Analysis of cell wall polysaccharides during storage of a local melon accession 'Wasada-uri' compared to the melon cultivar 'Prince'

Changes in cell wall polysaccharides associated with fruit softening under storage conditions at 20°C were compared between 'Wasada-uri' (a "five-carpel-type" melon accession) and 'Prince' (a "three-carpel-type" melon cultivar). Ethylene production in 'Prince' showed a peak on day-2 and decreased rapidly thereafter, while that of 'Wasada-uri' remained low until day-10. Carbon dioxide production in both varieties was highest at fruit harvest, and decreased rapidly during storage. Although flesh firmness in both varieties decreased continuously during storage, a distinct difference was observed, resulting in the firmness of 'Prince' flesh decreasing to between 16- 44% that of 'Wasada-uri'. In the "water- soluble" pectin fraction, uronic acid concentrations in 'Prince' increased linearly until day-5, while those of 'Wasada-uri' remained low. In the "Na₂CO₃-soluble" fraction, uronic acid concentrations in 'Wasada-uri' increased from day-3 to day-5, while those of'Prince' decreased from day-2 to day-10. Neutral sugar concentrations in the "Na₂CO₃-soluble" fraction decreased during storage, but there was no apparent difference between 'Wasada-uri' and 'Prince' melons.Inthe"Na₂CO₃-soluble "fraction, 'Wasada-uri' showed higher galactose, but lower arabinose concentrations compared to those of 'Prince'. Cellulose concentrations in 'Wasada-uri' were 15-43% higher than those of 'Prince', but the values changed slightly during storage. These results suggest that the long shelf-life of 'Wasada-uri' melon is due to the maintenance of cell wall integrity in the covalently-bound pectin polymers, and/or in the abundance of cellulosic polysaccharides.