A genetic study of the gametocidal effect of theLr19translocation of common wheat

The Lr19 translocation is preferentially transmitted to the progeny of a heterozygote due to the actions of at least two genes, Sd1 and Sd2 (new designation). However, only Sd2 occurs in the recombinant, Lr19-149, and often causes self-elimination of the recombined translocated segment in heterozygotes. The degree of segregation distortion is determined by the interaction of the Sd genes with polygenes (responder genes) on various wheat chromosomes. In this study suspected responder alleles derived from ‘Inia 66’ or ‘Indis’ (chromosomes 2A, 2B, 3B, 5B, 5D and 6D) appeared mostly to be partially dominant to overdominant over the ‘Chinese Spring’ derived alleles. A specific allele may not necessarily hafe-tfoe same effect (suppression or enhancement) in different genetic backgrounds. Responder genes may not fully compensate for the absence of a homologue in a hemizygote which may then produce effects quite different from those of the homo- and heterozygotes.