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

Abstract

Bottle gourd (Lagenaria siceraria) is an African crop with an ancient pantropicaldistribution. Morphological analyses and archaeological evidencesuggest the oceanic dispersals of wild bottle gourd fruits fromAfrica to Asia and the Americas by 10000–15000 B.P., followedby independent domestications on all three continents. AlthoughAfrican and New World landraces (ssp. siceraria) are morphologically distinct from Asian landraces(ssp. asiatica), siceraria-typemorphological characters in New Guinea germplasm has raised questionsconcerning the origins of Asian landraces, including whether or notthere was early germplasm exchange between Asia and the New World.Another area of confusion in bottle gourd systematics and evolutionconcerns the origins and circumscriptions of commercial cultivars,many of which have been subject to undocumented hybridization andselection practices over the past 100–200 years. To clarify theevolutionary histories of bottle gourd landraces and cultivars, 64random amplified polymorphic DNA (RAPD) markersrepresenting 30 primers were examined in 31 landraces and 43 cultivaraccessions of L. siceraria,as well as in a wild relative, L.sphaerica. Principal component analyses of thecorrelation matrices of the band presence/absence data revealedthe following: 1) southern African germplasm represents adivergent lineage from which several cultivars have been selected;2) New World germplasm is distinct and primarily of Africanorigin(s), but possesses Asian affinities as well; 3)landraces from New Guinea are not related to New World germplasm aspreviously hypothesized; 4) commercial cultivars are diverse intheir geographic origins and genetic compositions; and 5) theintegrity and circumscriptions of some cultivars have been confoundedby production practices allowing gene flow among cultivars.