Department of Entomology, Texas A&M University, College Station, TX 77843-2475, USA.
BASF Corporation, Morrisville, NC 27560, USA.
Toxins (Basel). 2019 Feb 9;11(2):102. doi: 10.3390/toxins11020102.
The corn earworm, Helicoverpa zea (Boddie), is a major pest of Bacillus thuringiensis (Bt) maize and cotton in the U.S.. Reduced efficacy of Bt plants expressing Cry1 and Cry2 against H. zea has been reported in some areas of the U.S.. In this study, we evaluated the occurrence and ear damage of H. zea on transgenic Bt maize expressing Cry proteins or a combination of Vip3A and Cry proteins in the field in Texas in 2018. We found that the occurrence of H. zea larvae and the viable kernel damage area on the ear were not different between non-Bt maize and Bt maize expressing Cry1A.105+Cry2Ab2 and Cry1Ab+Cry1F proteins. A total of 67.5% of the pyramided Bt maize expressing Cry1Ab+Cry1F+Vip3A was damaged by 2⁻4 instar larvae of H. zea. Diet bioassays showed that the resistance ratio against Vip3Aa51 for H. zea obtained from Cry1Ab+Cry1F+Vip3A maize was 20.4 compared to a field population collected from Cry1F+Cry1A.105+Cry2Ab2 maize. Leaf tissue bioassays showed that 7-day survivorship on WideStrike3 (Cry1F+Cry1Ac+Vip3A) cotton leaves was significantly higher for the H. zea population collected from Cry1Ab+Cry1F+Vip3A maize than for a Bt-susceptible laboratory population. The results generated from this study suggest that H. zea has evolved practical resistance to Cry1 and Cry2 proteins. Therefore, it is crucial to ensure the sustainable use of the Vip3A technology in Bt maize and cotton.
玉米穗虫，Helicoverpa zea（Boddie），是美国苏云金芽孢杆菌（Bt）玉米和棉花的主要害虫。在美国的一些地区，已报道 Cry1 和 Cry2 表达的 Bt 植物对 H. zea 的功效降低。在这项研究中，我们评估了 2018 年在德克萨斯州田间表达 Cry 蛋白的转基因 Bt 玉米和表达 Vip3A 和 Cry 蛋白组合的 Bt 玉米中 H. zea 的发生和穗部损伤。我们发现，H. zea 幼虫的发生和穗部活核损伤面积在非 Bt 玉米和表达 Cry1A.105+Cry2Ab2 和 Cry1Ab+Cry1F 蛋白的 Bt 玉米之间没有差异。总共 67.5%的 Cry1Ab+Cry1F+Vip3A 叠加 Bt 玉米被 2-4 龄 H. zea 幼虫破坏。饮食生物测定表明，从 Cry1Ab+Cry1F+Vip3A 玉米获得的 H. zea 对 Vip3Aa51 的抗性比为 20.4，而从 Cry1F+Cry1A.105+Cry2Ab2 玉米收集的田间种群。叶片组织生物测定表明，在 WideStrike3（Cry1F+Cry1Ac+Vip3A）棉花叶片上，来自 Cry1Ab+Cry1F+Vip3A 玉米的 H. zea 种群的 7 天存活率明显高于 Bt 敏感的实验室种群。本研究结果表明，H. zea 已对 Cry1 和 Cry2 蛋白产生了实际抗性。因此，确保 Vip3A 技术在 Bt 玉米和棉花中的可持续使用至关重要。
