GENETIC-MAPPING IN THE 1R.1D WHEAT-RYE TRANSLOCATED CHROMOSOMES

Translocation chromosomes 1R.1D(5+10)-1 and 1R.1D(5+10)-2 were produce d to improve bread-making quality in triticale and to manipulate the d osage of the Glu-DI gene in wheat. They involve transfers of segments of the long arm of chromosome 1D of bread wheat to the long arm of rye chromosome 1R. The translocated long arms of the chromosomes were map ped genetically in wheat and triticale using polymorphism for C-bandin g patterns, allelic variation of the Glu-D1 gene, and a telocentric ch romosome 1RL. The total frequency and the general distribution of reco mbination in the translocated arms was similar to that in normal long arms of group-1 chromosomes in wheat, rye, and triticale, except that the distal rye segments of the translocations showed a 15- to 20-fold increase in recombination frequency compared with normal IR. Despite m ajor differences in the physical structure of the translocated arms, b oth appeared very similar genetically, suggesting that genetic mapping is a poor indicator of the physical structure of translocations. Gene tic length of the 1DL segment in chromosome 1R.1D(5+10)-1 was 31 cM, m aking the chromosome unsuitable for Glu-D1 dosage manipulation in whea t. The potential of chromosome 1R.1D(5+10)-2 for wheat breeding needs further testing. However, both chromosomes behave normally in hexaploi d triticale.