Molecular Breeding for Drought Tolerant Maize in Sub Saharan Africa.

The International Maize and Wheat Improvement Center (CIMMYT), in collaboration with several public and private partners, is working on large scale projects that aim to develop and disseminate drought tolerant maize for sub Saharan Africa (SSA) using conventional breeding, Double Haploid (DH) technology and marker assisted breeding. These projects include the Drought Tolerant Maize for Africa (DTMA) and the Water Efficient Maize for Africa (WEMA) projects. For the molecular components of the two projects, CIMMYT has: (1) developed and implemented a quality control analysis protocols for genetic purity, genetic identity, and parentage verification; (2) developed and evaluated over 30 bi-parental marker-assisted recurrent selection (MARS) populations under 2-3 managed water stressed and 3-4 well watered environments; (3)  conducted 2-3 cycles of rapid cycling using single nucleotide polymorphic (SNP) markers with and without tests for significant association with drought-related traits; (4) initiated genetic gain studies in order to compare MARS with pedigree selection, and also compare rapid cycling with a subset of significant SNPs against genome-wide SNPs; (5) conducted meta QTL analyses across several MARS populations in order to explore if there are QTL with large phenotypic effects conserved across multiple genetic backgrounds and environments; and (6) conducted  genome-wide association mapping in order to characterize QTL that are linked with drought tolerance and resistance to biotic stresses relevant for the drought tolerant germplam in SSA across a diverse set of maize germplasm. A major QTL for maize streak virus (MSV) resistance on chromosome 1, which improves resistance on average by 25%, has been fine mapped, validated in several bi-parental populations, breeder-ready markers developed, and implemented in breeding programs. This presentation will highlight the main results generated from the two projects, challenges and future prospects in breeding for drought tolerance maize in SSA.