DOI: 10.1111/j.1365-3180.2009.00749.x Parasitic plant infection is partially controlled through symbiotic pathways 1 M FERNA ´ NDEZ-APARICIO*, N RISPAIL  , E PRATS  , D MORANDI à , J M GARCI ´ A-GARRIDO*, E DUMAS-GAUDOT à , G DUC§ & D RUBIALES   *CSIC, Estacio ´n Experimental del Zaidı´n, Granada, Spain,  CSIC, Institute for Sustainable Agriculture, Alameda Obispo s ⁄ n, Co ´rdoba, Spain, àUMR 1088 INRA ⁄ CNRS 5184 ⁄ UB, Plante-Microbe-Environnement, Dijon CEDEX, France, and §UMR 102, INRA, Ge ´ne ´tique et Ecophysiologie des Le´gumineuses, Dijon CEDEX, France Received 15 December 2008 Revised version accepted 1 September 2009 Summary Legumes are unique in interacting with Rhizobium, arbuscular mycorrhizal (AM) fungi, and parasitic plants. To dissect common parts of these three plant– organism interactions, infection by Orobanche crenata was studied in mutants with altered symbiotic pheno- types of Medicago truncatula and Pisum sativum. Oro- banche crenata inoculation of mutant lines carrying defective mutation in the genes dmi2 ⁄ sym19 and dmi3 resulted in an increase in O. crenata establishment. Similarly, inoculation of mutants carrying mutation in the gene sunn ⁄ sym29 that controls the autoregulation mechanism of the symbiosis, also lead to a significant increase in haustoria formation. Altogether, our results suggest that parasitic plant infection is partly controlled by both the conserved symbiotic pathway that mediates symbiont recognition and establishment and the auto- regulation mechanism that regulates the extent of colonisation by Rhizobium and AM fungi. Keywords: Medicago truncatula, Pisum sativum, Oroban- che crenata, bean broomrape, Rhizobium, mycorrhiza, symbiosis, parasitism. FERNA ´ NDEZ-APARICIO M, RISPAIL N, PRATS E, MORANDI D, GARCI ´ A-GARRIDO JM, DUMAS-GAUDOT E, DUC G& RUBIALES D (2009). Parasitic plant infection is partially controlled through symbiotic pathways. Weed Research. Introduction Plants are constantly interacting with organisms present within their rhizosphere. The arbuscular mycorrhizal (AM) fungi of the genus Glomeromycota establish symbiotic relationships with most plant species from mosses to dicotyledons concomitantly with the land colonisation by terrestrial plants (Kistner & Parniske, 2002). More recently during evolution, bacteria from the genus Rhizobium evolved the ability to induce the formation of a specific root organ, the nodules, in a more restricted number of plants, the Fabaceae. The nodules fix atmospheric nitrogen in exchange for plant carbohydrates (Kistner & Parniske, 2002). Host mutants impaired in both nodulation and mycorrhization have indicated that the signalling pathways controlling these symbiotic processes are largely overlapping (Duc et al., 1989; Sagan et al., 1995; Kistner & Parniske, 2002). Apart for these beneficial interactions, plants are also constantly challenged by pathogenic organisms, includ- ing the parasitic plants of the Striga, Orobanche and Phelipanche genera (Rubiales, 2003; Parker, 2009). These parasites have lost their autotrophic way of life during evolution and have evolved to parasitise most monocotyledonous and dicotyledonous plants. As with symbiotic interactions, a complex dialogue has to occur for efficient parasitisation of the host (Bouwmeester et al., 2003; Rispail et al., 2007; Ferna´ndez-Aparicio W R E 7 4 9 B Dispatch: 5.10.09 Journal: WRE CE: Aftab Begum Journal Name Manuscript No. Author Received: No. of pages: 7 PE: Sathiyaseelan Correspondence: M Ferna´ndez-Aparicio, CSIC, Estacio´n Experimental del Zaidı´n, Profesor Albareda 1, 18008 Granada, Spain. Tel: (+34) 958 181600 ext. 147; Fax: (+34) 957 499252; E-mail: monica.fernandez@ias.csic.es Ó 2009 The Authors Journal Compilation Ó 2009 European Weed Research Society Weed Research 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54