Abstract Water-stress commonly affects crops grown in arid and semi-arid regions. Apart from the direct impact of this abiotic stress on yield, a diverse community of herbivores can outbreak under these conditions, and plant responses to abiotic stress may alter plant defense responses that deter herbivores. Outbreaks of both generalist and specialist spider mites are strongly associated with hot and dry conditions in the field settings. To understand how water-stress impacts maize responses to spider mites, we conducted parallel greenhouse and field experiments with maize plants (B73 inbred line) subjected to optimal irrigation and water-stress conditions (50-60% and 5-10% volumetric water content (VWC), and 25-32% and 10-15% VWC, in the greenhouse and field, respectively). In addition to recording B73 responses to water-stress alone, we measured the population growth of the generalist twospotted spider mite (Tetranychus urticae, TSM) and the specialist Banks grass mite (Oligonychus pratensis, BGM) on optimally watered and water-stressed plants. We also measured plant defense protein activities (peroxidase (POD), polyphenol oxidase (PPO), chitinase (CHI) and trypsin inhibitor (TI)) at 1, 3, and 7 days post mite introduction for each irrigation treatment. For B73 plants exposed to water-stress, we observed increases in leaf temperature, leaf water potential, POD activity, as well as decreases in stomatal conductance and stem height. Populations of both mite species increased more rapidly on water-stressed B73 plants. While optimally irrigated B73 plants responded with similar plant defense activity to both mite species, combinations of plant water-stress and TSM herbivory resulted in increases in CHI and TI activity that were not observed for the respective treatments with BGM. Collectively, our results highlight a role for species-specific factors, possibly associated with herbivore host plant breadth, in impacting plant responses to herbivory in combination with an abiotic stress.

中文翻译：

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不同宿主专业化的蜘蛛螨对玉米水分胁迫和食草性联合的不同反应

摘要 干旱和半干旱地区的作物普遍受水分胁迫。除了这种非生物胁迫对产量的直接影响外，多种食草动物群落可能会在这些条件下爆发，植物对非生物胁迫的反应可能会改变阻止食草动物的植物防御反应。多才多艺和专科蜘蛛螨的爆发与野外环境中的炎热和干燥条件密切相关。为了了解水分胁迫如何影响玉米对叶螨的反应，我们对处于最佳灌溉和水分胁迫条件（50-60% 和 5-10% 体积含水量）的玉米植物（B73 自交系）进行了平行温室和田间试验(VWC)，温室和田间分别为 25-32% 和 10-15% VWC）。除了单独记录 B73 对水分胁迫的反应外，我们测量了双斑叶螨（Tetranychus urticae，TSM）和班克斯草螨（Oligonychus pratensis，BGM）在最佳浇水和水分胁迫的植物上的种群增长。我们还测量了每种灌溉处理在螨引入后 1、3 和 7 天的植物防御蛋白活性（过氧化物酶 (POD)、多酚氧化酶 (PPO)、几丁质酶 (CHI) 和胰蛋白酶抑制剂 (TI)）。对于暴露于水分胁迫的 B73 植物，我们观察到叶温、叶水势、POD 活性的增加，以及气孔导度和茎高的降低。在受水胁迫的 B73 植物上，两种螨类的数量增加得更快。虽然最佳灌溉的 B73 植物对两种螨类都有相似的植物防御活性，植物水分胁迫和 TSM 草食性的组合导致 CHI 和 TI 活性的增加，这在使用 BGM 的相应处理中未观察到。总的来说，我们的结果强调了物种特异性因素（可能与食草动物宿主植物的宽度有关）在影响植物对食草动物和非生物胁迫的反应方面的作用。