Novel species of Huntiella from naturally-occurring forest trees in Greece and South Africa.

Huntiella species are wood-infecting, filamentous ascomycetes that occur in fresh wounds on a wide variety of tree species. These fungi are mainly known as saprobes although some have been associated with disease symptoms. Six fungal isolates with typical culture characteristics of Huntiella spp. were collected from wounds on native forest trees in Greece and South Africa. The aim of this study was to identify these isolates, using morphological characters and multigene phylogenies of the rRNA internal transcribed spacer (ITS) region, portions of the ß-tubulin (BT1) and translation elongation factor 1α (TEF-1α) genes. The mating strategies of these fungi were also determined through PCR amplification of mating type genes. The study revealed two new species; one from Platanus orientalis in Greece and one from Colophospermum mopane and Senegalia nigrescens in South Africa. These novel taxa have been provided with the names, H. hellenica sp. nov. and H. krugeri sp. nov., respectively. The former species was found to have a homothallic and the latter a heterothallic mating system.

Insights into the phylogeny of Northern Hemisphere Armillaria: Neighbor-net and Bayesian analyses of translation elongation factor 1-α gene sequences.

Armillaria possesses several intriguing characteristics that have inspired wide interest in understanding phylogenetic relationships within and among species of this genus. Nuclear ribosomal DNA sequence-based analyses of Armillaria provide only limited information for phylogenetic studies among widely divergent taxa. More recent studies have shown that translation elongation factor 1-α (tef1) sequences are highly informative for phylogenetic analysis of Armillaria species within diverse global regions. This study used Neighbor-net and coalescence-based Bayesian analyses to examine phylogenetic relationships of newly determined and existing tef1 sequences derived from diverse Armillaria species from across the Northern Hemisphere, with Southern Hemisphere Armillaria species included for reference. Based on the Bayesian analysis of tef1 sequences, Armillaria species from the Northern Hemisphere are generally contained within the following four superclades, which are named according to the specific epithet of the most frequently cited species within the superclade: (i) Socialis/Tabescens (exannulate) superclade including Eurasian A. ectypa, North American A. socialis (A. tabescens), and Eurasian A. socialis (A. tabescens) clades; (ii) Mellea superclade including undescribed annulate North American Armillaria sp. (Mexico) and four separate clades of A. mellea (Europe and Iran, eastern Asia, and two groups from North America); (iii) Gallica superclade including Armillaria Nag E (Japan), multiple clades of A. gallica (Asia and Europe), A. calvescens (eastern North America), A. cepistipes (North America), A. altimontana (western USA), A. nabsnona (North America and Japan), and at least two A. gallica clades (North America); and (iv) Solidipes/Ostoyae superclade including two A. solidipes/ostoyae clades (North America), A. gemina (eastern USA), A. solidipes/ostoyae (Eurasia), A. cepistipes (Europe and Japan), A. sinapina (North America and Japan), and A. borealis (Eurasia) clade 2. Of note is that A. borealis (Eurasia) clade 1 appears basal to the Solidipes/Ostoyae and Gallica superclades. The Neighbor-net analysis showed similar phylogenetic relationships. This study further demonstrates the utility of tef1 for global phylogenetic studies of Armillaria species and provides critical insights into multiple taxonomic issues that warrant further study.

Canker Stain: A Lethal Disease Destroying Iconic Plane Trees.

In Europe, both Oriental plane and London plane trees are seriously threatened by the invasive fungal pathogen Ceratocystis platani (Walter) Engelbr. & T.C. Harr., the causal agent of canker stain disease (CSD) of plane trees. The fungus is considered to be indigenous to North America and was accidently introduced into Europe during World War II, where it continues to spread clonally. The impact of CSD in Europe can be compared with notorious tree diseases such as Dutch elm disease, chestnut blight, and more recently Ash dieback, which have all caused devastating losses to natural woody ecosystems and ornamental trees. In Italy and France, C. platani has caused widespread mortality to London plane trees and the pathogen has also been recorded in Switzerland and Spain. However, the most dramatic impact of the disease has been in Greece in natural stands of Oriental plane. The objective of this feature article is to review current knowledge regarding CSD and to highlight the dramatic and devastating nature of the disease. An important aim is also to highlight the risk of C. platani spreading northward in Europe and eastward to Asia in the natural and cultivated range of oriental and London plane.

Molecular and morphological characterization of Dothiorella casuarini sp. nov. and other Botryosphaeriaceae with diplodia-like conidia.

After recent changes to the taxonomy of the Botryosphaeriaceae species with diplodia-like (= dark, ovoid, often pigmented) conidia are considered to belong to at least three genera including Diplodia, Lasiodiplodia and Dothiorella. In a recent molecular phylogenetic study it became apparent that two groups of isolates with diplodia-like conidia required taxonomic revision. One group of isolates originated from Cupressus sempervirens in Greece and Cyprus and had been identified as D. pinea f. sp. cupressi based on morphological characteristics. The other isolates originated from a Casuarina sp. in Australia and were superficially similar to those in the first group based on their morphologically similar diplodia-like conidia. The aim of this study was to resolve the taxonomy of these two groups of isolates by combining the information from the multiple gene genealogies with morphological characters. The results showed that the isolates from C. sempervirens in Greece and Cyprus represent D. cupressi. The isolates from Casuarina in Australia belong to the more distantly related genus Dothiorella and represent a distinct species that is described here as Do. casuarini sp. nov.

Origin of Ceratocystis platani on Native Platanus orientalis in Greece and Its Impact on Natural Forests.

Canker stain of plane tree recently was reported in a small area of southwestern Greece on natural populations of the important riparian species, oriental plane tree, Platanus orientalis. The fungus Ceratocystis platani (= C. fimbriata f. platani) was successfully isolated from infected, stained wood of 15 dead or dying trees on the Peloponnese Peninsula. Genetic analyses of these 15 isolates from Greece, using nuclear and mitochondrial DNA fingerprints, showed the fungus to be identical to the genotype reported from Italy, France, and Switzerland. A polymerase chain reaction-based microsatellite analysis of eight polymorphic loci discovered a new microsatellite allele in one of the isolates from Greece, but this may be due to a mutation after introduction of a single strain. Earlier studies indicated that the most common European genotype had been introduced from eastern North America to Italy during World War II. The recent introduction to Greece appears to have originated from Italy, France, or Switzerland, rather than from eastern North America, where the fungus is native. The pathogen is having a dramatic impact on the natural population of P. orientalis in southwestern Greece, and containment measures should be imposed before it spreads throughout the natural range of this ecologically and historically important host.