Bt-toxin uptake by the non-target herbivore, Myzus persicae (Hemiptera: Aphididae), feeding on transgenic oilseed rape in laboratory conditions.

The potential non-target effects of genetically modified crops are some of the more debated topics within applied biotechnologies in agriculture and environmental risk assessment. The objective of the present research was to study the potential Bt-toxin uptake by the non-target herbivore Myzus persicae Sulzer (Hemiptera: Aphididae) feeding on transgenic oilseed rape plants (Brassica napus cv. 'Westar' lines GT 2-4) expressing the Cry1Ac endotoxin. A specific aim was to replicate our previous experiment in controlled laboratory conditions to avoid or minimize the risk of contamination leading to potential false positive results. The toxin levels in vernalized (V) and not-vernalized (not-V) transgenic oilseed rape plants was also monitored to better clarify the role of physiological processes on Bt-toxin expression. Cry1Ac expression in not-V plants (mean concentration±SE=167.8±5.7 μg kg-1 FW) showed a pattern of large variability, in comparison with V plants whose expression (mean concentration±SE=227.7±1.9 μg kg-1 FW) was significantly more stable. Cry1Ac toxin was detected in three aphid samples reared on V plants with a mean toxin concentration±SE of 4.8±0.6 μg Kg-1 FW and in three out of six samples of aphids reared on not-V plants (mean toxin concentration±SE=7.1±1.2 μg kg-1 FW). The mean Bt-toxin concentration of all the positive aphid samples was 5.9±1.0 μg kg-1 FW. Our results confirmed the findings of our previous experiment and highlighted the potential for Cry1Ac toxin uptake by aphids feeding on transgenic oilseed rape plants.