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Harpartap Mann, David Bedford, James Luby, Zata Vickers, and Cindy Tong

During storage, many apple (Malus ×domestica Borkh.) genotypes lose their desirable textural qualities, but some like `Honeycrisp', maintain their sensory Crispness and Firmness. To understand this differential response of genotypes to postharvest changes in texture, reliable and quantifiable methods of texture measurement are needed. This study integrated data from a snapping test, confocal laser scanning microscopy (CLSM), and sensory panels to study postharvest textural changes and to predict sensory textural attributes of Firmness, Crispness, Mealiness, and Juiciness. Three separate analyses on fresh, stored, and combined fresh and stored fruit data yielded different predictors for the same sensory attributes. Change in Crispness during storage was successfully predicted by change in Work during storage. Cell number and size were related to fresh fruit texture and its maintenance during storage. Unique textural properties of `Honeycrisp' were found to be inherited by its progeny.

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Harpartap S. Mann, Jennifer J. Alton, SooHee Kim, and Cindy B.S. Tong

During postharvest storage, apple [Malus pumila P. Mill.] fruit softens and its texture changes noticeably, with adverse effects on fruit quality. These changes are a result of degradation of the cell wall and middle lamella. Enzymes that cause changes in the cell walls have been characterized, but temporal distribution of their activities and their molecular regulation during storage is not well understood. ‘Honeycrisp’ fruit does not soften significantly during storage in contrast to fruit from ‘Macoun’, which softens significantly during storage. Contrasting phenotypes of ‘Honeycrisp’ and ‘Macoun’ were analyzed for changes in transcript levels of four cell-wall–modifying genes in fresh and 3-month-stored fruit from both cultivars. A suppression-subtractive hybridization experiment identified 15 cDNAs differentially expressed in fresh or 3-month-stored ‘Macoun’ fruit. Transcript levels of these 15 cDNAs were further quantified by quantitative real-time polymerase chain reaction (qRT-PCR) in fresh and 3-month-stored fruit from both ‘Macoun’ and ‘Honeycrisp’. The combination of a late increase in MdEXPA2 and decreased levels of MdPG and MdAFase1 transcript levels in ‘Honeycrisp’ fruit during storage may lead to its nonsoftening phenotype. Three cDNAs, potentially important for postharvest changes in apple fruit were also identified based on their different expression patterns in fresh and 3-month-stored ‘Macoun’ and ‘Honeycrisp’ fruit.