Oxalis tuberosa Molina (Oxalidaceae), commonly known as "oca," is an octoploid tuber crop with an important role in the diet and farming systems of traditional agriculturists in the central Andean highlands. Prior results of analysis of DNA sequences of chloroplast-expressed glutamine synthetase (ncpGS) identified two wild tuber-bearing taxa as putative genome donors of the octoploid cultigen: Oxalis picchensis of Peru, and an as-yet-unnamed taxon of Bolivia. Investigations are in progress using fluorescent AFLP as an independent data source to test this working hypothesis and to use oca as a model to study the human influence on evolutionary factors such as selection and geneflow in clonally-propagated crops. AFLP fingerprinting of oca cultivars is providing information about genotypic distributions and diversity (richness) and the role of sexual recombination in the formation of new genotypes. Oca genotypes as identified by AFLP data are also being compared with the folk taxonomy. Andean farmers divide oca folk cultivars into separate use-categories, similar to those reported for native Andean potatoes. Sweeter cultivars are cooked fresh after several days of exposure to sunlight, whereas acid cultivars are processed by freezing and drying into long-lasting khaya. Preliminary results of AFLP analysis found that certain acid cultivars differ markedly in their AFLP profiles from the sweet varieties, whereas the profiles of cultivars within each category are relatively similar. Some peaks (amplified products) that are present in sweet varieties but lacking in the acid varieties are also lacking in the wild tuber-bearing taxon of Bolivia that was suggested by ncpGS data to be one of the progenitors of cultivated oca. Further sampling is in progress to test whether these differences reflect different genomic compositions, separate origins of polyploidy, or other differences in the evolutionary histories of the two use-categories.

Key words: AFLP, crop evolution, folk taxonomy, Oxalidaceae, Oxalis, polyploidy