GENETIC VALIDITY OF RAPD MARKERS AT THE INTRA-SPECIFIC AND INTER-SPECIFIC LEVEL IN WILD BRASSICA SPECIES WITH N=9

The sequence homology of co-migrating RAPD markers within a genus, acr oss species, and among populations of a species was investigated. DNA was isolated from ten wild Brassica species with n = 9 and the RAPD pa tterns were established using three random primers. Five RAPD markers which appeared to be characteristic for the n = 9 species (genus level ), four markers which appeared to be species specific, and one populat ion-specific marker were isolated from agarose gels and hybridized to the RAPD profiles of the ten Brassica species. Two RAPD markers were c loned for comparison with gel-isolated RAPD fragment probes in hybridi zation experiments. Non-specific and background hybridization, occurri ng when gel-isolated fragments were used as probes, disappeared when c loned fragments were used. A total of 250 RAPD-marker hybridizations w ere scored according to visual presence or absence in a,eel lane. All except three markers hybridized as expected, resulting in an error rat e of 1.2%. The deviating results included a lack of hybridization alth ough a band was visible in the gel, a length polymorphism for one mark er, and a dual hybridization signal for two single-band markers.