Genetic relationships and patterns of genetic variation in cultivated and crop wild relatives of pitahayas: edible fruits in Selenicereus (Cactaceae)

Five Selenicereus species are well-known in the fruit market as dragon fruit, pitahaya, or pitaya. Native to the New World, pitahayas are considered underutilized crops with nutraceutical properties and easily propagated with a distribution that could potentially be extended to dry climates. Our goal is to understand the relationships of wild and cultivated populations and to determine genetic variation in a spatial scenario to discover hotspots of haplotype and genetic variation that will allow the conservation of valuable germplasm, as well as crop wild relatives. Sampling consisted of 170 individuals for three plastid molecular markers comprising the five cultivated species and as outgroups populations of four closely related species were included in the haplotype analyses. Genealogical relationships were determined, along with genetic variation in spatial patterns. The majority of the haplotypes were shared among the nine species in a geographic pattern; however, distant populations of different species also shared haplotypes. Selenicereus monacanthus displayed the highest genetic variation; its haplotype network is complex and intricate, probably related to the management to which the populations have been subjected, in which certain attributes suitable for cultivation and valuable for the fruit market have been selected. Historical evidence suggests that S. undatus has been cultivated in home gardens in the Maya area since pre-Columbian times, and the highest genetic diversity was found there. Conservation of wild crop relatives is important to preserve underutilized crops, therefore southern Mexico and northern Central America are the most relevant regions to protect genetic diversity of pitahayas.