Comparison of Bt maize hybrids with their non-transgenic counterparts and commercial varieties for resistance to European corn borer and for agronomic traits

The European corn borer (ECB), Ostrinia nubilalis (Hübner), is a major pest of maize (Zea mays L.) in Central Europe. In order to compare transgenic Bt maize hybrids with their non-transgenic counterparts and commercial hybrids, field trials and a laboratory bioassay were conducted. The field experiments were performed at four locations with natural and manual infestation of ECB larvae in 1998 and 1999. Transgenic Bt hybrids showed significantly lower means than their corresponding non-transgenic counterparts and commercial hybrids for all resistance traits (damage rating of stalks, number of larvae per plant, and percentage of damaged plants or ears under infestation). Bt hybrids containing the CryIA(b) gene under the control of green tissue and pollen-specific promoters (event 176) showed a significantly higher percentage of damaged ears than Bt hybrids carrying the CryIA(b) gene under the control of a constitutive promoter (Mon810). Bt and non-Bt hybrids showed no significant differences for all agronomic traits, except for plant height under insecticide protection and grain yield reduction under infestation, whereas Bt hybrids had significantly lower means than their non-transgenic counterparts and other commercial hybrids. All resistance traits were significantly correlated with grain yield reduction. The laboratory bioassay confirmed the level of antibiosis of Bt hybrids against neonate ECB larvae. Bt hybrids showed the highest level of ECB resistance and therefore are an attractive method of preventing ECB damage within an integrated pest-management system.