Role of phloem sap quality and exudation characteristics on performance of pea aphid grown on lucerne genotypes

摘要: The phloem sap of two lucerne (Medicago sativa L.) genotypes inducing differences in pea aphid, Acyrthosiphon pisum Harris (Homoptera: Aphididae) performances (weight, fecundity, survival), was collected by stylectomy (radio frequency microcautery). Sugars and amino acids were assayed. No significant difference their concentrations could be established between genotypes. It is thus unlikely that a substantial part the varietal resistance these to aphid related content sugars or acids. same conclusion drawn for sugar/amino acid ratio. profiles globally similar. They nevertheless allowed discrimination on few (alanine, leucine, isoleucine, arginine, ornithine) only. Moreover, degree can neither GABA concentration, nor sulfur acids, because constituants either absent, trace amounts, whatever genotype taken into account. Stylectomy parameters revealed some interesting exudation Average volume stylet average duration respectively 2.8 2.3 times higher susceptible genotype. These results suggest reduced flow sap, after puncturing sieve-tubes stylets resistant genotype; this result greater difficulty ingestion aphids settled suboptimal performances. Resumee La seve phloemienne de deux luzerne, sur lesquels le puceron du pois, Harris, presente des caracteristiques biologiques (poids, fecondite, survie) differentes, est collectee par stylectomie (microcauterisation l'aide frequences radio). Les sucres et les acides amines sont analyses. teneurs globales en totaux ne different pas selon l'origine la phloemienne. Il semble donc que ni concentration sucres, celle soient responsables effets observes d'antibiose luzerne l'egard pois. Le rapport sucres/acides parait non plus avoir une action determinante aphidiennes puisqu'il identique dans seves phloemiennes Si spectre globalement similaire cas, quelques doutes subsistent quant au role certains arginne, ornithine). Mais degre peut etre relie aux celles soufres, puisque ces soit absents, l'etat traces quel considere. Des nettes entre etudies apparaissent, relativement duree d'exsudation seve: effet, moyen recolte fois important sensible ‘resistant’; meme, moyenne elevee resistant. Ces derniers resultats suggerent un moindre ecoulement apres perforation tubes cribles aphidiens chez resistant, entrainant ainsi prise alimentaire difficile pour pucerons installes ce