The tree tomato is a familiar fruit crop of upland regions of the Andes of Colombia, Ecuador, and Peru. Tree tomatoes are also cultivated worldwide in subtropical climates, especially in New Zealand, where they are grown commercially for export. Although tree tomatoes belong to the same genus as the garden tomato, Solanum lycopersicum, the two taxa are not closely related. Rather, S. betaceum belongs to a clade of about 50 species that are phylogenetically closer to the spiny Solanums than to the tomato/potato clade. Despite its popularity and economic potential, the native range and wild relatives of the tree tomato have not been known with certainty. Recent investigations in the field and laboratory confirm that the closest wild relatives of S. betaceum include three endemic Bolivian taxa. Wild populations of S. betaceum have been located in southern Bolivia and adjacent northwestern Argentina. Wild S. betaceum plants are identical in morphological characters and ITS sequences to cultivated individuals and all wild S. betaceum accessions that have been tested thus far are self-compatible, like their cultivated counterparts. Solanum betaceum fruits are not important items of commerce in their native range, unlike the situation in northwestern South America. A hypothesis is that S. betaceum is a relatively recent, perhaps post-Conquest introduction into northwestern South America from southern Bolivia and northwestern Argentina. Self-compatibility arose via natural selection in wild populations rather than as a result of human selection. Questions for further investigation concern the extent of the native range and the identification of natural pollinators and dispersal agents of S. betaceum. The tree tomato holds much potential as an economic fruit crop and as a source of desirable breeding traits for the improvement of other solanaceous species.

Key words: Solanaceae, Solanum betaceum, Solanum, South America, tree tomato