Breeding Trials Show Promise against Viral Cassava Disease

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In short
Preliminary results of the trials have already shown that several of the new varieties are virtually unaffected by Cassava Brown Streak Disease and Cassava Mosaic Disease

Disease resistance trials for Cassava being conducted in 33 different locations across 5 African countries including Uganda are showing promise against the deadly Cassava Brown Streak and Cassava Mosaic Disease.

The two cassava diseases that have been rampant since the 90s are believed to have wiped out 500 cassava land acres in Uganda and most of the cassava growing countries.

The trial involving 25 shared varieties is the first-of-its-kind multi-country collaborative cassava breeding initiative in East and Southern Africa.

Dr Edward Kanju, a cassava breeder and coordinator of the  project, said that preliminary results of the trials have already shown that several of the new varieties are virtually unaffected by Cassava Brown Streak and Cassava Mosaic Disease.

The promising trend has also been positive in locations where disease pressure is extremely high from infected fields surrounding the trials.

"Although in many of the countries the varieties are undergoing their first year of trial, our initial results are already showing good promise. We will further validate the performance of these varieties by comparing them to local ones that have been selected as checks," he explained.

The trials are a major activity of the New Cassava Varieties and Clean Seed to Combat CBSD and CMD Project (5CP) which is funded by the Bill & Melinda Gates Foundation.

It is led by International Institute for Tropical Agriculture working in collaboration with the national agricultural research systems of Kenya, Uganda, Malawi, Mozambique, Tanzania, and Zambia where the trials are being conducted. The project is in its final year of implementation.

This regional initiative is aimed at speeding-up the breeding of cassava varieties with dual resistance Cassava Brown Streak and Cassava Mosaic Disease in the five countries where the diseases are of great concern.

Each of the countries, according a statement by International Institute for Tropical Agriculture (IITA) selected five of its best varieties in terms of performance against the two disease and shared them for the inter-country trials.

Dr Robert Kawuki, a Ugandan  Cassava breeder involved in the project told Uganda Radio Network that trials of the high-yielding and disease resistant cassava is going on in seven locations in the countries. Some of the districts involved in the trial include Kalangala, Nebbi and Pallisa among others.

The planting materials first underwent a rigorous clean-up exercise to ensure they are virus-free before being distributed as tissue culture plantlets.
This is the first time that breeders in the five countries have freely shared their best varieties in a concerted effort to tackle the two deadly diseases.
The virus cleaning was carried out by the Natural Resources Institute (NRI) and the Kenya Plant Health Inspectorate (KEPHIS). The material was forwarded to Genetics Technologies International Limited (GTIL), a commercial tissue culture company, for mass multiplication.

The plantlets were then certified virus-free by the Mikocheni Agricultural Research Institute (MARI) and IITA.
Dr James Legg, IITA virologist, highlighted another objective of the 5CP Project, which is the establishment of pilot clean seed distribution system in Tanzania which, he is leading.
"We are perfecting the cassava seed systems in Tanzania through a three-step approach: virus indexing, then rapid multiplication at a research station, and finally large-scale multiplication at a clean site in an area with low disease pressure."

 Another major development of the project is the establishment of rapid multiplication systems for mini-plants derived from virus-indexed tissue culture plantlets.
By using these rapid propagation techniques in screen houses, the team led by Dr Kiddo Mtunda, cassava researcher and Officer-in-Charge of the Sugarcane Research Institute (SRI) in Tanzania, and her team have been able to produce thousands of cassava plants in a few months.

 This success of this project offers promise not just for cassava producers in the target countries, but more widely to cassava producers throughout Africa.