Efeito da zigosidade em híbridos de milho transgênico a Dalbulus maidis (Hemiptera: Cicadellidae)

Abstract

The corn leafhopper Dalbulus maidis (Hemiptera: Cicadellidae) is responsible for causing losses in maize production by vectoring transmission of the pathogens Mayze bush stunt phytoplasma (MBSP), Corn stunt spiroplasma (CSS), and Maize rayado fino virus (MRFV). Deployment of transgenic technologies in maize crop is focused on the management of lepidopteran larvae, with the use of hybrids encoding Bt proteins from expression of only one allele of the transgenic gene. The addition of another allele is a recent approach that is promising for management of resistant larvae in maize crop. Thus, it is important to understand the effects of adding a transgenic allele on the infestation and injury of pests non-target of the technology to support the viability of using this management strategy. This work aimed at evaluating the influence of maize hybrids expressing the proteins Cry1F, Cry1A.105 + Cry2Ab2 in homozygosis in comparison with their versions in hemizygosis and a conventional hybrid on the occurrence of D. maidis, the diseases transmitted, and grain yield. Experiments were carried out in Lavras-MG and Jaboticabal-SP in two crop seasons, with three hybrids here referred to as H1, H2, and H3 containing the events TC1507 x MON89034 x NK603 (PowerCore™) with the transgenes in homozygosis and hemizygosis and a conventional hybrid, totaling seven treatments and four blocks as replicates. The number of D. maidis was recorded throughout plants vegetative stage, and the percentage of plants with the diseases symptoms at the reproductive growth stage of maize. Grain yield was recorded at physiological maturity in each location and crop season. Overall, homozygous and hemizygous hybrids did not differ for the incidence of D. maidis and diseases transmission, without negative effects with the addition of the transgenic allele in the homozygotes. Regarding grain yield, homozygous hybrids performed similar to the hemizygous and conventional hybrids, and the transgenic hybrids attained higher yields in the first seasons of both experiment sites. As conclusion, transgenic hybrids expressing the proteins Cry1F, Cry1A.105 + Cry2A in homozygosis state do not favor infestation of D. maidis and diseases transmission relative to the respective hemizygous versions. Zygosity also do not cause negative effects on maize grain yield.