Marker Assisted Breeding to Improve Grain Yield and Drought Tolerance in Tropical Maize

Marker-assisted selection can enhance breeding efficiency for quantitative traits. The international maize and wheat improvement center ( CIMMYT) has developed more than 34 bi-parental populations since 2009 and testcrosses of progenies derived from these populations were evaluated in two to four managed drought and three to four well-watered environments, followed by advancing the populations using either MARS or GS approaches. Here we report some of the results from these studies. Beyene et al. (2014a) compared genomic selection with pedigree selection across eight bi-parental tropical maize populations, and reported that the average gain from genomic selection per cycle across eight populations was 0.086 Mg ha-1. They also reported that average grain yield of C3-derived hybrids was significantly higher than that of hybrids derived from C0. Hybrids derived from C3 produced 7.3% higher grain yield than those developed through the conventional pedigree breeding method. In another study (Beyene et al., 2014 b) reported that the average gain per cycle using MARS across the ten populations was 0.1837 Mg ha-1 per cycle under WW and 0.045 Mg ha-1 under WS conditions.  Across WW trials, the average grain yield of C3 hybrids was significantly (P < 0.05) higher than those of C0, pedigree method and commercial checks. The studies demonstrated that MARS and genomic selection are more effective than pedigree-based conventional phenotypic selection for increasing genetic gains in grain yield under drought stress  and optima location in tropical maize.