Gene Flow in Cucurbita

Abstract

Cucurbita pepo and Cucurbita texana when artificially crossed produce fully fertile hybrids. Thus interspecific genetic exchange is possible. An attempt was made to monitor actual gene flow between these two taxa under both agricultural and natural conditions. Two synthetic populations were established for this purpose using experimental plants that were genetically marked by isozyme phenotype. At the end of the growing season progeny were electrophoresed. The resulting data quantified the event of genetic exchange between taxa, revealed the source of foreign genetic material, and thus established the distance over which gene flow occurred. It can be concluded from the data that since genetic exchange does indeed take place between the C. pepo complex and C. texana, their classification as two distinct and separate species is in question. The data also indicate that the previously published distance requirement for genetic isolation within the Cucurbita is incorrect.