Temporal sequence of cell wall disassembly events in developing fruits. 2. Analysis of blueberry (Vaccinium species)

Softening and pathogen susceptibility are the major factors limiting the marketing of blueberries as fresh fruits, and these traits are associated with fruit cell wall structure. However, few studies that characterize wall modifications occurring during development and ripening have been reported for this fruit. In this study the ripening-associated modifications of blueberry fruit cell walls (composition, pectin and hemicellulose solubilization, and depolymerization) at five stages of ripeness have been analyzed. Xylose was found to be the most abundant noncellulosic neutral sugar associated with fruit walls, and the observed high Xyl/Glc ratio suggested that xylans, which are usually a minor hemicellulosic fruit wall component, are abundant in blueberry. The pectic matrix showed increased solubilization at early and intermediate stages of ripening, but no changes were detected in late ripening. Furthermore, little reduction in pectin polymer size occurred during blueberry ripening. In contrast, hemicellulose levels decreased as ripening progressed, and a clear depolymerization of these components was observed. A model for cell wall degradation in this fruit is discussed.