| European corn borer (ECB), Ostrinia nubilalis Hübner, family Crambidae, order Lepidoptera, is a serious insect pest of maize ( Zea mays L.) in the United States. Losses to farmers resulting from ECB damage and control costs exceed {dollar}1 billion each year. An understanding of the genetic basis for ECB resistance should increase the efficiency of breeding for insect resistant varieties. The objectives of this study were to determine the number, genomic positions, and genetic effects of quantitative trait loci (QTL) conferring resistance to the first- and second-generation of European corn borer (1ECB, 2ECB), and to observe QTL × environment interactions. The study included 244 F2-3 families derived from the cross of B73 (susceptible) × Mo47 (resistant). Evaluating resistance against 1ECB, plants were manually infested at the eight- to ten-leaf stage of plant development. Leaf feeding damage was assessed three weeks after infestation with a visual rating scale. Evaluation for resistance to 2ECB involved manually infesting at anthesis stage of plant development. Approximately seven weeks later, stalks were split lengthwise and number and the length of tunnels visually estimated in inches. Plant height and rind penetrometer resistance were measured two weeks after flowering. Quantitative trait loci analyses for individual environments and combined across three environments were performed by composite interval mapping using QTL Cartographer. For 1ECB leaf feeding, nine QTLs were identified on chromosomes 1(three QTLs), 2, 4 (two QTLs), 5, 6, and 8. Seven QTLs for resistance to 2ECB tunnel length were found on chromosomes 2, 5 (two QTLS), 6 (two QTLs), 8, and 9. Twelve QTLs for resistance to 2ECB tunnel length adjusted for plant height were identified on chromosomes 1 (two QTLs), 2, 3 (two QTLs), 5, 6 (three QTLs), 8, 9, and 10. In addition, QTLs were identified for tunnel number (16 QTLS), plant height (11 QTLs) and rind penetrometer resistance (nine QTLs). In this experiment, a total of 47 QTLs for all traits were mapped in three individual environments and combined over environments. Nine (19%) QTLs were expressed in all three environments and combined, 17 (36%) were expressed in two environments and combined, and 21 (45%) were expressed only in single environment and combined. Inconsistency of QTLs across environments suggested need for breeders awareness when selecting markers linked to QTLs for marker-assisted selection (MAS). Further study on consistency of QTLs across populations is needed before applied breeding programs can fully utilized QTL information. |
