Genetic diversity of the Andean tuber-bearing species, oca (Oxalis tuberosa Mol.), investigated by inter-simple sequence repeats.

The Andean tuber-bearing species, Oxalis tuberosa Mol., is a vegetatively propagated crop cultivated in the uplands of the Andes. Its genetic diversity was investigated in the present study using the inter-simple sequence repeat (ISSR) technique. Thirty-two accessions originating from South America (Argentina, Bolivia, Chile, and Peru) and maintained in vitro were chosen to represent the ecogeographic diversity of its cultivation area. Twenty-two primers were tested and 9 were selected according to fingerprinting quality and reproducibility. Genetic diversity analysis was performed with 90 markers. Jaccard's genetic distance between accessions ranged from 0 to 0.49 with an average of 0.28 +/- 0.08 (mean +/- SD). Dendrogram (UPGMA (unweighted pair-group method with arithmetic averaging)) and factorial correspondence analysis (FCA) showed that the genetic structure was influenced by the collection site. The two most distant clusters contained all of the Peruvian accessions, one from Bolivia, none from Argentina or Chile. Analysis by country revealed that Peru presented the greatest genetic distances from the other countries and possessed the highest intra-country genetic distance (0.30 +/- 0.08). This suggests that the Peruvian oca accessions form a distinct genetic group. The relatively low level of genetic diversity in the oca species may be related to its predominating reproduction strategy, i.e., vegetative propagation. The extent and structure of the genetic diversity of the species detailed here should help the establishment of conservation strategies.