Examination of the hybrid origin of the wild potato Solanum ruiz-lealii Brücher

The common potato, tetraploid Solatium tuberosum spp. tuberosum L. (tbr), has a narrow genetic base but a large number of related tuber-bearing species that harbor genetic diversity for agronomic characters. The taxonomic status of Solatium ruiz-lealii Brücher (rzl), a diploid species endemic to Mendoza province, Argentina, is controversial. It has been described as a new species of non-hybrid origin and as a natural hybrid between S. kurtzianum Bitt. & Wittm. (ktz) and S. chacoense Bitt. (chc). The hypothesis of the hybrid origin of rzl is examined systematically for the first time by phenetic analyses of morphological and molecular (SSR markers) data, and cytological analyses of interspecific hybrids. The morphological, cytological and molecular data are congruent, and suggest that rzl is not a recent natural hybrid between the ktz and the chc populations studied but has probably originated by divergence of chc, or by hybridization between chc and another taxon.