Pear (Pyrus spp.) is one of the leading cultivated fruit trees of temperate regions, and it belongs to the subfamily Pomoideae in the family Rosaceae. The majority of cultivated pears are functional diploids (2n = 34). As a popular fruit in the world market, pear is widely cultivated on six continents with major production in China, USA, Italy, Argentina, Spain, Korea, Turkey, South Africa, Japan and Belgium. As the top ranked production country, China produces more than 60% of the world pear production.
Pears are among the oldest of the world’s fruit crops, likely to have originated during the Tertiary period (65–55 million years ago) in the mountainous regions of southwestern China, and from there, it spread on to both the East and West. As the center of origin, China has rich resources of wild germplasm. Moreover, large numbers of botanical varieties and cultivars are grown in a wide geographical range, except for Hainan, Hong Kong, and Macao.
The Pyrus genus is genetically diverse with more than four thousands of cultivars and accessions, but it can be divided into two major groups, Occidental pears (European pears) and Oriental pears (Asiatic pears). At least 22 primary species are well-recognized in Pyrus; however, only a few species, including P. bretschneideri, P. pyrifolia, P. ussuriensis, P. sinkiangensis and P. communis have been utilized for fruit production.
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