Originally published on cgiar.org by:International Institute of Tropical Agriculture (IITA) on Jun 30, 2010
The article by Donald G. McNeil, Jr. published in the New York Times last month on a disease wreaking havoc on cassava – an important staple in sub-Saharan Africa - was timely. It highlights the challenges posed by this not-so-new disease.
Known as the Cassava Brown Streak disease, it threatens the food security and livelihoods of over 200 million people. It emerged at a time when the region was just recovering from battling another deadly disease, the Cassava Mosaic Disease. These two diseases afflict the crop that provides more than 50 percent of the dietary calories of the majority of the population in sub-Saharan Africa, and pose the greatest threat to food security in the region.
Together, the two diseases cost Africa more than US$ 1 billion in damages every year. Unfortunately, small-scale farmers and poor consumers bear the blunt of these loses.
Although Brown Streak disease had been known in East Africa for many years, it had always been confined to lowland coastal areas. The new outbreak has spread rapidly to the relatively high altitude regions (over 3000 feet above sea level) of Uganda, Kenya, and Tanzania around the shores of Lake Victoria. Worse still, cassava in this region appears to be susceptible.
Brown streak causes greater economic damages than the mosaic disease as it destroys the roots – the more valuable part of the crop. Further, its symptoms are not always evident and reveal themselves only at harvest.
For many years, little attention has been paid to this ‘silent time bomb’, distracted perhaps by the more pressing concerns of the mosaic disease. However, a small but significant research effort was underway on the island of Zanzibar.
Almost three-quarters of the population of Zanzibar rely on agriculture for food and income, with cassava being the second most important staple after rice. With over 90 percent of the island’s subsistence farmers growing cassava, concerned authorities swung into action.
Zanzibar scientists and the International Institute of Tropical Agriculture, with support from the Rockefeller Foundation and other partners, bred new cassava varieties to combat the brown streak menace. In 2007, they released four tolerant varieties farmers across the country.
Aside from being tolerant to the disease, the new varieties yield twice as much as the local varieties while satisfying other local preferences such as taste and cooking texture. Although the varieties are not totally immune to the disease, their roots remain intact.
Farmers can confidently plant them and expect a hearty and pristine harvest. The new varieties have been welcomed by the farmers, and three years later, the island’s cassava production is stronger than ever.
The more immediate challenge is to get enough planting materials to meet the demand. Currently, only 10,000 cassava farmers out of the close to a million on the island alone are growing the improved varieties. The country’s government, IITA, and several development partners and donors such as Alliance for a Green Revolution in Africa have been engaged in intensive efforts to rapidly multiply these varieties to ensure they are available to as many farmers in the shortest possible time.
Efforts are also underway to replicate the Zanzibar success in the neighbouring countries and in the mid-altitude zones of Tanzania. Working with national partners, more than 15 varieties have been identified in Uganda and Tanzania that show acceptable tolerance levels even under the harshest disease pressure conditions. They are expected to be released in a year or two after further testing.
Most importantly, farmers will need to evaluate these new varieties under actual field conditions for resistance to both diseases, as well as for utilization characteristics. The best of these varieties will be used in further disease-resistance breeding programmes in other countries such as Burundi, Rwanda, Kenya, and DR Congo.
To accelerate the crop improvement process, the scientists are using some true and tested old but efficient tools, such as molecular marker-assisted breeding. Traditional breeding takes 8-12 years to come up with improved varieties, a luxury of time that affected famers cannot afford.
Though much remains to be done, Zanzibar’s success is inspiring. If replicated, this could provide the key to a brighter future for all cassava producers in Africa and, by extension, bring greater economic prosperity to the region.
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Catherine Njuguna, c.njuguna@cgiar.org
Corporate Communications Officer (East and Southern Africa)
IITA-Tanzania
Jeffrey T. Oliver, o.jeffrey@cgiar.org
Corporate Communications Officer (International)
Communication Office
IITA - Headquarters
Ibadan, Nigeria
About IITA (www.iita.org)
Africa has complex problems that plague agriculture and people's lives. We develop agricultural solutions with our partners to tackle hunger and poverty. Our award winning research for development (R4D) is based on focused, authoritative thinking anchored on the development needs of sub-Saharan Africa. We work with partners in Africa and beyond to reduce producer and consumer risks, enhance crop quality and productivity, and generate wealth from agriculture. IITA is an international non-profit R4D organization established in 1967, governed by a Board of Trustees, and supported primarily by the CGIAR.