Genetics of self-compatibility in dihaploids of Solanum tuberosum L. 3. Lethality of S-bearing translocation homozygotes

Summary Self-compatible (sc) plants from an I₁ of the sc dihaploid G254 and from the reciprocal F₁'s of crosses between G254 and another sc dihaploid, B16, were crossed with the self-incompatible (si) dihaploid G609. The 34 progenies thus obtained were tested for self-compatibility. Only 2 progenies consisted merely of sc plants, the remaining ones showing a homogeneous series of 1 : 1 ratios. It is concluded that homozygosity for the S-bearing translocation mostly leads to lethality. Evidence is presented, that lethality takes place in the very early stages of the embryo and endosperm development. On the basis of the results the expected sc : si ratios in G254 × B16 and reciprocal are calculated to be 3.3 : 1. This ratio was found indeed in our experiments. These findings support the hypothesis put forward in earlier publications in this series, that self-compatibility in G254 and B16 is based on the presence of an S-bearing translocation.