Polymorphism in Calotropis procera: preliminary genetic variation in plants from different phytogeographical regions of Egypt

Calotropis procera (Aiton) W. T. Aiton. (family: Asclepiadaceae) is an important medicinal shrub distributed in the tropical and subtropical regions of the world. In Egypt, it is distributed throughout different phytogeographical regions. Genetic analyses were performed to study polymorphism of 18 individual genotypes collected from six different localities across Egypt (Aswan, New Valley, Cairo-Suez road, Feran, Nuweibaa, and Arish), and to elucidate their population genetic relationships. Five Operon primers successfully generated reproducible polymorphic products. RAPD profiles revealed high levels of polymorphism for the studied individual genotypes (93.45 %). Both number and size of the amplified products varied considerably with different primers and a sum of 100 polymorphic and 7 monomorphic bands were generated in all the individuals under study. A total of 24 unique bands were also identified. The combination of all polymorphic bands generated by all five primers was enough to discriminate between the six different localities. The dendrogram constructed revealed that Aswan (south Nile Valley) and Feran valley (South Sinai mountain area) to be separated in two distinct clusters, while the other four localities in a third cluster. Similarity indices for the genetic distances showed that the highest similarity was (76.03 %) between the genotypes from Cairo-Suez road and Nuweibaa regions, while the lowest was between Feran and Nuweibaa genotypes (63.87 %). The study confirmed the high polymorphic nature of the species and showed that genotypes of the Aswan locality have a highly similar gene pool to genotypes of most localities. South Sinai Feran locality seems to be of a different genetic background. Future studies on material collected from other phytogeographical regions of the world, as well as, using other molecular marker techniques, will contribute to understanding of the species polymorphism and its phytogeographical relationships across different regions of the world.