Use of F2 Generations to Identify Inbreds with Favorable Alleles not Present in an Elite Hybrid
1989
Zanoni, Urs | Dudley, J. W.
Previous theory for estimating the relative number of favorable alleles (μG*) in a donor inbred (Iw) useful for improving the parents of an elite hybrid (I₁, I₂) was extended from use of inbred and F₁ data, to use of inbred and F₂, or F₁ and F₂ data. To compare the three methods of evaluating donor inbreds, maize (Zea mays L.) inbreds B73 and Mo17 crossed to three inbred lines of Stiff Stalk Synthetic (B84, H100, N7A), four of Lancaster (Pa91, H102, H95, Va26), and five of unrelated origin (B77, B75, B57, B79, N152), hybrid B73 ✕ Mo17, their F₂'s, and the inbreds per se were evaluated at two locations in 1986. Inbreds with the lowest and highest estimates of the relative number of favorable dominant alleles (μG*) not present in B73 ✕ Mo17 were the same whether inbred and F₂, F₁ and F₂, or inbred and F₁ data were used. Rankings of donor lines with intermediate μG* values varied with the method used. These differences in ranking may have resulted from failure of assumptions such as no epistasis or differences in precision in the evaluation of inbreds, F₁'s and F₂'s. The different generations resulted in some different assessments of the relative relationship of lines (Iw) to the parents of the elite hybrid and different decisions on whether to backcross prior to selfing. When improving a parental line for grain yield, the progress for other dominant or recessive traits could be predicted. Contribution from the Agronomy Dep., Univ. of Illinois. Supported in part by funds from the Illinois Agric. Exp. Stn. and by a gift from Ciba-Geigy.
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