POPULATION STRUCTURE IN CARICA PAPAYA IN PANAMA
Sandra Mardonovich, Richard Moore.
Miami University, Oxford, OH.
The biodiversity of wild relatives of crop species can be threatened by genetic introgression of cultivated traits from co-occurring cultivated varieties or feral escapees. The tropical fruit crop papaya (Carica papaya L.) originated in Mesoamerica, where today it is both cultivated and found in disturbed natural areas where it acts as a pioneer species. Thus, papaya serves as a model to study the effects of gene flow among cultivars and natural populations of their wild relatives. Naturally occurring papaya found near the purported center of domestication in northern Mesoamerica have rounded fruit similar in size to a tennis ball. In contrast, fruit found further south resemble the larger-fruited cultivated papaya, suggesting there has been introgression of cultivated crop traits into wild populations. Small-fruited papaya, though, have been reported as far south as Costa Rica, questioning this prediction. To further question this prediction, we sampled the morphology and genetic diversity of natural papaya populations in Panama, which extends beyond papaya’s hypothesized center of origin. Forty-two individuals were analyzed for qualitative and quantitative morphological traits in 4 regional populations in Panama. The levels and patterns of genetic diversity were measured using 20 molecular markers in 82 samples and compared to the diversity of 14 exotic cultivars to look for signs of genetic introgression from cultivars. STRUCTURE was implemented to determine cryptic population structure, and 2 of the 4 regional populations share genetic similarities with the cultivars. This data provides more insight into the domestication history of this important fruit crop.