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, highlighting the unique challenges posed by this not-so-new disease in the continent.
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. Combined, they cost Africa more than US$ 1 billion in damages every year. Unfortunately, small-scale farmers and poor consumers bear the brunt of these losses.
Although Brown Streak disease had been known in East Africa for many years, it had always been confined to lowl and coastal areas. The new outbreak has spread rapidly to the relatively high altitude regions (over 3000 feet above sea level) of Ug anda, 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 isl and 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 isl and’s subsistence farmers growing cassava, concerned authorities swung into action.
Zanzibar scientists and the Nigeria-based International Institute of Tropical Agriculture (IITA), 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 isl and’s cassava production is stronger than ever.
The more immediate challenge is to get enough planting materials to meet the dem and. Currently, only 10,000 cassava farmers out of the close to a million on the isl and alone are growing the improved varieties. The country’s government,
IITA, and several development partners and donors such as the 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 neighboring countries and in the mid-altitude zones of Tanzania. Working with national partners, more than 15 varieties have been identified in Ug anda 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, Rw anda, 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 farmers cannot afford.
Though much remains to be done, Zanzibar’s success has been 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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Pour plus d'informations, veuillez contacter :
Catherine Njuguna, c.njuguna@cgiar.org
Corporate Communications Officer (East and Southern Africa)
IITA-Tanzanie
Jeffrey T. Oliver, o.jeffrey@cgiar.org
Chargé de communication d'entreprise (international)
Bureau de la communication
IITA – Siège
Ibadan, Nigéria
À propos de l'IITA (www.iita.org)
L'Afrique est confrontée à des problèmes complexes qui minent l'agriculture et la vie des populations. Nous développons des solutions agricoles avec nos partenaires pour lutter contre la faim et la pauvreté. Notre recherche pour le développement (R4D), maintes fois récompensée, repose sur une réflexion ciblée et autorisée, ancrée dans les besoins de développement de l'Afrique subsaharienne. Nous travaillons avec des partenaires en Afrique et au-delà pour réduire les risques pour les producteurs et les consommateurs, améliorer la qualité et la productivité des cultures, et générer de la richesse grâce à l'agriculture. L'IITA est une organisation internationale de recherche pour le développement sans but lucratif, créée en 1967, dirigée par un Conseil d'administration et soutenue principalement par le CGIAR.
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