ブドウ‘巨峰’における1年枝の強さ, GA及びSADH葉面散布が側芽の壊死に及ぼす影響

Abstract

In order to make clear the cause of necrosis occurring in lateral buds in grapevines and its control measure, the effects of shoot vigor on the occurrence of bud necrosis, and also on the bud sprouting and the cluster development in the next spring were examined in a necrosis-sensitive cultivar, ‘Kyoho’. Further, the effects of foliar application of GA (gibberellic acid) and SADH (succinic acid-2, 2-dimethylhydrazide) before or after full bloom on the shoot growth and the occurrence of bud necrosis were studied in the same cultivar.Each lateral bud on a shoot consisted of a central bud and mostly two additional axillary buds in the cultivar, and the central bud deterioration was found in about 80% of the lateral buds at the nodes from the 6th to the 20th in the strong shoots (average length: 390cm) of a vigorous‘Kyoho’vine. On the other hand, only about 20% of them suffered from the necrosis in the weak shoots (average length: 88cm) of a moderately growing vine. When the data of the strong and weak shoots in both vines were combined, highly significant correlation (r=0.77**) was found between the shoot length and the percentage of the necrotic lateral buds below the 15th node. Further, when the strong (long) shoots were used as fruiting canes, they tended to show the lower rate of sprouting, the smaller number of florets per cluster and the shorter length of cluster.The spraying of GA solution at 100ppm against the leaves (from the 5th to the 9th) 9 days before or 7 days after full bloom remarkably acceralated the occurrence of the necrosis in the central buds of the lateral buds located at the wide range of nodes from the 1st to the 25th. Also, the number of axillary buds per lateral bud was extraordinarily increased by both treatments. Shoot growth, especially above the 10th node, was promoted more effectively by the prebloom application than the postbloom one.When the SADH solution was sprayed at 5, 000ppm against the leaves (from the 5th to the 9th) 14 days before or 10 days after full bloom, both of the treatments, particularly the prebloom application, significantly depressed the growth of internodes from the 10th to the 25th, and the occurrence of the necrotic buds at the wide range of nodes under the 25th.From these results, a close relationship is estimated between the occurrence of necrotic buds in the grape shoots and the level of endogenous GA in the buds, and it can be said that the foliar application of SADH before full bloom is very effective for controlling the necrosis.