Diagnostic markers for CMD2, a dominant gene for cassava mosaic disease resistance

Product Description/Background

CMD was first described in 1894, and is now considered one of the most damaging crop viruses in the world. Annual economic losses in East and Central Africa are estimated to be between 1.9 and 2.7 billion USD. Although cassava is also cultivated in Latin America and South East Asia, the disease is only found in Africa and the Indian sub-continent. In Africa productivity improvement is limited without the incorporation of resistance. However, susceptibility is variable among genotypes and sources of resistance have been identified.  The development of diagnostic molecular markers for the CMD2 dominant gene has been particularly helpful for introgression of resistance into high yielding genotypes. Gains from resistance can be highly significant.  For example, genetic variability components showing high heritability ranging from 92.3 to 99.6% and moderately high genetic gains of 54.1 to 99.6% for the parental cultivars in Ghana (Manu-Aduening et al, 2013). Table 1 lists the combination of markers that are being used in several breeding programs in Africa to develop resistant lines of cassava germplasm.  SNP markers are also being developed and will be made available in the near future.

Access/Availability

Markers cited above are freely available for use.  This information can be taken to any qualified laboratory for generation of markers and subsequent genotyping of germplasm materials.  In addition, the Integrated Breeding Platform Genotyping Service provides a set of options for users to access different marker service laboratories in the public and private sector with clear contractual conditions. The service identifies laboratories able to provide services for genetic diversity analysis and plant breeding applications and negotiates favourable terms for IBP clients. Laboratories are selected on the basis of competitive cost, fit with quality control requirements and expeditious delivery. Click here for a list and description of laboratories and services. Click on  Service request for details of how to access genotyping services through the platform. For additional information and help on using the IBP Marker Service, contact Chunlin He.

If you need assistance in the use of these markers refer to  IBP Breeding Services or for more information contact Mark Sawkins or Chunlin He.

Supporting Germplasm Resources

If it is determined that the local collection contains little or insufficient resistance to CMD, introgression of resistance from outsourced germplasm will be necessary.  The following improved lines from Nigeria would be excellent sources of CMD resistance in good agronomic backgrounds. UMCASS33 combines the high quality of South American germplasm with the durability and disease resistance of African lines. All have been developed with the use of the CMD2 markers.

UMCASS33 (disease resistant, high yielding)

TMS92/0057 (drought resistant, CMD resistant and moderate yield)

TMS92/0067 (drought resistant, CMD resistant, moderate yield,)

TMS98/0581 (drought resistant, CMD resistant, good yield)

TMS91/0234 (drought resistant, CMD resistant, moderate yield)

For more information and ordering germplasm contact:

Emmanuel Okogbenin

NRCRI - National Root Crops Research Institute

Umudike, Nigeria

E.Okogbenin@cgiar.org

Supporting publications

E. Okogbenin, C.N. Egesi, B. Olasanmi, O. Ogundapo, S. Kahya, P. Hurtado, J. Marin, O. Akinbo, C. Mba, H.Gomez, C. de Vincente, S.Baiyer  Molecular Marker Analysis and Validation of Resistance to Cassava Mosaic Disease in Elite Cassava Genotypes in Nigeria. Crop Science 2012 Vol. 52 No. 6, p. 2576-2586

Joseph Akwasi Mnu-Aduening, Bright Boakye Pepra, Adelaide Agyeman. Genetic variability of cassava progenies developed through introgression of cassava mosaic disease resistance into Ghanaian landraces.  Journal of Crop Science and Biotechnology.  March 2013, Volume 16, Issue 1, pp 232-28.

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