Figure 1

North Carolina 3 Design employed for mapping QTL. The P₁ line indicates the control line (CI13), whereas the P₂ line indicates the line expressing the lethal effect (LI4). These lines were reciprocally crossed to produce the F₁ generation, which was crossed among itself to produce the F₂ generation. Individual F₂-males (i = 1 to 240) were backcrossed to both P₁ and P₂ and thereafter frozen until marker genotype was scored. The resulting backcross progeny (B_1i and B_2i) was placed at restrictive conditions to assess longevity and expression of the lethal effect. As reference material, the parental lines and both reciprocal F₁ crosses were also assessed (not shown).