In fruit production, fruit thinning is required to maximize fruit quality and to protect the mother trees. However, thinning is troublesome and laborious work. Fruit self-thinning is the spontaneous elimination of pollinated flowers or fruits within a week to a month after pollination. Since the fruit self-thinning trait has the potential to improve fruit trees, a number of studies using fruit crops such as apple, orange, and tomato have been conducted to clarify the underlying mechanisms. The Japanese pear accession ‘Chojuro’ and its descendants ‘Niitaka’, 162-29, and ‘Akiakari’ have this trait. To identify the pattern and trigger of thinning in the accessions, we pollinated all flowers on the flowering day and recorded the numbers of retained and abscised fruits and the order of flowering in the cluster. The number of retained flowers/fruits in a cluster was widely variable in ‘Chojuro’ and ‘Niitaka’, but was uniform at 3 to 6 fruits per cluster in 162-29 and ‘Akiakari’. In 162-29 and ‘Akiakari’, the earlier the flower opened, the more likely it was to be retained in the cluster, similar to previous observations in apple. In contrast, ‘Chojuro’ and ‘Niitaka’ fruits abscised independently of the flowering order. Therefore, the pattern of fruit self-thinning in pear depends on the accession. To identify the trigger for fruit self-thinning, we analyzed changes in the levels of endogenous auxins and abscisic acid. The results implicate auxin and, to a lesser extent, abscisic acid in fruit self-thinning. Retained fruits showed temperature-dependent transient auxin accumulation, which may trigger self-thinning in pear.

在水果生产中，需要疏果以最大程度地提高水果质量并保护母树。但是，细化是麻烦且费力的工作。果实自我变稀是在授粉后一周至一个月内自发消除授粉的花朵或果实。由于水果的自我稀疏性状具有改善果树的潜力，因此进行了许多研究，使用水果作物（例如苹果，橙子和番茄）来阐明其潜在机制。日本梨登录号“ Chojuro”及其后代“ Niitaka”（162-29）和“ Akiakari”具有此特征。为了确定种质稀疏的模式和诱因，我们在开花当天对所有花朵进行了授粉，并记录了保留和脱落的果实的数量以及簇中开花的顺序。在“ Chojuro”和“ Niitaka”中，一簇中保留的花朵/水果的数量变化很大，但在162-29和“ Akiakari”中，每簇中有3至6个水果是均匀的。在162-29年和'Akiakari'中，花开得越早，越可能将其保留在簇中，这与以前在苹果中观察到的情况相似。相反，“ Chojuro”和“ Niitaka”果实的开花顺序与开花无关。因此，梨果实自稀的模式取决于品种。为了确定水果自我变薄的诱因，我们分析了内源性生长素和脱落酸水平的变化。结果暗示生长素和（在较小程度上）脱落酸可以使水果变稀。保留的果实显示出温度依赖性的短暂生长素积累，这可能触发梨的自稀。