Development of diagnostic probes allowing the identification of male-sterile and male-fertile cytoplasms in beets

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All current sugarbeet cultivars are based on the only one type (the Owen type) of male-sterile cytoplasm. This cytoplasmic uniformity renders the crop vulnerable to cytoplasm-specific diseases, and a broadening of the cytoplasrnic variation is desirable. The objective of this study was to screen Beta vulgaris and B.maritima germplasm accessions for differences in their mtDNAs, using the diagnostic probes to identify new male-sterile cytoplasm's.We developed 31 probes prepared from a mitochondrial DNA clone bank of sugarbeet. These probes were sequentially used for Southern blot analysis of total DNA from the germplasm accessions. The results indicated that most of the wild beet accessions have novel types of rnitochondrial genomes and that only few are completely identical to previously known genomes such as the Owen type and normal fertile genomes. The novel mitochondrial genome type can be classified into two categories, the first one being similar to known genomes, and the second representing a mosaic organization of genome. We also found that several wild beets possessing the novel mitochondrial genomes show pollen sterility. It is thus of interest to determine whether or not the novel mitochondrial genome types detected here are correlated with cytoplasmc male sterility.