Diversity and genetic structure in natural populations of Croton linearifolius (Euphorbiaceae) based on molecular markers

Croton linearifolius Mull. Arg, an endemic species of Brazil, has insecticidal activity proven. To the detriment of its importance as a natural resource, the studies of this species are incipient, as well as the strategies applied to its management and conservation. The diversity and genetic structure in 61 individuals of C. linearifolius collected in the National Forest Contendas do Sincora (NFCS) were estimated. Estimates were based on analysis of the amplification profile of nine combinations of pairs of resistance gene analogs (RGA) primers and eight inter simple sequence repeat (ISSR) primers. A total of 134 markers (81.3% polymorphic) were generated. Bayesian analysis indicated as most likely a structuring into two groups. Based on the molecular analysis of variance (AMOVA) it was possible to verify that 64% (p rand <0.01) of the variation occurs within the regions, and a significant amount (36%) (p rand <0.01) was attributed to variations between regions, indicating genetic structure between them. The AMOVA results were corroborated with the Principal Coordinate Analysis (PCoA), indicating an association between the distribution of variability and the geographical distribution of the collection regions. The probable mechanisms pollination and dispersion would justify, at least in part, the genetic structuring observed for C. linearifolius.   Key words: Conservation, genetic variability, genetic polymorphism, resistance gene analogs (RGA) marker, inter simple sequence repeat (ISSR) marker.