title: Corn defense responses to nitrogen availability and subsequent performance and feeding preferences of beet armyworm (Lepidoptera: Noctuidae).
abstract: Many studies have reported the effect of nitrogen (N) fertilization on plant constitutive defense responses; however, little is known about their effects on plant induced defense patterns and its consequence for insect herbivores. In our experiments, the effects of N availability on growth, nutritional quality (N content, protein/carbohydrate [P:C] ratio, modified gross energy [MGE]), and constitutive phenolics of corn, Zea mays L. were quantified. Moreover, the indirect effects of N fertilization on the beet armyworm, Spodoptera exigua Hübner through larval performance and feeding preference were examined. N fertilization increased plant growth, and depressed defense traits by increasing N content and the P:C ratio, as well as decreasing the constitutive concentration of phenolics. Subsequently, beet armyworm showed higher performance and preferentially fed on high-N corn because of its low defense traits. After beet armyworm feeding, high-N corn significantly deterred larval feeding, and had negative effects on the performance of beet armyworm through decreasing P:C ratio and increasing induced phenolics. On the contrary, there were no significant changes in P:C ratio and phenolics in low-N corn after feeding damage. Larval performance and preference were also not affected by induced compounds in low-N corn, which suggested that the expression of induced defense was dependent on N availability. The result indicates that N availability can exert a variety of bottom-up effect on plant defense patterns to influence insect population dynamics, and thereby may represent a source of variation in plant-insect interactions.
authors.affiliation: Department of Entomology, College of Plant Protection, Nanjing Agricultural University, Key Laboratory of Monitoring and Management of Crop Diseases and Pest Insects, Ministry of Agriculture, Nanjing, Jiangsu 210095, China. renlili1984@gmail.com
authors.forename: Li-Li
authors.initials: LL
authors.lastname: Ren
authors.forename: Giles
authors.initials: G
authors.lastname: Hardy
authors.forename: Zhu-Dong
authors.initials: ZD
authors.lastname: Liu
authors.forename: Wei
authors.initials: W
authors.lastname: Wei
authors.forename: Hua-Guo
authors.initials: HG
authors.lastname: Dai
mesh_terms: D000375:Aging; D000818:Animals; D002851:Chromatography, High Pressure Liquid; D004305:Dose-Response Relationship, Drug; D005247:Feeding Behavior; D005308:Fertilizers / Q000032:analysis; D060434:Herbivory; D007814:Larva / Q000502:physiology; D009584:Nitrogen / Q000378:metabolism*; D011897:Random Allocation; D013053:Spectrophotometry; D018411:Spodoptera / Q000502:physiology*; D003313:Zea mays / Q000187:drug effects / Q000378:metabolism*
chemical_list: D005308:Fertilizers; D009584:Nitrogen