COMPENSATED MONOSOMIC 5B-TRISOMIC 5A PLANTS IN TETRAPLOID WHEAT
Tetraploid wheat plants monosomic 5B-trisomic 5A were obtained by crossing nullisomic 5B-tetrasomic 5A plants of Triticum aestivum with T. durum and backcrossing five times with T. durum. These plants were found to carry a translocated 5A-5D chromosome. By self-pollination they originated plants carrying both a 5A-5D and 5B-5D translocated chromosome. In the latter the break point was located distally to the pairing suppressor gene. The translocations must have occurred by homoeologous pairing and recombination in the long arm of chromosomes of the group 5. F1 hybrids of monosomic 5B-trisomic 5A plants with rye and Aegilops sharonensis showed high homologous pairing when 5B was absent. Pairing promotion associated with the terminal segment of the long arm of 5D attached to the 5B-5D chromosome end was detected. It was suggested that the long arm of chromosomes of the homoeologous group 5 of wheat might carry two separate loci with genes for antagonistic effects on the pairing of chromosomes.