Maintaining Genetic Resources of Peach Palm (Bactris gasipaes Kunth): The Role of Seed Migration and Swidden-fallow Management in Northeastern Peru

Abstract

Knowledge of the effects of farmer practices on population genetic parameters of peach palm (Bactris gasipaes Kunth) is relevant to the improvement and conservation of the palm's genetic resources. Microsatellite markers were used to assess genetic diversity and population structure of peach palm in swiddenfallow agroforestry systems in northeastern Peru. The study covered eight communities, comprising two study areas 160 km apart -one occupied by indigenous Amerindians and the other by mixed race campesinos. Simultaneous analysis of an ex situ peach palm germplasm collection provided a means to compare population genetic parameters. Farmers who were surveyed on seed selection practices for peach palm reported that an average of only four palms (4.3 for campesino and 1.5 for indigenous populations) were used to provide seed for the establishment of the forest gardens sampled. As expected, inbreeding coefficients observed within communities were relatively high (f = 0.105 À 0.210), however, observed heterozygosities within communities were also high (0.625-0.741). A metapopulation approach was used to describe migration within and among regions, implying a hierarchical structure of gene flow which maintains relatively high levels of genetic diversity. Seed migration was found to occur over longer distances ( 600 km) and at a higher frequency (46% of palms sampled) in the indigenous study area, and a proportionally greater number of alleles was found (49 vs. 43 over three loci) with twice as many private alleles occurring only in the indigenous populations. The farmers' practice of preserving remnant palms through successive swidden generations may have contributed to the maintenance of alleles by reducing the severity of founder effects. Although the campesino study area exhibited a significant (20% of the variation; p < 0.01) isolation-by-distance relationship across 35 km distance, in general, both study populations had relatively limited genetic structure (h=0.012-0.03), which is believed to have resulted from the exchange of seeds over long distances and periods of time.

Origin and Dispersal of Domesticated Peach Palm

“…They also confirm the commonness of both long and middle distance gene flow and introgression reported by various authors (Adin et al, 2004;Couvreur et al, 2006;Cole et al, 2007;Hernández-Ugalde et al, 2011). The fact that they do not fully validate the landrace hierarchy can be attributed to the design of the Core Collection (Cristo-Araújo et al, 2015), since this was not designed primarily to study the origin and dispersal of peach palm, but to support the management of peach palm germplasm at INPA.…”

“…Two accessions from the relatively spineless Guatuso populations of the Utilis landrace in Central America are assigned to the northern western Amazonia group, suggesting that spinelessness may not have been selected in situ but may be due to long distance dispersal, and the accessions from Coari, previously classified with the Putumayo landrace (Rodrigues et al, 2005), are assigned to the southern western Amazonia group, some 500 km to the west. Seed exchange networks had previously been identified within the Pampa Hermosa landrace in southern western Amazonia (Adin et al, 2004), as well as long distance gene flow between the southern and the northern western Amazonian groups (Cole et al, 2007), so this admixture is not surprising and may not be due to germplasm bank error.…”

Peach palm (Bactris gasipaes) in tropical Latin America: implications for biodiversity conservation, natural resource management and human nutrition

“…Since peach palm is a long-lived perennial and a predominantly outcrossing species, one can expect its populations and landraces to contain high levels of genetic diversity (Hamrick and Godt 1996;Mora-Urpí et al 1997). In addition, extensive human dispersal up to a distance of 600 km has further stimulated gene flow and low differentiation (Cole et al 2007). A review of studies on genetic variation within and between populations, using different types of markers and considering allelic richness (A), expected heterozigosity (He) and genetic differentiation (Gst), supports those observations (Table 1).…”

“…At the same time low genetic differentiation and the exchange of seed material over extensive areas have been observed, at least in the Peruvian Amazon (Adin et al 2004;Cole et al 2007). Since peach palm, as a perennial, has a lengthy generation period, the risk of genetic erosion in cultivated populations is low, so on-farm conservation might be a good alternative for large germplasm collections (Van Leeuwen et al 2005).…”

Diversidade genética molecular de progênies de dendezeiro

“…De acordo com esses autores, há maior variância genética dentro de cada grupo de dendezeiro do que entre os dois grupos avaliados. Resultados contrastantes também foram observados por Cole et al (2007), com três locos microssatélites, e por Couvreur et al (2006), com oito locos, ao avaliar populações de pupunheira (Bactris gasipaes Kunth). Esses trabalhos mostram o comportamento geral das populações de espécies alógamas.…”