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http://www.worldwatch.org/node/6486
New Cassava Varieties Promise Food Security in Zanzibar
by Catherine Njuguna on July 29, 2010
Millions of cassava farmers in eastern and central Africa are in distress from viral cassava diseases that are sweeping across the region and ravaging their crops. But their counterparts on the popular tourist island of Zanzibar are undergoing a quiet revolution using new disease-resistant and high-yielding varieties that were introduced three years ago.
The four varieties, Kizimbani, Mahonda, Kama, and Machui, have given cassava a new lease on life after the crop was devastated by the two main diseases afflicting the region: brown streak disease and mosaic disease. The diseases, which are spread by white flies, cost Africa’s cassava sector more than US$1 billion in damages every year. Small-scale farmers – among the poorest in the region – bear most of the economic effects.
Cassava mosaic disease first appeared in Uganda in the mid-1980s and spread rapidly in cassava-growing areas of eastern and central Africa through the sharing of infected planting materials and via the white fly vector. Following the development and deployment of resistant and tolerant varieties and widespread awareness-raising on ways to curb the mosaic’s spread, scientists, governments, non-governmental organizations, and farmers were able to bring the disease nearly under control. Then the cassava brown streak struck. This disease had been around for much longer but was confined to the coastal low-altitude areas of Eastern Africa and around Lake Malawi. From 2004, it started spreading rapidly to mid-altitude areas that were recovering from the mosaic, sending scientists back to the drawing board.
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