Mitochondrial minisatellite polymorphisms in fodder and sugar beets reveal genetic bottlenecks associated with domestication

Historically, sugar beets were selected from fodder beets. We used mitochondrial minisatellite loci to analyze cytoplasmic genetic diversity in fodder beet and sugar beet. Among the 8 sugar beet accessions examined we identified 3 multi-locus haplotypes. These 3 haplotypes were a subset of 5 haplotypes identified among the 29 fodder beet accessions examined. All but one haplotype in fodder beet comprised, in turn, a subset of 12 haplotypes identified previously in leaf beets. Such apparent decreases in cytoplasmic genetic diversity must result from genetic bottlenecks associated with domestication and the ensuing breeding processes. We also detected the haplotype associated with the male-sterile Owen cytoplasm of sugar beet in the fodder beet gene pool. Furthermore, the presence of a 39 kDa protein associated with the Owen cytoplasm was confirmed in two fodder beet plants by Western blot analysis. These results lead us to speculate that the Owen cytoplasm may have originated in fodder beet, from which sugar beet was derived.