ANATOMICAL AND PHYSIOLOGICAL-RESPONSES OF MELTING-FLESH AND NONMELTING-FLESH PEACHES TO POSTHARVEST CHILLING

A study to compare the response to postharvest chilling (4 degrees 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 mor e susceptible to the development of mealiness than NMF types. Cell sep aration in mealy fruit was demonstrated by the release of mesocarp cel ls to an aqueous medium, allowing determination of mealiness severity. At a histological level, chilling brought about an impressive expansi on of the intercellular spaces in MF mesocarp tissue but did not affec t NMF fruit. A decrease in flesh electrical resistance after 1 week of chilling was observed only in MF fruit. However, electrical resistanc e increased in MF and NMF fruit following 2 and 3 weeks at 4 degrees C . Electrical resistance also decreased with ripening of MF fruit but d id not change when NMF fruit were ripened. Unlike NMF fruit, the MF ge notypes FL 90-21W and FL 91-16 showed an increase in respiration rate due to chilling. The rate of ethylene production decreased after 1 wee k at 4 degrees C in MF and NMF genotypes, However, two MF and two NMF genotypes exhibited rising ethylene levels after the second week of st orage at 4 degrees C, while ethylene production in one MF and one NMF genotype continued to decline.