A Design III Study of Linkage Disequilibrium for Percent Oil in Maize1

Abstract

The objectives of this study were 1) to estimate additive and dominance genetic variance and the average degree of dominance for percent oil in the F2 and F8 randommated generations of a cross between Illinois High Oil (IHO) and Illinois Low Oil (ILO) maize (Zea mays L.) strains using Design III and 2) to measure the effect of linkage bias on such estimates.The following results were obtained: 1) The estimate of additive genetic variance was about eight ✕ larger than that of dominance genetic variance in the F2 and about four ✕ larger in the F6; 2) The estimate of additive variance in the F8 was half that in the F2 suggesting that many loci controlling percent oil were linked in the coupling phase in the parents; 3) The estimate of dominance variance in the F6 did not differ from the F2 indicating a lack of effect of linkage on dominance variance which could be interpreted as indicating that genes with dominant action are distributed throughout the genome with map distances approximating independent inheritance or that some genes are dominant for low oil while others are dominant for high oil; 4) Estimates of the average degree of dominance were 0.508 for the F2 generation and 0.681 for the F8. Both estimates are significantly different from zero and from one, but not from each other.