Relationship between Fruit Quality and Length of Bearing Shoot in Apple ‘Kinshu’

Abstract

To develop a tree management strategy for the recently bred apple cultivar ‘Kinshu,’ we investigated the frequency distribution of bearing shoot length and its effect on fruit quality. Length distribution showed a bimodal curve, in which the most frequent shoot length was 30 cm, and the mean length was more than 20 cm. Short (≤ 5 cm), middle (5.1–10 cm), and long (≥ 10.1 cm) shoots accounted for approximately 20, 5, and 75%, respectively. Compared with 2022, when the crop loads and fruit quality were normal, more shoots and fruits were set in 2023. This resulted in lower fruit quality without a large reduction in the leaf-fruit ratio, probably due to light interception. Fruit size was negatively correlated with bearing shoot length in 2022 but not 2023. Fruit acidity slightly increased with shoot length across both years, and similar slight increases in firmness and the starch index indicated that maturation may be delayed in fruits on longer shoots. However, these quality changes with shoot length were small when compared with the quality variation observed within fruits on similar length shoots. Moreover, there were no clear relationships between shoot-length and color or soluble solid content. As a result, the effect of bearing shoot length was relatively small. In ‘Kinshu,’ the frequent longer bearing shoots are associated with a stable high leaf-fruit ratio, which allows a stable, high yield, but can reduce light penetration. Thus, it is suggested that exploration of adequate pruning/tree-training may be effective to determine how to obtain a stable, high yield of high-quality fruits.