Genetic Diversity and Geographical Differentiation in Asian Common Wheat (Triticum aestivum L.), Revealed by the Analysis of Peroxidase and Esterase Isozymes

Abstract

Genetic structure of Asian wheat (Tritium aestivum L.) was investigated by the analysis of two isozymes, using 648 wheat landraces. Gene diversity over all populations was 0.254, and the trend of an eastward decline was observed. By cluster analysis and principal co-ordinate analysis based on genetic distance among populations, thirty-three populations were classified into six clusters, and it was indicated that Asian wheat could be divided into at least three lineages. The first lineage of wheat consisted of populations from Turkey to Sichuan (China), suggesting the spread of wheat to southwest China through the ancient Myanmar route. Wheat populations introduced to China through this route were mostly of the red-grain type, and it was considered that wheat adapted to humid and rather hot condition in southern slope of Himalaya had been selected and introduced to China. The second lineage comprised of populations from the areas along the so-called “Silk Road”. Wheat is commonly cultivated under dry and cold condition in these areas, and was characterized by the frequent distribution of white-grain type. The third lineage contained populations from the coastal area of China and Korea, and genetic relationship with the second lineage was suggested. The result of the present study indicated that Asian wheat is genetically and geographically differentiated, and that different types of genetic resources could be found depending on the growing condition and the lineage of wheat populations.