EFFECTS OF DEFOLIATION AND FRUIT THINNING ON OCCURRENCE OF WATERCORE FRUIT IN JAPANESE PEAR (PYRUS-PYRIFOLIA NAKAI)HOSUI

Effects of defoliation and fruit thinning on the occurrence of waterco re fruit in Japanese pear (Pyrus pyrifolia Nakai) 'Hosui' were examine d. 1. Defoliation significantly reduced the occurrence of watercore fr uit. However, at harvest, the fruit were small and had a green ground color. Furthermore, they had a lower specific gravity and soluble soli ds concentration, and firmer flesh than those of the control. 2. Trees which were thinned excessively, leaving only 2, 4 and 8 fruits per m( 2) canopy, had a higher incidence of watercore fruit. The fruit at har vest were larger than those of the control, which had 12 fruits per m( 2) canopy, but they had lower specific gravity and greener ground colo r. Watercore occurred especially around the stalk cavity and below the skin; these symptoms are similar to those of fruit produced under abn ormal climate conditions such as a cool summer. Thus, watercore of Jap anese pear 'Hosui' is considered to be caused by higher source-sink ra tio of the tree.