Morphophylogenetic study revealed that Erysiphe gracilis (powdery mildew of evergreen oaks, Erysiphales) is a species complex consisting of six different species

Evolutionary dependence of host type and chasmothecial appendage morphology in obligate plant parasites belonging to Erysipheae (powdery mildew, Erysiphaceae)

Evolutionary relationships between the morphological and ecological traits of fungi are poorly understood. The appendages of chasmothecia, which are sexual reproductive organs of Erysiphaceae, are considered to play a crucial role in the overwintering strategies of these fungi on host plants. Previous studies suggested that both the host type and appendage morphology evolved at the same nodes and transitioned from complex appendages on deciduous hosts to simple appendages on herb/evergreen hosts. However, the evolutionary dependence between host type and appendage morphology remains unproven owing to the limited species data used in analyses. To elucidate the evolutionary relationship between host type and appendage morphology, we used phylogenetic comparative methods (PCMs) to investigate the state transition, ancestral state, evolutionary dependence, and contingent evolution within Erysipheae, the largest and most diverse tribe in Erysiphaceae. Our PCMs, based on a comprehensive data set of Erysipheae, revealed that the most ancestral states were deciduous host types and complex appendages. From these ancestral states, convergent evolution toward the herb/evergreen host types and simple appendages occurred multiple times at the same nodes. For the first time in Erysiphaceae, we detected an evolutionary dependence between host type and appendage morphology. This is one of the few examples in which evolutionary dependence between host phenology and morphological traits in plant-parasitic fungi was demonstrated using PCMs. Appendage simplification on herb/evergreen hosts and complications on deciduous hosts can be reasonably explained by the functional advantages of each appendage type in different overwintering strategies. These expected appendage functions can explain approximately 90% of host type and appendage morphology combinations observed in the analyzed taxa. However, our results also highlighted the occurrence of evolutionary shifts that deviate from the expected advantages of each appendage morphology. These seemingly irrational shifts might be interpretable from the flexibility of overwintering strategies and quantification of appendage functions.

Phylogeny and taxonomy of the genera of Erysiphaceae, part 4: Erysiphe (the "Uncinula lineage")

This is the fourth contribution within an ongoing series dedicated to the phylogeny and taxonomy of powdery mildews. This particular installment undertakes a comprehensive evaluation of a group previously referred to as the "Uncinula lineage" within Erysiphe. The genus Erysiphe is too large to be assessed in a single paper; thus, the treatment of Erysiphe is split into three parts, according to phylogenetic lineages. The first paper, presented here, discusses the most basal lineage of Erysiphe and its relationship to allied basal genera within tribe Erysipheae (i.e., Brasiliomyces and Salmonomyces). ITS+28S analyses are insufficient to resolve the basal assemblage of taxa within the Erysipheae. Therefore, phylogenetic multilocus examinations have been carried out to better understand the evolution of these taxa. The results of our analyses favor maintaining Brasiliomyces, Bulbomicroidium, and Salmonomyces as separate genera, at least for the interim, until further phylogenetic multilocus data are available for additional basal taxa within the Erysipheae. The current analyses also confirmed previous results that showed that the "Uncinula lineage" is not exclusively composed of Erysiphe species of sect. Uncinula but also includes some species that morphologically align with sect. Erysiphe, as well as species that had previously been assigned to Californiomyces and Typhulochaeta. Numerous sequences of Erysiphe species from the "Uncinula lineage" have been included in the present phylogenetic analyses and were confirmed by their position in well-supported species clades. Several species have been sequenced for the first time, including Erysiphe clintonii, E. couchii, E. geniculata, E. macrospora, and E. parvula. Ex-type sequences are provided for 16 taxa including E. nothofagi, E. trinae, and E. variabilis. Epitypes are designated and ex-epitype sequences are added for 18 taxa including Erysiphe carpophila, E. densa, and U. geniculata var. carpinicola. The new species Erysiphe canariensis is described, and the new names E. hosagoudarii and E. pseudoprunastri and the new combination E. ampelopsidis are introduced.

Phylogeny and taxonomy of the genera of Erysiphaceae, part 1: Golovinomyces

Powdery mildews are a monophyletic group of obligate plant pathogenic fungi in the family Erysiphaceae. Powdery mildews are economically important in that they cause damage to many agriculturally significant crops and plants in ecologically important habitats. In this contribution, we introduce a new series of publications focusing on the phylogeny and taxonomy of this group, with an emphasis on specimens collected from North America. The first part of the series focuses on the genus Golovinomyces and includes a section detailing the powdery mildew species concept. We conducted analyses of Golovinomyces spp. with available rDNA sequence data from GenBank and supplemented the data set with rDNA (ITS, 28S, IGS) as well as protein-coding (GAPDH) data from 94 North American collections. Many of the species evaluated are included in phylogenetic and morphological analyses for the first time, including the American species G. americanus, G. brunneopunctatus, G. californicus, G. greeneanus, G. hydrophyllacearum, and G. sparsus. A special emphasis was placed on acquiring ex-type or ex-epitype sequences or presenting reference sequences for phylogenetic-taxonomic purposes. Three new species, G. eurybiarum, G. galiorum, and G. malvacearum, are described, and the new combinations G. fuegianus, G. mutisiae, and G. reginae are introduced. Ex-holotype sequences of Erysiphe sparsa (≡ G. sparsus) reveal that it should be reduced to synonymy with G. ambrosiae, and ex-epitype sequences of G. valerianae reveal that it should be reduced to synonymy with G. orontii. Multiple epitypes are designated with ex-epitype sequences.

Heluta V, Liu SY, Feng J, Takamatsu S. Phylogeny and taxonomy of Erysiphe species (powdery mildew: Erysiphaceae) occurring on the ash trees (Fraxinus spp.)

The genus Fraxinus (Oleaceae), known as ash trees, currently comprises 43 recognized species that are distributed in temperate and subtropical regions of the northern hemisphere. Two Erysiphe (sect. Uncinula) species have been known on Fraxinus spp. so far. In this study, Fraxinus powdery mildews from different areas of the world were collected to make molecular and morphological analyses. These specimens are divided into three distinct molecular phylogenetic groups, which are distinguishable by their morphology and/or host preference. The powdery mildew occurring on F. apertisquamifera and F. lanuginosa is described as a new species, E. fraxinea. Epitypes are designated for E. fraxinicola and E. salmonii. Applying previous traditional species delimitations, various hosts were shared by E. fraxinicola as well as E. salmonii, but the current analyses strongly suggest strict host specificity among these three powdery mildew species. Evolutionary timing calculated by molecular clock analysis suggests co-evolution of powdery mildews with their Fraxinus hosts.

Phylogeny and taxonomy of powdery mildew caused by Erysiphe species on Corylus hosts

Erysiphe species (powdery mildews) on Corylus and Ostrya hosts (Betulaceae subfam. Coryloideae) in Asia and North America are widespread pathogens on these economically and ecologically valuable nut crops. An improved understanding of their phylogeny and taxonomy is of ecological and applied importance. Phylogenetic analyses and morphological reexaminations conducted in this study revealed a higher degree of diversity and cryptic speciation than reflected in earlier species concepts. North American collections on C. cornuta, which were previously assigned to E. corylacearum, proved to constitute a species of its own and are herein introduced as E. cornutae, sp. nov. Two additional North American species, E. coryli-americanae, sp. nov. and E. ostryae, sp. nov., have been detected on C. americana and O. virginiana and are described. They are morphologically similar to E. cornutae, but genetically distinct. Based on phylogenetic analyses, E. corylacearum is an Asian species confined to various Asian Corylus species. Sequence data retrieved from Japanese type material of E. corylicola revealed that this species clusters with sequences from E. elevata on Catalpa species, distant from all other Erysiphe species on Corylus. Morphologically similar, yet distinct, specimens on C. sieboldiana, which were previously assigned to E. corylicola, form a distinct, distant clade. The species involved is described herein as E. pseudocorylacearum, sp. nov. Additionally, an unusual infection of C. sieboldiana in Japan by E. syringae has been shown by means of sequence data. The phylogeny and taxonomy of Erysiphe species belonging to the Corylioideae are discussed in detail, and a key to the species concerned is provided.

Morphophylogenetic analyses revealed that Podosphaera tridactyla constitutes a species complex

Podosphaera tridactyla (s. lat.) is a powdery mildew species occurring on a wide range of Prunus spp. almost worldwide. We have investigated the phylogeny of the Po. tridactyla complex, with special emphasis on potential aspects of cryptic speciation. The results suggested that Po. tridactyla represents a species complex consisting of at least 12 different species. Based on detailed morphological examinations and molecular sequence analyses, we propose dividing Po. tridactyla s. lat. into 10 species, encompassing 7 new species (Po. ampla, Po. pruni-avium, Po. pruni-cerasoidis, Po. prunigena, Po. pruni-lusitanicae, Po. prunina, and Po. pruni-japonicae) and 3 known species (Po. longiseta, Po. salatai, and Po. tridactyla s. str.). Oidium passerinii on Pr. laurocerasus is confirmed as a synonym of Po. tridactyla s. str. Epitypes are designated for Po. tridactyla and Oidium passerinii.