Spatial distribution of lineages of oak powdery mildew fungi in France, using quick molecular detection methods

Abstract

Abstract• Powdery mildew is a major fungal disease of oaks in Europe. Recent studies using internal transcribed spacer (ITS) sequences suggested the presence of four different lineages (putative species). The objective of the study was to investigate the spatial distribution of these lineages/species and, in particular, to test the hypothesis of a spatial differentiation, at various scales: regional (France), altitudinal (a Pyrenean transect) and local (within a forest plot).• Detection methods for the four ITS types were developed: (1) single strand conformation polymorphism analysis (SSCP); (2) PCR amplifications, for which specific primers were designed. SSCP proved to be efficient for the detection of Erysiphe alphitoides and E. quercicola types. In contrast, the rarer ITS types corresponding to E. hypophylla and Phyllactinia guttata (sensu lato) were only detected by specific amplification.• The study confirmed the strong predominance of the ITS sequence associated with E. alphitoides at all spatial scales (with a frequency higher than 80%). Isolates presumably belonging to E. quercicola (i.e. with same ITS type), a recently described species not yet recorded in Europe, were also found in all French regions at a significant frequency (15% at national level).• No pattern of spatial differentiation between the putative species could be demonstrated: E. alphitoides was often found in association with different ITS types in the same region, the same tree, and even in the same lesion. Mots-clés :Erysiphe alphitoides / Erysiphe quercicola / espèces sryptiques / Erysiphales / ITS / invasion biologique Résumé -Distribution spatiale de lignées d'oïdium des chênes en France analysée à l'aide d'outils rapides de caractérisation moléculaire.• L'oïdium est l'une des maladies fongiques les plus importantes sur chênes en Europe. Des études récentes basées sur l'internal transcribed spacer (ITS) ont suggéré l'implication de quatre lignées (espèces putatives) différentes. L'objectif de l'étude était de caractériser la distribution spatiale de ces lignées/espèces et en particulier de tester l'hypothèse d'une différenciation spatiale à plusieurs échelles : régionale (France), altitudinale (transect pyrénéen) et locale (au sein d'une parcelle forestière).• Des méthodes de détection des quatre types d'ITS ont été développées : (1) analyse SCCP ; (2) amplification par PCR de l'ITS par des amorces spécifiques. La SSCP a permis de détecter facilement les ITS correspondant à E. alphitoides et E. quercicola. Par contre, les ITS plus rares correspondant à E. hypophylla et Phyllactinia guttata (sensu lato) n'ont été détectés que par amplification spécifique.• L'étude a confirmé la forte prédominance (avec une fréquence supérieure à 80 %) de la séquence d'ITS associée à E. alphitoides. Les isolats présentant la même séquence d'ITS qu'E. quercicola, espèce récemment décrite et encore non mentionnée en Europe, ont également été retrouvés dans toutes les régions françaises à une fréquence importante (15 % en moyenne pour l'échantillonnage...

European oak powdery mildew: impact on trees, effects of environmental factors, and potential effects of climate change

“…However, another species, Erysiphe quercicola first described on oak in Japan by Takamatsu et al (2007), was detected in about 20 % of oak powdery mildew samples. Two other species, Erysiphe hypophylla and Phyllactinia roboris were far less frequent, representing only few percent of the samples (Mougou-Hamdane et al 2010).…”

“…Mougou et al (2008) showed that the same symptoms can be associated with four different powdery mildew lineages (probably cryptic species) currently co-existing in Europe. In a large survey in France, Erysiphe alphitoides, the species which was described in 1911, was the most common species (Mougou-Hamdane et al 2010). However, another species, Erysiphe quercicola first described on oak in Japan by Takamatsu et al (2007), was detected in about 20 % of oak powdery mildew samples.…”

An evolutionary ecology perspective to address forest pathology challenges of today and tomorrow

“…In particular, recent studies using DNA sequences have clarified the taxonomic confusion that existed for some important forest pathogens, leading to revisions such as the split of the red band needle blight of Pinus into two distinct species: Dothistroma septosporum and Dothistroma pini (Barnes et al 2004), the redefinition of the genus Ceratocystis (de Beer et al 2014), and the description and characterization of the Gibberella fujikuroi complex (Kvas et al 2009). Another example is oak powdery mildew in Europe, which was shown to be associated with four different cryptic species often coexisting in the same stands: Erysiphe alphitoides, Erysiphe quercicola, Erysiphe hypophylla, and Phyllactinia roboris (Mougou et al 2008;Mougou-Hamdane et al 2010). The geographic origin of these species is still hypothetical , as is the possibility that some of them evolved in sympatry in their region of origin, as a result of evolutionary branching.…”

First Report of Ampelomyces quisqualis from Sycamore and Crape Myrtle and Its Potential as a Mycoparasite of Powdery Mildew

“…In Korea, Ampelomyces has been revealed on 19 species of the genus Erysiphe and occurs on a wide range of plants [7]. To our knowledge, there were no previous published literature records of this species as a mycoparasite of powdery mildew disease on sycamore (Platanus occidentalis L.) and crape myrtle (Lagerstroemia indica L.) hosts.Many researches on A. quisqualis has focused on its potential use as a biocontrol agent against powdery mildews on various crops and woody plants [8,9]. At present, a few Ampelomyces isolates have already been registered as biocontrol agents of powdery mildews, e.g.…”

“…Many researches on A. quisqualis has focused on its potential use as a biocontrol agent against powdery mildews on various crops and woody plants [8,9]. At present, a few Ampelomyces isolates have already been registered as biocontrol agents of powdery mildews, e.g.…”