Submitted to: Systematic Botany
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/20/2008
Publication Date: 7/21/2008
Citation: Ames, M., Salas, A., Spooner, D.M. 2008. A morphometric study of species boundaries of the wild potato Solanum series Piurana (solanaceae) and putatively related species from seven other series in Solanum sect. Petota. Systematic Botany. 33:183-192. Interpretive Summary: The cultivated potato of world commerce, technically known as Solanum tuberosum, contains many wild species relatives that are of use as breeding stock to improve traits of the potato crop such as improved disease resistance, higher yields, and improved processing qualities such as the ability to produce better fries and chips. The USDA funds the taxonomic characterization of these wild species because taxonomy provides breeders guides to the choice of species to use in their breeding programs. Twenty years ago there were 232 wild potato species recognized, but taxonomic work since then has continued to reduce this number to a latest estimate of 188 species, and continuing taxonomic work is continuing to reduce this number. This study reexamines the number of species in a group of wild potato species technically known as the Solanum Piurana group, and other wild potato species that we think are related to these species, using data from the overall form of the plants (morphological data) in field plots in Peru. These 33 species are very similar, and we can only easily distinguish four of them. We are following up this study with a genetic study of these plants by analyzing DNA characters technically called DNA sequencing to see if this technique can better define more than four species where there were 33 before. The revised classification of these wild species to result from these studies will be an improvement of the classification that occurs today, and will aid potato breeders in choosing species to use in their potato improvement programs.
Technical Abstract: There are about 190 wild potato (Solanum section Petota) species distributed from the southwestern United States to central Argentina and adjacent Chile and Uruguay. Their overall morphological similarity has led to widely conflicting taxonomic treatments. Solanum series Piurana is one of 21 series that has been recognized within section Petota in the latest comprehensive taxonomic treatment by Hawkes in 1990. They are distributed from southern Colombia, south through Ecuador to central Peru. The limits of the series and validity of its constituent species are unresolved. We provide the first comprehensive morphological phenetic study of the series, to include some putatively related species in series Conicibaccata, Cuneoalata, Ingifolia, Megistacroloba, Simplicissima, Tuberosa and Yungasensa, through an examination 188 living germplasm accessions of 33 species, planted in replicated plots in Peru. Only four well-defined phenetic groups were supported. Continuing work is exploring molecular support for the monophyly of these selected species in these eight series, and support for its constituent species. If more than four species are supported, they will be defined morphologically only with difficulty by using a series of character states that overlap in range (polythetic support).