Horticultural Science and Technology 원예과학기술지 ISSN:1226-8763(Print) 2465-8588(Online)

This study aimed to investigate why empty branches occur in ‘Shine Muscat’ grapevines. Moreover, it also aimed to understand the bud characteristics of grapevines by examining bud development, the occurrence of various necrosis types and inflorescence primordium formation. The rate of inflorescence primordium formation was highest in September for young vines and in October for adult vines. In contrast, the rate was rather low in March of the following year. The rate of blooming during the flowering period of the following year was higher than the rate of inflorescence primordium formation during all investigation periods. This is likely because inflorescence primordia are continuously formed in accessory buds during environmental dormancy. However, several empty branches were found in both young and adult vines. According to the location of node, the necrosis rates of primary and accessory buds were high, and the rate of inflorescence primordium formation was low in the 1st node. Therefore, higher than medium pruning could increase grape yields. Leaves should be pruned up to the nodes before and after the 5th node, which has a relatively low rate of necrosis and a high rate of inflorescence primordium formation. Monthly comparisons showed that the rate of primary bud necrosis increased during the dormancy period, and the inflorescence primordium formation rate was lower in adult vines compared to in young and gibberellic acid (GA)-treated vines. There were no significant differences in bud characteristics among the branch lengths in both young and adult vines. However, it was determined that the branch length in GA-treated vines should be at least 80 cm in order to increase the rate of inflorescence primordium formation. In addition, if the thickness of the branch is either too thick or thin, it negatively affects the rates of necrosis and the formation of the inflorescence primordium. Therefore, it is advantageous to maintain the thickness of branches between the 3rd and 4th nodes to 8.5–11.5 mm for young vines and 10.0–11.5 mm for adult vines. Furthermore, longer and thicker branches in GA-treated vines were found to be more advantageous for the formation of inflorescence primordium.