Department of Entomology, University of Nebraska, Lincoln, Nebraska, United States of America.
CropScience Division, Bayer AG, Chesterfield, Missouri, United States of America.
PLoS One. 2023 Jul 10;18(7):e0288372. doi: 10.1371/journal.pone.0288372. eCollection 2023.
Field-evolved resistance of the western corn rootworm (WCR), Diabrotica virgifera virgifera LeConte, to Bacillus thuringiensis Berliner (Bt) proteins Cry3Bb1 and Cry34/35Ab1 (now classified as Gpp34Ab1/Tpp35Ab1) expressed in the pyramid SmartStax® has been documented in areas of the United States (U.S.) Corn Belt. SmartStax® PRO is a recently registered rootworm-active pyramid containing the same Bt proteins expressed in SmartStax® plus DvSnf7 dsRNA. Little to no published data is available comparing efficacy of the technologies or potential effects of dietary exposure on adult WCR fitness. Therefore, experiments were conducted to compare effects of adult WCR dietary exposure to SmartStax® and SmartStax® PRO on life history parameters and efficacy of the technologies in the field with both Bt-susceptible and Bt-resistant WCR populations. WCR life history parameters evaluated included adult longevity, head capsule width, egg production, and egg viability. Results of small-plot field trials indicated that both technologies provided a high level of root protection when a Bt-susceptible WCR population was present. Root protection was reduced on SmartStax® but maintained on SmartStax® PRO when WCR Bt resistance occurred. Lifetime egg production was the key life history parameter that was significantly reduced when either Bt-susceptible or Bt-resistant adult WCR were fed SmartStax® or SmartStax® PRO diet. A potential fitness advantage was apparent as egg production was significantly higher in the Bt-resistant than Bt-susceptible population. The similar response by the Bt-susceptible WCR population to SmartStax® and SmartStax® PRO indicates that results were caused by sublethal dietary exposure to Bt proteins. Adult size (males < females) and egg viability (high: >95%) were not significantly different among treatments but longevity results were inconsistent between years. Collectively, the field efficacy and life history parameter data expand existing knowledge of SmartStax® and SmartStax® PRO technologies, which will inform practical WCR resistance management programs.
田间选育的西部玉米根虫（WCR）对表达在金字塔型 SmartStax®中的苏云金芽孢杆菌（Bt）蛋白 Cry3Bb1 和 Cry34/35Ab1（现归类为 Gpp34Ab1/Tpp35Ab1）的抗性已经在美国玉米带的一些地区得到证实。SmartStax® PRO 是一种最近注册的根虫活性的金字塔型产品，其中含有与 SmartStax®相同的 Bt 蛋白，并表达了 DvSnf7 dsRNA。目前可用的比较这些技术的效果或膳食暴露对成虫 WCR 适应性潜在影响的公开数据很少。因此，进行了实验以比较成虫 WCR 对 SmartStax®和 SmartStax® PRO 的膳食暴露对这两种技术在田间的效果以及对 Bt 敏感和 Bt 抗性 WCR 种群的影响。评估的 WCR 生活史参数包括成虫寿命、头壳宽度、产卵量和卵活力。小面积田间试验的结果表明，当存在 Bt 敏感的 WCR 种群时，这两种技术都能提供高水平的根保护。当 WCR 对 Bt 产生抗性时，SmartStax®上的根保护减少，但 SmartStax® PRO 上的根保护得以维持。终生产卵量是当 Bt 敏感或 Bt 抗性成虫 WCR 喂食 SmartStax®或 SmartStax® PRO 饮食时显著降低的关键生活史参数。当 Bt 敏感或 Bt 抗性的成虫 WCR 喂食 SmartStax®或 SmartStax® PRO 饮食时，产卵量明显更高，这表明存在潜在的适应性优势。Bt 敏感的 WCR 种群对 SmartStax®和 SmartStax® PRO 的类似反应表明，结果是由对 Bt 蛋白的亚致死膳食暴露引起的。成虫大小（雄性<雌性）和卵活力（高：>95%）在处理之间没有显著差异，但寿命结果在不同年份之间不一致。总的来说，田间功效和生活史参数数据扩展了对 SmartStax®和 SmartStax® PRO 技术的现有认识，这将为实际的 WCR 抗性管理计划提供信息。
