Genetics of Self-compatibility in Dihaploids of Solanum Tuberosum L. 2 Detection and Identification of all possible incompatibility and compatibility genotypes in six F1's from Interdihaploid crosses.

Two self-compatible (SC)dihaploids, G254 and B16, and one self-incompatible (si)dihaploid, G609, from Solunum tuberosum L. were intercrossed reciprocally. Segregation ratios SC : si : pc (pseudocompatible)were determined in all 6 Fi's in three successive years and critically tested and discussed. Genotypes at the S-locus could be assigned to the dihaploid parents and the S-allele on the translocation in sc G254 identified as S1. Using these genotypes all SC and si genotypes were derived which could be expected in the Fi's. Incompatibility groups were detected in each Fi from the results of complete diallels involving si plants. The genotype of each group was identified by test crosses. Compatibility groups could be both detected and identified by crossing in each F1 the sc plants as females with the already identified si sibs. In this way a complete series of 6 si testers and corresponding sc genotypes was obtained involving four alleles at the S-locus and S1 and Sx on the translocation. Certative disadvantage of pollen carrying the translocation could be ruled out as a possible cause of unexpected ratios. The hypothesis of an S-bearing translocation as the cause of self-compatibility could account for all results on the assumption that translocation homozygotes are lethal and the S-allele on the translocation is active in the pollen only.