Overview of the origins and history of the five major cucurbit crops: issues for ancient DNA analysis of archaeological specimens

The gourd family, Cucurbitaceae, contains five vegetable crops of worldwide importance, the pumpkins and squash (Cucurbita spp.), watermelons (Citrullus lanatus), melons (Cucumis melo) and cucumbers (Cucumis sativus). Here is presented a synopsis of the origin and history of these cucurbit crops. Historical records of the use of cucurbits by people take the form of archaeobotanical finds, iconography and literature. The weight of the evidence indicates that Cucurbita spp. were first cultivated in the Americas at least 10,000 years ago, and that by 1492 ce a number of cultivar-groups of pumpkins and squash had been developed by indigenous American peoples. Watermelons were cultivated in northeastern Africa at least 4,000 years ago, first probably as a source of fresh water. Melons and cucumbers are native to Asia, probably initially cultivated for the use of the young fruits as vegetables. Melons spread to eastern Africa at an early date, but cucumbers are probably a more recent domesticate and spread westwards later, reaching Europe in early medieval times. Sequencing of cucurbit plant genomes and advances in ancient DNA research offer much promise for obtaining an improved assessment of cucurbit crop origins, specifically the genetic constitution and geographical home of ancestral source populations. Next-generation genomic sequencing, if applied to an appropriate array of archaeological cucurbit remains and modern germplasm, could contribute much to the understanding of the history and evolution under domestication of cucurbit crops.