Comparison of Fruit Development Characteristics and Sucrose Metabolizing Enzyme Activity in Different Kiwifruit Cultivars

The study was conducted to examine the relationship between fruit development and sucrose metabolizing enzyme activities in the fruit of some kiwifruit cultivars grown in Jeju, Korea. The fruit characteristics and sucrose metabolizing enzyme activities were evaluated during fruit development in yellow-fleshed cv. 'Halla Gold', 'Sweet Gold' and 'Goldone' and green-fleshed cv. 'Garmrok'. Fruits were enlarged rapidly at the early stage of fruit development and dry matter showed a gradual increase by harvesting time. Starch content continued to increase by about 140 DAA, was maintained by 170 DAA, and thereafter decreased drastically. The level of soluble sugar was low by 120 DAA and then increased rapidly by harvesting time. The sucrose degradation activities of sucrose synthase (SS) and acid invertase decreased gradually by 120-140 DAA with a small difference depending on cultivars, but those of neutral invertase remained constantly low during fruit development. The sucrose synthesizing activities of sucrose phosphate synthase and SS maintained low levels of 140 and 100 DAA, respectively and then increased gradually. The results indicate that 100-120 DAA is a turning point in a changing pattern of fruit weight and soluble sugar content that combined with a change in sucrose metabolizing enzyme activities.