International teams are working to bring cassava genetics into the 21st
century and help food-insecure countries.
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| 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.
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Cassava crop showing tubers with growing crop in background
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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.
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
