Grants 2003

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Project Description

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1. Embryo rescue and multiplication of F₁ and BC₂ progenies that possess resistance to CMD, CGM, and CBB, followed by marker-assisted selection (MAS) to identify genotypes that combine resistance to the above biotic stresses.

2. Shipment of 191 F₁ and 335 BC₂ progenies as tissue culture plantlets from CIAT to Mikocheni Agricultural Research Institute (MARI), Tanzania and hardening of the introductions in the screen house at Kibaha Sugarcane Research Institute (KSRI).

3. Molecular diagnostics for cassava frog skin disease (CFSD) at MARI under supervision of the Post-entry Quarantine Official from the Tanzania Tropical Pesticides Research Institute (TPRI) in the screen house and at harvest time.  All varieties were found to be free of CFSD.

4. Field establishment of the improved introductions at the Alavi Estate, Kibaha, in preparation for establishment of a crossing block between the improved introductions and local cassava varieties early in 2005.

5. Five Agricultural Research Institutes (ARI - Mikocheni, Maruku, Naliendele, Ukiriguru and Kibaha) in Tanzania collected 83 local cassava varieties from the Eastern and Southern coastal region, and 61 varieties from the Lake region.  The varieties from the Eastern and Southern region were established at the Alavi estate, Kibaha, while those from the Lake Zone were established at ARI Maruku, Kagera, in the Lake region.  Almost all local varieties collected in the Lake Zone regions showed moderate to severe symptoms of CMD, CBB and CGM at three months of age supporting the previous findings by COSCA, that most of the local cassava varieties grown by farmers are susceptible to pests, and underscoring the need for this project.  Morphological and molecular characterization, using simple sequence repeat (SSR) markers, of the collections was initiated.

6. Selection of parents for the establishment of a crossing block for the development of populations for genetic mapping of tolerance mechanisms to cassava brown streak disease (CBSD). Genetic relationships among ten resistant (R) and four susceptible (S) potential parents was conducted using 12 SSRs. See attached dendrogram. As a result of this, and other agronomic and phenological character considerations, Kigoma Red (R), Namikonga (R), Nanchinyaya (R), Albert (S), Kibaha (S) and Mreteta (S) were selected as parents.

7. Molecular characterization of 100 farmer varieties (39 from Lake Zone, 39 from Eastern Zone and 22 from Southern Zone) and 35 improved varieties previously developed at Amani, using 13 SSR markers.  Analysis of data is on-going.

8. Initiation of molecular diagnostics of CMD and CBSD for free flow of cassava materials between the Lake, Eastern and Southern Zones.

9. Establishment of crossing blocks at Chambezi sub-station using the local populations from the Eastern and Southern Zones and the introduced varieties from CIAT.

10. Planting of a crossing block at Chambezi sub-station and Naliendele establishment for CBSV mapping populations.

11. Postgraduate training (MSc and PhD) on course