Induction of small-segment-translocation between wheat and rye chromosomes.

A new approach to produce wheat-rye translocation, based on the genetic instability caused by monosomic addition of rye chromosome in wheat, is described. 1 283 plants from the selfed progenies of monosomic addition lines with single chromosome of inbred rye line R12 and complete chromosome complement of wheat cultivar Mianyang 11 were cytologically analyzed on a plant-by-plant basis by the improved C-banding technique. 63 of the plants, with 2n = 42, were found containing wheat-rye translocation or substitution, with a frequency of 4.91%. Compared with the wheat parent, other 32 plants with 2n = 42 exhibited obvious phenotypic variation, but their component of rye chromosome could not be detected using the C-banding technique.In situ hybridization with a biotin-la-beled DNA probe was used to detect rye chromatin and to determine 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 small-segment-translocation (SS translocation). The physical mapping of the translocated small segments of rye chromosomes indicated that alien insertion could occur in both the terminal and intermediate regions of wheat chromosomes. The technique described appeared to be an effective means to induce SS translocation. The wide application of SS translocation in the study of molecular cytogenetics and plant breeding is also discussed.