Introgression scheme adopted for the production of recombinant heterotic NILs. The two NILs (NIL-BB and NIL-HH) were designed to introgress the target QTL (red bar) in the B73/B73 and in the H99/H99 genotype, respectively, while being isogenic anywhere else in the genome. Each pair of NILs was independently obtained starting from different RIL-F4:5 individuals (RHL-F4:5) selected because heterozygous at the target QTL. These were crossed twice to the corresponding RIL-F11:13 as recurrent parent, resulting in the introgression of target QTL into different highly homozygous B73 × H99 recombinant genetic backgrounds. As an example, a back-cross to a hypothetical RIL-F12:13 homozygous B73/B73 at both flanking markers (M1 and M2) is represented. Application of marker-assisted selection (MAS) is reported alongside arrows which indicate (pseudo)-backcross and selfing generations. Vertical bars represent a chromosome portion of individual plants; blue, pink and green color denote respectively genotypes B73/B73, H99/H99 and B73/H99. Genotypes indicated at the QTL are those expected in absence of double recombination events. Abbreviations: RHL, residual heterozygous line; ΨBC1, pseudo-backcross one; BC1, backcross one; BC1-S1 and BC1-S2, first and second selfing generations.
Pea et al. BMC Genomics 2013 14:61 doi:10.1186/1471-2164-14-61