Chloroplast DNA diversity in the genus Rubus (Rosaceae) revealed by Southern hybridization

The variability in chloroplast DNA type of 20 Rubus genotypes was examined by Southern hybridization. DNA extracted from the Rubus accessions was digested with two restriction enzymes (EcoRI and EcoRV) and heterologous chloroplast DNA sequences from barley and pea were used as probes to detect Rubus chloroplast DNA sequences on Southern blots of Rubus total DNA. Restriction fragment length polymorphism was detected and a total of 92 restriction fragments were generated by the probe/enzyme combinations examined. Cladistic principles based on the parsimony assumption were used to assemble a phylogenetic tree based on chloroplast restriction fragment length data. The phylogenetic tree grouped the taxonomically defined species and is in general agreement with information based on morphological criteria. However, the Japanese red raspberry R. illecebrosus was shown to have diverged considerably in terms of evolutionary time from other species in subg. Idaeobatus. Furthermore, the molecular approach provides a quantitative estimate of the relationship between species that is difficult to obtain from morphological data. In order to complement the chloroplast DNA information a ribosomal DNA probe was also included in the analysis and provided further information on the phylogenetic relationships within Rubus.