Effect of split pit on maturation of ‘shimizu hakuto’ peach on trees

Abstract

Split pit in peach [Prunus persica (L.) Batsch] fruit is an internal disorder characterized by the splitting or fracture of the lignified endocarp known as the stone or pit. It is empirically known that split-pit peach fruit mature earlier than normal fruit on trees, thereby leading to frequent preharvest fruit drop in split-pit fruit. However, studies that accurately compare split-pit and normal fruit maturation and/or focus on the physiological mechanism underlying this difference in maturation are limited, partly due to the lack of an effective method to distinguish split-pit fruit from normal fruit on trees. Recently, we demonstrated that an acoustic vibration method could be effectively used for the nondestructive detection of split pit in unpicked peach fruit on trees. In this study, we applied this method to distinguish normal fruit from split-pit fruit and evaluate maturation on trees. Comparison of pairs of normal and split-pit fruit grown at a near-canopy position for three consecutive years (2018–2020) revealed that split-pit fruit matured earlier than normal fruit in most pairs. The average harvest date difference was approximately three days, at least under the experimental conditions in 2020. The amount of ethylene produced from seeds was significantly larger in immature split-pit fruit than immature normal fruit collected at fruit development stage from late June to early July, suggesting that the increased ethylene production from seeds during the fruit development stage is a possible cause of early maturation in split-pit fruit. From the results obtained, we discuss the effect of split pit on the maturation of peach fruit on trees in relation to practical cultivation management to reduce problems caused by split pit.