Abstract The northern corn rootworm (NCR), Diabrotica barberi Smith & Lawrence, is an economic pest of maize in the U.S. Corn Belt. The objective of this study was to determine the baseline susceptibility of a laboratory NCR strain to Bt proteins eCry3.1Ab, mCry3A, Cry3Bb1, and Cry34/35Ab1 using seedling, single plant, and diet-toxicity assays. Plant assays were performed in greenhouse using corn hybrids expressing one of the Bt proteins and each respective near-isoline. Diet-toxicity assays, consisting of Bt proteins overlaid onto artificial diet were also conducted. In both plant assays, significantly more larvae survived Cry34/35Ab1-expressing corn compared with all other Bt-expressing corn, and larvae that survived eCry3.1Ab-expressing corn had significantly smaller head capsule widths compared with larvae that survived Cry34/35Ab1-expressing corn. In seedling assays, larvae surviving eCry3.1Ab-expressing corn also had significantly smaller head capsule widths compared with larvae that survived mCry3A-expressing corn. Additionally, larvae that survived mCry3A-expressing corn weighed significantly more than larvae surviving eCry3.1Ab- and Cry34/35Ab1-expressing corn. In single plant assays, no significant differences in larval dry weight was observed between any of the Bt-expressing corn. In diet assays, LC50s ranged from 0.14 (eCry3.1Ab) to 10.6 µg/cm2 (Cry34/35Ab1), EC50s ranged from 0.12 (Cry34/35Ab1) to 1.57 µg/cm2 (mCry3A), IC50s ranged from 0.08 (eCry3.1Ab) to 2.41 µg/cm2 (Cry34/35Ab1), and MIC50s ranged from 2.52 (eCry3.1Ab) to 14.2 µg/cm2 (mCry3A). These results establish the toxicity of four Bt proteins to a laboratory diapausing NCR strain established prior to the introduction of Bt traits and are important for monitoring resistance evolution in NCR field populations.

中文翻译：

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北玉米根虫实验室菌株 Diabrotica barberi（鞘翅目：Chrysomelidae）对幼苗、单株植物和饮食毒性测定中苏云金芽孢杆菌性状的基线敏感性

摘要 北方玉米根虫 (NCR) Diabrotica barberi Smith & Lawrence 是美国玉米带中的一种玉米经济害虫。本研究的目的是使用幼苗、单株植物和饮食毒性试验确定实验室 NCR 菌株对 Bt 蛋白 eCry3.1Ab、mCry3A、Cry3Bb1 和 Cry34/35Ab1 的基线敏感性。在温室中使用表达 Bt 蛋白之一和每种近等值的玉米杂种进行植物测定。还进行了由覆盖在人工饮食上的 Bt 蛋白组成的饮食毒性试验。在这两种植物试验中，与所有其他表达 Bt 的玉米相比，表达 Cry34/35Ab1 的玉米中存活的幼虫明显更多，而在 eCry3 中存活的幼虫明显更多。与在表达 Cry34/35Ab1 的玉米中存活的幼虫相比，表达 1Ab 的玉米具有明显更小的头囊宽度。在幼苗试验中，与在表达 mCry3A 的玉米中存活的幼虫相比，在表达 eCry3.1Ab 的玉米中存活的幼虫的头囊宽度也明显更小。此外，在表达 mCry3A 的玉米中存活的幼虫比在表达 eCry3.1Ab 和 Cry34/35Ab1 的玉米中存活的幼虫重得多。在单株试验中，在任何表达 Bt 的玉米之间未观察到幼虫干重的显着差异。在饮食分析中，LC50s 的范围从 0.14 (eCry3.1Ab) 到 10.6 µg/cm2 (Cry34/35Ab1)，EC50s 的范围从 0.12 (Cry34/35Ab1) 到 1.57 µg/cm2 (mCry3A)，IC50.18d 范围内) 至 2.41 µg/cm2 (Cry34/35Ab1)，MIC50 范围为 2.52 (eCry3.1Ab) 至 14.2 µg/cm2 (mCry3A)。