Domestication of Peach Palm in Southwestern Amazonia

The peach palm (Bactris gasipaes Kunth) is the only Neotropical palm domesticated by Native Americans. Its place of origin as a crop (B. gasipaes var. gasipaes) has been debated for more than a century, with three hypotheses currently in discussion: southwestern Amazonia; northwestern South America; or multiple origins in the distribution of the wild relatives (B. gasipaes var. chichagui). The small amount of archaeological data available supports the second hypothesis, but they contrast dramatically with the molecular-genetic analyses that support the first or the third, depending on how they are interpreted. On morphological grounds, two of the three types of var. chichagui are plausible candidates for wild ancestral populations. All the molecular-genetic analyses have identified a deep division between the landraces of cultivated peach palm in western Amazonia to Central America and those in southwestern to eastern Amazonia. The first analysis using isoenzymes linked the Tembe population (Bolivia) with the Pará landrace (eastern Amazonia), and these were distant from the western landraces. Multiple RAPD and SSR analyses identified the same deep division, which was interpreted by the group of researchers in Brazil as a single domestication in southwestern Amazonia with two dispersals, while another group working in Costa Rica interpreted it as three domestication events. Analysis with nuclear markers does not allow discrimination among the hypotheses, because gene flow may occur via pollen and seed. A new analysis with two sequences from the chloroplast genome, which has maternal inheritance and is therefore more appropriate to test the hypothesis, suggests that the cultivated peach palm was domesticated once in southwestern Amazonia, with two dispersals. One dispersal started in the upper Ucayali River basin, in southeastern Peru, and then throughout western Amazonia, northwestern South America and southern Central America. Another dispersal started in the upper Madeira River basin and then along the Madeira River into eastern Amazonia. New explorations in southwestern Amazonia are critical to identify the exact location of the original events.