Genetic Analysis and Fine Mapping of a Spontaneously Mutated Male Sterility Gene in ssp. .

Male sterility has been widely used in hybrid seed production in Brassica, but not in ssp. , and genetic models of male sterility for this subspecies are unclear. We discovered a spontaneous mutant in ssp. A series of progeny tests indicated that male sterility in ssp. follows a three-allele model with , , and The male sterility locus has been mapped to chromosome A07 in BC and F populations through genotyping by sequencing. Fine mapping in a total of 1,590 F plants narrowed the male sterility gene to a 400 kb region, with two SNP markers only 0.3 cM from the gene. Comparative gene mapping shows that the gene in ssp. is different from the gene of ssp. , despite that both genes are located on chromosome A07. Interestingly, the DNA sequence orthologous to a male sterile gene in , , is within 400 kb of the locus. The orthologs of ssp. were sequenced, and one KASP marker (BrMs_indel) was developed for genotyping based on a 14 bp indel at intron 4. Cosegregation of male sterility and BrMs_indel genotypes in the F population indicated that from and from are likely to be orthologs. The BrMs_indel marker developed in this study will be useful in marker-assisted selection for the male sterility trait.