INDUCTION OF SMALL-SEGMENT-TRANSLOCATION BETWEEN WHEAT AND RYE CHROMOSOMES

A new approach to produce wheat-rye translocation, based on the geneti c instability caused by monosomic addition of rye chromosome in wheat, is described. 1 283 plants from the selfed progenies of monosomic add ition lines with single chromosome of inbred rye line R12 and complete chromosome complement of wheat cultivar Mianyang 11 were cytologicall y analyzed on a plant-by-plant basis by the improved C-banding techniq ue. 63 of the plants, with 2n = 42, were found containing wheat-rye tr anslocation or substitution, with a frequency of 4.91%. Compared with the wheat parent, other 32 plants with 2n = 42 exhibited obvious pheno typic variation, but their component of rye chromosome could nor be de tected using the C-banding technique. In situ hybridization with a bio tin-labeled DNA probe was used to detect rye chromatin and to determin e the insertion sites of rye segments in the wheat chromosomes. In 20 out of the 32 variant wheat plants, small segments of rye chromosomes were found being inserted into different wheat chromosomes and form sm all-segment-translocation (SS translocation). The physical mapping of the translocated small segments of rye chromosomes indicated that alie n insertion could occur in both the terminal and intermediate regions of wheat chromosomes. The technique described appeared to be an effect ive means to induce SS translocation. The wide application of SS trans location in the study of molecular cytogenetics and plant breeding is also discussed.