Tuesday, March 25, 2014

Cassava - A Crop for Now and the Future

International teams are working to bring cassava genetics into the 21st century and help food-insecure countries.
Cassava plant drawings

Cassava is a starchy, tuberous root first domesticated about 10,000 years ago in South America. Also dubbed manioc, cassava may be more familiar to many as tapioca—tiny pearls of starch used to thicken pies and jams.

For about 800 million people in the tropics, however, it is a staple, not a baking aid.

Now, concerted efforts at crossbreeding and genomic selection have created novel versions of cassava that could dramatically boost yields, ward off malnutrition and grow in a wide range of conditions.
The typical cassava shrub produces unassuming brown roots with snowy white or creamy coloured interiors. 
A cassava crop is perennial—after maturing for at least eight months roots can be harvested for a few years. New plants grow easily from cuttings. The root is carbohydrate-rich, protein-poor and must be boiled, roasted, fermented or otherwise processed to tame compounds that can produce toxic hydrogen cyanide during digestion.  In Africa, 500 million depend on the root as their main staple.

Because many cassava consumers live in developing countries, the plant has not received the intense breeding that has benefited crops more familiar to the Western world such as corn, wheat and rice. In the past decade, however, cassava has started to garner attention. China and Thailand use it to make high-quality starch, and some countries see the crop as a potential biofuel. What’s more, cassava will likely do well in the world’s changing climate; it survives drought when other crops have failed and flourishes in warmer temperatures.  For many years Thailand has exported cassava chips to Europe to use in poultry feeds.

Big boost in yield
Among the latest and most impressive breeding successes comes from Nagib Nassar, a cassava breeder and professor emeritus of genetics at the University of Brasilia. He has developed a new variety that could dramatically boost yields. Each of his plants produces about 14 kilograms of edible roots after one year whereas traditional varieties yield just two to three kilograms.

These are not the only new cassava varieties out there, with others including a cassava high in vitamin A, which turns the root orange, and one with extra protein.  Work is also advancing on varieties resistant to other problems including brown streak disease, green mites that devastate leaves, cassava bacterial blight that browns stems and defoliates the plants and cassava mosaic virus that yellows leaves and stunts plant growth.

Cassava crop showing tubers with growing crop in background

Getting to the next generation

These promising varieties could be just the beginning in a cassava revolution. “There is a growing recognition for the importance of food security in the most food-insecure areas," says Jim Lorenzen, a senior program officer at the Bill and Melinda Gates Foundation, a major supporter of cassava research. The foundation aided researchers in the sequencing of the cassava genome and awarded $25 million in late 2012 to a massive international effort called the Next Generation Cassava Breeding (NEXTGEN) project, which aims to jump-start genetic improvement of cassava. "It’s a very good time for cassava research," Lorenzen says.
He notes that this attitude is reflected in more researchers focusing on cassava and intense interest from African leaders, including Nigeria’s Minister of Agriculture and Rural Development, Akinwumi Adesina.
Millions of small famers and their families stand to benefit from cassava researchers’ efforts.

By the end of 2014, more than 9,000 farmers are scheduled to grow Nassar’s chimeras in Brazil. Expect to hear more about the starchy root in the future, as new varieties help feed the tropical world

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