Genetic basis of silk resistance (Antibiosis) to the corn earworm in six crosses of maize lines: Statistical methodology
1997
Bondari, K. | Wiseman, B.R.
The genetic basis of resistance (antibiosis) in maize silks to larvae of corn earworm (CEW), Helicoverpa zea (Boddie), was studied in six crosses of resistant and susceptible inbred lines of maize, Zea mays (L). For each breeding line, crosses were made between parental (P1 and P2) lines to produce F1 seed. The F1 plants were selfed to produce F2 seed and backcrossed to each parent to produce BC1 (F1 x P1) and BC2 (F1 x P2) seed. No attempt was made to produce reciprocal crosses since no evidence of significant maternal effects for these crosses existed . Silk from plants of all six generations (P1, P2, F1, F2, BC1, and BC2) was evaluated by recording 8-day weight of CEW larvae fed on a silk diet. A three-parameter additive-dominance model and a six-parameter digenic additive-dominance/ epistatic model were used to analyze generation means by the method of variance-weighted least squares. The genetic control of resistance to CEW larvae was determined in terms of additive-dominance gene action as well as contributions due to epistatic effects of genes at different loci. Results of the simple and joint scaling tests indicated genetic control for silk resistance to CEW, but the gene action differed from one type of cross to another. In the cross Zapalote chico x P1340856, the three-parameter additive-dominance model proved adequate and genes controlling resistance in P134()856 are dominant to those of Z. chico. However, in most crosses, non-allelic interactions were present, thus the fit of the additive-dominance model to the data was considered inadequate.
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