Cassava varieties show promise against deadly diseases

A farmer and a researcher evaluating cassava varieties
Copyright: J. Recha/CCAFS

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  • New cassava varieties are being trialled in Africa to tackle deadly diseases
  • The varieties are expected to boost cassava production and food security
  • An expert says the new varieties could be more appealing to consumers

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[NAIROBI] Simultaneous trials being conducted in 33 locations across five African countries are showing good resistance to two deadly cassava diseases: Cassava Brown Streak Disease (CBSD) and Cassava Mosaic Disease (CMD).
The trials being undertaken in Kenya, Malawi, Mozambique, Tanzania and Uganda are part of a project that aims to identify disease-resistant cassava varieties suitable for various African sites.
“The environment where cassava is grown varies greatly in soil fertility and altitude,” says Edward Kanju, a cassava breeder with the International Institute of Tropical Agriculture (IITA) in Dar-es-Salaam, Tanzania, in an interview with SciDev.Net last month (9 August). “We aim to identify the best suitable varieties for specific environments.”

“We expect that those varieties that meet farmers’ preferences will be highly adopted for wide cultivation.”

Edward Kanju, IITA


Kanju adds that the resistant varieties that were the earliest to be planted in Tanzania are to be harvested this month.
Earlier evaluation shows that the new varieties have promising results. For instance, whereas CBSD could be found in up to 70 per cent of fields with old cassava varieties, zero or nearly zero per cent of the fields with the new varieties has the deadly disease.
The four-year, US$5.7 million project, which is administered by the IITA, is funded by the Bill and Melinda Gates Foundation.
Kanju tells SciDev.Net: “Farmers will be involved in the selection of varieties that meet their preferred characteristics in terms of agronomic, taste and end-use. We expect that those varieties that meet farmers’ preferences will be highly adopted for wide cultivation.”
The outcome that will be increased cassava production and improvement in food security and poverty alleviation will be realised probably in more than five years after the project.
According to Kanju, scientists are conducting the trials using proper experimental design and recommended farming practices such as plant spacing and weed management.
Both CBSD and CMB cause yield losses valued at over US$1 billion annually, according to Kanju.
He notes that the collaboration across the five African countries is significant because “the breeders agreed to share their elite genetic resources that have benefited each other”.
Jane Ininda, a Kenya-based crop breeder and an associate programme director of Partnerships for Seeds in Africa, an institution that supports seeds producers in many African countries, says the initiative is timely given the two diseases affect many families in Sub-Saharan Africa where cassava is a major staple.

“Cassava Brown Streak Disease started in Uganda and spread rapidly to almost all African countries in Eastern and Southern Africa.  It has been reported in Kenya, Malawi, Mozambique, Rwanda, Tanzania, Uganda, Zambia and recently in Democratic Republic of Congo,” says Ininda. “It is a most prudent initiative to resolve this constraint at the household level across all countries in Africa.”
Ininda explains that the two diseases interfere with the quality of leaves that are used as vegetable and the tubers that are eaten, adding that cassava breeding could help produce varieties that appeal to consumers.
According to Ininda, a cassava variety with resistance to brown streak disease could yield up to four times more than a susceptible variety.
 This piece was produced by SciDev.Net’s Sub-Saharan Africa English desk.