ANALYSIS OF RYE B-CHROMOSOME STRUCTURE USING FLUORESCENCE IN-SITU HYBRIDIZATION (FISH)

Fluorescence in situ hybridization (FISH) has been used to analyse the structure of the rye B chromosome. Genomic in situ hybridization (GIS H) demonstrates the high level of overall similarity between A and B c hromosomes of rye, as well as the presence of a number of specific seq uences. The B-specific repeat families D1100 and E3900 have been analy sed in terms of their physical location and possible contiguity. Rye B s contain members of the rye-specific dispersed repetitive family R173 , as well as centromeric regions similar to those of the As. The B chr omosomes analysed in our study lack detectable rDNA sequences. Anomalo us results have been obtained with a number of subtelomeric repetitive probes from rye. Bs usually lack these sequences, but evidence is pre sented that in some cases A-B translocation events may relocate such s equences from the As to the Bs. These data are discussed in the contex t of current models for the origin of the B chromosome.