Fig. 2

Sequential fine-mapping of the major QTL qMrdd2 in maize. Six F₆ (a), 10 F₈ (b), 7 F₉ (c) and 9 F₁₀ (d) recombinants and their corresponding recombination types are shown. For each recombinant type, the chromosomal composition at qMrdd2 is shown as black, white or gray rectangles, corresponding to heterozygous “80007”/”80044”, homozygous “80007”/”80007” and homozygous “80044”/”80044”, respectively. All progeny were genotyped using markers within the heterozygous “80007”/”80044” segment. The DSI value was calculated for each plant of the three genotypes. A significant difference (P < 0.05) in DSI between homozygous “80007”/”80007” and homozygous “80044”/”80044” indicated the presence of qMrdd2 in the heterozygous region of their parental recombinant(s) and that the recombinant(s) was segregating (S). However, this was not the case between the two homozygous genotypes, suggesting the absence of qMrdd2 in the heterozygous region and that their parental recombinant(s) was not segregating (NS). Based on analysis of both genotype and phenotype for all recombinant types, the map of qMrdd2 was refined from an ~ 15-Mb region to an ~ 577-kb region flanked by markers S31 and S42. DP: deduced phenotype, No. P: number of recombinant plant progeny, “80007”: progeny with a homozygous “80007” genotype, H: progeny with a heterozygous “80007”/”80044” genotype, “80044”: progeny with a homozygous “80044” genotype