Evidence for pre-domestication (called “hansaibai”) of chestnut was found at the location of the Sannai-Maruyama ruins (3500–2000 BCE) 17, 18. et Zucc.) began is a difficult but interesting question. When domestication of Japanese chestnut ( Castanea crenata Sieb. The oldest known nut remains were found in the Omiya-no-moriura ruins (10,900–10,700 BCE), in which carbonized and peeled nuts were discovered 16. Thus, it is quite important to co-analyze cultivated and wild populations to clarify the genetic history of both population types.Ĭhestnut utilization in Japan dates back to the Jomon period (14,000–300 BCE). Conversely, gene flow from cultivars to wild individuals has influenced the genetic diversity of wild populations of several crops 11, 12, 13, 14, 15. The domestication process has been studied in many crops, and several key genes selected during domestication have been identified 3, 4, 5, 9, 10. Thus, wild individuals are interesting for plant breeders as a potential source of genes that have been lost during domestication. In contrast, wild individuals distributed in various areas have become adapted to different ecological situations, with the result that wild collections derived from divergent areas have greater genetic diversity than do cultivars in some species 6, 7, 8. Cultivated plants generally have good morphotypes for cultivating and harvesting 1, 2 and bear large fruits or nuts 3, 4, 5. Cultivated plants have been selected by humans for food and other useful materials. In plant species, there are large phenotypic differences between cultivated and wild forms. To conserve wild individuals carrying true “wild” genetic clusters, these individuals should be collected and preserved by ex situ conservation programs. These results suggested that the genetic structure of some wild individuals in natural stands was influenced by gene flow from cultivars. Parentage analyses between cultivars and wild individuals identified 26 wild individuals presumed to have a parent–offspring relationship with a cultivar. Bayesian structure analyses showed that wild individuals were roughly classified according to geographical distribution along the Japanese archipelago, except that some wild individuals carried the genetic cluster prevalent in cultivars. Assignment tests suggested that cultivars were relatively similar to populations from central to western Honshu. Genetic distance analysis revealed that wild populations in the Kyushu region are genetically distant from other populations, whereas other wild and cultivar populations are comparatively similar. We assessed 3 chestnut cultivar populations and 29 wild chestnut populations (618 accessions). Understanding the genetic diversity of this species and the relationships between cultivated and wild chestnut is important for clarifying its breeding history and determining conservation strategies. et Zucc.), the only fruit tree species domesticated in Japan, has been cultivated alongside natural stands since prehistorical times. Japanese chestnut ( Castanea crenata Sieb.
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