Changes of pectic substances and polygalacturonase activity during fruit development of various peach cultivars with degrees of fruit softening

摘要

This study was carried out to investigate changes of pectic substances and polygalacturonase (PG) activity during fruit development in 'Mibaekdo', 'Okubo', and 'Yumyeong' peaches. Flesh firmness of the three cultivars decreased during fruit development. The rate of decrease in flesh firmness in 'Mibaekdo' was higher than in 'Okubo' or 'Yumyeong' at harvest. Uronic acid tended to increase during fruit development in cell wall materials, and rapidly increased during mature stage in water-soluble materials. Especially, the uronic acid contents in 'Mibaekdo' increased more greatly than those in 'Okubo' and 'Yumyeong' during mature stage. PG activities of the three cultivars were low at early development stage, but greatly increased at mature stage. Especially. PG activity was rapidly increased in 'Mibaekdo', a fast softening cultivar. The contents of rhamnose and galacturonic acid were greatly increased at mature stage and the changes were coincident with the changes of PG activity. Therefore, PG wasassumed to be important in fruit ripening and softening during fruit development in peach trees.