CBSD is a major threat to food security in the ASARECA region and the development of resistant cultivars is therefore of primary importance to farmers Cassava brown streak disease (CBSD) and cassava mosaic disease (CMD) is becoming the most devastating viral disease that severely reduce cassava  production  in  large  areas  of  Eastern  and  central  Africa.  CBSD  is  caused  by  two  virus species, Cassava brown streak virus (CBSV) and  Ugandan cassava brown streak virus (UCBSV). 

In this innovation to identify molecular markers associated with resistance to Cassava Brown Streak Disease (CBSD) two F1 mapping populations were generated between a CBSD resistant genotype (Nachinyaya and Kiroba) and a CBSD susceptible genotype (AR37-80 . The F1 populations were genotyped  for 16 SSR markers to determine the  integrity of the populations and  identify genuine crosses, selfs and off-types. Over 250 true F1 offspring from each cross were genotyped using over 500 SNP  markers. SNP-based genetic  linkage  maps were developed  based on these results. Over 200  new  SNP  markers  were  placed  on  the  genetic  linkage  map  of  cassava.  The  significance  of CBSD resistance markers is that they facilitate the  introgression of the CBSD resistance trait into farmer-preferred cassava varieties.

Once  molecular  markers associated with CBSD resistance  are generated, breeders will  be able to apply Marker-Assisted Selection (MAS) and improve the accuracy and speed of breeding for CBSD resistance.

The innovation has been developed and is suitable for up scaling/promotion in laboratories at IITA in Tanzania and BeCA in Kenya.

Two F1 mapping populations have been made and genotyped. Genetic linkage maps have also been developed. 

The ultimate beneficiaries of this technology are cassava breeders
The dissemination, scaling out/up approaches Were publication of research findings in a journal
Publication  of  research  findings  in  journals  reaches  wider  circulation  globally  among  sorghum breeders and researchers

Essential partners/stakeholders) to be involved in the further scaling out/up    
Key partners needed in the scaling up process are:

• Cassava Breeders and researchers,
• National Cassava breeding Programs  
• Students
• Biotechnology companies
• National and international Cassava data bases

Current extent of reach of intended users of molecular markers associated with Cassava Brown Streak Disease (CBSD) in Cassava. The innovation has not reached national cassava breeding programs in the region.

Challenges  encountered  in  respect  to  further  dissemination,  adoption  and  scaling  up/out  of molecular markers associated with Cassava Brown Streak Disease (CBSD) in Cassava.  

• This  is  basic research which  calls  for  awareness among policy  makers to facilitate sustained funding
• Availability of good molecular laboratory facilities

Recommendation for addressing challenges

• Create awareness among policy makers and end users on the innovation
• Forge collaboration linkages with laboratories in advanced countries

Lessons learnt  

• Need for early awareness by policy makers of the use of this modern tool in the development of CBSD varieties in cassava.
• There  is  need  for  forge  collaboration  linkages  with  advanced  laboratories  for  testing  the  fine mapping innovations.
• Social, environmental, policy and market conditions necessary to catalyse fine mapping work
• Programmes that increase policy makers awareness
• Conducive institutional mechanisms for cassava variety release

Lead scientist; Dr. Ferguson Morag,
Scientist, BecA-ILRI campus
P.O. Box 30709-, 00100, Old Naivasha Road,
Nairobi, Kenya
Tel: 254 20 4223069
Fax: 254 20 422 3001
Email: m.ferguson@cgiar.org