THE TRANSFER OF THINOPYRUM-DERIVED LEAF-RUST RESISTANCE FROM COMMON WHEAT TO DURUM-WHEAT

The leaf rust resistance gene on chromosome 7AL of 'Chinese Spring' transfer no. 12 derived from Thinopyrum ponticum, was transferred to durum wheat by standard backcrossing. In 'Agatha' and 'Indis' a leaf rust resistance gene from Thinopyrum ponticum and Thinopyrum distichum respectively, is found on a translocated segment on chromosome arm 7DL. The use of the 'Langdon' disomic D-chromosome substitution lines for 7A and 7B resulted in the recovery of tetraploid leaf-rust resistant lines from the crosses with 'Agatha' in the B2F1 generation. Tetraploid lines carrying the 'Indis' translocation segment were recovered in the B2F2 generation. The F2 segregation ratios for rust resistance after selfing or back-crossing generally fitted a 1:1 ratio indicating non-transmission of the translocation segments in the male gametes. Homozygous resistant plants were not obtained. Meiotic instability was observed in 28 chromosome B1F2 derivatives of the crosses between 'Chinese Spring' transfer no. 12 and durum wheat.