Abstract In view of the economic and environmental importance of Bertholletia excelsa Bonpl. for the Amazon and the reducing natural habitat area of this species, the present study proposes to examine genetic variability among accessions of Brazil nut from the Amazon rainforest. Seventeen native Brazil nut genotypes were sampled from Sinop-MT and the genomic DNA were amplified using 15 inter-simple sequence repeat (ISSR) markers. The percent polymorphism and the polymorphism information content (PIC) of each primer were determined. The primers amplified 84.62% of the polymorphic bands and 15.38% of the monomorphic bands. The PIC for each primer ranged from 0 to 0.68. The Unweighted Pair Group Method with Arithmetic Mean (UPGMA) was the most efficient in group representation, as it showed the highest cophenetic correlation coefficient (CCC = 0.92), the lowest stress (12.31%) and the lowest distortion (1.51%). The use of ISSR markers was an efficient tool in the study of genetic diversity among Brazil nut genotypes, and the genetic diversity found can be used for conservation and pre-breeding programs for this crop.

RESUMO O jatobá (Hymenaea courbaril L.) é uma espécie que apresenta importância ecológica e ocorre em diferentes regiões geográficas do Brasil. Conhecer e avaliar a existência de locais com maior variabilidade genética pode auxiliar em programas e ações de conservação. Neste contexto, o presente estudo objetivou avaliar a diversidade genética e a estrutura em populações naturais de jatobá com ocorrência na Amazônia mato-grossense por meio de marcadores ISSR. Foram amostrados 54 indivíduos em 3 populações, sendo uma no município de Marcelândia (MA=24) e duas no município de Alta Floresta (Comunidade Central AF=17 e Pista do Cabeça PC=13 indivíduos). DNA genômico total foi extraído de tecido foliar pelo método CTAB. Os 54 indivíduos foram genotipados com 10 primers ISSR. Foram amplificados um total de 110 fragmentos, sendo 78,2% polimórficos. Os maiores índices de diversidade foram encontrados na população de MA (H=0.25; I=0.37 e %P=65.45). A distância genética foi maior entre as populações dos dois municípios (0.17 entre MA e AF; 0.16 entre MA e PC). A análise de variância molecular (AMOVA) indicou que 31.79% da variância total está entre populações e 68.21% dentro de populações. Há diversidade genética nas populações nativas de jatobá na Amazônia mato-grossense. Recomenda-se que sejam preservados indivíduos de ambas as populações, a fim de garantir a manutenção da variabilidade genética e a conservação efetiva da espécie na Amazônia mato-grossense.

ABSTRACT Jatobá (Hymenaea courbaril L.) is a species that shows ecological importance and occurs in different geographic regions in Brazil. Knowing and evaluating the existence of places with higher genetic variability can help in conservation programs and actions. In this context, the present study aimed to evaluate the genetic diversity and structure in natural populations of Jatobá with occurrence in Mato Grosso Amazon through ISSR markers. Fifty-four individuals were sampled in three populations, being one in the municipality of Marcelândia (MA=24) and two in the municipality of Alta Floresta (Comunidade Central AF=17 and Pista do Cabeça PC=13 individuals). Total genomic DNA was extracted from the leaf tissue by the CTAB method. The 54 individuals were genotyped with 10 ISSR primers. A total of 110 fragments were amplified, being 78.2% polymorphic. The greatest diversity indices were found in the population from MA (H=0.25; I=0.37 and %P=65.45). The genetic distance was higher among the populations of the two municipalities (0.17 between MA and AF; 0.16 between MA and PC). The analysis of molecular variance (AMOVA) indicated that 31.79 % of the total variance is among populations and 68.21 % within populations. There is genetic diversity in native populations of Jatobá in Mato Grosso Amazon. We recommend that individuals from both populations be preserved, in order to ensure the maintenance of genetic variability and the effective conservation of species in Mato Grosso Amazon.