title: Phosphorus supply, arbuscular mycorrhizal fungal species, and plant genotype impact on the protective efficacy of mycorrhizal inoculation against wheat powdery mildew.
abstract: A potential alternative strategy to chemical control of plant diseases could be the stimulation of plant defense by arbuscular mycorrhizal fungi (AMF). In the present study, the influence of three parameters (phosphorus supply, mycorrhizal inoculation, and wheat cultivar) on AMF protective efficiency against Blumeria graminis f. sp. tritici, responsible for powdery mildew, was investigated under controlled conditions. A 5-fold reduction (P/5) in the level of phosphorus supply commonly recommended for wheat in France improved Funneliformis mosseae colonization and promoted protection against B. graminis f. sp. tritici in a more susceptible wheat cultivar. However, a further decrease in P affected plant growth, even under mycorrhizal conditions. Two commercially available AMF inocula (F. mosseae, Solrize®) and one laboratory inoculum (Rhizophagus irregularis) were tested for mycorrhizal development and protection against B. graminis f. sp. tritici of two moderately susceptible and resistant wheat cultivars at P/5. Mycorrhizal levels were the highest with F. mosseae (38 %), followed by R. irregularis (19 %) and Solrize® (SZE, 8 %). On the other hand, the highest protection level against B. graminis f. sp. tritici was obtained with F. mosseae (74 %), followed by SZE (58 %) and R. irregularis (34 %), suggesting that inoculum type rather than mycorrhizal levels determines the protection level of wheat against B. graminis f. sp. tritici. The mycorrhizal protective effect was associated with a reduction in the number of conidia with haustorium and with an accumulation of polyphenolic compounds at B. graminis f. sp. tritici infection sites. Both the moderately susceptible and the most resistant wheat cultivar were protected against B. graminis f. sp. tritici infection by F. mosseae inoculation at P/5, although the underlying mechanisms appear rather different between the two cultivars. This study emphasizes the importance of taking into account the considered parameters when considering the use of AMF as biocontrol agents.
authors.affiliation: Unité de Chimie Environnementale et Interactions sur le Vivant (UCEIV), Université du Littoral Côte d'Opale, SFR Condorcet FR CNRS 3417, 50, Rue Ferdinand Buisson, 62228, Calais Cedex, France.
authors.forename: G
authors.initials: G
authors.lastname: Mustafa
authors.affiliation: Unité de Chimie Environnementale et Interactions sur le Vivant (UCEIV), Université du Littoral Côte d'Opale, SFR Condorcet FR CNRS 3417, 50, Rue Ferdinand Buisson, 62228, Calais Cedex, France.
authors.forename: B
authors.initials: B
authors.lastname: Randoux
authors.affiliation: Unité de Chimie Environnementale et Interactions sur le Vivant (UCEIV), Université du Littoral Côte d'Opale, SFR Condorcet FR CNRS 3417, 50, Rue Ferdinand Buisson, 62228, Calais Cedex, France.
authors.forename: B
authors.initials: B
authors.lastname: Tisserant
authors.affiliation: Unité de Chimie Environnementale et Interactions sur le Vivant (UCEIV), Université du Littoral Côte d'Opale, SFR Condorcet FR CNRS 3417, 50, Rue Ferdinand Buisson, 62228, Calais Cedex, France.
authors.forename: J
authors.initials: J
authors.lastname: Fontaine
authors.affiliation: Unité de Chimie Environnementale et Interactions sur le Vivant (UCEIV), Université du Littoral Côte d'Opale, SFR Condorcet FR CNRS 3417, 50, Rue Ferdinand Buisson, 62228, Calais Cedex, France.
authors.forename: M
authors.initials: M
authors.lastname: Magnin-Robert
authors.affiliation: Unité de Chimie Environnementale et Interactions sur le Vivant (UCEIV), Université du Littoral Côte d'Opale, SFR Condorcet FR CNRS 3417, 50, Rue Ferdinand Buisson, 62228, Calais Cedex, France. lounes@univ-littoral.fr.
authors.forename: A
authors.initials: A
authors.lastname: Lounès-Hadj Sahraoui
authors.affiliation: Unité de Chimie Environnementale et Interactions sur le Vivant (UCEIV), Université du Littoral Côte d'Opale, SFR Condorcet FR CNRS 3417, 50, Rue Ferdinand Buisson, 62228, Calais Cedex, France.
authors.forename: Ph
authors.initials: P
authors.lastname: Reignault
mesh_terms: D059827:Agricultural Inoculants / Q000254:growth & development; D005838:Genotype; D038821:Mycorrhizae / Q000145:classification / Q000502:physiology*; D010572:Pest Control, Biological / Q000379:methods; D010758:Phosphorus / Q000737:chemistry / Q000494:pharmacology*; D010935:Plant Diseases / Q000382:microbiology* / Q000517:prevention & control*; D018515:Plant Leaves; D018517:Plant Roots / Q000382:microbiology; D036226:Seedlings; D014908:Triticum / Q000235:genetics / Q000382:microbiology*
chemical_list: D010758:Phosphorus
keywords: Arbuscular mycorrhizal fungi; Biocontrol; Phosphorus; Powdery mildew; Wheat genotype