THEORETICALLY EXPECTED SEGREGATION RATIOS OF GENOTYPIC AND PHENOTYPICCLASSES IN THE F(2) AND BACK-CROSSES FOR DIGENICALLY CONTROLLED MARKER TRAITS LINKED TO THE SINGLE GAMETOPHYTIC S-LOCUS

The methods of genetic analysis in plants with the monogenic gametophy tic self-incompatibility system have been developed and presented in t his paper. Theoretically expected segregation ratios of genotypic clas ses in the F2 and back-crosses are calculated for digenically controll ed marker traits when only one or both structural loci are linked to t he S locus. The segregation ratios of phenotypic classes for different types of gene interaction (suppression, polymery, complementary genes , etc.) were obtained. It has been shown that the segregation ratios i n the F2 depend on the fact, whether plants in the F1 are cis- or tran sheterozygotes. This is one of many investigated peculiarities of gene tic analysis in plants with gametopytic self-incompatibility system. T he dependence of the segregation ratios both in the F2 and back-crosse s on the frequency of recombinations between the S locus and structura l loci was studied. It has been shown that the expected segregation ra tios of genotypic classes are determined unambiguosly for different ty pes of gene interaction (except suppression) and the values of recombi nation coefficients. Therefore, on the basis of two different, non-men delian, segregation ratios in the F2 it is possible to find out the mo de of inheritance of a trait under investigation. On the same basis, t he coefficients of recombination between structural loci and S-locus c an be determined. To analyze the ambiguos situation with a gene-suppre ssor, an additional information should be used. The segreration ratio in a back-cross (with the parental plant or with its progeny from the forced self-pollination) allows in his case to distinguish between two assumed values of recombination coefficients resulting in the same se greration ratio in the F2.