A short history of Lagenaria siceraria (bottle gourd) in the Roman provinces: morphotypes and archaeogenetics

Lagenaria siceraria (Molina) Standl. (bottle gourd) is pantropic and displays large variation in fruit and seed shape. Two subspecies are currently recognized: the African L. siceraria ssp. siceraria and the Asian L. siceraria ssp. asiatica. The Asian type of bottle gourd belongs to the earliest domesticated plants in the Americas. In Europe, bottle gourd only appears with some frequency from the Roman period onwards. The paper is the study of ancient DNA (aDNA) and seed morphology of one almost complete bottle gourd fruit from the Roman site of Oedenburg/Biesheim–Kunheim, France (1st century a.d.), and from individual seed finds from the Roman vicus of Petinesca–Vorderberg, Switzerland (3rd century a.d.), both recovered from waterlogged layers. Width and length measurements of seeds show large variation. Based on the index of width to length, seeds from both sites differ significantly (p < 0.0001 Mann–Whitney) suggesting that there were different variants present north of the Alps. Genetically, the bottle gourd fruit from Roman Oedenburg/Biesheim–Kunheim and one commercial cultivar L. siceraria cv. ‘Herkuleskeule’ are of Asian origin as identified by three Asian and African specific chloroplast markers. These results support an early and long-lasting presence of the Asian type of domestic bottle gourd in Europe. No chloroplast markers were found in the seeds from Petinesca–Vorderberg. However preserved nuclear high copy 5.8S rDNA fragments correctly matched to Cucurbitaceae, further supporting the evidence for preservation of DNA in waterlogged plant remains.