Molecular Tools for Marker-assisted Breeding of High Pro-vitamin A Maize

Breeding provitamin A biofortified maize is the best option for mitigating vitamin A malnutrition in Sub-Saharan Africa. Breeder friendly PCR-based allele specific markers of three key genes - PSY1, lcyE and crtRB1- have been developed and utilized in marker assisted selection. We report the effects of these markers in a panel of diverse tropical yellow maize inbred lines that have mixed genetic backgrounds of temperate and tropical germplasm to identify the most effective predictive markers.  Markers crtRB1-5’TE and crtRB1-3’TE were strongly associated with provitamin A content. The alleles detected by these two functional markers were in high linkage disequilibrium (R2=0.75) and occurred in relatively high frequency (18%). Genotypes combining the favorable alleles at the two loci (N=20) displayed a 3.22 fold average increase in β-carotene content compared to those genotypes lacking the favorable alleles (N=106). The PSY1 markers were monomorphic across 47 all of the inbred lines. The functional DNA markers for lcyE were associated with lutein, and with ratio of carotenoids in the alpha and beta branches, but not with provitamin A levels. However, the combined effects of the two genes were stronger than their individual effects on all carotenoids. Tropical adapted maize inbred lines which harbor favorable alleles of crtRB1-5’TE and 3’TE functional markers display higher levels of provitamin A and can be used as donor parents. Validated markers can be used to expedite the development of provitamin A biofortified maize varieties adapted to growing conditions and consumer preferences in developing countries