The cytogenetic effect of heterochromatin in hexaploid triticale

Abstract

Isogenic lines with the presence and absence of the telomeric heterochromatic block of a rye chromosome have been isolated from an advanced strain of hexaploid triticale. The heterochromatic region is the largest one in the whole chromosome complement of this strain. Plants with the region absent have about one third less univalents at first meiotic metaphase as compared to plants with the region present. In plants where one homologue carries the region and the other does not, this rye chromosome pair forms an open bivalent or univalents in most of the PMCs. In these plants univalents of this rye chromosome constitute about one third of the total number of univalents. These data show that heterochromatin plays a major role in meiotic pairing failure and cytological instability of triticale. Analysis of progenies of selfed plants heterozygous for the presence of the heterochromatic region indicates a tendency to selection against the homologue carrying the region. In these progenies plants homozygous for the absence of the region are overrepresented on the expense of plants that are homozygous for the presence of the region. The results are discussed in relation to the present knowledge about the properties of heterochromatin and in relation to triticale breeding. © 1976 Mendelian Society of Lund