ウンシュウミカン若木の着果程度及び摘果が果実の形質, 翌年の着花などに及ぼす影響

Abstract

Six-year-old trees of‘Miyagawa Wase’, an early ripening satsuma mandarin, bearing various fruit loads under natural condition were selected (non-fruit-thinning tree group). Trees in almost the same range of fruit load as in the non-fruit-thinning tree group were obtained by thinning fruits on heavily loaded trees (fruit-thinning tree group). The influences of fruit load and fruit thinning treatments on the fruit character, flower bud formation in the following season and the other components were investigated.1. The Brix of juice was higher with an increasing index of fruit load (No. of fruits per 10, 000 leaves) in the fruit-thinning tree group. However, the changes in Brix with increasing index of fruit load were small and the correlation between these two components was very low in the non-fruit-thinning tree group.2. In the lower range of index of fruit load, the Brix of juice in fruit-thinning trees was lower than that in non-fruit-thinning trees which were similarly loaded. When fruits were mixed and classified by fruit size, the Brix of larger fruit was lower in both group. Also the Brix of fruit in the fruit-thinning tree group was lower than that of the same size fruits in the non-fruit-thinning tree group.3. The more severe fruit thinning resulted in a lower Brix value independent of the fruit load in both groups of trees (the intensity of fruit-thinning treatment in non-fruit-thinning tree group was considered as zero percent).4. Acid concentration of juice correlated positively with index of fruit load in both tree group. When fruits were mixed and classified by fruit size, the acid concentration of similar size fruit was almost the same in both group. Fruit thinning therefore, seems to have little affect on the acid concentration of juice.5. The average weight per fruit decreased with increasing fruit load in both tree group, with no clear difference between the two tree group.6. In the non-fruit-thinning tree group, the summer shoot leaves in that year sprouted considerably regardless of fruit load. There was less sprouting in the fruit-thinning tree group and this decreased with increasing fruit load, to almost no sprouting at a index of fruit load of above 600.7. Trees of both groups having a low fruit load flowered abundantly much in the following year. The flowering in the fruit-thinning tree group was lower than that in the non-fruit-thinning tree group at similar fruit load. The flowering was insufficient to expect a normal yield at a index of fruit load of more than 550 in the non-fruit-thinning tree group, and more than 450 in the fruit-thinning tree group.