Data from: Pest tradeoffs in technology: reduced damage by caterpillars in Bt cotton benefits aphids

The rapid adoption of genetically engineered (GE) plants that express insecticidal Cry proteins derived from Bacillus thuringiensis (Bt) has raised concerns about their potential impact on non-target organisms. This includes the possibility that non-target herbivores develop into pests. Although studies have now reported increased populations of non-target herbivores in Bt cotton, the underlying mechanisms are not fully understood. We propose that lack of herbivore-induced secondary metabolites in Bt cotton represents a mechanism that benefits non-target herbivores. We show that, because of effective suppression of Bt-sensitive lepidopteran herbivores, Bt cotton contains reduced levels of induced terpenoids. We also show that changes in the overall level of these defensive secondary metabolites are associated with improved performance of a Bt-insensitive herbivore, the cotton aphid, under glasshouse conditions. These effects, however, were not as clearly evident under field conditions as aphid populations were not correlated with the amount of terpenoids measured in the plants. Nevertheless, increased aphid numbers were visible in Bt cotton compared with non-Bt cotton on some sampling dates. Identification of this mechanism increases our understanding of how insect-resistant crops impact herbivore communities and helps underpin the sustainable use of GE varieties.表达源自苏云金芽孢杆菌（Bacillus thuringiensis, Bt）杀虫Cry蛋白的转基因（GE）作物的快速推广应用，引发了学界对其可能对非靶标生物造成潜在影响的担忧，其中包括非靶标植食性昆虫演变为农业害虫的风险。尽管现有研究已报道转Bt棉花（Bt cotton）中的非靶标植食性昆虫种群数量有所上升，但其背后的调控机制尚未完全阐明。本研究提出，转Bt棉花中缺乏植食性昆虫诱导产生的次生代谢产物（secondary metabolites），这一现象可作为使非靶标植食性昆虫获益的潜在机制。研究结果证实，由于转Bt棉花可有效抑制对Bt敏感的鳞翅目（Lepidoptera）植食性昆虫，其诱导型萜类化合物（terpenoids）的含量显著降低。本研究同时发现，这类防御性次生代谢产物的整体水平变化，与对Bt不敏感的植食性昆虫——棉蚜（cotton aphid）在温室环境下的生存表现提升存在显著关联。不过，在田间环境中上述效应并未表现得如此清晰——因为棉蚜种群数量与植株中测得的萜类化合物含量并无明显相关性。尽管如此，在部分采样日期中，转Bt棉花内的棉蚜数量仍明显高于非转Bt棉花（non-Bt cotton）。对这一机制的解析，可深化我们对抗虫作物如何影响植食性昆虫群落的认知，并为转基因（GE）品种的可持续利用提供理论支撑。