The geographical diversity of the frequency of the Glu-D1f allele in Asian common wheat, and the transmission route through which the wheat may have reached Japan

Abstract

The frequency of the high-molecular-weight (HMW) glutenin Glu-D1 alleles in Japanese, Chinese, and other Asian common wheat varieties was analysed in order to investigate a possible transmission route for common wheat to Japan. Although the frequency varied among the areas, the allele Glu-D1f was present in wheat from northern and southern Japan, in Xinjiang, Nanjing, Zhejiang, and Beijing in China, and in Afghanistan. However, a high frequency of the Glu-D1f allele was found predominantly in southern Japan. It was not detected in wheat from any other Asian region. This distribution of an adaptively neutral character suggests a specific route of transmission for common wheat to eastern China and Japan. It was introduced from Afghanistan, carried to Xinjiang (in north-west China), Nanjing, and Zhejiang (in south-east China), and then to southern Japan along the so-called Silk Road. It is believed that cultivated common wheat originated in the Middle and Near East and was carried along the Silk Road through China to the Far East, Japan. The latter country is the most geographically remote region from the origin of common wheat. During the course of its long journey and its adaptation to diverse local environments, Japanese common wheat has developed a unique composition of glutenin Glu-D1 alleles.