IDENTIFICATION AND MAPPING OF RAPD AND RFLP MARKERS LINKED TO A FERTILITY RESTORER GENE FOR A NEW SOURCE OF CYTOPLASMIC MALE-STERILITY IN BETA-VULGARIS SSP. MARITIMA

The present study shows that the recently described mitochondrial H ha plotype is associated with cytoplasmic male-sterility (CMS). This new source of CMS appears to be different from the mitotype E-associated C MS most frequently found in natural populations. A mitotype H progeny with a sexual phenotype segregation was used to identify a gene restor ing male fertility (R1H). Using bulk segregant analysis (BSA), nine RA PD markers linked to this restorer locus were detected and mapped. The comparison with other Beta genetic maps shows that the closest RAPD m arker, distant from R1H by 5.2 cM, belongs to the same linkage group a s the monogermy locus. In order to determine the position of R1H more precisely, four RFLP loci within this linkage group were mapped in the segregating progeny. It thus became possible to construct a linkage m ap of the region containing the RFLP, RAPD and R1H loci. The closest R FLP marker was located 1.7 cM away from R1H. However, a nuclear gene r estoring the 'Owen' CMS which is currently used in sugar beet breeding is reportedly linked to the monogermy locus, raising the question of a possible identity between the new CMS system and the 'Owen' CMS.