DNA fingerprinting demonstrates extremely low levels of genetic variation among blackberry cultivars grown in Finland

Most blackberry plants cultivated in Finland closely resemble the American species Rubus allegheniensis. Thirty nine such blackberry accessions in the University of Helsinki clone collection were studied by hybridization-based DNA fingerprinting and compared with some known cultivars of R. allegheniensis derivation. 'Imperial' appears to be identical to the old cultivar 'Majestat', but 'Earliest of All' differs considerably. In addition, 37 of the accessions analysed also have DNA fingerprints that appear to be completely identical to that of 'Majestat'! The remaining two accessions, although identical to each other, exhibit one band not found in 'Majestat' that is probably caused by a somatic mutation.