Sufficient assimilate provision to fruits in different positions within an inflorescence: a critical factor determining the morphogenesis and development of Yatu in ‘Yali’ pear (Pyrus bretschneideri Rehd.)

Abstract

ABSTRACT In ‘Yali’ pears (Pyrus bretschneideri Rehd.) there is extra tissue formed on one side of the fruit, near the pedicel, causing a shape like a duck head termed Yatu, which is based on the Chinese phonetic alphabets of the raised duck head. The cell number of Yatu tissue has been known to be a direct factor influencing Yatu formation. The Yatu formation status among the fruits within an inflorescence is different, although the reason is not yet clear. Here, the per cent of first-order fruits with Yatu was 1.36 times higher than that of sixth-order fruits. The fruits with typical Yatu in first-order fruits were 3.52 times higher than in sixth-order fruits. The shorter peduncles of first-order fruits developed with a 1.25 times greater diameter compared to sixth-order fruits. The longitudinal diameter of the cross-section of vascular bundles was significantly higher in first-order fruits than in sixth-order fruits. The relatively higher GA3 and ZR levels, lower ABA content at second day before bloom (DBB) promoted the vascular bundle development. These results suggest that the well-developed vascular bundles, relatively higher GA3 content, and lower ABA content promoted Yatu development. The first-order fruits have a higher ability to form Yatu than sixth-order fruits.