Abstract
A B-chromosome of rye (Secale cereale L.) found in the Japanese strain ‘JNK' was revealed to pair with one of the A-chromosomes. A spontaneous A-B chromosome translocation could be verified by pairing studies and testcrosses to defined trisomics and wheat-rye addition lines. They showed that the long arm of rye chromosome 3R is involved in the rearrangement. Obviously, a terminal segment, including a large terminal heterochromatin block, was transferred to the terminal region of the long arm of the B-chromosome. A possible relationship between the interchange and the origin of the B chromosome is discussed.
