Molecular markers in the breeding of ornamentals

The applicability of DNA fingerprinting using mini-and microsatellite sequences to the identification of genotypes and the establishment of genetic distances between them was assessed for carnation and rose. The probability of two offspring from the crossing of similar genotypes having identical DNA fingerprints (DFPs) was found to be 1.8 × 10^-6 for carnation and 2 × l0^-8 for rose. A comparison of genetic relationships within and between categories based on known genetic history, to genetic relationships deduced from DFPs, revealed a perfect match for both flower types. In carnation, rank correlation analyses of the results yielded by each of three probes of different origin (two mini-and one microsatellite) revealed very good agreement between them. Hence it is apparent that DFPs of ornamentals can be used for both cultivar identification and the establishment of genetic relatedness and evolutionary kinship. Potential future applications of DFPs, such as the mapping and monitoring of loci controlling important horticultural traits, should also be of great assistance to ornamental breeding. Using the random amplified polymorphic DNA (RAPD) technique, we identified a marker linked to "non-bullheaded" flowers in carnation. The relationship between the amplified DNA fragment and the trait was observed in all fullsibs analyzed, as well as in halfsibs and in different varieties. The fragment was cloned and sequenced, and a DNA probe which was applicable to selection for this trait, irrespective of variety, was constructed. In the long run, identification of this locus will pave the way for a characterization of the gene(s) responsible for the "bullheaded" phenotype.