Arbuscular mycorrhizal fungi colonisation of Cry3 toxin-producing Bt maize and near isogenic maize

Despite the fact that, on average, approximately 5-6 metric tons/ha of Bt maize stubble enter the soil on more than 170 million of hectares worldwide, the environmental impact of genetically modified maize plants on the arbuscular mycorrhizal fungi (AMF) is poorly known. In this study, the mycorrhizal colonisation on the roots of Bt maize (DAS-59122-7) and its near isogenic line was examined during the whole vegetation period. Cry3 toxin-producing Bt maize and its near isogenic line were grown in an experimental field in Julianna-major, Nagykovácsi, Hungary. DAS-59122-7 maize produces Cry34Ab1, Cry35Ab1 toxins and pat proteins for herbicide tolerance. The study assessed whether similar arbuscular mycorrhizal colonisation can be observed on the root of the Bt and near isogenic maize line and whether there are any differences in the temporal dynamics of AMF development. The arbuscular, hyphal and the arbuscular mycorrhizal fungi colonisation were higher in the near isogenic line as compared to its Bt counterpart, but no significant effect of the maize line was found as regards vesicle colonisation. The intensity of the arbuscular infection increased over time during plant maturation. DAS-59122-7 Bt maize had a negative effect on the initial development of AMF under field conditions, but no difference was seen in the case of the last two sampling dates (day 82 and 135). The reason of the latter is still not known.