The aim of this work was to determine intra and intergenetic similarity among three Brachiaria species for germplasm accesses and commercial cultivars using RAPD markers. Seeds were used as DNA source. 10 decamer 'primers' were selected among 120 'primers', and 107 polymorphic bands were used to perform the analysis of molecular variance (Amova), Jaccard similarity coefficient and species fixation index. 24.4% of the total variability was contained between species and 75.6% within species, with a species fixation index (FST) of 0.24. The tree showed that two major branches were formed: one with the three outgroup species and another with the species, the latter split into three minor branches: one with all B. ruziziensis samples; another with all B. decumbens accessions and three of B. brizantha; and the last with two B. brizantha accesses, all commercial cultivars and B. decumbens cv. 'Basilisk'. It was possible to group, through RAPD, Brachiaria accesses and cultivars. The genetic variability index between species was considered low, and somewhat low when compared with autogamous species. B. brizantha showed the highest genetic variability and the lowest FST, which means that there is a higher intra specific genetic flux than the others.
Brachiaria; molecular markers; genetic variability; dendrogram; genetic fixation index