Genetic marker tells squash domestication story

January 07, 2002

In the January 8 Proceedings of the National Academy of Sciences, researchers from the Smithsonian Tropical Research Institute (STRI), The Cucurbit Network and the University of Puerto Rico establish mitochondrial DNA analysis as a powerful tool for understanding relationships among flowering plants. A comparison of mtDNA from cultivated squash, pumpkins, gourds and their wild ancestors strongly supports hypotheses based on archeological and ethnobotanical evidence for six, independent domestication events in the New World. Even Oris Sanjur, who conducted the genetic analysis was "surprised by the resolution" offered by the nad1 gene as a genetic marker.

As excellent sources of edible, protein-rich seeds, members of the genus Cucurbita were among the first plants to be domesticated in the New World. As one of the three sisters (corn, beans and squash) cropping system, squash is prominent in the creation stories of indigenous Americans. In the Iroquois version, corn sprouts from the chest of Sky Woman, squash springs from her belly and beans grow from her hand.

For the last two decades, scientists have pushed to fill in many gaps in the history of agriculture in the humid tropics where archaeological evidence is extremely hard to come by. Last year, Dolores Piperno, archaeologist and staff scientist at the Smithsonian Tropical Research Institute in Panama and colleagues reported the first use of Cucurbita in the Americas at the end of the last ice age (10,000 years ago) based on the presence of tiny plant remains called phytoliths at a site in Ecuador.

Whereas archaeological plant remains tell us that cultivated plants were present at a given time and place, mtDNA sequence data showing similarities among a domesticate and a specific wild population can unambiguously identify the geographic region where prehistoric gardeners first planted the wild ancestors in their gardens, a "promising breakthrough" according to Kenneth Olsen, plant population geneticist at North Carolina State University, who has studied the origins of manioc by sequencing nuclear genes. The silver-seeded squash found in U.S. markets, according to this analysis, may have been domesticated in the area of Mexico where indigenous Americans first domesticated corn. Olsen finds the paper's identification of two separate domestications of Cucurbita pepo, "particularly intriguing" as the relationships of wild and domesticated C. pepo populations have long been a source of contention. The new mtDNA evidence also shows that northeastern Mexico should be seriously considered as a possible region of domestication for one of the lineages of C. pepo squash, which was formerly thought to have originated in eastern North America.

Mitochondrial DNA genetic markers, widely used to gain insight into the relationships among animal species, will surely continue to add to the story of the evolution of crop plants and their wild relatives.

Copies of the article are now available to reporters from the PNAS news office, tel. (202) 334-2138, or e-mail .
The Smithsonian Tropical Research Institute (STRI), with headquarters in Panama City, Panama, is one of the world's leading centers for basic research on the ecology, behavior and evolution of tropical organisms.

Smithsonian Tropical Research Institute

Related Relationships Articles from Brightsurf:

Gorilla relationships limited in large groups
Mountain gorillas that live in oversized groups may have to limit the number of strong social relationships they form, new research suggests.

Electronic surveillance in couple relationships
Impaired intimacy, satisfaction, and infidelity in a romantic relationship can fuel Interpersonal Electronic Surveillance (IES).

'Feeling obligated' can impact relationships during social distancing
In a time where many are practicing 'social distancing' from the outside world, people are relying on their immediate social circles more than usual.

We can make predictions about relationships - but is this necessary?
'Predictions as to the longevity of a relationship are definitely possible,' says Dr Christine Finn from the University of Jena.

Disruptions of salesperson-customer relationships. Is that always bad?
Implications from sales relationship disruptions are intricate and can be revitalizing.

Do open relationships really work?
Open relationships typically describe couples in which the partners have agreed on sexual activity with someone other than their primary romantic partner, while maintaining the couple bond.

The 7 types of sugar daddy relationships
University of Colorado Denver researcher looks inside 48 sugar daddy relationships to better understand the different types of dynamics, break down the typical stereotype(s) and better understand how these relationships work in the United States.

Positive relationships boost self-esteem, and vice versa
Does having close friends boost your self-esteem, or does having high self-esteem influence the quality of your friendships?

Strong family relationships may help with asthma outcomes for children
Positive family relationships might help youth to maintain good asthma management behaviors even in the face of difficult neighborhood conditions, according to a new Northwestern University study.

In romantic relationships, people do indeed have a 'type'
Researchers at the University of Toronto show that people do indeed have a 'type' when it comes to dating, and that despite best intentions to date outside that type -- for example, after a bad relationship -- some will gravitate to similar partners.

Read More: Relationships News and Relationships Current Events is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to