Male‐Fertility Restoration in Crosses of R5 with Soft Red Winter Wheats1

The inheritance of male‐fertility restoration was studied in crosses of the spring wheat restorer germplasm line R5 with cms ‘Monon’ and cms ‘Redcoat’ soft red winter wheat (Triticum aestivum L.) cultivars with T. timopheevii Zhuk. cytoplasm. Two greenhouse cycles of Fl's, F2's, BC1's, along with the restored parent, and malesterile parents, were grown to provide two sets of data. Genetic hypotheses were postulated as expected ratios of fertile: semi‐sterile: sterile plants and data were tested for goodness of fit by chi‐square analyses. The BC1F2 populations and F3 populations were grown in the field to determine the proportion of families segregating for sterility. Results from the cms Monon/R5 crosses indicated the presence of two partially dominant complimentary restorer factors in the greenhouse and field environments. Complete fertility restoration was expressed only when both dominant factors were present to either the homozygous or heterozygous condition. Results from the cms Redcoat/R5 crosses suggested the presence of three dominant factors in the greenhouse environment, but segregation in the field environment suggested that only two factors were involved. The complete restoration of fertility of F1 plants in the environments tested suggests that R5 is a valuable source of restorer factors for developing R‐lines for hybrid soft red winter wheats.