Effect of Environment on Resistance to the European Corn Borer (Lepidoptera: Crambidae) in Maize

The European corn borer, Ostrinia nubilalis (Hu¨ bner) (Lepidoptera: Crambidae), is a major pest of maize, Zea mays L., in many temperate parts of the world. Genotype-by-environment interaction effects can make relative performance unpredictable and may hamper selection for resistance to European corn borer. The objective of this study was to determine the effect of environment on genotypic reaction to European corn borer resistance in maize. A set of 12 maize inbred lines was chosen to represent a range of European corn borer responses. Eleven testing environments ranged from Delaware, Ohio, Illinois, Iowa, Nebraska, Missouri, to Mississippi. For length of stalk tunneling, environmental and genotypic main effects (estimated by restricted maximum likelihood) were \u3e20- and 10-fold larger than their interaction effect, respectively. Length of tunneling means for genotypes (across environments) ranged from 10.1 to 35.4 cm. Several putatively resistant genotypes grouped with the susceptible checks, B73 and Mo17. By breaking factors and the interaction into single degree of freedom components, we observed that GEMS-0001 had significant crossover interactions toward less susceptibility in both Mississippi and the Nebraska environments. Environments displaying several crossover interactions indicated that European corn borer screening at these sites would not necessarily apply to other locations, whether due to small differences in experimental conduct and/or environmental effects. The five most resistant genotypes were fairly consistent across environments. Because all environments except Illinois used larvae from the same insectary, and these environments differed in damage intensity and rankings, it is unlikely that insect biotype was a factor contributing to genotype-by-environment effects