Watercore in Fruits

Watercore is a physiological internal disorder affecting apples and pears, in which the intercellular air spaces of the flesh become filled with liquid, resulting in tissues with translucent appearance. Watercore is associated with fruit maturity as well as the presentation of varietal differences in susceptibility in apples and pears. Susceptibility is thus considered a heritable character. Watercore is promoted by low or high air temperatures during the preharvest period, large fruit, poor calcium concentration, high nitrogen and boron nutrition, a high leaf-to-fruit ratio, excessive fruit thinning, high or low light exposure, growth in volcanic ash soil, ethrel (ethephon) and gibberellin treatment, and girdling of the trunk and limbs. Mild watercore symptoms can disappear in storage, but when severe, internal browning and large cavities can develop. The fleshy tissue of apples with watercore has a higher sorbitol and sucrose concentration and lower glucose concentration than tissue without watercore. Watercore is also accompanied by changes in membrane permeability during maturation and ripening. A decrease in the expression of sorbitol transporter, leading to sorbitol accumulation in the intercellular spaces and subsequent flooding of tissues, has also been suggested.