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

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:

• Year-round availability.

• Tolerance to extreme (environmental) stress conditions.

• 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.

• Cassava is also increasingly used for animal feed.

• More resistant to locusts.

• Successive picking does not significantly reduce the growth of the plant or the alternative food supply -- the root tuber.

Path-Breaking Work

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 Brasيlia. "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.

Read Also:

• Genetically Modified “Risq”

• The Battle of the Corn

 

The Sea Set on Fire Genetically Engineered Cassava: A New Salvation for Africa? Modern Health Care Acknowledges the Principles of the Past Journal of an Herbalist: The Ethics of Healing The Deadly Arsenal of the Rogue State The Scientific Collapse of Materialism Smallpox Vaccine: A New Kind of Terrorism? The Battle of the Corn Health & Science Archive Search Articles