Dissection of the genetic basis of heterosis in an elite maize hybrid by QTL mapping in an immortalized F2 population

The genetic basis of heterosisfor grain yield and its components was investigated at the single- and two-locus levels using molecular markers with an immortalized F2 (IF2) population, which was developed by pair crosses among recombinant inbred lines (RILs) derived from the elite maize hybrid Yuyu22. Mid-parent heterosisof each cross in the IF2 population was used to map heterotic quantitative trait loci. A total of 13 heterotic loci (HL) were detected. These included three HL for grain yield, seven for ear length, one for ear row number and two for 100-kernel weight. A total of 143 digenic interactions contributing to mid-parent heterosiswere detected at the two-locus level involving all three types of interactions (additive × additive = AA, additive × dominance = AD or DA, dominance × dominance = DD). There were 25 digenic interactions for grain yield, 36 for ear length, 31 for ear row number and 51 for 100-kernel weight. Altogether, dominance effects of HL at the single-locus level as well as AA interactions played an important role in the genetic basis of heterosisfor grain yield and its components in Yuyu22.