a histological level, chilling brought about an impressive expansion of the intercellular spaces in MF mesocarp tissue but did not affect NMF fruit. A decrease in flesh electrical resistance after 1 week of chilling was observed only in MF fruit. However, electrical resistance increased in MF and NMF fruit following 2 and 3 weeks at 4 °C. Electrical resistance also decreased with ripening of MF fruit but did not change when NMF fruit were ripened. Unlike NMF fruit, the MF genotypes FL 90-21W and FL 91-16 showed an increase in respiration rate due to chilling. The rate of ethylene production decreased after 1 week at 4 °C in MF and NMF genotypes. However, two MF and two NMF genotypes exhibited rising ethylene levels after the second week of storage at 4 °C, while ethylene production in one MF and one NMF genotype continued to decline.
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