Detection of Cry1Ab toxin in the leaves of MON 810 transgenic maize

The distribution of Cry1Ab toxin was detected in the leaves of genetically modified maize of genetic event MON 810 by enzyme-linked immunosorbent assay. Cry1Ab toxin contents in the leaves at reproductive (milk, R3) phenological stage were measured to be between 3,878 and 11,148 ng Cry1Ab toxin/g fresh weight. Toxin content was significantly lesser (significant difference (SD) = 1,823 ng Cry1Ab toxin/g fresh leaf weight, p < 0.01) in leaves at the lowest leaf level, than at higher leaf levels, probably due to partial leaf necrotisation. A substantial (up to 22%) plant-to-plant variation in Cry1Ab contents in leaves was observed. When studying toxin distribution within the cross and longitudinal sections of single leaves, lesser variability was detected diagonally, with approximately 20% higher toxin concentrations at or near the leaf vein. More significant variability (SD = 2,220 ng Cry1Ab toxin/g fresh leaf weight, p < 0.01) was seen lengthwise along the leaf, starting at 1,892 ng Cry1Ab toxin/g fresh weight at the sheath and rising to maximum concentration at the middle of the lamella. Cry1Ab toxin content may suffer significant (SD = 2,230 ng Cry1Ab toxin/g fresh leaf weight, p < 0.01) decreases in the leaf due to necrotisation. The results indicate that the longitudinal dimension of the leaf has more significance for sampling purposes than the diagonal position.