Relationship between the Temperature Characteristics and the Occurrence of Watercore at Various Altitudes in ‘Hongro’ and ‘Fuji’ Apples

This study investigated the aspects of watercore symptoms due to climate condition in three different regions (coast: a coastal farm at an altitude of 12 meters, plains: an inland farm at an altitude of 44 meters, mountain: a highland farm at an altitude of 541 meters) in the Jeonbuk area of ‘Hongro’ and ‘Fuji’ apples (Malus domestica Borkh). The pattern of watercore occurrence showed a water-soaked form without various regional distinctions, with the watercore tending to move toward the ovary as the apples approached maturity. In addition, ‘Hongro’ had a higher degree of watercore occurrence than ‘Fuji’ apples. As a result of comparing the watercore occurrence and temperature characteristics associated with the fruit maturation period, the results for ‘Hongro’ and ‘Fuji’ apples were found to be closely related to the daily maximum temperature when it exceeded 30°C and the daily minimum temperature when it was less than 10°C, respectively. Therefore, watercore occurrence in ‘Hongro’ apples was found to be a ‘maturity, high-temperature responsive type’ caused by high temperatures, and that in ‘Fuji’ apples was a ‘maturity, low-temperature responsive type’ caused by low temperatures during the fruit maturation period. Among the fruit quality factors, the number of seeds was significantly higher in normal fruits than in watercored fruits, but there were no significant differences in other factors. The relative free sugar contents were in the order of fructose > sucrose, glucose > sorbitol for the two cultivars. Also, watercored tissue showed higher sorbitol levels and lower glucose and sucrose levels than normal tissue (in normal fruit and normal tissue inside the watercored fruit).