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Dr.
Nagib Nassar’s interest in cassava began in the early 70’s.
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Over
800 million people throughout Africa, Asia and North America subsist on an
edible tuber better known as cassava, reported to be the highest producer of
carbohydrates amongst staple crops. According to the United Nations Food and
Agriculture Organization (FAO), cassava ranks fourth amongst food crops in
developing countries after rice, maize and wheat.
Mentioning
cassava immediately brings to mind the name of Dr. Nagib Nassar, professor at
the Universidade de Brazilia, recognized as friend to the cassava plant for over
28 years.
Nassar’s interest in cassava began early in the 1970s, when he taught African
crop biology at the Institute of African Studies in Cairo University. "All
indications referred to it as a possible salvation for Africa from the famines
that spread through the continent that decade," he says. But although its
popularity as a staple compares with cereal grains in northern climates, most
cassava varieties are low in protein – less than one percent, compared with
about seven percent in staple grains commonly grown in temperate zones. Most
varieties also contain potentially toxic concentrations of cyanogenic glycosides
that are reduced to innocuous levels through cooking.
Nassar
started his actual research when he moved to Brazil, supported by
the International Development
Research Center (IDRC), as part of the cassava breeding research program
supported during the 1970s and 1980s. This research was nominated for this
year’s World Food
Prize. The prize, worth $250,000 and considered by some to be the
international development equivalent of the Nobel Prize, will be awarded on
October 24, 2002.
Dr
Nagib Nassar’s goal was to collect wild cassava species in their natural
habitats in central and northeastern Brazil, evaluate their economic value,
build them into a living collection, and cross them with domesticated cassava
varieties using biotechnology to build up hybrids with less undesirable
characteristics. He carried out work for the Institute of African Studies,
then the International Institute of Tropical Agriculture (IITA) in Ibadan,
Nigeria
Nassar
collected some 42 wild cassava species native to Brazil. He still propagates
them in a living collection at the Universidade de Brazilia where he teaches,
for evaluation and crossbreeding with domesticated varieties. He says he has
produced some 14 hybrids. This has been challenging because, over millions of
years, the process of natural selection led to the development of substantial
interspecies barriers, making crossbreeding difficult, but the results gave the
last word.
Amazing
results
Among
his first hybrids was one that nearly doubled cassava’s protein content.
This was amazing because usually when a wild species is crossed with a
cultivated one, both desirable and undesirable traits result and normally it
takes tens of generations to increase protein content by 20 to 30 %, but this
was not the case here. The hybrid combined high productivity with low
concentrations of cyanogenic glycosides. Along the way, the collection has also
helped save these wild species from extinction.
Another
hybrid – Nassar says it’s the most fascinating to him – was apomictic
(capable of producing hybrid seed without sexual fertilization). Breeders can
use apomixis to preserve a plant hybrid’s desirable characteristics. This line
was bacteria- and virus-resistant, and after a single generation the root’s
nutritional quality was surprisingly high. He’s continuing to work on apomixis
in cassava and hopes to release his first apomictic clone to Brazilian farmers
for commercial use in two to three years.
But what caused Dr. Nagib Nassar to undergo research on cassava in the hope of
finding a salvation for Africa? This question can only properly be answered by
taking a closer look at the cassava plant itself.
Cassava,
under the spotlight
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Cassava
is the highest producer of carbohydrates amongst staple crops.
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Cassava or Manihot esculenta is a shrubby, tropical, perennial plant that grows
1 - 3 meters tall, is well known in the temperate zone and is considered to be
the most important tropical root crop. Portuguese sailors introduced the plant
to Africa from Brazil in the 16th century.
Cassava
production is about 165 million metric tons/year especially in Africa where a
recent study indicated that cassava provides a larger income in this continent
than any other crop in the cassava production area. It is a main staple in
Nigeria, Uganda, Kenya, Tanzania, and Congo, and widely grown also in Brazil,
Thailand and Zaire.
Starchy
roots and tubers have been the staple food in many low-income countries for
centuries, the cellulose content and other non-starch polysaccharides playing an
important role. These are collectively referred to as dietary fiber; some
epidemiological evidence suggests that increased fibre consumption may
contribute to the decrease of a number of diseases such as diabetes and
cardio-vascular diseases.
Cassava
is low in some essential amino acids. It is therefore important to mix cassava
with a wide variety of other foods such as vegetables, cereals, fish or other
animal products in order to get a good protein quality in the diet. Cassava is
low in fat - or lipids. Since cassava contains low lipid content it is not a
rich source of fat- soluble vitamins.
Another
nutrient worth mentioning is vitamin C, which is found in an appreciable amount
in cassava leaves. How rich a ready-to-eat meal is in terms of vitamin C depends
on how cassava is prepared.
About
15% of the world’s production in 1993 was exported to Europe and Japan mainly
for industrial purposes, as it is used to make flour, breads, tapioca, sugar,
laundry starch, textiles, and in the pharmaceutical paper industries.
A
problem with cassava is the poisonous cyanides that must be disarmed before
consumption. The subsequent process of drying, or heating / frying breaks down
cyanohydrins present in cassava to yield hydrogen cyanide that is highly
volatile and thus evaporates into the air at 27 degrees Celsius rendering the
tuber safe for consumption. If insufficiently processed and consequently
consumed by a person who has a shortage of the sulfur containing amino acids
that detoxify cyanide, there is a risk of either acute poisoning with severe
sudden illness and death, or a later onset of an acute form of non-progressive
paralysis known as konzo. Konzo outbreaks have only been identified in
certain rural areas of Africa like the Central African Republic, Mozambique,
Tanzania, and Zaire.
Besides
its high calorie production and its industrial uses, cassava has some more
useful characteristics:
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Year-round
availability.
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Tolerance
to extreme (environmental) stress conditions.
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It
can be grown, then left stored in the ground for long periods as a hedge
against future hunger – a "famine food" for poor farmers.
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Cassava
is also increasingly used for animal feed.
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More
resistant to locusts.
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Successive
picking does not significantly reduce the growth of the plant or the
alternative food supply -- the root tuber.
Path-Breaking
Work
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Will
cassava be Africa’s salvation?
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For
his work, Nassar has been nominated for the World Food Prize for five successive
years, each time by Dr Joachim Voss, formerly of IDRC and now director general
of the International Center for Tropical Agriculture (CIAT), based in Colombia.
Voss
says: "His contribution, really, is to very early on identify the potential
of some of the wild species for improving domesticated cassava. Cassava is
notoriously difficult to breed. Nagib started looking at, and using molecular
biology approaches to get those characteristics fixed in commercial
cassava."
He added that he nominated Nassar because, from a scientific viewpoint, his work
has been path breaking. Both high-protein and apomictic cassava strains hold
tremendous potential for Africa’s poorest people. He acknowledges, however,
that competition for the prize may mean Nassar will never win.
Nassar
says that, if he wins the award, he’ll dedicate it to supporting younger
cassava researchers at the Universidade de Brasília. "I have already
stepped toward this and started from my personal savings a fund at the
university for this purpose," he says.
In
spite of the many opinions about biotechnology, Nassar’s idea is a noble one,
adding one step forward towards saving Africa.
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