Molecular relationships in subtribe Brassicinae (Cruciferae, tribe Brassiceae)

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Abstract
Restriction-site variation for 17 endonucleases was compared in the large single-copy region of the chloroplast genome in 74 taxa of the genera Brassica, Coincya, Diplotaxis, Eruca, Erucastrwn, Hirschfeldia, Raphanus, Sinapidendron, Sinapis, and Trachystoma (subtribe Brassicinae, tribe Brassiceae, Cruciferae). A total of 422 restriction-site mutations was observed, with 228 (54%) showing variation among taxa. Phylogenetic analyses indicated a clear division of the subtribe into two main lineages designated here as Rapa–Oleracea and Nigra. Polyphyly was evident in five genera (Brassica, Diplotaxis, Erucastrum, Sinapis, and Trachystoma) as indicated by their placement in both lineages and (or) further separation into groups within a lineage. The genera Coincya, Hirschfeldia, and Sinapidendron were monophyletic within the Nigra lineage, as were Eruca and Raphanus in the Rapa–Oleracea lineage. Four major groups were recognized within each lineage. The lowest levels of chloroplast DNA divergence were observed among taxa belonging to the same cytodeme or crossing group and were highest for Brassica rapa and Brassica oleracea versus Brassica nigra at 2.10–3.91% and 2.00–3.78%, respectively. The chloroplast DNA data were incongruent with traditional taxonomic circumscription of 5 of the 10 genera but concordant with other data sets that support the close genetic relatedness of all 10 genera. Key words: Brassica, Coincya, Erucastrum, Sinapidendron, Trachystoma, chloroplast DNA restriction-site variation.

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