The Origins of Domesticated Sunflower (Helianthus annuus L.)

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With funding provided by the National Science Foundation, Dr. David Lentz and his associates will conduct fieldwork and laboratory experiments to determine whether the modern domesticated sunflower (Helianthus annuus L.) is derived from: 1) a wild progenitor from populations in eastern North America, as previously hypothesized; 2) a wild population from Mexico; or 3) or the result of two separate domestication events. The issue of domesticated sunflower origins has been reopened because of recently discovered archaeobotanical remains of fully domesticated H. annuus from deep deposits at the San Andres site in the Gulf Coast region of Tabasco, Mexico. Radiocarbon age determinations +- 50 B.P. These findings represent the earliest indisputable record of domesticated sunflower. The San Andres sunflower seeds probably were imported into Tabasco as full-fledged domesticates because Tabasco lies to the south of the modern distribution of wild sunflowers. The precise location of sunflower domestication is unknown at present, but Mexican regions north of Veracruz with suitable habitat and wild populations of H. annuus now seem likely as possible areas of origin.The methodological approaches will include a major fieldwork component followed by laboratory analyses. The fieldwork will focus on collecting modern wild sunflower specimens from northern Mexico, the southwestern U.S., and the midwestern U.S. These collections will provide raw material for the taxonomic and molecular analyses that will enable the team to identify wild progenitor populations of domesticated sunflower.Previous authors have argued for an eastern North American origin for domesticated sunflower based on archaeobotanical data from several sites in the Mississippi River Basin and the recognition of sunflower as one of the keystone species in what eventually developed into the Eastern Agricultural Complex (EAC) of North American cultigens. Interestingly, sunflower was the only major cultigen that formerly was unchallenged as an eastern North American domesticate; now that origin, at least as a unique domestication event, appears in doubt. In addition to its anthropological implications, locating ancestral wild populations has significant practical applications for expanding the genetic base of a valuable resource; sunflower is one of the world's major oilseed crops with an annual global production of over 26 million metric tons. Once located, these ancestral sunflower populations, as valuable genetic reservoirs, will represent meaningful targets for conservation.