DISSERTATION RESEARCH: Origins and Evolution of Oxalis Tuberosa, a Polyploid Domesticate

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9623227 DOYLE The tuber crop Oxalis tuberosa, or "oca", was domesticated in the Andes region of South America long before Inca times. It has the potential for widespread cultivation, but unlike the potato, another Andean native, oca is still little known in the rest of the world. Oca is among the many crops, such as potatoes, maize and wheat, that are polyploid, in this case with eight sets of chromosomes (most plants and animals have two sets). The origins of oca can be more accurately evaluated by identifying its closest relatives among wild species of Oxalis, and by determining the origin of its eight sets of chromosomes. The extra chromosome sets may have arisen during domestication, either by duplication of those present in a single progenitor species or by hybridization among two or more progenitors. In this study, Eve Emshwiller, under the direction of Jeffrey Doyle, will use evidence from DNA sequences, chromosome number, and the form and anatomy of the plants to determine the phylogenetic relationships among oca and its wild relatives. In particular, the researchers will determine if wild tuber-bearing Oxalis species, recently discovered in Bolivia, represent the progenitor(s) of oca. Knowledge of the distribution of genetic diversity in cultivated oca and its relatives will shed light on the geographic origins and history of domestication. The results of the study will provide information crucial for efforts to conserve the biodiversity of the crop and its wild relatives, and will inform a related ethnobotanical study that is investigating human influences on the genetic variability of the crop.