Malformed Fruits in `Niitaka' Pear Influenced by Pruning Strength, GA and Mepiquat Treatment

Abstract

This study was carried out to observe the effects of the pruning strength and the growth regulator on shoot growth and fruit shape in Pyrus pyrifolia cv. Niitaka. GA paste (GA) was known as a promoter of malformed fruits, but Mepiquat as an inhibitor. Light pruning treatment, of which removed the half of lateral shoots, decreased leaf area, weight, thickness, and the length of shoots and internodes in comparison to severe pruning. The occurrence of calyx perpetual fruit (CPF) in fruitlet stage was higher about 45% in severe pruning than in light pruning. Light pruning decreased malformed fruit by 10% compared to severe pruning at harvest stage, but there was no difference in soluble solid content of fruits between two treatments. Also light pruning decreased fruit weight. GA paste treatment on 50 days after full bloom significantly increased fruit weight, but Mepiquat decreased. In treatment of Mepiquat and GA the occurrence of malformed fruit was 31.3% and 35%, respectively and the index of symmetry was higher than control. Therefore, these results suggested that the light pruning has a positive effect on the production of symmetry fruit.