Analyses of molecular data from chloroplast ndhF and nuclear ITS sequences have identified six to seven major clades within the genus Solanum (Solanaceae). For the most part, these clades do not conform to the traditional Solanum subgenera. Exceptions to this pattern are the aneuploid Australasian subgenus Archaesolanum and the majority of species in the spiny subgenus Leptostemonum, each of which appear to form monophyletic groups. Closely related to subgenus Leptostemonum are the non-spiny sections Brevantherum, Extensum, Lepidotum, Geminata (including Holophylla pro parte), Gonatotrichum, Pachyphylla, and Cyphomandropsis. Solanum allophyllum and the spiny species S. wendlandii form a clade within this group which may either be basal in Leptostemonum or placed outside the spiny Solanums. Woodiness and branched hairs are commonly found in members of this larger clade. Solanum sections Solanum, Parasolanum, Dulcamara, Jasminosolanum and Holophylla pro parte form another discrete clade composed of taxa placed by D’Arcy (1991) in subgenera Minon, Potatoe, and Solanum. The potatoes (section Petota) comprise a clade with the tomatoes (section Lycopersicum) and members of sections Anarrichomenum, Basarthrum, Etuberosum, Juglandifolium, Regmandra, Pteroidea, and Herpystichum, uniting taxa of subgenera Potatoe and Bassovia. The African non-spiny taxa represented by S. terminale, S. quadrangulare, and S. aggregatum in this analysis form an isolated clade within the genus. The genera Normania and Triguera, notable for their unusual morphology and distribution, are nested within Solanum and constitute a well-supported clade with no clear relationship to other Solanum groups. These data allow Solanum to be cleaved into several well-supported subgeneric units, some of which are diagnosable by morphological synapomorphies.

Key words: ITS, ndhF, Solanaceae, Solanum