野生二粒小麦(Triticum dicoccoides)与普通小麦(T.aestivum)A、B染色体组的同源性分析

Homology Analysis of A and B Genomes between Wild Emmer (T. dicoccoides) and Common Wheat(T. aestivum)

以普通小麦农家种、野生二粒小麦和野生二粒小麦与节节麦合成的双二倍体为材料,运用SSR分子标记方法对野生二粒小麦与普通小麦A、B染色体组的同源性进行了研究。结果表明:(1)野生二粒小麦与普通小麦A、B染色体组的遗传相似系数仅为0.189,存在较大的差异,推测野生二粒小麦与普通小麦的A、B染色体组在长期的进化过程中形成了各自完整的、平衡的遗传体系;(2)野生二粒小麦与普通小麦A和B染色体组各自的遗传相似系数分别为0.264、0.125,结合两个染色体组的聚类结果,发现A、B染色体组在进化上是不同步的,且A染色体组比B染色体组更为保守;(3)通过比较人工合成的双二倍体与普通小麦的遗传结构,发现双二倍体基因组的简单重复序列发生了明显的变化,印证了“小麦异源多倍体形成初期就发生了遗传物质变化”的观点。

In the history of wheat evolution studies, T. dicoccoides has been recognized to be the tetraploid ancestor of T. aestivum. To study the homology of genome A and B between T. dicoccoides and T. aestivum, germplasm resources of 13 accessions from T. aestivum, 12 accessions from T. dicoccoides and 4 accessions of the allopolyploid synthesized between T. dicoccoides and Ae. tauschii were analyzed by SSR (simple sequence repeat) markers. The results indicated that: (1) The genetic similarity between T. dicoccoides and T. aestivum on genomes A and B was 0.189, and the similarities of the accessions within genome A and genome B were 0.264 and 0.125 respectively. Therefore, it could be concluded that a considerable degree of genetic differentiation has occurred within genome A and genome B of the two species, and importantly, these two genomes have formed integrated and balanced genetic systems during the evolution from T. dicoccoides to T. aestivum; (2) Through comparison of the genetic similarities and dendrograms of genome A and genome B between T. dicoccoides and T. aestivum, the genetic similarity of these two species on genome A was higher than that on genome B, meaning that genome A and genome B had different evolutionary speeds and genome A was more conservative than genome B during the evolution. The reason of the phenomena might be that genome B of T. aestivum had several diploid donors, and thus the genetic background of genome B was more instable and complicated than genome A during the evolution;(3) Obvious changes of simple sequence repeats between the allopolyploid and T. aestivum could be applied to support the conclusion that the genetic background had been changed even in the early stage during the formation of allopolyploid plant.