Production of deletion stocks and deletion mapping in common wheat

本研究的首席研究员(Endo，T.)发现与小麦有亲缘关系的野生物种圆柱型山羊草的一种特殊染色体在普通小麦中引起高比率的染色体结构变化。利用这条染色体，他在21条小麦染色体上产生了436条缺失，并建立了缺失基因库。然而，人们怀疑背景染色体的构成中除了缺失外，还存在一些异常。本研究旨在(1)对缺失群体进行详细的细胞遗传学研究，(2)产生纯合或半合子缺失群体，(3)通过缺失作图构建小麦染色体图谱。通过1993~1995年的研究，对小麦21条染色体(3条基因组，7条同源群)的全部缺失染色体进行了细胞学检查，澄清了以下事实：(1)当染色体臂上的缺失超过一定的大小时，不能使其纯合，因为它们的二体缺失没有达到或导致染色体的狭窄(Sears And Sears 1978)。(2)当获得缺失纯合子时，这些植株总是被发现存在易位染色体，可能涉及缺失的染色体片段。(3)组织学观察发现缺失库中存在易位，但在缺失染色体中几乎不可能检测到微小的间质缺失。因此，产生了大量的缺失库，并确认了它们的染色体组成。利用缺失库，小麦染色体的全缺失作图有望取得进展。

The head investigator of this study (Endo, T.) discovered that a specific chromosome of an wild species, Aegilops cylindrica, related to wheat, causes a high rate of chromosomal structural changes in common wheat. Utilizing this chromosome, he produced 436 deletions in 21 wheat chromosomes and has established the deletion stocks. However, it was suspected that there were some aberrations in the background chromosome constitutions other than deletions. Also, there were some deletion chromosomes whose authenticity was doubted.The present study was conducted (1) to study the deletion stocks cytogenetically in detail, (2) to produce homozygous or hemizygous deletion stocks, and (3) to construct wheat chromosome maps by deletion mapping. Through the studies of 1993 to 1995, the cytological examination of all the deletion chromosomes of 21 wheat chromosomes (three genomes and seven homoeologous groups) was completed, and the following facts were clarified. (1) The deletions in the chromosome arms, whose disomic losses were not achieved or cause stenlity (Sears and Sears 1978), could not be made homozygous when they exceeded certain sizes. (2) When deletion homozygotes were obtained with the deletions not expected to become homozygous, those plants were always found to have a traslocation chromosome, probably involving the deleted chromosomal segment. (3) Translocations in the deletion stockes were recognized by chtological observations, but it was almost impossible to detect minor interstitial deletions in the deletion chromosomes. Thus, a large number of deletion stocks have been produced and their chromosomal constitutions were confirmed. It is expected that using the deletion stocks, full-scale deletion mapping of wheat chromosomes will be progressed.