Structure of the rye midget chromosome analyzed by FISH and C-banding

The diminutive "midget" chromosome derived from rye (Secale cereale) was analyzed by C-banding and fluorescence in situ hybridization (FISH) using DNA probe pSau3A9 that is located in the centromeres of cereal chromosomes. FISH signals were detected at one end and overlapped one of the two telomeres of the midget, indicating that the midget is a telocentric chromosome. The FISH and C-banding results show that the centromere of the midget chromosome is smaller than those of normal wheat and rye chromosomes. These results indicate that one of the breakpoints occurred in the middle of the centromere of rye chromosome 1R during generation of the midget.