Marquardt Paul T, Krupke Christian H, Camberato James J, Johnson William G
Purdue University Department of Botany and Plant Pathology, West Lafayette, IN, USA.
Pest Manag Sci. 2014 May;70(5):763-70. doi: 10.1002/ps.3611. Epub 2013 Aug 27.
Combining herbicide-resistant and Bacillus thuringiensis (Bt) traits in corn (Zea mays L.) hybrids may affect insect resistance management owing to volunteer corn. Some Bt toxins may be expressed at lower levels by nitrogen-deficient corn roots. Corn plants with sublethal levels of Bt expression could accelerate the evolution of Bt resistance in target insects. The present objective was to quantify the concentration of Bt (Cry3Bb1) in corn root tissue with varying tissue nitrogen concentrations.
Expression of Cry3Bb1 toxin in root tissue was highly variable, but there were no differences in the overall concentration of Cry3Bb1 expressed between roots taken from Cry3Bb1-positive volunteer and hybrid corn plants. The nitrogen rate did affect Cry3Bb1 expression in the greenhouse, less nitrogen resulted in decreased Cry3Bb1 expression, yet this result was not documented in the field.
A positive linear relationship of plant nitrogen status on Cry3Bb1 toxin expression was documented. Also, high variability in Cry3Bb1 expression is potentially problematic from an insect resistance management perspective. This variability could create a mosaic of toxin doses in the field, which does not fit into the high-dose refuge strategy and could alter predictions about the speed of evolution of resistance to Cry3Bb1 in western corn rootworm Diabrotica virgifera virgifera LeConte.
由于自生玉米的存在，在玉米（Zea mays L.）杂交种中结合抗除草剂和苏云金芽孢杆菌（Bt）性状可能会影响昆虫抗性管理。一些Bt毒素在缺氮的玉米根中可能会以较低水平表达。具有亚致死水平Bt表达的玉米植株可能会加速目标昆虫对Bt抗性的进化。目前的目标是量化不同组织氮浓度下玉米根组织中Bt（Cry3Bb1）的浓度。
根组织中Cry3Bb1毒素的表达高度可变，但从Cry3Bb1阳性自生玉米和杂交玉米植株获取的根中，Cry3Bb1的总体表达浓度没有差异。氮肥用量确实会影响温室中Cry3Bb1的表达，较少的氮会导致Cry3Bb1表达降低，但这一结果在田间并未得到证实。
记录了植株氮素状况与Cry3Bb1毒素表达之间呈正线性关系。此外，从昆虫抗性管理的角度来看，Cry3Bb1表达的高度变异性可能存在问题。这种变异性可能会在田间形成毒素剂量的镶嵌分布，这不符合高剂量避难所策略，并且可能会改变对西部玉米根萤叶甲（Diabrotica virgifera virgifera LeConte）对Cry3Bb1抗性进化速度预测。
