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 pantropical distribution. Morphological analyses and archaeological evidence suggest the oceanic dispersals of wild bottle gourd fruits from Africa to Asia and the Americas by 10000-15000 B.P., followed by independent domestications 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 raised questions concerning the origins of Asian landraces, including whether or not there was early germplasm exchange between Asia and the New World. Another area of confusion in bottle gourd systematics and evolution concerns the origins and circumscriptions of commercial cultivars, many of which have been subject to undocumented hybridization and selection practices over the past 100-200 years. To clarify the evolutionary histories of bottle gourd landraces and cultivars, 64 random amplified polymorphic DNA (RAPD) markers representing 30 primers were examined in 31 landraces and 43 cultivar accessions of L. siceraria, as well as in a wild relative, L. sphaerica. Principal component analyses of the correlation matrices of the band presence/absence data revealed the following: 1) southern African germplasm represents a divergent lineage from which several cultivars have been selected; 2) New World germplasm is distinct and primarily of African origin(s), but possesses Asian affinities as well; 3) landraces from New Guinea are not related to New World germplasm as previously hypothesized; 4) commercial cultivars are diverse in their geographic origins and genetic compositions; and 5) the integrity and circumscriptions of some cultivars have been confounded by production practices allowing gene flow among cultivars.