Solanum sessiliflorum Dunal

Commentary from Whalen et al. (1981):

The cocona is highly variable in fruit size, form and flavor (Pahlen, 1977), and there is abundant evidence that these variations are commonly recognized and named on a local scale by residents of the upper Amazon Basin where the plant is indigenous. Indians of the Río Cenepa in Departamento Amazonas, Peru use four names to refer to locally grown morphs of S. sessiliflorum. Schultes and Romero-Castañeda (1962) have documented the presence of many locally named cultivars in Amazonian Colombia. They believed two of these were sufficiently distinctive to be considered species separate from S. sessiliflorum, and they proposed the names S. alabile and S. georgicum to refer to them.

Solanum alabile, from the Putumayo River of Colombia, has very large, globose fruits up to 10 cm in diameter, sweeter and less acidulous than other forms of S. sessiliflorum. The authors conceded that the species status of S. alabile was questionable. We view the plant as an extreme in a spectrum of fruit variation and choose not to accord it nomenclatural recognition. The form does not seem to be consistently distinguishable by any characters other than those of the fruit, and plants with similar large berries occur sporadically elsewhere throughout the range of S. sessiliflorum.

Another form, called S. georgicum by Schultes and Romero-Castañeda (var. georgicum here), is of great interest as a possible progenitor of S. sessiliflorum cultivars. The stems and leaves of var. georgicum are prickly, and the berries globose and relatively small, characters that are likely to be ancestral in S. sessiliflorum . Loss of prickles and increase in size and variability of fruits would have been predictable results of human selection upon var. georgicum-like ancestors during the process of domestication. No other characters distinguish var. georgicum from var. sessiliflorum. The two are fully interfertile (Heiser, 1972), and at least one population is known (at Limoncocha, Ecuador) in which the distinguishing characters segregate freely (Heiser, 1971). The var. georgicum is narrowly restricted in distribution, found only in lowlands just east of the Andes in Ecuador and extreme southern Colombia. If the large-fruited, unarmed cultivars of S. sessiliflorum have indeed been derived from var. georgicum, then an origin in that region would be suggested.

Schultes and Romero-Castañeda (1962) provided a useful summary of the introduction of the cocona into international horticulture. Apparently, the species was never grown outside the Amazon Basin until 1949, when it was established at the Instituto Interamericano de Ciencias Agricolas in Turrialba, Costa Rica. From Costa Rica, the cocona was soon disseminated to other experiment stations, botanic gardens, and agricultural concerns under the misapplied name, S. hyporhodium. The spread of the species as a domesticate in the Amazon Basin, however, predated the Costa Rica introduction by many years and probably preceded the arrival of European man. Humboldt and Bonpland collected the species in 1800 on the upper Orinoco River, where it was presumably found in association with indian dwellings and where it already had an established indigenous name, tupiru. The ca. 1812 collection that typifies S. sessiliflorum came from Pará, far down the Amazon from the region where the species is native. The plant was very likely in cultivation there then, as it is now, under the name cubiu.

It is regrettable that the name S. sessiliflorum must supplant the more widely used S. topiro to refer to the cocona. According to Index Kewensis, both epithets originated in the same Dunal work, the Solanorum Synopsis of 1816, with S. topiro published on an earlier page. In fact, S. sessiliflorum was proposed two years earlier in 1814 in Dunal’s treatment of Solanum for Poiret’s supplement to Lamarck’s Encyclopédie Méthodique. The name was one of several validly published there that were missed in the compilation of Index Kewensis.