Calyx Abscission in Pear (Pyrus spp.) Cultivars and Its Inheritance

During pear fruit development, calyx can abscise from fruitlet following petal fall. The calyx abscission varies with pear cultivars. The presence of calyx on pear fruit makes the fruit shape calyx end protruded. In the present study, the degrees of the calyx abscission were examined in 120 Southern-type Asian pear (Pyrus pyrifolia), 52 Nothern-type Asian pear (P. ussuriensis), and 34 European pear (P. communis) cultivars, and its inheritance was investigated using cross combinations between the Southern-type Asian pear cultivars showing different degrees of calyx abscission. Majority of the cultivars produced 10% or 90% calyx-perpetual fruit, but the cultivars producing both calyx-perpetual and -deciduous fruit were in minor frequency. The cultivars producing 10% calyx-perpetual fruit were in higher frequency in Southern-type Asian, Nothern-type Asian, and European pears in that order, while those producing calyx-perpetual fruit were in higher frequency in European, Nothern-type Asian, and Southern-type Asian pears in that order. In the cross between the parents producing 10% calyx-perpetual fruit, most of the F1 seedlings also produced 10% calyx-perpetual fruit. In the cross between the parents producing 90% calyx-perpetual fruit, on the contrary, most of the F1 seedlings also produced 90% calyx-perpetual fruit. When the paternal parent produced 10% calyx-perpetual fruit, most of the F1 seedlings also produced 10% calyx-perpetual fruit regardless of the degree of calyx abscission in the maternal parent. When the cross was between the maternal parent producing 10% calyx-perpetual fruit and the paternal parent showing different degrees of calyx abscission, the F1 seedlings showed similar degrees of the calyx abscission to those in the paternal parent. These results suggest that the characteristics of the calyx abscission is influenced more greatly by the paternal parent than by the maternal parent, and the calyx abscission in Southern-type Asian pears is a qualitative trait which is governed by dominant gene(s).