title: Nitrogen nutrition of tomato plant alters leafminer dietary intake dynamics.
abstract: The leafminer Tuta absoluta (Meyrick) is a major pest of the tomato crop and its development rate is known to decline when nitrogen availability for crop growth is limited. Because N limitation reduces plant primary metabolism but enhances secondary metabolism, one can infer that the slow larval development arises from lower leaf nutritive value and/or higher plant defence. As an attempt to study the first alternative, we examined the tomato-T. absoluta interaction in terms of resource supply by leaves and intake by larvae. Tomato plants were raised under controlled conditions on N-sufficient vs. N-limited complete nutrient solutions. Plants were kept healthy or artificially inoculated with larvae for seven days. Serial harvests were taken and the N, C, dry mass and water contents were determined in roots, stems and leaves. Leaf and mine areas were also measured and the N, C, dry mass and water surface densities were calculated in order to characterize the diet of the larvae. The infestation of a specific leaf lessened its local biomass by 8-26%, but this effect was undetectable at the whole plant scale. Infestation markedly increased resource density per unit leaf area (water, dry mass, C and N) suggesting that the insect induced changes in leaf composition. Nitrogen limitation lessened whole plant growth (by 50%) and infested leaflet growth (by 32-44%). It produced opposite effects on specific resource density per unit area, increasing that of dry mass and C while decreasing water and N. These changes were ineffective on insect mining activity, but slowed down larval development. Under N limitation, T. absoluta consumed less water and N but more dry mass and C. The resulting consequences were a 50-70% increase of C:N stoichiometry in their diet and the doubling of faeces excretion. The observed limitation of larval development is therefore consistent with a trophic explanation caused by low N and/or water intakes.
authors.affiliation: UMR LAE, INRA, Université de Lorraine, 54500 Vandœuvre-lès-Nancy, France.
authors.forename: Victoire
authors.initials: V
authors.lastname: Coqueret
authors.affiliation: UR PSH, INRA, 84000 Avignon, France.
authors.forename: Jacques
authors.initials: J
authors.lastname: Le Bot
authors.affiliation: UMR LAE, INRA, Université de Lorraine, 54500 Vandœuvre-lès-Nancy, France.
authors.forename: Romain
authors.initials: R
authors.lastname: Larbat
authors.affiliation: UMR ISA, INRA, CNRS, Université Nice Sophia Antipolis, 06900 Sophia Antipolis, France.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Desneux
authors.affiliation: UMR LAE, INRA, Université de Lorraine, 54500 Vandœuvre-lès-Nancy, France.
authors.forename: Christophe
authors.initials: C
authors.lastname: Robin
authors.affiliation: UR PSH, INRA, 84000 Avignon, France. Electronic address: stephane.adamowicz@inra.fr.
authors.forename: Stéphane
authors.initials: S
authors.lastname: Adamowicz
mesh_terms: D000818:Animals; D002244:Carbon / Q000378:metabolism; D007814:Larva / Q000254:growth & development / Q000502:physiology; D018551:Solanum lycopersicum / Q000737:chemistry / Q000254:growth & development* / Q000378:metabolism*; D009036:Moths / Q000254:growth & development / Q000502:physiology*; D009584:Nitrogen / Q000378:metabolism*; D018515:Plant Leaves / Q000737:chemistry / Q000254:growth & development / Q000378:metabolism; D014867:Water
chemical_list: D014867:Water; D002244:Carbon; D009584:Nitrogen
keywords: Faeces; Frass; Hydroponics; Insect development; Nitrogen; Solanum lycopersicum; Tuta absoluta