Previous studies have raised the hypothesis that laboratory-reared insects may lose their ability to induce plant defenses because induction-associated gut bacteria may be eliminated by antibiotics used in artificial diets. The present study was conducted to determine whether maize (Zea mays L., Poaceae) responses to Spodoptera frugiperda (JE Smith) (Lepidoptera: Noctuidae) differ when field-collected vs. laboratory-reared insects are feeding. One fifth instar from the laboratory or field was released onto a resistant or a susceptible landrace variety at vegetative stages 4 and 6 (V4 and V6), or plants remained uninfested. Five days later, damage was estimated and sections of maize leaves were fed to forth instars in a Petri dish assay to assess the effects of previous feeding on weight gain, leaf consumption, and nutritional indices of conspecifics. Initially, field-collected larvae caused more damage on V4, but not on V6 maize plants, than laboratory-reared larvae. In V6 plants, the resistant variety showed less leaf damage than the susceptible variety. In a Petri dish assay, there were no differences between effects of laboratory-reared and field-collected larvae on the measured parameters, but larvae from both sources promoted increased susceptibility in maize plants at the V4, but not the V6 stage. This was characterized by higher weight gain and higher efficiency of conversion of ingested food (ECI) (on both maize varieties), and lower metabolic cost (MC) (on one variety) when S. frugiperda larvae fed on leaves pre-infested with laboratory-reared larvae compared to leaves of uninfested plants. Conversely, S. frugiperda larvae fed on leaves pre-infested with field-collected larvae consumed a greater amount of leaf tissue (on both varieties) compared to leaves of uninfested plants. A similar experiment with neonates showed no effects of landrace variety or previous infestation on insect weight and survival, but insects obtained a higher body weight when fed on V4 compared to V6 plants. In conclusion, S. frugiperda laboratory-reared larvae were equally able as field-collected larvae to induce susceptibility in V4 maize plants, and maize plants were more resistant to the pest at the V6 than at the V4 stage.

中文翻译：

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玉米对草地夜蛾的抗性及其与地方品种、植物阶段和幼虫来源的关系

先前的研究提出了一种假设，即实验室饲养的昆虫可能会失去诱导植物防御的能力，因为人工饮食中使用的抗生素可能会消除与诱导相关的肠道细菌。本研究旨在确定玉米（Zea mays L., Poaceae）是否对草地夜蛾有反应（JE Smith）（鳞翅目：夜蛾科）在野外采集的昆虫与实验室饲养的昆虫进食时有所不同。来自实验室或田间的五分之一龄在营养阶段 4 和 6（V4 和 V6）时被释放到抗性或易感的地方品种上，或者植物保持未受侵染。五天后，估计损坏情况，并在培养皿测定中将玉米叶片部分饲喂至四龄，以评估先前饲喂对同种体重增加、叶片消耗和营养指数的影响。最初，与实验室饲养的幼虫相比，田间采集的幼虫对 V4 玉米植株造成的损害更大，但对 V6 玉米植株则不然。在 V6 植物中，抗性品种比易感品种表现出更少的叶片损伤。在培养皿测定中，实验室饲养的和田间采集的幼虫对测量参数的影响没有差异，但两种来源的幼虫都促进了 V4 阶段玉米植株的易感性，但不是 V6 阶段。其特点是体重增加更高，摄入食物转化效率 (ECI) 更高（两种玉米品种），以及较低的代谢成本 (MC)（一种品种），当与未感染植物的叶子相比，草地贪夜蛾幼虫以预先感染实验室饲养的幼虫的叶子为食。相反地，草地贪夜蛾相比未受侵染植物的叶子喂养幼虫叶预先出没有场收集幼虫消耗叶组织的更大的量（在两个品种）。一项类似的新生儿实验表明，地方品种或以前的侵染对昆虫的重量和存活率没有影响，但与 V6 植物相比，用 V4 喂养的昆虫获得了更高的体重。总之，S. frugiperda实验室饲养的幼虫与田间采集的幼虫同样能够诱导 V4 玉米植株的易感性，并且玉米植株在 V6 阶段比 V4 阶段对害虫的抗性更强。