Mapping of factors for resistance to leaf-blade feeding by European corn borer (Ostrinia nubilalis) in maize

The European corn borer (ECB) Ostrinia nubilatis Hubner is an important pest of maize in the U.S. Breeding for resistance to leaf-feeding by ECB can be more efficient if the genetic basis for resistance is better understood. The objectives of this study were (i) to locate and characterize the genetic factors controlling resistance to leaf blade feeding by ECB larvae in temperate lines and (ii) to compare the locations of the quantitative trait loci (QTLs) detected in the F-2:3 and F-6:8 generations of the same maize population derived from the cross of inbred lines Mo17 and H99. One hundred and fifty F-2:3 lines and the parents and 185 F6:8 lines and the parents were grown in replicated trials in 1989 and 1995, respectively. Plots were infested with ECB larvae and visual leaf blade feeding ratings were obtained for each plot. Lines were genotyped with RFLP and SSR loci and a linkage map was developed. QTL analysis was performed with composite interval mapping. The heritability of family means was 0.77 in the F-2:3 generation and 0.91 in the F-6:8 generation. The QTLs explained around 50% of the phenotypic variance in both generations. Five QTL were detected in each generation. A QTL on linkage group 4 near umc123 and a QTL on linkage group 7 near umc110 were detected in both generations. Significant epistatic interactions among QTL were detected in both generations. Several loci that showed significant interactions did not have significant main effects, indicating that important epistatic interactions will be missed if only interactions between QTLs with significant main effects are tested. Marker-assisted selection will be most efficient when main effects and interaction effects of QTL are included in the selection criteria.