Assessment of genetic relatedness among cultivars of Pyrus pyrifolia and species native to east Asia by DNA analysis

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Genetic relationships of Pyrus pyrifolia and other Pyrus species native to east Asia were ambiguous. The origin of Japanese pear has two theories : 1.Development of Pyrus serotina native to Japan, 2.Imports from Pyrus pyrifolia (Sand pears) native to Central China. The theory for importing from China has an advantage, but the genetic relationship between Japanese pear and sand pear is unclear, therefore, the conclusion has not come yet. The research objective is to clarify the genetic relationships of Pyrus pyrifolia and other Pyrus species native to east Asia. We have cloned PPOMT1, similar t to O-methyltransferase, expressed in ripening fruits of Japanese pear and European pear, not in Chinese pear. We found this ripening gene was deleted in Chinese pear and that this is a useful marker for Pyrus classification. A few cultivars of sand pear have this gene and high homology to sequence of Japanese pear. This confirms the import theory. We classified ethylene synthetic genotypes of over 100 cultivars by ACC synthase genes (PPACS1 and PPACS2). This information is critical for making breeding strategies in Asian pears. Moreover, a total of 118 Pyrus spp.and cultivars native to east Asia were subjected to RAPD analysis. Some pear cultivars from Shikoku region were subclustered with some Chinese pears originated in Zhejiang province.