Genetic diversity and phylogenetic relationships among and within Amaranthus spp. using RAPD markers

Random Amplified Polymorphic DNA (RAPD) markers were used to investigate genetic diversity and phylogenetic relationships among 10 species belonging to the genus Amaranthus L. The results showed that the polymorphism in cultivated species was lower than that in wild ones, reflecting the selection pressures of domestication on genetic diversity in cultivated species. A specific RAPD marker was detected for each of A. powellii PI 572262, A. tricolor PI 462129, A. palmeri PI 607455, A. caudatus PI 511679 and A. quitensis PI 511744. The overall mean similarity index of amplified fragments generated by RAPD primers on genomic DNA of Amaranthus accessions indicated that A. hypochondriacus was the closest grain amaranth to A. hybridus, followed by A. caudatus and A. cruentus. A. tricolor had a maximum genetic distance from grain amaranth species, confirming its morphological classification in a distinct subgenus Albersia. Similarly, the accessions of A. palmeri were separated in a distinct cluster, supporting its classification in a distinct subgenus Acnida. A. hybridus accessions were gathered together with grain amaranth species, thereby supporting the single progenitor hypothesis for grain amaranths. A. spinosus was separated on a distinct principal coordinate axe, indicating its low correlation with other species and confirming its morphological classification in a distinct section, i.e. Centrusa.