BELLAGIO, ITALY (6 MAY 2013)— Cassava experts are reporting new
outbreaks and the increased spread of Cassava Brown Streak Disease or
CBSD, warning that the rapidly proliferating plant virus could cause a
50 percent drop in production of a crop that provides a significant
source of food and income for 300 million Africans.
The “pandemic” of CBSD now underway is particularly worrisome because
agriculture experts have been looking to the otherwise resilient
cassava plant—which is also used to produce starch, flour, biofuel and
even beer—as the perfect crop for helping to feed a continent where
growing conditions in many regions are deteriorating in the face of
climate change.
“Cassava is already incredibly important for Africa and is poised to
play an even bigger role in the future, which is why we need to move
quickly to contain and eliminate this plague,” said Claude Fauquet, a
scientist at the International Center for Tropical Agriculture (known
by its Spanish acronym CIAT) who heads the Global Cassava Partnership
for the 21st Century (GCP21). “We are particularly concerned that the
disease could spread to West Africa and particularly Nigeria—the
world’s largest producer and consumer of cassava—because Nigeria would
provide a gateway for an invasion of West Africa where about 150
million people depend on the crop.”
Fauquet and his colleagues in the GCP21—an alliance of scientists,
developers, donors and industry representatives—are gathering at the
Rockefeller Foundation Bellagio Center in Italy this week for a
conference dedicated to “declaring war on cassava viruses in Africa.”
A “Silent Killer” Emerges: CBSD on Warpath from East to West
First identified in 1935 in East Africa and little-known until about
ten years ago, CBSD has emerged as the most serious threat among the
various cassava viruses. Infections can claim 100 percent of a
farmer’s harvest without the farmer’s knowledge. The leaves of
infected plants can look healthy even as the roots, cassava’s most
prized asset, are being ravaged underground. The tell-tale signs of
the disease are brown streaks in the root’s flesh that, when healthy,
provides a rich source of dietary carbohydrates and industrial starchy
products.
There have been recent reports of new outbreaks in the Democratic
Republic of the Congo—the world’s third largest cassava producer—and
Angola, where production has boomed in recent years. The spread of the
disease to West Africa and particularly Nigeria is a major cause for
concern, experts say, because the country now produces 50 million tons
of cassava each year and has made a big bet on cassava for its
agricultural and industrial development in the near future.
Nigeria is the first African country to massively invest in the
potential of cassava to meet the rapidly growing global demand for
industrial starches, which are used in everything from food products
to textiles, plywood and paper. Nigeria hopes to mimic the success of
countries in Southeast Asia, where a cassava-driven starch industry
now generates US$5 billion per year and employs millions of
smallholder farmers and numerous small-scale processors.
CMD—a Scourge for Cassava on the African Continent
Scientists at the conference will also consider options for dealing
with another devastating virus—the Cassava Mosaic Disease (CMD). CMD
has plagued the whole African continent for over a century, each year
removing a minimum of 50 million tons of cassava from the harvest.
The disease is caused by several viruses and the African continent
witnessed several major CMD epidemics over the past decades, the most
recent and devastating of which occurred in the 1990s in East and
Central Africa. Great success was achieved in combating the CMD
pandemic through developing and disseminating varieties that were
resistant to CMD. In fact, by the mid-2000s, half of all cassava
farmers were benefiting from these varieties in large parts of East
and Central Africa. But by a cruel twist of nature, both improved and
local varieties all succumbed to the ‘new’ pandemic of CBSD.
Unexpected Plot Twist: Whiteflies Ambush a Climate-Resilient Crop
Interest in cassava has intensified across Africa as rising
temperatures and shifting rainfall patterns caused by climate change
threaten the future viability of food staples such as maize and wheat.
Cassava has been called the “Rambo root ” for its extraordinary
ability to survive high temperatures and tolerate poor soils. But
rising temperatures now pose a threat to cassava because they appear
to be one of several factors causing an explosion in whiteflies, which
carry the viruses that cause CMD and CBSD and pass it along as they
feed on the plant’s sap.
Compounding the effects of rising temperatures, scientists also think
that genetic changes have led to the emergence of “super” whiteflies.
This toxic mix of circumstances affecting a tiny fly threatens to
shoot down the “Rambo root,” bringing the misery of food insecurity to
vast swathes of Africa.
“We used to see only three or four whiteflies per plant; now we’re
seeing thousands,” said James Legg, a leading cassava expert at the
International Institute of Tropical Agriculture (IITA). “You literally
have a situation where human beings are competing for food—with
whiteflies.”
Farmers also help spread the disease by planting new fields with
infected stem cuttings. Scientists note that while it would take
several years for the disease to spread across the continent via
whiteflies alone, infected stem cuttings could spark outbreaks in new
areas overnight.
Experts to Develop Plan to Stop Viruses in their Tracks
At the Italy meeting, experts will discuss a variety of tactics for
combating virus diseases, such as developing more disease-resistant
varieties like those recently released in Tanzania. Efforts to breed
high-yielding, disease-resistant plants suitable for Africa’s various
growing regions will involve going to South America, where cassava
originated, and working with scientists to mine the cassava gene bank
at CIAT in Colombia—the biggest repository of cassava cultivars in the
world.
The expert team will also discuss a more ambitious plan: how to
eradicate cassava viruses altogether. The aim will be to develop a
bold regional strategy that will gradually, step-by-step,
village-by-village, replace farmers’ existing infested cassava plants
with virus-free planting material of the best and most resistant
available cultivars. Approaches will include new molecular breeding
and genetic engineering technologies to speed up the selection and
production of CMD and CBSD resistant cassava cultivars more appealing
to farmers.
There also will be discussions about cost-effective and
environmentally sustainable ways to control whiteflies, as well as
proposals for new surveillance systems that can better track and stop
the disease from spreading. Scientists will also discuss new research
into the potential threat African cassava producers face from the
introduction of new diseases currently found outside the continent.
“It’s time for the world to recalibrate its scientific priorities,”
Fauquet said. “More than any other crop, cassava has the greatest
potential to reduce hunger and poverty in Africa, but CBSD and other
viruses are crippling yields. We need to treat CBSD and other
destructive viruses like the smallpox of cassava—formidable diseases,
but threats we can eradicate if everyone pulls together.”
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Founded in 2003, the Global Cassava Partnership for the 21st Century
(GCP21) is a not-for-profit international alliance of 45 organizations
and coordinated by Claude Fauquet and Joe Tohme of the International
Center for Tropical Agriculture (CIAT). It aims to fill gaps in
cassava research and development in order to unlock the potential of
cassava for improving food security and also increasing incomes of
poor farmers through work to develop industrial products from cassava.
GCP21 is providing updated information regarding the crop, the
scientists working on cassava and cassava R&D projects in the world.
The International Center for Tropical Agriculture (CIAT)—a member of
the CGIAR Consortium—develops technologies, tools, and new knowledge
that better enable farmers, especially smallholders, to make
agriculture eco-efficient—that is, competitive and profitable as well
as sustainable and resilient. Eco-efficient agriculture reduces hunger
and poverty, improves human nutrition, and offers solutions to
environmental degradation and climate change in the tropics. With
headquarters near Cali, Colombia, CIAT conducts research for
development in tropical regions of Latin America, Africa, and Asia.
www.ciat.cgiar.org
The International Institute of Tropical Agriculture (IITA) is a
nonprofit research-for-development organization that works with
partners in Africa and beyond to tackle hunger and poverty by reducing
producer and consumer risks, enhancing crop quality and productivity,
and generating wealth from agriculture. IITA is a member of the CGIAR
Consortium.www.iita.org
Additional Institutions attending the Third Strategic Meeting of the
Global Cassava Partnership for the 21st Century, Bellagio, Italy:
International Potato Center (CIP), leader of CGIAR’ Research Program
on Roots, Tubers and Bananas (RTB); CGIAR Fund; Food and Agriculture
Organization of the United Nations (FAO); International Fund for
Agricultural Development (IFAD); World Bank; the African Development
Bank (AfDB); United States Agency for International Development
(USAID); Bill & Melinda Gates Foundation; Syngenta Foundation for
Sustainable Agriculture; Catholic Relief Services (CRS); Kenya
Agricultural Research Institute (KARI); Mikocheni Agricultural
Research Institute (MARI), Tanzania; Deutsche Sammlung von
Mikroorganismen und Zellkulturen GmbH (DSMZ), Germany; Natural
Resources Institute (NRI), UK; Tel Aviv University, Israel; Institute
of Resources Assessment (IRA), Tanzania; National Agricultural Crops
Resources Research Institute (NACRRI), Uganda.