摘要
According to conventional theory, little genomic changes should occur in homozygous and stable amphiploids of the grass family, particularly those involving polyploid wheat as a parent. In the present study, however, extensive genomic changes were detected in two octoploid partial amphiploids of common wheat (Triticum aestivum L.)_wheatgrass (Agropyron intermedium (Host) P.B.=Elytrigia intermedia (Host) Nevski=Thinopyrum intermedium (Host) Barkworth and Dewey), namely Zhong 3 and Zhong 5, by RFLP analysis using 10 low_copy, wheat chromosome_specific sequences and 33 representative homoeologous group_specific sequences as probes. Genomic changes involved loss of wheat hybridization fragment(s) and/or acquisition of new fragment(s). Uniformity of the RFLP patterns among 5 individual plants taken respectively from Zhong 3 and Zhong 5 in two successive generations, suggested that genomic changes probably had occurred in the early few generations after octoploid amphiploid formation, and remained essentially static thereafter. The highly similar RFLP patterns between Zhong 3 and Zhong 5, which had identical genomic constitution but differed from each other due to involvement of different wheat varieties as parents imply that genomic changes were probably not at random. Possible causes for the extensive and rapid genomic changes in the newly formed plant amphiploids, as well as their implications for polyploid genome evolution and breeding application are discussed.
根据传统理论，在禾本科特别是在含有多倍体小麦为亲本的禾本科纯合、稳定的双二倍体中应存在极少的基因组变异。然而，利用１０个小麦低拷贝染色体专化序列和３３个具代表性的部分同源群专化序列为探针，对２个普通小麦（ＴｒｉｔｉｃｕｍａｅｓｔｉｖｕｍＬ．）＿天蓝冰草（Ａｇｒｏｐｙｒｏｎｉｎｔｅｒｍｅｄｉｕｍ（Ｈｏｓｔ）Ｐ．Ｂ．＝Ｅｌｙｔｒｉｇｉａｉｎｔｅｒｍｅｄｉａ（Ｈｏｓｔ）Ｎｅｖｓｋｉ＝Ｔｈｉｎｏｐｙｒｕｍｉｎｔｅｒｍｅｄｉｕｍ（Ｈｏｓｔ）ＢａｒｋｗｏｒｔｈａｎｄＤｅｗｅｙ）八倍体部分双二倍体（即中３和中５）的ＲＦＬＰ分析结果表明，２个双二倍体均发生了广泛的基因组变异。这些变异包括小麦亲本杂交片段的消失和／或新片段的产生。对分别取自２个连续自交世代的中３和中５各５个单株的ＤＮＡ分析结果发现，同一双二倍体中，２个世代的各５个单株的ＲＦＬＰ谱带在所分析的序列中完全一致。这一结果表明，基因组变异可能发生在双二倍体形成后的早期世代；之后，便相对稳定地遗传下来。中３和中５具有相同的基因组构成，但由于其小麦亲本的不尽一致使二者存在遗传上的差异。据此，二者间变化后的ＲＦＬＰ图谱的高度相似暗示基因组变异可能不是随机发生。文中对新近形?
