Assessment of the genetic diversity and population structure of Jatropha curcas accessions in Brazil using ISSR markers
The oleaginous species Jatropha curcas (Euphorbiaceae) exhibits significant potential as a source of biodiesel, but the scarcity of information regarding genetic variability within the species limits its possible exploitation. We examined the genetic diversity and relationships among 97 accessions of J. curcas originating from the Brazilian states of Piauí, Maranhão, Ceará, Bahia, and Minas Gerais. One-hundred ISSR markers were tested and 11 selected for genotyping. Among 307 loci generated by these markers, 96 % were polymorphic. Genetic similarities between accessions were estimated from Jaccard coefficients and the corresponding similarity matrix, and genetic relationships were determined from the dendrogram constructed using the unweighted pair group method with arithmetic average (UPGMA) technique. Nei’s genetic diversity indices varied between 0.0256and 0.1703, while Shannon’s information indices ranged from 0.0374 to 0.1926. The number of alleles varied from 1.0619 to 1.3257 and the effective number of alleles ranged between 1.0438 and 1.1496. The inter-population genetic coefficient differentiation was 0.6306, while analysis of molecular variance revealed that genetic divergence among populations was highly significant (p< 0.001), expressed by a fixation index (ΦST) of 0.4452. Pair-wise analysis of ΦST confirmed an inter-population diversity of 44.52% and an intra-population variation of 55.48%. UPGMA analysis allowed the separation of the accessions into four genotypic groups. We conclude that there is significant genetic diversity among the populations of J. curcas and that this variability is mainly due to intra-population genetic diversity.