Diversity in landraces and cultivars of bottle gourd (Lagenaria siceraria;Cucurbitaceae) as assessed by random amplified polymorphic DNA

Bottle gourd (Lagenaria siceraria) is an African crop with an ancient pantr opical distribution. Morphological analyses and archaeological evidence sug gest the oceanic dispersals of wild bottle gourd fruits from Africa to Asia and the Americas by 10000-15000 B.P., followed by independent domesticatio ns on all three continents. Although African and New World landraces (ssp. siceraria) are morphologically distinct from Asian landraces (ssp. asiatica ), siceraria-type morphological characters in New Guinea germplasm has rais ed questions concerning the origins of Asian landraces, including whether o r not there was early germplasm exchange between Asia and the New World. An other area of confusion in bottle gourd systematics and evolution concerns the origins and circumscriptions of commercial cultivars, many of which hav e been subject to undocumented hybridization and selection practices over t he past 100-200 years. To clarify the evolutionary histories of bottle gour d landraces and cultivars, 64 random amplified polymorphic DNA (RAPD) marke rs representing 30 primers were examined in 31 landraces and 43 cultivar ac cessions of L. siceraria, as well as in a wild relative, L. sphaerica. Prin cipal component analyses of the correlation matrices of the band presence/a bsence data revealed the following: 1) southern African germplasm represent s a divergent lineage from which several cultivars have been selected; 2) N ew World germplasm is distinct and primarily of African origin(s), but poss esses Asian affinities as well; 3) landraces from New Guinea are not relate d to New World germplasm as previously hypothesized; 4) commercial cultivar s are diverse in their geographic origins and genetic compositions; and 5) the integrity and circumscriptions of some cultivars have been confounded b y production practices allowing gene flow among cultivars.