Ecogeographical differentiation in east Asian wheat, revealed from the geographical variation of growth habit and Vrn genotype

Growth habit, heading date and Vrn genotype were examined for wheat landraces cultivated in China, Korea and Japan, to study their ecogeographical differentiation in east Asia. Spring type landraces accounted for 43.6% of the whole, and the frequency varied between the localities, being closely related to the degree of winter coldness. Spring type landraces mainly adapted to north and south China where average January temperature is under -7 °C and over 4 °C, respectively. On the contrary, winter type adapted to areas of average January temperature from -7 °C to 4 °C. As to heading date, significant difference was not observed between spring and winter type landraces but between localities, and those cultivated in north China were significantly later in heading. It is therefore indicated that spring type mainly adapts to areas where wheat is sown in spring to avoid frost injury, and where winter temperature is not low enough to vernalize winter type wheat. Genetic analysis for spring type landraces showed that the relative frequency of four Vrn genes was different with each other. Vrn3 was most widely and frequently found among the four genes, followed by Vrn1 and Vrn2. Only seven landraces proved to be the carrier of Vrn4. The frequency was also different between localities. Genotype with Vrn1 plus other dominant gene(s) adapted to spring sowing to avoid severely cold winter in north China, while genotype with only Vrn3 adapted to winter sowing in south China and southwest Japan. It is therefore concluded that at least three ecotypes, differing in growth habit and Vrn genotype, are allopatrically distributed in east Asia, as a result of adaptation to winter coldness in each locality.