Climate change

Yams – a main staple in Africa, Asia

Climate fluctuations make life difficult for the plants we eat. Unlike us, they can’t move if it’s too hot, too cold, or they don’t have enough water.

This is the story of the humble yam. These are not to be confused with the orange flesh sweet potato. If you didn’t know, while yams and sweet potatoes both have orange flesh (though yams are much lighter – often white), they are in different plant species. Yams are also native to Africa and Asia, while sweet potatoes originated in South America. And, if you’re shopping in the United States, you’re most likely buying sweet potatoes.

Both yams and sweet potatoes are root crops. They both store well. And, they both provide a lot of nutrition. That’s about where the similarities stop.

Man holding pick and a bunch of large yams he's just harvested

Late maturing D rotundata yams produce several small tubers. Credit: P Vernier

Yams are a main staple of many meals in the tropics. They are even sweeter than sweet potatoes, but starchier. In addition, yams must be cooked in order to be eaten – the heat destroys naturally-occurring toxins in the tubers. They have been used as medicine, and are also culturally important. Yam wild relatives grow in many unique environments. Some species of yam grow in deserts, where they survive with almost no water.

Although people only eat a few different species of yams, scientists have identified almost 600 different types. Knowing family relationships helps breeders and farmers identify the best species to use to overcome insect, disease and climate pressure. But we actually don’t know a lot about how different yams are related to another.

New work from the University of British Columbia and The Royal Botanic Gardens, Kew, is exploring the relationships among yam species using DNA sequencing. They are studying a combination of museum specimens, wild collected plants and plants that live in botanical gardens. They have started determining what the ancient relationships are.

Complicating things further is the fact that many of these species can cross with each other, and then can be grown as clones. The researchers probed the plant’s DNA and identified the genetic relationships between these widely used species, even identifying a new cousin of the winged Yam (Dioscorea alata), which is grown across the world.

Research that helps us understand the family tree of these unique species will help breeders and farmers use more family members, and will help yam continue to be on tables for years to come.

Provided by Michael Kantar, University of Hawaii, and Marybel Soto Gomez, University of British Columbia

Read about more crop wild relatives in these blogs!

Conserving crop wild cousins

Frank Meyer, an early plant explorer

The cranberry: a very American berry

Call of the wild sunflower

And, be sure to visit our main Crop Wild Relative Week page for more information!

About us: This blog is sponsored and written by members of the American Society of Agronomy and Crop Science Society of America. Our members are researchers and trained, certified, professionals in the areas of growing our world’s food supply while protecting our environment. We work at universities, government research facilities, and private businesses across the United States and the world.

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