Diversidade genética em populações de castanheira-do-brasil (Bertholletia excelsa H. B. K.)

Abstract

The Brazil nuts (Bertholletia excelsa H.B.K.) is a symbol tree of the Amazon, which provides a great social, ecological and economic development for the region. In the first four months of 2012, total exports of Brazil nuts reached 4,940 tons, generating revenues of US$ 6.5 million, a figure 65.6% higher than in the same period of 2011. Despite high values of production and export of Brazil Nuts, and the extreme importance it has in the economy, studies show that excessive collection in forests jeopardizes the future of the species. It is through the genetic diversity that species are maintained over time, allowing the evolutionary adaptation of the species as a result of environmental changes. The objective of this work was to study the genetic diversity among and within populations of Brazil nuts by AFLP markers. One hundred and fifty subjects were evaluated, two populations from Aruanã Farm, one from Parintins and two from Manaus. The DNA of these individuals was extracted by CTAB method, based on the protocol of Doyle and Doyle (1987), with some adaptations and quantified. In analyzes, we used four primer combinations (E + ATC / M + CCA + E AGC / M + CAT, E + AGC / M + CCA E + ACA / M + CAC) that generated 306 polymorphic bands (93.3%). Genetic differentiation within and among populations was tested by analysis of molecular variance (AMOVA), using the Genes software (Cruz, 2006a). The genetic distances of Jaccard were used in a cluster analysis of UPGMA type (Unweighted Pair-Group Method by Arithmetic Averages), using the Genes program, and bootstrap test was conducted with 5,000 permutations. Results indicated that the presence of genetic divergence is greater within populations (51.88%) than among populations (48.11%). The Fst value was equal to 0.48. Two groups were formed in interpopulational grouping: the first consisted of individuals from Aruanã Carolina, Aruanã Brastor and Manaus IFAM (planted), and the second presented individuals from Parintins and Manaus Airport (natural). AFLP markers were efficient in the characterization of natural populations and cultured Brazil nuts.