IDENTIFICATION OF THE E3900 FAMILY, A 2ND FAMILY OF RYE CHROMOSOME-B SPECIFIC REPEATED SEQUENCES

A second family of highly repeated sequences has been identified on th e B chromosome of rye (Secale cereale). The E3900 family was detected as a variant band in EcoRI digests of +B DNA. A clone of the basic rep eat of the family was obtained, and the organization of the family was investigated by genomic hybridization. The E3900 family has no appare nt homology to the A chromosome sequences of rye or other members of t he Gramineae. The family has been localized by in situ hybridization t o the end of the long arm of the rye B chromosome. The previously char acterized E1100 sequence shows in situ hybridization to the same locat ion as the E3900 family. These results are discussed in light of curre nt theories of the origin of B chromosomes.