Great Lakes Cassava Initiative (GLCI) and preventing spread of viruses causing Cassava Brown Streak Disease (CBSD)

International Case Study

Great Lakes Cassava Initiative (GLCI) and preventing spread of viruses causing Cassava Brown Streak Disease (CBSD)

The Great Lakes Cassava Initiative (GLCI) goal was to distribute clean planting material of disease tolerant or resistant varieties to 1.15 million  farmers to six countries.

Funders

Funded through GLCI, a project co-ordinated by Catholic Relief Services and funded by the Bill and Melinda Gates Foundation.

Within the context of an existing disease (Cassava Mosaic Disease, CMD) and an emergent disease (Cassava Brown Streak Disease, CBSD), The Great Lakes Cassava Initiative (GLCI) had an overall goal of distributing clean planting material of disease tolerant or resistant varieties to 1.15 million  farmers to six countries—Burundi, Democratic Republic of Congo, Kenya, Rwanda, Tanzania and Uganda—during the four years of the project period. 

The target farmers were poor and vulnerable, though not exclusively, and the project policy was zero tolerance to contributing to the spread of CMD and CBSD by distributing diseased material.

With this goal in mind, GLCI was set up with five components—partnership, disease, training, seed and farmer groups. 

  • Partnership was the overarching component to coordinate the different aspects of technical work needed to achieve the goal of the project. 
  • The disease component aimed to study CBSD when there was little known of the disease and to ensure that diseased material did not get distributed to low disease and disease-free areas. 
  • The training component was responsible for building capacity for the local partners and farmer groups to become technically and managerially capable of serving as delivery channels to produce and disseminate the clean planting materials for the beneficiaries. 
  • The farmer group component established, registered, characterized, trained and monitored the farmer groups and ensured that they produced quality planting material and disseminated it systematically. Monitoring and evaluating (M&E) and gender were not set up as components but rather as programming activities that cut across all components. Together they made up the integrated research and development program.

Cassava is a major subsistence crop in many parts of the world, providing more than half of the dietary calories for half of the population of sub-Saharan Africa. In recent years, cassava crops in the east African countries of Kenya, Tanzania and Uganda have seen an emergence of cassava brown streak disease (CBSD), with reported yield losses up to 70%. 

Identification of CBSVs based on symptoms is reported as unreliable because the symptoms are inconsistently expressed in leaf, stem and root and are difficult to distinguish from mite damage and nutrient disorders. Also, there is no evidence of any symptom differences between CBSV and UCBSV, making differentiation of CBSVs by visual symptoms impossible.

For these reasons, a diagnostic test is required to accurately identify the presence of viruses for research, policy (e.g. quarantine) and planting material multiplication purposes.

Fera's Solution

The first RT-PCR assay for the detection of CBSV was developed using only the small number of sequences available at the time, and recently, gel-based conventional RT-PCR assays for the detection of both viruses and a real-time RT-PCR assay for CBSV have been developed. Real-time PCR is widely recognized as providing greater sensitivity than both ELISA and conventional PCR. 

However, the most significant advantages of the technique are realized in routine testing of samples: the absence of a gel electrophoresis step enables larger sample numbers to be processed at a reduced cost and the closed tube system effectively eliminates post-PCR contamination and resultant false positive results.



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