Chromosome pairing in diploid substitution rye and addition rye with wheat chromosomes

Chromosome pairing was studied at metaphase I in PMCs by C-banding in diploid rye plants with 1–3 monosomic-substitution wheat chromosomes and 1 monosomic-addition wheat chromosome. In plants with chromosome 5A, no univalents were found. In other plants with 1 monosomic-substitution wheat chromosome (7A, 2A, or 1A), only rye univalents occurred, on average 0.02–0.18 per PMC. Wheat chromosomes paired with homoeologous rye chromosomes in bivalents. The addition chromosome 6A occurred as a univalent with a frequency of 0.92 per PMC. In plants with 2–3 monosomic-substitution wheat chromosomes, no univalents were found. In 2 diploid rye plants with substitution chromosomes 2A, 5A and in 1 plant with 2A, 7A, wheat chromosomes paired mainly with rye homoeologues, but sometimes they paired with each other, forming heteromorphic wheat bivalent. In the other 3 plants with wheat chromosomes 2A, 5A, 2 plants with 2A, 7A, and 4 plants with 5A, 7A, a reverse situation was observed: nonhomoeologous wheat chromosomes paired with one another (forming a heteromorphic bivalent) more frequently than with rye homoeologues. In plants with 3 substitution wheat chromosomes (2A, 5A, 7A), 2 of them paired with each other, forming first of all a heteromorphic ring bivalent, while the third wheat chromosome paired with a rye chromosome in a ring bivalent or rarely in a rod bivalent. Wheat chromosomes sporadically occurred in multivalents. The presented data show that the rye genome promotes both homoeologous pairing of wheat and rye chromosomes and nonhomoeologous pairing of wheat chromosomes.