Chromosome pairing and synaptonemal complex formation in hexaploid wheat, monoisosomic and diisosomic for the long arm of chromosome 5B

Abstract

Chromosome pairing and synaptonemal complex formation have been analyzed at the ultrastructural level in spread microsporocyte nuclei of allohexaploid wheat, monoisosomic and diisosomic for the long arm of chromosome 5B. In addition spread pachytene nuclei of two Danish winter wheat cultivars, Vuka and Kraka have been analyzed. It is shown that in wheat diisosomic for the long arms of chromosome 5B synaptonemal complex formation is arrested when about 40% of the complement has synapsed. The number of lateral components involved in multiple associations at zygotene appears to be slightly lower than in euploid wheat. In wheat monoisosomic for the long arm of chromosome 5B synapsis is arrested when about 55% of the complement is combined with a synaptonemal complex. As synapsis is almost complete in euploid wheat this indicates that the short arm of chromosome 5B affects the extent of synapsis. The Danish winter wheat variety Vuka has, as is the case for euploid wheat, an almost complete pairing with synaptonemal complexes. In all nuclei one or more pairing partner exchanges were identified. © 1988 Carlsberg Laboratory.