Farmer holding a diseased cassava in Zanzibar

AGRA/Stella Kihara

[LUSAKA] Africa's cassava industry must improve the distribution of new disease resistant varieties of the root vegetable to farmers across the continent, say scientists.

Cassava breeders from eight African countries gathered to discuss challenges in cassava production at a meeting in Zanzibar this month (4–5 October), convened by the Alliance for a Green Revolution in Africa (AGRA) and Tanzania's Ministry of Agriculture.

Cassava — a tropical plant grown for its starchy roots — is an important food crop in much of Africa. Although African cassava production has grown from 90 to 145 million tonnes in the last four years, and is expected to double over the next 20 years, disease has dogged attempts to increase yields even further.

Cassava viruses, specifically the brown streak and mosaic viruses, are a problem for many farmers across Africa. The brown streak virus destroys leaf tissue and makes cassava roots corky and inedible. The mosaic virus causes the plant's leaves to wither, retarding root growth.

Cassava breeders have had little commercial support in creating and distributing new breeds because seed companies — normally a major avenue for distributing new crop varieties — are not interested because it is a vegetative propagated crop and does not reproduce via seeds.

As a result, AGRA is supporting efforts to breed, distribute and encourage farmers to adopt new varieties resistant to the viruses.

The alliance recently awarded three grants totalling US$553,692 to breeders at national research organisations in Kenya, Malawi and Tanzania to develop new resistant breeds. It has also granted US$157,500 to support rapid distribution of four disease resistant cassava varieties on the Tanzanian islands of Pemba and Zanzibar.

George Bigirwa, programme officer for seed production systems at AGRA, said the project has already released the four varieties to farmers in Zanzibar. The local government is also backing a programme that encourages farmers propagate and sell plant materials at an agreed low cost to other local farmers. Farmers in Malawi have also adopted the model.

Bigirwa says AGRA is also working with policymakers to design more realistic regulations for new varieties, and is encouraging breeders to work more closely with local regulatory bodies.