Grain yield of initial Bt corn hybrid introductions to farmers in the northern Corn Belt

摘要

European corn borer (ECB; Ostrinia nubilalis), is a major pest of maize in North America. Recently, seed companies have begun to offer control of this pest by introducing synthetic genes derived from Bacillus thuringiensis spp. kurstaki (Bt) into the maize genome. The yield of Bt hybrids was compared with adapted high yielding non-Bt hybrids, and Bt hybrid yield evaluated under economically significant ECB infestation. Experiments were established in the field at three locations in 1995 and one location during 1996. Three groups of hybrids were evaluated: transformed hybrids with the Bt gene, closely related "isoline" hybrids without the Bt gene, and "standard" high yielding hybrids adapted to these locations. ECB infestation treatments consistedof natural infestation, inoculation four times during the growing season, and insecticide application resulting in an ECB "free" treatment. Grain yield of Bt maize hybrids was not affected by ECB. Yield of isoline hybrids was 10% lower than both standardand Bt hybrids regardless of ECB treatment. Yield of Bt hybrids was 4 to 8% greater than standard hybrids when inoculated with ECB. However, yield of Bt hybrids was 8% less than standard hybrids when an insecticide was applied. Yield of initial Bt hybrid introductions was equivalent to or better than standard hybrids, except in environments with low ECB.