Genetics of fertility restoration in cytoplasmic male sterile Phaseolus vulgaris L. : 1. Cytoplasmic alteration by a nuclear restorer gene.

Restoration of fertility in cytoplasmic male sterile Phaseolus vulgaris by line R-351 was controlled by a single gene. The restorer gene (Fr) displayed incomplete dominance leading to partial restoration of fertility in F1 generations; full restoration was not achieved until the F2 generation. Once full restoration of fertility was produced in the F2 generation, no segregation for sterility was observed in subsequent generations derived from heterozygotes Frfr, either by testcrossing (restored × maintainer) or in F3 progenies. Implications of the irreversible nature of this restoration are discussed.