Abstract Ricinus L., is a monotypic genus of Euphorbiaceae, which is represented by a species: Ricinus communis L. Its seeds contain a high amount of oil that possess several biological activities. R. communis is a variable species and several studies have been conducted to clear it’s among populations diversity. Meanwhile, scares and incomplete infraspecific studies are available for Iranian castor populations. In this study, we extracted the nuclear genomes of nine castor populations using C-TAB protocol and amplified them using ten SCoT molecular primers to evaluate within and among populations genetic diversity. GenAlex, STRUCTURE, GenoDive, PopGene and PopART software were used for statistical analyses. The parameters of genetic polymorphism indicated a low level of genetic diversity exists among the populations. However, a great proportion of the significant genetic diversity belonged to among populations. In addition, other estimated parameters such as the rate of gene flow, total genetic variation in the pooled populations and observed among the populations, average variation within each population, standardized measure of genetic differentiation and MDS plot approved the AMOVA results. Based on the Nei’s genetic distance and structure analysis, two main genotype groups and some intermediates were detected among the populations. However, the populations clustering pattern was not in accordance with phytogeographical mapping of the populations. It seems that the evaluated populations belong to two forms and some hybrids, which are created by an ancestral gene flow. Lack/ a low rate of gene flow due to asynchrony in flowering time and long geographic distance between populations and occurrence of a low rate of mutation have been led to the uniformity of the genetic structure of most populations. We can introduce these forms for further breeding programs to produce some hybrids that have a great potential to grow under stressful habitats.
