RAPD VARIATION IN SWEET-POTATO (IPOMOEA-BATATAS (L.) LAM) CULTIVARS FROM SOUTH-AMERICA AND PAPUA-NEW-GUINEA

The island of New Guinea is considered a secondary center on diversity for sweetpotato, because of its range of isolated ecological niches a nd large number of cultivars found within a small area. Information of genetic diversity in Papua New Guinea (PNG) sweetpotato is essential for rationalizing the global sweetpotato germplasm collection. Using r andom amplified polymorphic DNA (RAPD), we compared the genetic variat ion and genetic diversity in 18 PNG cultivars versus 18 cultivars from South America. The analysis of molecular variance revealed large gene tic diversity in both groups of cultivars. The within-group (among ind ividuals) variation accounted for 90.6% of the total molecular varianc e. However, the difference between PNG and South American groups is st atistically significant, although it explained only 9.4% of the total molecular variance. The PNG cultivars are also less divergent than the ir South American ancestors as the mean genetic distance in PNG group is significantly smaller than that of South American group. The lower level of genetic diversity in PNG cultivars was also reflected by mult idimensional scaling. This study shows that PNG cultivars, after many years of isolated evolution in an unique agro-ecological environment a re substantially divergent from their ancestors in South America. The genetic diversity level in PNG cultivars is significantly lower than t hat in South American cultivars. It thus provides a baseline for conti nuing studies of genetic diversity in different sweetpotato gene pools .