The two diseases have been rapidly spreading through the Great Lakes African countries from the war-torn Democratic Republic of Congo to Rwanda, Burundi, Kenya, Uganda, Tanzania, Mozambique and Malawi, nearly reaching epidemic proportions as all the varieties grown by the farmers were susceptible.
They pose the greatest threat to the production of Africa and Tanzania’s second most important food crop after maize, providing over half of the dietary calories to over half of the total rural and urban population in sub-Saharan Africa. The varieties, code-named Pwani, Mkumba, Makutupora and Dodoma, can easily double cassava production in the country with their potentially high yields ranging from 23-51t/ha against the current average yield of 10t/ha.
They are a result of eight years of collaborative work between researchers from Tanzanian Agricultural Research Institutes (ARIs), the International Institute of Tropical Agriculture (IITA) and the International Centre for Tropical Agriculture (CIAT). They were developed through conventional breeding supported by advanced biotechnology tools, molecular marker-assisted breeding, to speed up the process.
Two of the varieties, Pwani and Mkumba, are targeted to the coastal belt and the other two, Makutupora and Dodoma, to the semi arid areas of Central Tanzania. Pwani has the highest potential yield of 51t/ha while Mkumba -which farmers liked due to its high dry matter and sweet taste- the lowest at 23.1t/ha.
According to Dr. Geoffrey Mkamilo, the Team Leader of Cassava Research in Tanzania, the farmers will be very relieved and happy as they have been eagerly awaiting the new varieties to confront the deadly diseases. “CBSD has been very devastating because its symptoms are not always clear. Farmers looking forward to a good harvest get a rude shock when they harvest and discover the useless rotten roots,” he explained.
“As a result, many of them had abandoned this hardy crop that performs relatively well even under harsh conditions such as poor soils and little rainfall.” The research project was funded by the Rockefeller Foundation (RF) and the Alliance for a Green Revolution in Africa (AGRA).
The Generation Challenge Program of the Consultative Group on International Agricultural Research Centers (CGIAR) contributed funds for farmer participatory trials to test for resistance and productivity under actual farm conditions and to complete tests required by the National Variety Release Committee before the new varieties could be officially released to farmers.
Dr. Edward Kanju, a cassava breeder with IITA-Tanzania, who was also involved in the research, says that the varieties were developed by crossing local varieties with those introduced from Latin America from CIAT in Colombia and are the result of eight years of research.
“We used local varieties from Tanzania as sources of resistance to CBSD and for local adaptation and those from CIAT as sources of high yield and resistance to CMD and cassava green mites,” he said.