A possible effect of b-chromosomes on metaphase I homologous chromosome association in rye

Abstract

The metaphase I association of rye chromosomes was examined both in normal plants (2n - 14) and in plants with rye B chromosomes (2n = 14 + Bs) using the C-banding technique. It was found that B chromosomes (Bs) affect homologous chromosome association. B isochromosomes (iso-Bs) were present in several plants; their presence was deduced, in addition to the morphology of chromosomes at mitosis, from the meiotic association between the two arms of the B and it was confirmed by its C-banding pattern. The strongest increase in rye metaphase association (measured as bound arms) was produced by the presence of the iso-B short (iso-BS) chromosome. The comparison of chromosome association between plants with and without Bs seems to point to the existence of a promoting effect on meiotic chromosome association by Bs, and in particular by the short arm. © 1991 The Genetical Society of Great Britain.