Synaptonemal complex formation in two allohexaploid festuca species and a pentaploid hybrid

Abstract

Festuca arundinacea and Festuca gigantea are allohexaploids (2n = 6x = 42), that have bivalent pairing at metaphase I of meiosis. Analysis of the synaptonemal complexes of these species and of a pentaploid hybrid between F. gigantea and tetraploid Lolium perenne showed that initial synapsis in the allohexaploids is mostly between homologous chromosomes though some multivalents are formed, but in the hybrid most of the chromosomes associate as multivalents. It is concluded that the mechanism controlling bivalent formation in these species acts mainly at zygotene by restricting pairing to homologous chromosomes, but also at pachytene preventing cross-overs in the small number of homoeologous associations that have occurred. In the hybrid, where pairing control is ineffective, the mechanism fails at both stages. © 1993 The Genetical Society of Great Britain.