Large-scale selection of lines with deletions in chromosome 1B in wheat and applications for fine deletion mapping

Terminal deletions of chromosome 1B in common wheat were selected on a large scale. The gametocidal gene of Aegilops cylindrica was used as the inducer of chromosome breakage. First, genes for endosperm storage proteins located on both arms of chromosome 1B were used as the selection markers. However, it was found that the chromosome breakage occurred during female gametogenesis, causing genotypic inconsistency between the embryo and endosperm. Thus, we isolated plants with terminal deletions in chromosome 1B by C-banding. Of 1327 plants examined, 128 showed aberrations in chromosome 1B: 47 in the short arm, 76 in the long arm, and 5 in both arms. The present deletions tended to have the breakpoint at more proximal regions than those produced previously by T.R. Endo and B.S. Gill. Using 33 deletion lines produced in this study and 34 lines previously produced, we mapped 39 RFLP loci and a nucleolar organizer region (NOR) on a specific region of chromosome 1B. The NOR was found to consist of two subregions with different repetitive units, which were termed NOR-B1d and NOR-B1p. Based on this fine deletion map and genotypic inconsistency between embryo and endosperm, the features of the gametocidal gene are discussed.