Assessing genetic diversity of sweet potato (Ipomoea batatas (L.) Lam.) cultivars from tropical America using AFLP

The sweet potato genebank at the International Potato Center (CIP) maintain s 5,526 cultivated I. batatas accessions from 57 countries. Knowledge of th e genetic structure in this collection is essential for rational germplasm conservation and utilization. Sixty-nine sweet potato cultivars from 4 geog raphical regions (including 13 countries) of Latin America were randomly sa mpled and fingerprinted using AFLP markers. A total of 210 polymorphic and clearly scorable fragments were generated. A geographic pattern of diversit y distribution was revealed by mean similarity, multidimensional scaling (M DS), and analysis of molecular variance (AMOVA). The highest genetic divers ity was found in Central America, whereas the lowest was in Peru-Ecuador. T he within-region variation was the major source of molecular variance. The between-regions variation, although it only explains 10.0% of the total div ersity, is statistically significant. Cultivars from Peru-Ecuador, with the lowest level of within region diversity, made the most significant contrib ution to the between region differentiation. These results support the hypo thesis that Central America is the primary center of diversity and most lik ely the center of origin of sweet potato. Peru-Ecuador should be considered as a secondary center of sweet potato diversity.