Estimativa da diversidade genética e avaliação do sistema reprodutivo de Copaifera multijuga Hayne em populações naturais na Amazônia Ocidental

Abstract

Copaiba (Copaifera multijuga Hayne) is an Amazonian species that is massively exploited to obtain oleoresin, generating millions of reais for the Brazilian economy. Many studies have investigated the phytochemical properties and applications of this raw material. On the other hand, there are few initiatives aimed at the genetic characterization of native populations of this species. In this sense, this study was subdivided into three chapters and had the following main objectives: (1) evaluation the outcrossing parameters and the predominant mating system in a native population of C. multijuga; (2) develop and characterize specific microsatellite markers previously unavailable for the species; (3) estimate the levels of diversity in four geographically distinct populations and the differentiation between them. In (1) woody samples were collected from 48 trees for the population study using a set of five heterologous microsatellite markers. Of these, 15 trees were selected to make up the group of maternal genitors for the mating system study. Leaf samples were collected from 20 open-pollinated juvenile progenies of each maternal genitor, obtained from natural regeneration (n=300). To develop specific markers, next-generation sequencing (NGS) technology was used on the Ion Torrent PGM™ platform and 47 trees were used for characterization and validation (2). Finally, in (3) 48 samples were collected from oleoresin-producing and non-producing trees in four locations (Manaus, Iranduba, Maués and Novo Aripuanã) (N=192). Seven specific microsatellite markers were used at this stage. In general, the main genetic parameters were estimated: observed (Ho) and expected (He) heterozygosity, total number of alleles (A), fixation index (f), multilocus (tm) and unilocus (ts) outcrossing rates, Polymorphic Information Content (PIC), paired FST tests, number of probable genetic clusters (K) and the like. The population evaluated in (1) showed high levels of genetic diversity both in the adult trees (Ho: 0.742; He: 0.743) and in the offspring (Ho: 0.685; He: 0.685). Mating occurred predominantly by outcrossing (tm: 0.88 - 1.00), of which 4.1% corresponded to mating between relatives (tm - ts). Of the 19 loci developed in (2), 14 had their amplification conditions standardized. The CmH05 locus was disregarded in the analysis because it is monomorphic. Mean levels of genetic diversity of over 0.63 (Ho: 0,672; He: 0,636) and an mean number of alleles of 5.4 were obtained. According to the PIC estimates, all the loci were considered highly (=9) or moderately informative (=3), with the exception of CmH11 with a value of less than 0.2. In (3), the set of markers used was considered highly informative, with values of PIC̅ greater than 0.57. A total of 63 alleles (A) were detected, as well as the presence of private alleles in all populations except the one sampled in Iranduba (IRB). The general average of He ranged from 0.630 to 0.742 and Ho from 0.462 to 0.643. Differentiation between populations was significant (FST = 0.218, p < 0.001) and the Bayesian approach converged to form 4 well-defined clusters (K). In addition, three potential barriers to gene flow were observed, possibly explained by the correlation between the ecological characteristics of the species and the geomorphology of the collection region (hydrographic network). The results obtained in this study are fundamental for investigating how anthropogenic pressures can impact the genetic heritage of C. multijuga. In addition, they may be beneficial in making decisions about the best conservation strategies for this important Amazonian species.