Preferential Transmission in Bread Wheat of a Chromosome Segment Derived from Thinopyrum distichum (Thunb.) Löve

A Thinopyrum distichum chromosome segment translocated on chromosome arm 7DL. of the line ‘Indis’, was shown to be preferentially transmitted in crosses with other bread wheats. The translocated segment carries a gene for leaf rust resistance and produces a null condition for the endopeptidase product, EP‐Dla. These characters were used to follow the transmission of the translocated chromosome in segregating and testcross progenies derived by crossing ‘Indis’ to four bread wheat cultivars. The severity of the gametocidal response in the heterozygotes ranged from a virtually exclusive transfer of the translocation to an almost normal transmission of the homologues. In some genetic backgrounds an intermediate level of transmission occurred. In the F1 with a gametocidal response, the transmission of the normal chromosome 7D was reduced in both sexes, but the reduction may be more severe in the male germline.