Moar William, Khajuria Chitvan, Pleau Michael, Ilagan Oliver, Chen Mao, Jiang Changjian, Price Paula, McNulty Brian, Clark Thomas, Head Graham
Monsanto Co., St. Louis, Missouri, United States of America.
PLoS One. 2017 Jan 6;12(1):e0169175. doi: 10.1371/journal.pone.0169175. eCollection 2017.
There is a continuing need to express new insect control compounds in transgenic maize against western corn rootworm, Diabrotica virgifera virgifera (LeConte) (WCR). In this study three experiments were conducted to determine cross-resistance between the new insecticidal DvSnf7 dsRNA, and Bacillus thuringiensis (Bt) Cry3Bb1; used to control WCR since 2003, with field-evolved resistance being reported. Laboratory susceptible and Cry3Bb1-resistant WCR were evaluated against DvSnf7 dsRNA in larval diet-incorporation bioassays. Additionally, the susceptibility of seven field and one field-derived WCR populations to DvSnf7 (and Cry3Bb1) was assessed in larval diet-overlay bioassays. Finally, beetle emergence of laboratory susceptible and Cry3Bb1-resistant WCR was evaluated with maize plants in the greenhouse expressing Cry3Bb1, Cry34Ab1/Cry35Ab1, or DvSnf7 dsRNA singly, or in combination.
The Cry3Bb1-resistant colony had slight but significantly (2.7-fold; P<0.05) decreased susceptibility to DvSnf7 compared to the susceptible colony, but when repeated using a field-derived WCR population selected for reduced Cry3Bb1 susceptibility, there was no significant difference (P<0.05) in DvSnf7 susceptibility compared to that same susceptible population. Additionally, this 2.7-fold difference in susceptibility falls within the range of DvSnf7 susceptibility among the seven field populations tested. Additionally, there was no correlation between susceptibility to DvSnf7 and Cry3Bb1 for all populations evaluated. In greenhouse studies, there were no significant differences (P<0.05) between beetle emergence of susceptible and Cry3Bb1-resistant colonies on DvSnf7 and Cry34Ab1/Cry35Ab1, and between DvSnf7 and MON 87411 (DvSnf7 + Cry3Bb1) for the Cry3Bb1-resistant colony. These results demonstrate no cross-resistance between DvSnf7 and Cry3Bb1 against WCR. Therefore, pyramiding DvSnf7 with Bt proteins such as Cry3Bb1 and Cry34Ab1/Cry35Ab1 will provide a valuable IRM tool against WCR that will increase the durability of these Bt proteins. These results also illustrate the importance of using appropriate bioassay methods when characterizing field-evolved resistant WCR populations.
持续需要在转基因玉米中表达新的昆虫控制化合物，以对抗西部玉米根萤叶甲，即 Diabrotica virgifera virgifera（LeConte）（WCR）。在本研究中，进行了三项实验，以确定新型杀虫 DvSnf7 dsRNA 与苏云金芽孢杆菌（Bt）Cry3Bb1 之间的交互抗性；自 2003 年以来，Cry3Bb1 一直用于控制 WCR，且已有田间进化抗性的报道。在幼虫饲料掺入生物测定中，对实验室敏感和 Cry3Bb1 抗性的 WCR 进行了 DvSnf7 dsRNA 评估。此外，在幼虫饲料覆盖生物测定中，评估了七个田间和一个田间衍生的 WCR 种群对 DvSnf7（和 Cry3Bb1）的敏感性。最后，在温室中，用单独表达 Cry3Bb1、Cry34Ab1/Cry35Ab1 或 DvSnf7 dsRNA 或组合表达的玉米植株，评估了实验室敏感和 Cry3Bb1 抗性 WCR 的甲虫羽化情况。
与敏感群体相比，Cry3Bb1 抗性群体对 DvSnf7 的敏感性略有下降，但显著下降了 2.7 倍（P<0.05）；但当使用为降低 Cry3Bb1 敏感性而选择的田间衍生 WCR 种群重复实验时，与同一敏感种群相比，DvSnf7 敏感性没有显著差异（P<0.05）。此外，这种 2.7 倍的敏感性差异落在了所测试的七个田间种群中 DvSnf7 敏感性的范围内。此外，对于所有评估种群，对 DvSnf7 和 Cry3Bb1 的敏感性之间没有相关性。在温室研究中，敏感和 Cry3Bb1 抗性群体在 DvSnf7 和 Cry34Ab1/Cry35Ab1 上的甲虫羽化情况之间，以及 Cry3Bb1 抗性群体在 DvSnf7 和 MON 87411（DvSnf7 + Cry3Bb1）之间，没有显著差异（P<0.05）。这些结果表明 DvSnf7 和 Cry3Bb1 对 WCR 不存在交互抗性。因此，将 DvSnf7 与 Bt 蛋白如 Cry3Bb1 和 Cry34Ab1/Cry35Ab1 进行叠加，将为对抗 WCR 提供一种有价值的综合抗性管理工具，并将提高这些 Bt 蛋白的耐久性。这些结果还说明了在表征田间进化抗性 WCR 种群时使用适当生物测定方法的重要性。
