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Fundamental differences between Cry1Ab-based Bt-bioinsecticides and MON 810 maize varieties render these technologies not equivalent. While the former contain at least five different crystalline (Cry) toxins, the latter produce a single Cry1Ab toxin as active ingredient. Moreover, the lectin type toxin protein produced by these plants is a truncated version of microbial Cry1Ab. The majority of the results reported for Cry1Ab content is, therefore, subject to correction between microbial Cry1Ab protoxin and plant-expressed preactivated Cry1Ab toxin, and the latter is not a registered insecticide active ingredient. Cry1Ab toxin is produced continuously and not at the highest concentration in those plant parts, where the pest occurs. In turn, MON 810 maize does not comply with IPM principles, as control cannot be limited to the period of pest damage above threshold level. The target insect, Ostrinia nubilalis is a practically inconsiderable pest in Hungary, therefore, the use of MON 810 maize is mainly groundless. Pollen settling on Urtica dioica, Rubus spp. or Datura stramonium near or in maize fields may exert toxicity on caterpillars of protected butterflies, e.g. the peacock butterfly (Nymphalis io). Decaying Bt-maize material potentially affect other non-target organisms. Occurrence of Cry1 toxin resistance in pests is facilitated by the fact that MON 810 maize produces only a single Cry protein, preactivated Cry1Ab toxin.

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Successful applications of toxins derived from Bacillus thuringiensis (Bt) strains in Bt-based bioinsecticides and more recently in Bt-plants in crop protection have enhanced the importance of analytical quantification of Cry toxin dosages for studies on various topics including environmental risk assessment (ERA), resistance management, quality control and regulatory compliance. It is essential to follow-up distribution and environmental degradation of these lectin type, crystalline (Cry) toxin proteins showing insect specificity at order level. Thus, Cry1Ab toxin produced by Bt-maize of genetic event MON 810 is specific to lepidopteran species. Widely used analytical methods for detection of Cry toxins are enzyme-linked immunosorbent assay (ELISA) systems. Reported Cry1Ab toxin concentrations in MON 810 maize show high variability: order of magnitude differences have been observed among various plant parts from different varieties, cultivated at different locations, and sometimes even within the same plant variety at a single location. Besides biological sources of variability, numerous analytical problems have been identified and are reported in this report, influencing the results of quantitative determination of Cry1Ab toxin and explaining the high variability among documented data on toxin content. Conclusions in every case refer to genetic event MON 810, but can be extended to other genetic events producing Cry1Ab toxin.

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