Changes in cell wall polysaccharides and quality of strawberry fruits from summer to autumn

Two strawberry cultivars, ‘Summer Tiara’ (a hybrid of a June-bearing cultivar and an ever-bearing (EB) cultivar) and ‘ES-10’ (an EB cultivar), were grown from July to November, 2015 at Yamagata Shonai Agricultural Technique Improvement Research Office, Japan. Changes in the fruit quality in cell wall polysaccharides, as affected by climacteric conditions, were compared. The fruit of ‘Summer Tiara’ was heavier overall than that of ‘ES-10’. The total sugar concentration increased as the growing temperature decreased, and there was no difference in the concentration between the two cultivars. ‘ES-10’ was characterized by a higher reducing sugar concentration and a lower sucrose concentration than those of ‘Summer Tiara’. In contrast to the total sugar concentration, the polyphenol concentration was greater at higher growing temperatures, especially in ‘Summer Tiara’. Fruits harvested in summer were softer than those harvested in autumn, and such a fruit softening was closely associated with the solubilization of pectin and hemicelluloses. The fruit of ‘ES-10’ were firmer than those of ‘Summer Tiara’, because of the higher uronic acid concentrations in the ionically-bound pectin fraction. ‘Summer Tiara’ was characterized by a higher phenol: acetic acid:water (PAW)-soluble solid concentration than that of ‘ES-10’ which means that a larger amount of the solubilized pectin polymers in ‘Summer Tiara’ were transferred into the PAW-soluble fraction.