Effect of Bt zygosity in transgenic maize hybrids to the non-target pest Dalbulus maidis

The corn leafhopper Dalbulus maidis causes corn production losses mainly by acting as vector of pathogenic mollicutes and virus. Transgenic technologies that encode insecticidal proteins from Bacillus thuringiensis (Bt) are focused on the management of lepidopteran larvae in transgenic plants that traditionally express only one Bt allele. Adding another allele in transgenic plants is a recent and promising approach to managing resistant larvae, and it is important to know how the additional allele affects infestation and injury of non-target pests. This study evaluated the influence of maize hybrids with the genes cry1F, cry1A.105, and cry2Ab2 in homozygosis and hemizygosis compared with a conventional hybrid on the occurrence of D. maidis, transmitted diseases, and grain yield. Experiments were performed in two locations and two crop seasons in Brazil using three isogenic transgenic hybrids with three Bt proteins in homozygosis and hemizygosis and one conventional non-Bt hybrid. The numbers of D. maidis were recorded on plants across the vegetative stage, and disease symptoms were assessed at reproductive stage. Grain yield was recorded at the end of experiments. Homozygous and hemizygous hybrids did not differ for D. maidis incidence and transmitted diseases. Homozygous and hemizygous hybrids exhibited similar grain yields, and the transgenic Bt hybrids provided greater yields than the conventional hybrid in the first season in both locations. In conclusion, transgenic hybrids expressing three Bt proteins in homozygosis do not favor D. maidis infestation and diseases transmission compared to the hemizygous versions, and Bt zygosity has no negative effect on grain yield.