title: Can Oak Powdery Mildew Severity be Explained by Indirect Effects of Climate on the Composition of the Erysiphe Pathogenic Complex?
abstract: Coinfection by several pathogens is increasingly recognized as an important feature in the epidemiology and evolution of plant fungal pathogens. Oak mildew is induced by two closely related Erysiphe invasive species (Erysiphe alphitoides and E. quercicola) which differ in their mode of overwintering. We investigated how climate influences the co-occurrence of the two species in oak young stands and whether this is important for the disease epidemiology. We studied the frequency of flag-shoots (i.e., shoots developing from infected buds, usually associated with E. quercicola) in 95 oak regenerations over a 6-year period. Additionally, in 2012 and 2013, the oak mildew severity and the two Erysiphe spp. relative frequencies were determined in both spring and autumn in 51 regenerations and 43 1-year-old plantations of oaks. Both the frequency of flag-shoots and the proportion of Erysiphe lesions with E. quercicola presence were related to climate. We showed that survival of E. quercicola was improved after mild winters, with increase of both the flag-shoot frequency and the proportion of Erysiphe lesions with E. quercicola presence in spring. However, disease severity was not related to any complementarity effect between the two Erysiphe spp. causing oak powdery mildew. By contrast, increased E. alphitoides prevalence in spring was associated with higher oak mildew severity in autumn. Our results point out the critical role of between-season transmission and primary inoculum to explain disease dynamics which could be significant in a climate-warming context.
authors.affiliation: First author: UMR1136 IAM, INRA, Université de Lorraine, Nancy, F-54280 Champenoux, France; second author: Ministère de l'agriculture, de l'agro-alimentaire et de la forêt DGAL-SDQPV, Département de la Santé des Forêts, 251 rue de Vaugirard, 75732, Paris cedex 15, France; and second, third, and fourth authors: UMR1202 BIOGECO, INRA, University of Bordeaux, F-33610 Cestas, France.
authors.forename: Benoit
authors.initials: B
authors.lastname: Marçais
authors.affiliation: First author: UMR1136 IAM, INRA, Université de Lorraine, Nancy, F-54280 Champenoux, France; second author: Ministère de l'agriculture, de l'agro-alimentaire et de la forêt DGAL-SDQPV, Département de la Santé des Forêts, 251 rue de Vaugirard, 75732, Paris cedex 15, France; and second, third, and fourth authors: UMR1202 BIOGECO, INRA, University of Bordeaux, F-33610 Cestas, France.
authors.forename: Dominique
authors.initials: D
authors.lastname: Piou
authors.affiliation: First author: UMR1136 IAM, INRA, Université de Lorraine, Nancy, F-54280 Champenoux, France; second author: Ministère de l'agriculture, de l'agro-alimentaire et de la forêt DGAL-SDQPV, Département de la Santé des Forêts, 251 rue de Vaugirard, 75732, Paris cedex 15, France; and second, third, and fourth authors: UMR1202 BIOGECO, INRA, University of Bordeaux, F-33610 Cestas, France.
authors.forename: Damien
authors.initials: D
authors.lastname: Dezette
authors.affiliation: First author: UMR1136 IAM, INRA, Université de Lorraine, Nancy, F-54280 Champenoux, France; second author: Ministère de l'agriculture, de l'agro-alimentaire et de la forêt DGAL-SDQPV, Département de la Santé des Forêts, 251 rue de Vaugirard, 75732, Paris cedex 15, France; and second, third, and fourth authors: UMR1202 BIOGECO, INRA, University of Bordeaux, F-33610 Cestas, France.
authors.forename: Marie-Laure
authors.initials: ML
authors.lastname: Desprez-Loustau
mesh_terms: D001203:Ascomycota / Q000235:genetics / Q000254:growth & development*; D002980:Climate; D005843:Geography; D058865:Introduced Species; D016015:Logistic Models; D010935:Plant Diseases / Q000382:microbiology*; D018520:Plant Shoots / Q000382:microbiology; D029963:Quercus / Q000382:microbiology*; D012621:Seasons; D013696:Temperature
keywords: Erysiphe quercicola; Quercus; cryptic species