Pear Genomics

Abstract

Pear, like the other pip fruit species apple and quince, belongs to the sub-family Maloideae in the Rosaceae, sharing a basic chromosome number of x = 17 which indicates a polyploidy origin. The genus Pyrus is believed to have arisen during the Tertiary period in the mountainous regions of western China. Dispersal and speciation is believed to have followed the mountain chains both east and west (Rubzov, 1944; Zeven and Zhukovsky, 1975). Wild pears can be found in the entire Eurasian zone. In Europe they are mostly Pyrus communis L. subsp. pyraster (L.) and in the Caucasus, P.caucasica (Fed.) Browicz. These pear trees produce small fruits of variable characteristics, which were probably picked and preserved dried by early humans. Domestication occurred from the better-fruited trees. As for apple, grafting played a key role in the diffusion of improved genotypes in Central Asia and in Eastern Mediterranean area. According to Hedrick et al. (1921), European pear culture was well established in Greece and cultivars with distinct names were propagated as early as 300 B.C. Oriental pears, which arose independently, were also grown in China for more than 2000 years (Kikuchi, 1946).