Detection of a 4DL chromosome segment translocated to rye chromosome 5R in an advanced hexaploid triticale line Bronco 90

Bronco 90 is an advanced line of hexaploid triticale and was reported to be a 2D(2R) chromosome substitution type. In F₁ hybrids of this triticale with bread wheat, however, a meiotic configuration of 16 bivalents and 10 univalents was frequently observed indicating the presence of an additional D(R) chromosome substitution or D/R translocation. To determine the chromosome constitution of Bronco 90, C-banding and fluorescent in sire hybridization techniques were applied to somatic and meiotic metaphase chromosomes. These analyses revealed that in Bronco 90, the terminal 7% of the long arm of rye chromosome 5R is derived from the long arm of chromosome 4D. This translocated chromosome (5RS.5RL-4DL) and telosome 4DL formed metaphase I bonds at a frequency of 71%, demonstrating the significance of small terminal chromosome segments for pairing. This novel rye-wheat translocation is probably generated by homoeologous crossing-over because the distal region of 5RL is known to be homoeologous to that of 4DL. Possible association of this translocation with the absence of hairy peduncle character in Bronco 90 is discussed.