Production of deletion stocks and deletion mapping in common wheat

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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.