Tracing back the origin of pumpkins (Cucurbita pepossp.pepoL.) in Mexico

Cucurbita pepo is an economically important crop, which consists of cultivatedC. pepo ssp.pepo , and two wild taxa (C. pepo ssp.fraterna andC. pepo ssp.ovifera ). We aimed at understanding the domestication and the diversity ofC. pepo in Mexico. We used two chloroplast regions and nine nuclear microsatellite loci to assess the levels of genetic variation and structure forC. pepo ssp.pepo 's landraces sampled in 13 locations in Mexico, five improved varieties, oneC. pepo ssp.fraterna population and ornamentalC. pepo ssp.ovifera . We tested four hypotheses regarding the origin ofC. pepo ssp.pepo 's ancestor through approximate Bayesian computation:C. pepo ssp.ovifera as the ancestor;C. pepo ssp.fraterna as the ancestor; an unknown extinct lineage as the ancestor; andC. pepo ssp.pepo as hybrid fromC. pepo ssp.ovifera andC. pepo ssp.fraterna ancestors.Cucurbita pepo ssp.pepo showed high genetic variation and low genetic differentiation.Cucurbita pepo ssp.fraterna andC. pepo ssp.pepo shared two chloroplast haplotypes. The three subspecies were well differentiated for microsatellite loci.Cucurbita pepo ssp.fraterna was probablyC. pepo ssp.pepo 's wild ancestor, but subsequent hybridization between taxa complicate definingC. pepo ssp.pepo 's ancestor.