Inducement of chromosome translocation with small alien segments by irradiating mature female gametes of the whole arm translocation line

Haynaldia villosa Schur. (syn. Dasypyrum villosum Candargy, 2n=14, VV) has been proved to be an important genetic resource for wheat improvement. The development of translocation with small alien chromosome segments, especially interstitial translocation, will be helpful for better utilization of its useful genes. Up to now, most of the reported Triticum aestivum-H. villosa translocation lines are involved in a whole arm or large alien fragments. In this paper, we report a highly efficient approach for the creation of small chromosome segment translocation lines. Before flowering, the female gametes of wheat-H. villosa 6VS/6AL translocation line were irradiated by C-60(O)-gamma ray at 160 Rad/M dosage rate and three dosages (1600, 1920, 2240 Rad). Anthers were removed from the irradiated florets on the same day and the florets were pollinated with normal fresh pollens of T. aestivum cv. Chinese Spring after 2 - 3 days. Genomic in situ hybridization (GISH) at mitosis metaphase of root-tip cell of M-1 plants was used to detect the chromosome structural changes involving 6VS of H. villosa. Among the 534 M-1 plants screened, 97 plants contained small segment chromosome structural changes of 6VS, including 80 interstitial translocation chromosomes, 57 terminal translocation chromosomes and 55 deletion chromosomes. For the 2240 Rad dosage treatment, the inducement frequencies of interstitial translocation, terminal translocation and deletion were 21.02%, 14.01%, and 14.65%, respectively, which were much higher than those previously reported. The M-2 seeds were obtained by backcrossing of 74 M-1 plants involving 146 chromosomes structural changes of 6VS, and it was found that the structural aberrations in the M-1 plants could be transmitted to their progenies. Irradiating mature female gametes of whole arm translocation is a new and highly efficient approach for creation of small segment chromosome structural changes, especially for interstitial translocations.