Improving cassava, the bread of the tropics

February 02, 2012 01:41 am | Updated 02:17 am IST

IMPORTANT CROP: Cassava is the staple food of about 500 million Africans. Photo: K.K. Mustafah

IMPORTANT CROP: Cassava is the staple food of about 500 million Africans. Photo: K.K. Mustafah

Recently I received an email from Mr Bill Gates and was torn between the horns of a dilemma. On one horn, I was all agog with excitement that he seems to know me.

The other horn was the worry that it might be the usual spam mail from the ubiquitous rich widow from Cote d'Ivoire, who would share her fortune if only I emailed her my bank details.

Curiosity overriding caution, I recklessly opened the mail to find it to be the 2012 Annual Letter from Bill Gates, detailing the activity of the Bill and Melinda Gates Foundation.

What it described was a remarkable commitment of $2 billion to helping poor farm families, most of which are led by women, boost their productivity while preserving the land for future generations. Compare this with a total of $3 billion per year spent by the entire world on researching the seven most important crops. Of these, cassava (or tapioca) is one. It is the staple food of about 500 million Africans; Nigeria is the world's largest producer of this tuber.

And it has been affected by two virus-infected diseases, both carried by white flies — the Cassava Mosaic Disease affecting the (edible) leaves, and the other Brown Streak Disease which rots and kills cassava roots.

The Gates Foundation is committing money to help win these and to increase cassava's nutritional content and reduce its inherent toxins.

Cassava is eaten in many parts of India as well. We call it Kuchi Kizhangu or Maravallli Kizhangu in Tamil, Kappa in Malayalam, Kavva pendalam in Telugu, Mara Genasu in Kannada and Simla Alu in Hindi. Its powdered form is tapioca, and when it is made into pearls, we call it sago, sabudana or Jawwarisi , and make sabudana vada, upma, payasam and so forth.

Just like potato, maize and chillies, cassava too is an import to the rest of the world, a gift by Portuguese sailors who brought it from Brazil to Africa and Asia. Within centuries, it replaced traditional African crops as Africa's most important food crop, and has come to be called “Bread of the Tropics” and when disease strikes it, it hits the health and livelihood of millions of people.

It is thus vital not only to conquer these diseases but also improve the nutritional content in this plant.

The book “Nutritive values of Indian Food and The Planning of Satisfactory Diets,” the Bible of India's Food Science (and perhaps the most useful book published by Indian science agencies for its people), lists that 60 per cent of tapioca is water, and each edible portion offers 157 calories coming from 389 carbohydrates, 1.2 g minerals, 0.6 g fibre, 0.7 g proteins and 0.2 g fat.

Thankfully it is rich in calcium. Eating it day in and day out might fill the stomach but not offer enough nutrition.

It is towards this challenge that the international group termed Biocassava Plus has been put together, with the aims to (a) increase by six-fold the content and bioavailability of zinc and iron, (b) increase four-fold its proteins content, (c) increase by ten-fold the vitamin A and E content, (d) develop virus-resistant varieties of cassava, (e) delay the post- harvest deterioration of cassava tubers, and (f) decrease by ten-fold its cyanogens content.

Item (f) above is particularly important. Raw cassava contains two types of compounds which generate the mortal poison HCN upon decomposition. The indigenous people of Brazil and Africa have found ways to remove the poison.

Peeling the roots, soaking them in water for a couple of days, then drying and cooking solves much of the problem. (Is this not eerily reminiscent of the paralysis caused by eating kesari dal ( lathyrus sativus ); fortunately for us, IARI scientists have found ways to make toxin-free varieties of its plants).

Tapioca, which is processed from cassava in a similar way, is also safe.

Biocassava Plus is an international collaborative endeavour, with team members from the National Root Crop Institute of Nigeria, Kenya Agricultural Institute, and the Danforth Plant Science Center at St Louis, MO, USA. The team has been able to make some exciting advances; one of them is to increase the levels of an enzyme in cassava roots which increases the amounts of protein and free amino acids while reducing residual cyanogen levels ( Narayanan et al., PLoS One 6, e21996, 2011 ) and the other is to use miRNA technology to increase the resistance of the plant to attack by the viruses ( Patil et al, Mol Plant Pathol 12, 31-41, 2011 ).

These are two fine examples of the use of the latest arsenals of molecular biology in the service of the poor.

For a composite review of the advances made in the field, please see Sayre et al, The BioCassava plus program: biofortification of cassava for sub-Saharan Africa. Annu Rev Plant Biology 62, 251-72, 2011.

Such advances in plant sciences cannot be done by selective breeding or grafting alone.

We need to use the latest methods of biotechnology — be it introducing new genes, knocking out existing genes, adding material to the soil (biofortification), or other such methods.

Tests in the lab and in the field, followed by safety studies are essential before releasing it to the world. Biocassava Plus has decided to do all these and expects to release its products only by 2017.

And we hope these will be freely available to all, and not be owned by monopolies, since half the controversy today about biotechnologically developed materials is about ownership and monopoly.

The Gates Foundation is supporting the activities of Biocassava Plus — an example of the commitment of the world's richest to help serve the world's poorest.

One therefore expects that it will ensure that Cassava 2.0 will be freely available to all.

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