1. MAGIC population in cowpea for facilitating gene discovery for drought tolerance related traits
Moukoumbi, Y.D1*., R. Yunus2, N. Yao3, M. Gedil1, L. Omoigui1 and O. Boukar1
1 International Institute of Tropical Agriculture (IITA), Nigeria
2 Ahmadu Bello University, Zaria, Nigeria
3 Biosciences eastern and central Africa - International Livestock Research Institute (BecA - ILRI) Hub, Nairobi, Kenya
*Corresponding author: – Cowpea Breeder - IITA Kano
Abstract
Cowpea (Vigna unguiculata L.) is an important grain legume crop in the drier regions of West and Central Africa because of its high protein (25%), vitamin, and mineral contents. It has the advantage of adapting to different types of soil and inter-cropping systems and becomes an important economic crop in many developing regions in Sub Saharan Africa. Fifteen drought tolerant cowpea reference lines for West Africa were identified and most of them have been used separately in breeding for drought tolerance in cowpea to develop multiple introgression lines. The goal of this project is to develop at least 1,000 Recombinant Inbred Lines (RIL) derived from Multi-parent Advanced Generation Inter-Crosses (MAGIC) population that will be used for locating QTLs associated with drought tolerance related traits. Eight drought tolerant varieties were selected based on morphological traits related to drought tolerance at seedling stage and molecular screening with 125 SSR markers distributed throughout the cowpea genome. F1s (two way) progeny derived from 28 combinations were generated and they are being assessed genotypically and phenotypically. The work is still in progress and we expect that the novel allele rearrangements and greater genetic diversity in these MAGIC population derived from mating cycles will facilitate the discovery and manipulation of new forms of allelic variability. Also, the highly recombined MAGIC population will be used directly as source materials for the identification of breeding lines adapted to different drier environments in Africa.
Key words: MAGIC, drought, multiple introgression
Founder lines
- Eight drought tolerant varieties were selected based on morphological traits related to drought tolerance at seedling stage (Fig.2) following modified protocol from Muchero et al. (2013) and molecular screening with 125 SSR markers distributed throughout the cowpea genome (Fig.3 and Fig.4).
- F1s were generated and they are being assessed genotypically and phenotypically.
Fig.2. Fifteen cowpea varieties screened and eight selected for drought tolerant related traits
Africa.
Background
- Cowpea (Vigna unguiculata L.) is an important grain legume crop in the drier regions of West and Central Africa because of its high protein (25%), vitamin, and mineral contents. It has the advantage of adapting to different types of soil and inter-cropping systems. and becomes an important economic crop in many developing regions in sub-Saharan Africa.
Multi-parent Advanced Generation Inter-Crosses (MAGIC) was first
introduced by Mott et al. (2000). It was coined by Mackay and Powell (2007) and advocated by them and Cavanagh et al. (2008) for crops (Fig. 1).
- It is an advanced method to increase the precision of genetic markers linked to the Quantitative Trait Loci (QTL ) for fine – mapping of QTLs for multiple traits in the same population.
-Fifteen drought tolerant cowpea reference lines for West and Central Africa were identified and most of them have been used separately in breeding for drought tolerance in cowpea to develop multiple introgression lines.
-The goal of this project is to develop at least 1,000 Recombinant Inbred Lines (RIL) derived from MAGIC population that will be used for locating QTLs associated with drought tolerance related traits.
Fig.3. Molecular screening of cowpea varieties (improved, released and elite breeding lines for major target traits showed by SSR 6188
Crossing scheme
Half diallel-mating was used with eight selected drought tolerant cowpea varieties as founder lines.
Fig.4. Two groups showed based on seed size, drought tolerance, Striga and Bacterial blight resistance using un-weighted neighbours joining method
Future activities
At least 10,000 SNPs markers will be used to provide 500 – 1,000 polymorphic markers;
Develop at least 1,000 Recombinant Inbred Lines (RIL) derived from MAGIC population that will be used for phenotyping to identify markers for drought tolerance related traits;
Highly recombined MAGIC population will be used directly as source materials for development of breeding lines and varieties adapted to different drier regions of West and Central Africa and shared with NARS partners.
Table: MAGIC population development timeframe
References
Cavanagh, C., M. Morell, I. Mackay and W. Powell From mutations to MAGIC: resources for gene discovery, validation and delivery in crop plants. Curr. Opin. Plant Biol. 11: 215–221.
Mackay, I., and W. Powell Methods for linkage disequilibrium mapping in crops. Trends Plant Sci. 12:57–63. doi: /j. tplants
Mott, R., C.J. Talbot, M.G. Turri, A.C. Collins, and J. Flint A method for fine mapping quantitative trait loci in outbred animal stocks. Proc.Natl. Acad. Sci. USA 97:12649– doi: /pnas
Muchero, W., P.A. Roberts, N.N. Diop, I. Drabo, N. Cisse, T.J. Close, S. Muranaka, O. Boukar and J.D. Ehlers Genetic Architecture of Delayed Senescence, Biomass, and Grain Yield under Drought Stress in Cowpea. PLoS ONE 8(7): e70041.
doi: /journal.pone
Fig.1. MAGIC population development in cowpea adapted from Cavanagh et al. (2008)