Yams are an important food crop in Africa, where the tubers are eaten by 60 million people every day, as well as in other parts of the world. But despite the yam's importance as a food source, science doesn't really know that much about yams or exert much effort in conserving them. That needs to change, says the Global Crop Diversity Trust (GCDT), which has launched a worldwide effort to collect, catalogue and preserve thousands of yam varieties before many of them disappear.

It is not an unlikely scenario, as some yam varieties or species are already endangered. In Uganda, for example, a variety of climbing yam known locally as imbama faces extinction and is now found only in remote, mountainous areas. The climbing yam grows on vines that, as their name implies, climb tall trees—but most of the trees in the Bugisu region of Uganda have been cut down to make room for fast-growing human settlements and agriculture, according to a report in the Uganda news Web site The New Vision. A banana blight, which killed many trees in 2001, further hurt the imbama's chances for survival.

To prevent further loss of important crops, the GCDT hopes to collect genes from 3,000 yam varieties in Africa, China the Philippines and other countries. It is a tough task: unlike seed-crop species, you can't collect and preserve yam seeds, because they are tubers and don't produce seeds that can be dried like many other plants do. Instead, tissue samples for the yam project are being cryopreserved in liquid nitrogen by the International Institute for Tropical Agriculture (IITA) in Ibadan, Nigeria.

In addition to preserving the biodiversity of the yams, the project aims to find the yam varieties with the greatest crop yields and strongest resiliency to disease and climate change. "It's really akin to putting money in the bank," Cary Fowler, executive director of the GCDT in Rome, said in a prepared statement. "All crops routinely face threats from plant pests, disease, or shifting weather patterns, and a country's ability to breed new varieties to overcome these challenges is directly tied to what they have in the bank, not just in terms of financial resources but in terms of the diversity in their crop collections."

A single yam tuber can be as large as 2.5 meters long and weigh up to 70 kilograms, making them a productive and valuable crop for farmers.

There have been other collections of yam biodiversity, but some varieties were lost in Ivory Coast's 2002 civil war, and another collection in the Togolese Republic was destroyed in a fire.


Photo: Yam tubers, via the International Institute for Tropical Agriculture on Flickr