Genetic variability of Lepidium meyenii and other Andean Lepidium species (Brassicaceae) assessed by molecular markers

A phylogenetic survey based on similarity levels was performed for 29 cultivated accessions of maca (Lepidium meyenii Walp.) and 27 accessions of wild species of Lepidium from Ecuador, Peru and Bolivia, with RAPD markers. Chromosome counts for each accession were also performed. The similarity tree matrix separated in two main branches: cultivated and wild species. The similarity level among cultivated accessions was high (0.952 or higher) indicating a low level of polymorphism. Within the wild species, two main secondary branches could be resolved, of which one was subdivided into two tertiary branches. Morphological evaluation of the wild species accessions within each main group identified three wild species: (1) L. bipinnatifidum, consisting mostly of tetraploids and a single octoploid accession; (2) L. kalenbornii, consisting only of tetraploid accessions; and (3) L. chichicara, consisting mostly of octoploid and a few tetraploid accessions. Clustering by principal coordinates analysis supported the results obtained by the similarity tree matrix. These results indicate that none of the three wild species is related enough to be considered ancestral to the cultivated L. meyenii. Three accessions of intermediate position may be of hybrid origin. None of the wild species was found to be diploid, which suggests that polyloidy has been an important adaptation to high altitude habitats in these species. (C) 1998 Annals of Botany Company