Salicylic acid (SA), a phytohormone, has been considered to be a key regulator mediating plant defence against pathogens. It is still vague how SA activates plant defence against herbivores such as chewing and sucking pests. Here, we used an aphid-susceptible wheat variety to investigate Sitobion avenae response to SA-induced wheat plants, and the effects of exogenous SA on some defence enzymes and phenolics in the plant immune system. In SA-treated wheat seedlings, intrinsic rate of natural increase (rm), fecundity and apterous rate of S. avenae were 0.25, 31.4 nymphs/female and 64.4%, respectively, and significantly lower than that in the controls (P < 0.05). Moreover, the increased activities of phenylalanine-ammonia-lyase, polyphenol oxidase (PPO) and peroxidase in the SA-induced seedlings obviously depended on the sampling time, whereas activities of catalase and 4-coumarate:CoA ligase were suppressed significantly at 24, 48 and 72 h in comparison with the control. Dynamic levels of p-coumaric acid at 96 h, caffeic acid at 24 and 72 h and chlorogenic acid at 24, 48 and 96 h in wheat plants were significantly upregulated by exogenous SA application. Nevertheless, only caffeic acid content was positively correlated with PPO activity in SA-treated wheat seedlings (P = 0.031). These findings indicate that exogenous SA significantly enhanced the defence of aphid-susceptible wheat variety against aphids by regulating the plant immune system, and may prove a potential application of SA in aphid control.

中文翻译：

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外源水杨酸提高了蚜虫易感小麦对谷蚜 Sitobion avenae (F.) 的抗性（半翅目：蚜科）

水杨酸 (SA) 是一种植物激素，被认为是介导植物防御病原体的关键调节剂。SA 如何激活植物对食草动物（如咀嚼和吸吮害虫）的防御仍不清楚。在这里，我们使用了一种对蚜虫敏感的小麦品种来调查稻瘟病菌对 SA 诱导的小麦植物的反应，以及外源 SA 对植物免疫系统中某些防御酶和酚类物质的影响。在 SA 处理的小麦幼苗中，内在自然增长率 (r米)、繁殖力和无产率燕麦沙门氏菌分别为 0.25、31.4 若虫/雌和 64.4%，显着低于对照组（磷< 0.05)。此外，SA 诱导的幼苗中苯丙氨酸解氨酶、多酚氧化酶 (PPO) 和过氧化物酶的活性增加明显取决于采样时间，而过氧化氢酶和 4-香豆酸：CoA 连接酶的活性在 24、48 时受到显着抑制。和 72 h 与对照相比。动态水平p外源SA显着上调小麦植株96 h香豆酸、24和72 h咖啡酸和24、48和96 h绿原酸。然而，在 SA 处理的小麦幼苗中，只有咖啡酸含量与 PPO 活性呈正相关（磷= 0.031)。这些发现表明，外源SA通过调节植物免疫系统显着增强了蚜虫易感小麦品种对蚜虫的防御能力，并可能证明SA在蚜虫防治中的潜在应用。