Williams Livy, Rodriguez-Saona Cesar, Castle Del Conte Sandra C
USDA-ARS, U.S. Vegetable Laboratory, 2700 Savannah Highway, Charleston, SC 29414, USA.
Rutgers University, Philip E. Marucci Blueberry and Cranberry Research Center, 125a Lake Oswego, Chatsworth, NJ 08019, USA.
AoB Plants. 2017 Jul 17;9(5):plx032. doi: 10.1093/aobpla/plx032. eCollection 2017 Sep.
Natural or synthetic elicitors can affect plant physiology by stimulating direct and indirect defence responses to herbivores. For example, increased production of plant secondary metabolites, a direct response, can negatively affect herbivore survival, development and fecundity. Indirect responses include increased emission of plant volatiles that influence herbivore and natural enemy behaviour, and production of extrafloral nectar that serves as a food source for natural enemies after their arrival on induced plants. Therefore, the use of elicitors has potential for the study of basic aspects of tritrophic interactions, as well as application in biorational pest control, i.e. an 'attract and reward' strategy. We conducted a field study to investigate the effects of methyl jasmonate, an elicitor of plant defence responses, on three trophic levels: the plant, herbivores and natural enemies. We made exogenous applications of methyl jasmonate to transgenic cotton and measured volatile emission, extrafloral nectar production and plant performance (yield). We also assessed insect abundance, insect performance, and parasitism and predation of brown stink bug, , eggs in methyl jasmonate-treated and untreated control plots. Application of methyl jasmonate increased emission of volatiles, in particular, (+)-limonene and (3)-4,8-dimethyl-1,3,7-nonatriene, and production of extrafloral nectar, but not yield, compared with the control treatment. Despite increased volatile and extrafloral nectar production, methyl jasmonate application did not affect plant bug performance, or mortality of egg masses, and only marginally influenced insect abundance. Mortality of eggs varied over the course of the study. Overall, methyl jasmonate treatment affected cotton plant-induced responses, but not the insects that inhabit the plants. Our results were probably influenced by reduced natural enemy colonization of cotton from adjacent non-crop habitats, and subsequent low within-field population recruitment. Much remains to be learned about the effects of exogenous application of plant-produced 'enhancers' on the behaviour of natural enemies before crop physiology can be manipulated to enhance pest control.
天然或合成诱导子可通过刺激植物对食草动物的直接和间接防御反应来影响植物生理。例如，植物次生代谢产物产量增加这一直接反应，可对食草动物的生存、发育和繁殖能力产生负面影响。间接反应包括植物挥发性物质释放增加，这会影响食草动物和天敌的行为，以及产生花外蜜露，当天敌到达被诱导的植物上后，花外蜜露可作为它们的食物来源。因此，诱导子的使用在研究三级营养相互作用的基本方面具有潜力，同时也可应用于生物合理害虫防治，即一种“吸引并奖励”策略。我们进行了一项田间研究，以调查植物防御反应诱导子茉莉酸甲酯对三个营养级的影响：植物、食草动物和天敌。我们将茉莉酸甲酯外源施用于转基因棉花，并测量挥发性物质释放、花外蜜露产量和植物表现（产量）。我们还评估了茉莉酸甲酯处理地块和未处理对照地块中的昆虫数量、昆虫表现以及棕色 stink bug 的卵的寄生和捕食情况。与对照处理相比，茉莉酸甲酯的施用增加了挥发性物质的释放，特别是(+)-柠檬烯和(3)-4,8-二甲基-1,3,7-壬三烯，以及花外蜜露的产量，但对产量没有影响。尽管挥发性物质和花外蜜露产量增加，但茉莉酸甲酯的施用并未影响植物蝽的表现，也未影响卵块的死亡率，仅对昆虫数量有轻微影响。在研究过程中，卵的死亡率有所变化。总体而言，茉莉酸甲酯处理影响了棉花植株的诱导反应，但对栖息在植株上的昆虫没有影响。我们的结果可能受到来自相邻非作物栖息地的棉花上的天敌定殖减少以及随后田间种群补充率低的影响。在能够操纵作物生理以加强害虫防治之前，关于外源施用植物产生的“增强剂”对天敌行为的影响，仍有许多需要了解的地方。
