Preferential occurrence of wheat-rye meiotic pairing between chromosomes of homoeologous group 1

Summary Wheat-rye homoeologous pairing in both ABRR and (0–7)A(0–7)BRR plants takes place preferentially between homoeologous chromosomes of group 1. This suggests either a much greater affinity between wheat and rye chromosomes for this group or more efficient pairing initiation because of common nucleolar organizer activities. 1A–1R associations were more frequent than 1B–1R associations though in both cases pairing was restricted mostly to the long arms. From the variation in these particular chromosome arms the three following factors might hinder the wheat-rye pairing: regular homologous pairing of rye chromosomes, presence of prominent telomeric C-bands in rye chromosomes or occurrence of wheat-wheat homoeologous pairing.