Abstract
Cucurbita pepo is a worldwide cultivated
vegetable ofAmerican origin.Most of thewidely grown
commercial types are known as summer squashes and
belong to the elongated forms of C. pepo ssp. pepo
(Cocozelle, Vegetable marrow and Zucchini groups).
These forms were developed in Europe after the arrival
of the first American landraces through a process of
selection and fixation that led to a loss of genetic
diversity. Part of the genetic variability of the first
American cultigens remains intact in diverse landraces
that are still cultivated for self-consumption and sale inlocal markets. Using the first collection of genomic and
EST-derived microsatellites that has just become available
for the species, we compared the natural variation
present in a collection of Spanish landraces with that of a
set of commercial varieties and hybrids, representing
current summer squash market offerings. A total of 194
alleles allowed us to distinguish all the genotypes, even
those that were closely related. In general, Cocozelle
and Vegetable marrow, groups with considerably long
histories, were more variable than the Zucchini group,
of more recent origin. We found significant genetic
diversity among landraces.The variation present among
landraces belonging to the Zucchini group was larger
than that of the commercial cultivars. Cluster, principal
coordinate and population structure results suggested
that the variation of the Spanish landraces has not been
extensively used in breeding. Commercial summer
squashes can therefore benefit from this underexploited resource
