(A) A quantitative trait locus (QTL) scan of transmission ratio distortion in F3 progeny of F2 hybrids reveals unlinked modifier QTLs on Chromosome 9 and 14, in addition to the primary effect of MDL11 genotype. LOD score trace is smoothed, with a window size of four markers. B Genotype at CenH3A, which is centered under the Chromosome 14 modifier QTL, significantly influences D transmission in hybrids. Means ± 1 SE are shown for the eight F2 genotypic classes: DD- and Dd at MDL11and GG (IM160/IM767 M. guttatus), NG160 (heterozygote with M. guttatus allele from IM160 parent), NG767 (heterozygote with M. guttatus allele from IM767 parent), and NN (M. nasutus) at CenH3A. Total n = 146.