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GMO-FREE REGIONS & PRODUCTS: Non-GE solution found for cassavaroot-rot devastation in Africa



                                 PART I
------------------------------- GENET-news -------------------------------
TITLE:  Africa's cassava comeback
SOURCE: New Scientist, UK
AUTHOR: Fred Pearce
URL:    http://environment.newscientist.com/channel/earth/mg19426002.000-
africas-cassava-comeback.html
DATE:   19.04.2007
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Africa's cassava comeback

Mzee Hamis is a proud man. For half a century he fed his three wives and
brought up 18 children on his 2-hectare plot on the island of Zanzibar
in east Africa. His fields of cassava were his store cupboard, yielding
food when other crops failed. Then one day, four years ago, the cupboard
was bare. "The bushes looked healthy," he says. But when he dug them up
to harvest the tubers, he found every last one had rotted away. "I had
lost my entire crop. We were hungry and I was desperate."

What he didn't know then was that his crop was the first known victim of
a plague caused by a new and virulent strain of the cassava brown streak
virus that is now spreading across eastern and central Africa. Crop
scientists are scrambling to devise new varieties of cassava, also known
as manioc, that are resistant to the virus. However, they are
constrained by a lack of basic knowledge about both cassava and the
brown streak virus. Meanwhile, the virus is causing hundreds of millions
of dollars' worth of damage and threatening the livelihoods of tens of
millions of the world's poorest people.

Agronomists may regard cassava as a poor man's standby, but it is the
most important subsistence crop in Africa. Even as the virus advances,
African farmers harvest around 120 million tonnes a year. That is a
third of a kilogram a day for every single citizen of the continent,
more than twice as much as any other crop (see Graph). Cassava is vital
for food security: it is Africa's drought crop and war crop. In some
places it is virtually the only thing standing between millions of
people and starvation.

Cassava tolerates poor soils and survives drought better than most
crops. "Cassava will grow virtually in the bush," says cassava expert
Alfred Dixon of the International Institute for Tropical Agriculture
(IITA) in Ibadan, Nigeria. "It needs little tending and can be harvested
at any time." When the rains fail and neighbouring fields of corn die,
cassava's leaves stay green and its tubers swollen, ready for roasting,
boiling or grinding into flour. When armies invade and villagers flee
for their lives, they know that once they return home after the soldiers
have gone - weeks, months or even years later - the cassava will still
be there in the overgrown fields, ready for harvesting.

The cassava brown streak virus is changing all that, says Haji Saleh of
the agriculture ministry in Zanzibar. Other pests and viruses that
afflict cassava - notably the cassava mosaic virus, which has been
advancing across east Africa since the late 1980s - leave visible marks
on the foliage and always spare some of the crop, he says. Brown streak
is a stealth virus.

"It destroys everything in the field - and you don't even know it until
you try to harvest," says Saleh. As Hamis discovered, the leaves may
appear healthy even when the roots have rotted away. A field apparently
fit to feed a family may turn out to be worthless.

The brown streak virus has been known since 1935, when British
scientists reported it in coastal Tanganyika (now Tanzania). Until
recently it remained largely confined to Tanzania's low-lying coastal
plains. In the past five years, however, it has become substantially
more virulent and begun spreading across the continent - apparently
starting from Hamis's farm.

The virus is now a threat to the whole of sub-Saharan Africa. It has
invaded Kenya and moved round the shores of Lake Victoria into Uganda,
where it has spread across the entire country in the past two years.
From there it has entered the Democratic Republic of the Congo. It has
also moved south, spreading into Malawi, Zambia and Mozambique, from
where it seems poised to move right across southern Africa.

Where the virus strikes, cassava yields tumble. In Tanzania they have
fallen by between 50 and 80 per cent in the past five years, says
Caroline Herron, a cassava researcher at IITA's branch in Dar es Salaam.
The economic damage to the incomes of poor Tanzanian farmers is
conservatively estimated at more than $50 million a year.


Fighting back

Herron's team have begun a fightback but are hampered by a lack of basic
knowledge about cassava and its diseases. Much of the literature dates
back to the 1950s and earlier. Since then, cassava has languished at the
bottom of the pecking order for research funds.

It is hard to tackle a disease when you don't even know how it is
spread. Since the 1930s, cassava researchers have assumed that the brown
streak vector is an insect called whitefly, which also spreads cassava
mosaic virus. Herron, however, says that while whitefly can transmit the
virus, it is not the most important vector. The most likely transmission
medium, she says, is people.

Cassava will not grow from seed and has to be propagated from cuttings.
Farmers frequently swap cuttings, and those swaps are increasingly
taking place over long distances thanks to migration, refugees and
traders. Africans are travelling today as never before. Just as HIV has
spread across Africa with the movement of people, so too is the brown
streak virus spreading. Without proof, however, it is difficult to
justify enforcing measures such as quarantine.

A second approach is to develop new varieties of cassava that resist the
virus. Here the IITA researchers, led by plant breeder Edward Kanju, are
having more success.

Starting where the virus itself did, in Zanzibar, they have toughened up
some popular local varieties by cross-breeding them with other, less
popular varieties that seem to tolerate the new virus.

The first trials have proved successful, and farmers are clamouring for
the new varieties - especially one based on a local variety called
kiroba, which is a favourite because of its sweet taste and smooth
texture. Last month the Zanzibar ministry officially released some of
the new varieties to farmers, moving from trials to a fully operational
project.

"I get four sacks from my field instead of one now," says Ameir Salum,
who took part in the trials on his 2-hectare farm near Kidinni. He
points out a plot containing the new variety - still known simply as
"variety 452". Alhaj Ameir in nearby Mahonda village says he would have
abandoned cassava altogether if he hadn't been able to join the trials.
"Before, my whole plot was destroyed by the virus." But variety 452 is
better, he says. "It tastes good, too. My children won't eat rice any
more because they want to eat this."

One challenge is how to propagate the new varieties fast enough to allow
every farmer to grow them. Using traditional methods, each plant
provides only eight to ten cuttings, which take six months to mature. To
speed things up, IITA is training farmers in a method of rapid
multiplication in which small fragments of stem are planted, allowing up
to 150 new plants to be grown from one old one.

The trials are going so well that some researchers now see a bright
future for cassava. One such enthusiast is Adebayo Abass at IITA in Dar
es Salaam. He sees cassava as the vanguard of a range of traditional
crops fighting the tide of upstart imports like corn, wheat and
potatoes. "In my ideal world, all sorts of traditional African crops
will be grown. We will bake using cassava flour. We won't eat French
fries - we'll eat African fries made of cassava," he says. And sure
enough, in the market of Stone Town, the old quarter of Zanzibar city,
food stall holders say their biggest sellers among locals and tourists
alike are roasted cassava and fried cassava chips.

Hamis also sees great promise for the crop. It may be too late for him
to benefit from any cassava boom: he is 75 now and in increasingly poor
health. But he believes his sons could have a bright future farming
cassava. Maybe all of Africa can too.


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                                 PART II
------------------------------- GENET-news -------------------------------
TITLE:  Solution found for cassava root-rot devastation in Africa
SOURCE: International Institute of Tropical Agriculture, Tanzania
AUTHOR: Press Release
URL:    http://www.iita.org/cms/details/news_details.aspx?
articleid=1004&zoneid=81
DATE:   24.04.2007
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Solution found for cassava root-rot devastation in Africa

Dar es Salaam, Tanzania - Scientists of the International Institute of
Tropical Agriculture (IITA) have developed varieties resistant to
Cassava Brown Streak Disease (CBSD) in collaboration with their
counterparts at the National Agricultural Research Systems in Tanzania.
This dreaded root rot-causing disease has been ravaging the cassava belt
in the Great Lake region.

The causal pathogen is Cassava brown streak virus (CBSV). The disease
causes yield losses in cassava of 20-80%, affecting peoples' livelihoods
all over Eastern Africa. For example, the disease is the most limiting
factor in the food security efforts of Tanzania where 40 million people
depend on the crop for their daily calorie intake. In economic terms,
CBSD causes an annual loss of about US$50 million for the farmers in
Tanzania. Dr Caroline Herron, IITA plant pathologist studying the
dynamics of the virus in East Africa, says "In the last five years, CBSD
has also been observed in Kenya, Uganda, Rwanda, Burundi, the Democratic
Republic of Congo, Zambia, Malawi, and Mozambique."

Dr Edward Kanju, IITA cassava plant breeder, and Mr Haji Saleh, from the
Ministry of Agriculture, Kizimbani, Zanzibar, say that "The farmers
involved in the participatory breeding project "drove" the government to
officially release the CBSD field-resistant cultivars. The challenge is
now to replace the susceptible plants with the newly released resistant
varieties."

New Scientist in its current issue (21 April 2007, no:2600) features a
detailed story about "Africa's cassava comeback" providing further
background information about the problem of this devastating disease and
the solution.

###
For further details contact:
Mr Taye Babaleye, Public Relations Manager, t.babaleye@cgiar.org
Dr Caroline Herron, Plant Pathologist, c.herron@cgiar.org


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