Protect Vital Cassava Farming in Africa

Cassava is a starchy root crop whose tubers are a primary food source for about 800 million people worldwide, including about 250 million people who live in Africa. A relative to the rubber plant, cassava grows well in marginal conditions: its leaves remain green during Africa’s seasonal droughts. The fallen leaves give enough nutrients back to the soil that the subsistence farmers can grow it without fertilizer. Also, the cassava tolerates poor farming, making it a crop that can be grown, for example, by a farmer who is weak from malaria.

For having such a central role in the diets of so many, though, the cassava tuber is a relatively poor source of some important nutrients. Dr. Richard Sayre, head of the BioCassava Plus Project, envisioned a "super" cassava with more protein, zinc, iron, vitamin A, and vitamin E. Additional goals for the Project included increasing the size of its tubers, reducing its toxin levels (tubers contain varying levels of a form of poisonous cyanide), and boosting the plant’s resistance to diseases.

Five years ago, the Bill and Melinda Gates Foundation gave Dr. Sayre and the BioCassava Plus Project a $12 million grant to use genetic engineering to significantly improve the cassava. Because cassava is propagated by cuttings, genetic engineering methods represent a time-saving shortcut over conventional selective breeding. Before too long, however, cassava "improvement" was forced to encompass the challenge of a terrible new viral disease that still threatens Africa’s food supply. It injected a new urgency to the scientists’ work.

A virus mutation in 2004 spurred an "explosive" spread of the Brown Streak Disease from the East Africa coastal lowlands to the higher inland areas, including Uganda. These viruses are spread by tiny whiteflies. Unlike the tamer coastal version, the newer Uganda strain kills cassava plants and riddles the tubers with brown discoloration, rendering them inedible, as shown in the photo. Brown Streak Disease (for its markings on stems) has created an emergency for many farmers who are left without enough plants to produce cuttings for the upcoming season.

In the face of this cassava crisis, plant scientists have met or exceeded the goals of their research proposals, including resistance to the devastating new virus. In mid-2009, Dr.Claude Fauquet, an expert in the single-strand DNA geminiviruses that infect cassava, announced that he and his team had succeeded in creating a strain of cassava that is resistant to both versions of Cassava Brown Streak Disease. They used the same technique – called RNA interference – that had been used to create disease-specific resistance in new papaya and plum tree varieties. Dr. Fauquet’s achievement with cassava that is resistant to the Brown Streak Diseases builds on the success in increasing protein by a factor of 4, iron by a factor of 4, and vitamin A by a factor of 30, not to mention the other goals reached or exceeded.

The hope is that the new cassava will succeed during field trials in East Africa and be available to the farmers there by 2015, if not sooner. (Genetically modified crops are always carefully field-tested.)

The epicenter for U.S.-based cassava research is in St. Louis, Missouri, at the Donald Danforth Plant Sciences Center. It is home to Dr. Fauquet as well as the BioCassava Plus Project and Dr. Sayre, the grant awardee, who joined the staff in 2008. Indeed, the DanforthCenter has been a powerhouse for cassava research for a long time. Although the Center was founded in 1998, two of its most esteemed plant virologists, Dr. Fauquet and Dr. Roger Beachy, were pioneers in this area of study: in 1991, while at the Scripps Research Institute, they co-founded the International Laboratory for Tropical Agriculture Biotechnology (ILTAB).

Dr. Fauquet also founded (and still co-chairs) the Global Cassava Project. He pushed for the sequencing of the cassava genome, an initiative also funded by the Gates Foundation. The genome sequence was completed in 2009 by a team led by University of Arizona scientists and a subsidiary of Roche called 454 Life Sciences, the world leader in genome-related technology. Free access to the genome data is expected to be an invaluable resource to future endeavors.

Interest in cassava extends beyond food: China now grows it for ethanol, and a recent study of it grown in Alabama for ethanol was promising.

Indications are that experienced plant scientists in Africa who were, in large part, trained in the United States, are recognizing the need for more agriculture doctoral programs in their universities. They have been inspired by the many scientists who are responding to Africa’s cassava crisis. They liken current efforts to help Africa’s farmers to those of agriculture professors of the U.S. land grant universities during India’s Green Revolution. They helped India learn to "feed itself" during the 1950s to 1960s; by the late 1980s, India had become a net exporter of food.

Today, genetic engineering is not without its critics. However, according to a 2009 report in the Chronicle of Higher Education, most students studying agriculture in Africa’s universities argue in favor of genetic engineering. One of the new doctoral students interviewed for that article noted that GE technology could halve the time required to develop better crops for the hungry continent. "Africa missed out on the Green Revolution," he said, "so we shouldn’t miss out on the Genetic Revolution too."

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