Adaptation and genetic differentiation in common wheat revealed by the analysis of SCAR markers

在东亚，中国西北部以旱作春小麦为主，中国东南部以湿性冬小麦为主。为了解东亚小麦品种间的遗传分化和生态分化，本研究以中国小麦品种中国、韩国和日本的56个小麦地方品种为材料，利用随机扩增多态性DNA技术分析了东亚小麦品种间的遗传分化和生态分化。特别是春型小麦分化明显。Em基因的PCR-RFLP分析和序列分析表明，小麦地方品种在5‘端非翻译区存在4个位点的突变，可分为A、B、C型。在EmH_2A基因3‘端非翻译区也检测到单点突变(+，-)。这些PCR-RFLP的地理变异在春型小麦、Em的B型和东部地区常见的“+”型EmH_2A之间又表现出明显的差异。3种类型的Em在不同品种群中的出现频率不同，这3种类型的Em在不同品种中的频率不同。尤其是在春型小麦中，Em的B型只出现在I、III、IV三个类群中。在B型中，Em基因的ABA反应可能发生改变，因为ABA反应元件中经常存在碱基替换。这些结果表明，Em的B型是为了适应中国东南部和东部的秋播和/或潮湿条件而选择的，从而建立了一个独特的品种群，该品种群在遗传上与中国北部和西部的品种有所区别。

In east Asia, spring wheat is mainly cultivated under dry condition in north/west China, while winter wheat adapted to wet condition is predominant in south/east China. Therefore, they should exhibit different adaptability to abiotic stresses such as low temperature and drought.In the present study, RAPD polymorphism as adaptatively neutral marker and PCR-RFLP polymorphism for ABA responsive genes (Em and EmH2A) were analyzed, to understand the genetic and ecological differentiation in east Asian wheat.Genetic differentiation between north/west China and south/east China was clearly indicated by RAPD analysis for 56 wheat landraces of China, Korea and Japan. Clear differentiation was observed specially among spring type wheat. PCR-RFLP and sequence analysis for Em gene revealed the existance of four site changes in 5' untranslated region, and wheat landraces were classified into three types (A, B and C types). A single site change (+, -) was also detected in 3' untranslated region of EmH2A gene. Geographical variation of these PCR-RFLP showed clear difference again among spring type wheat, type B of Em and "+" type of EmH2A being frequent in eastern areas. The frequency of three types of Em was different between cultivar clusters classified by RAPD polymorphism. Specially in spring type wheat, type B of Em was only seen in three clusters (I, III and IV). In type B, ABA response of Em gene could be changed, since base substitution was frequently found in ABA responsive element. It was indicated from these results that type B of Em was selected for the adaptation to autumn sowing and/or wet condition in south/east China, being resulted in the establishment of a unique cultivar group which was genetically differentiated from those of north/west China.