There are two evolutionary pathways in the genus of Brassica, one is rapa/oleracea lineage and the other is nigra lineage. Based on the morphological characteristics and nuclear RAPD or RFLP markers, genus Raphanus was thought more closely related to nigra lineage than to rapa/oleracea lineage (Song et al., 1990; Thormann et al., 1994). RFLP data of both chloroplast and mitochondria revealed that Raphanus is more closely related to rapa/oleracea lineage (Palmer and Herbon, 1988; Warwick and Black, 1991; Pradhan et al., 1992). We have previously demonstrated that Raphanus sativus is more closely related to nigra lineage using nuclear intergenic spacer between 5S rDNA and internal transcribed spacer region between 18S and 25S rDNA. In this study, we analyzed DNA sequences from different regions of chloroplast and showed that Raphanus sativus was closely related to rapa/oleracea lineage than to nigra lineage. These results suggest that Raphanus sativus is a hybrid between B. rapa/oleracea and B nigra lineages as proposed by Song et al (1990). The split time between these two lineages and the divergent time of Raphanus was also determined based on these chloroplast DNA sequences.
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