B Chromosomes and Chromosome Pairing in Lolium perenne × Festuca arundinacea Hybrid

Abstract

ALTHOUGH many crop plants evolved by interspecific hybridization and polyploidy, for example wheat (Triticum aestivum) and oats (Avena sativa), the production of synthetic species combining the genomes of diverse species has had little impact in plant breeding. This is chiefly because of failure to establish synthetic polyploids with the meiotic stability of natural polyploids. In natural polyploids, chromosome pairing is confined to homologous chromosomes with the result that only bivalents are formed and this ensures regular disjunction and disomic inheritance. In wheat, diploid-like chromosome pairing is controlled by a gene or genes on chromosome 5B which suppress the pairing of homoeologous chromosomes¹. Reports of similar control in the cultivated oat have been made^2,3. Moreover, it has been recently shown that B chromosomes can have a comparable effect in suppressing homoeologous chromosome pairing in polyploids^4,5.