Genetic Diversity Among Wild and Cultivated Populations of Annatto (Bixa orellana) from Brazilian Amazonia

Annatto (Bixa orellana L.) is a tropical crop originated in America, with the Amazonian region considered the center of origin of the species. Annatto is a promising crop because of its dye (bixin), widely used in the pharmaceutical, food, cosmetics and textiles industry. According to the systematic study of the genus, five species of Bixa are recognized, but only B. orellana is widely cultivated. The aim of this study was to evaluate the genetic diversity among cultivated and wild annatto from the Brazilian Amazonia. Were evaluated 490 cultivated and 169 wild annatto accessions from six states in the Amazonian region, using 16 microsatellite markers developed by this research group in a previous study. A total of 254 alleles were detected, with an average of 12 alleles per locus. We highlight a clear separation between the two groups of accessions, cultivated and wild, identified in the Bayesian analyzes and Neighbor-Joining trees, supported by the high value of F_ST(0.140). Wild accessions had higher rates of diversity in relation to cultivated, demonstrated by the allelic richness and observed and expected heterozygosity. Higher levels of diversity found in wild populations can be partly attributed to the absence of anthropic selection, as occurs in cultivated access. Our data suggest the existence of genetic relationship among wild types and cultivated annatto, indicated by moderate levels of gene flow between populations. These results will help us to identify possible centers of domestication for this crop and to understand the evolution and domestication of annatto in Amazonia.