Nuclear fertility restorer genes map to the same linkage group in cytoplasmic male-sterile bean

Fertility restoration in cytoplasmic male-sterile plants (CMS) by nuclear restorer genes is one of the few useful systems for studying nuclear-mitochondrial interactions in higher eukaryotes. In CMS bean there exist multiple independently identified nuclear genes that restore fertility. Two restorer genes (Fr and Fr₂) have been characterized previously. We have genetically characterized two additional restorer genes; both restorers are single genes that behave similarly to Fr₂. We compared the linkage relationship of all four independently identified restorer genes to understand the relationship among these loci further. All four genes map to the same linkage group. It was not possible to distinguish between the two newly identified restorer genes and Fr₂. We suggest that they may be allelic.