Cheng-Ming Tian

Cytospora species associated with walnut canker disease in China, with description of a new species C. gigalocus.

Cytospora species associated with canker disease are presently difficult to identify because of lack of ex-types cultures with molecular data, few distinguishable characters, and only Internal transcribed spacer (ITS) sequence data is available for most Cytospora strains in GenBank. We report on Cytospora species from the walnut tree in China. Collections were subjected to morphological and phylogenetic study. The relatedness of species associated with walnut canker were established using combined ITS, nrLSU, β-tubulin, and actin gene sequence data. Cytospora atrocirrhata, Cytospora chrysosperma, Cytospora sacculus, and a new species, Cytospora gigalocus, were identified causing canker disease of walnut. Cytospora gigalocus is formally described and compared with most similar species. Cytospora chrysosperma and C. sacculus have previously been recorded from walnut, whereas C. atrocirrhata is reported as associated with walnut canker for the first time. This is the first study that has established the Cytospora species causing walnut canker in China using a multi-phasic approach. All species are recorded as being associated with walnut canker disease in China for the first time.

Diaporthe rostrata, a novel ascomycete from Juglans mandshurica associated with walnut dieback

Diaporthe rostrata sp. nov., collected from Juglans mandshurica in China, is described and illustrated in this paper. The new species is introduced based on its holomorphic morphology plus support from phylogenetic analysis. The sexual and asexual morphs produce rostrate host tissue around the necks on infected branches or twigs and have aseptate alpha conidia, while the sexual morph produces 1-septate ascospores. The new species is compared with other taxa from Juglans spp.

Phylogeny and taxonomy of the scab and spot anthracnose fungus Elsinoë (Myriangiales, Dothideomycetes)

Species of Elsinoë are phytopathogens causing scab and spot anthracnose on many plants, including some economically important crops such as avocado, citrus, grapevines, and ornamentals such as poinsettias, field crops and woody hosts. Disease symptoms are often easily recognisable, and referred to as signature-bearing diseases, for the cork-like appearance of older infected tissues with scab-like appearance. In some Elsinoë-host associations the resulting symptoms are better described as spot anthracnose. Additionally the infected plants may also show mild to severe distortions of infected organs. Isolation of Elsinoë in pure culture can be very challenging and examination of specimens collected in the field is often frustrating because of the lack of fertile structures. Current criteria for species recognition and host specificity in Elsinoë are unclear due to overlapping morphological characteristics, and the lack of molecular and pathogenicity data. In the present study we revised the taxonomy of Elsinoë based on DNA sequence and morphological data derived from 119 isolates, representing 67 host genera from 17 countries, including 64 ex-type cultures. Combined analyses of ITS, LSU, rpb2 and TEF1-α DNA sequence data were used to reconstruct the backbone phylogeny of the genus Elsinoë. Based on the single nomenclature for fungi, 26 new combinations are proposed in Elsinoë for species that were originally described in Sphaceloma. A total of 13 species are epitypified with notes on their taxonomy and phylogeny. A further eight new species are introduced, leading to a total of 75 Elsinoë species supported by molecular data in the present study. For the most part species of Elsinoë appear to be host specific, although the majority of the species treated are known only from a few isolates, and further collections and pathogenicity studies will be required to reconfirm this conclusion.

Cytospora from Ulmus pumila in Northern China

Cytospora species are cosmopolitan, and commonly associated with dieback and canker diseases of numerous hosts. In the present study, isolates were collected and identified from diseased branches or twigs of Ulmus pumila in northern China. The morphological characteristics and multilocus phylogeny (act1, ITS, LSU, tefA and tubB) indicate four distinct lineages with high branch support, i.e., C. carbonacea, C. chrysosperma, C. ribis and C. pruinopsis sp. nov. Cytospora pruinopsis is distinguishable from the other Cytospora spp. on Ulmus by its single conidiomatal locule with one ostiole per disc, and its smaller conidia. This study represents the first attempt to clarify the taxonomy of Cytospora spp. associated with canker and dieback symptoms of Ulmus pumila in northern China.

Two new species and one new record of Melampsora on willows from China

Two new species of rust fungi, Melampsora salicis-purpureae sp. nov. and M. salicis-argyraceae sp. nov., and a new record, M. iranica, are described from China based on morphological characteristics and molecular phylogeny of the internal transcribed spacer (ITS1 and ITS2) regions including 5.8S of the ribosomal RNA gene. Melampsora salicis-purpureae on Salix purpurea was characterized by amphigenous uredinia, subepidermal teliospores, and relatively shorter teliospores and amphigenous telia. Melampsora salicis-argyraceae on S. argyaceae possessed sparse spines on urediniospores, epiphyllous telia and subepidermal teliospores with slightly thickened apex. In addition, specimens on S. alba and S. psammophyla were identified as M. iranica.

The C2H2 transcription factor VdMsn2 controls hyphal growth, microsclerotia formation, and virulence of Verticillium dahliae

Verticillium dahliae is a notorious pathogen that causes vascular wilt disease in numerous plant species worldwide. The fungus produces melanized microsclerotia, which helps it survive adverse environmental conditions that it may encounter within its hosts and in the soil. Previously, we determined that the high osmolarity glycerol (HOG) pathway is involved in the environmental stress response of V. dahliae. In this study, we investigated the function of VdMsn2, a homologue of the yeast C2H2 transcription factor Msn2, which is predicted to function as a downstream player in the HOG pathway. Disruption of VdMsn2 has a discernible effect on hyphal growth and septation, but not on diverse stresses including hyperosmotic stresses and cell wall inhibitory agents. Furthermore, we show that VdMsn2 deletion mutants produce significantly more microsclerotia than the wild-type and exhibit attenuated virulence to smoke trees because of poor penetration. Taken together, our findings suggest that VdMsn2 controls hyphal growth, microsclerotia formation, and virulence but does not significantly contribute to stress responses in V. dahliae.

Melanconis (Melanconidaceae) associated with Betula spp. in China

Melanconis is a monotypic genus in Melanconidaceae and mostly restricted to hardwood trees in Betulaceae, as endophytes and plant pathogens. During a routine forest pathogens investigation of canker disease in China, some melanconidaceous fungi were observed on Betula spp. with various symptoms. The primary objective of the present study was to identify species of Melanconidaceae associated with canker and dieback of Betula spp. in China. In the present study, we investigated 45 isolates using morphology and multi-gene phylogenetic analyses based on the internal transcribed spacers (ITS), nuclear large subunit rDNA (LSU), RNA polymerase II subunit 2 (rpb2), translation elongation factor 1-α (tef1-α) and β-tubulin (tub). Three melanconidaceous taxa were identified: Melanconis betulae sp. nov., M. itoana and M. stilbostoma. This is the first phylogenetic study evaluating species of Melanconis associated with canker and dieback disease of Betula spp. in China, resulting in the description of a novel species and the report of M. itoana as a new record.

Integrating a Numerical Taxonomic Method and Molecular Phylogeny for Species Delimitation of Melampsora Species (Melampsoraceae, Pucciniales) on Willows in China

The species in genus Melampsora are the causal agents of leaf rust diseases on willows in natural habitats and plantations. However, the classification and recognition of species diversity are challenging because morphological characteristics are scant and morphological variation in Melampsora on willows has not been thoroughly evaluated. Thus, the taxonomy of Melampsora species on willows remains confused, especially in China where 31 species were reported based on either European or Japanese taxonomic systems. To clarify the species boundaries of Melampsora species on willows in China, we tested two approaches for species delimitation inferred from morphological and molecular variations. Morphological species boundaries were determined based on numerical taxonomic analyses of morphological characteristics in the uredinial and telial stages by cluster analysis and one-way analysis of variance. Phylogenetic species boundaries were delineated based on the generalized mixed Yule-coalescent (GMYC) model analysis of the sequences of the internal transcribed spacer (ITS1 and ITS2) regions including the 5.8S and D1/D2 regions of the large nuclear subunit of the ribosomal RNA gene. Numerical taxonomic analyses of 14 morphological characteristics recognized in the uredinial-telial stages revealed 22 morphological species, whereas the GMYC results recovered 29 phylogenetic species. In total, 17 morphological species were in concordance with the phylogenetic species and 5 morphological species were in concordance with 12 phylogenetic species. Both the morphological and molecular data supported 14 morphological characteristics, including 5 newly recognized characteristics and 9 traditionally emphasized characteristics, as effective for the differentiation of Melampsora species on willows in China. Based on the concordance and discordance of the two species delimitation approaches, we concluded that integrative taxonomy by using both morphological and molecular variations was an effective approach for delimitating Melampsora species on willows in China.

A morphological and molecular survey of Japanese Melampsora species on willows reveals a new species and two new records

During morphological and molecular phylogenetic studies of Melampsora species on willows, one novel species, Melampsora salicis-reinii sp. nov., and two new records, M. ribesii-viminalis and M. ribesii-purpureae, are described from Japan. Melampsora salicis-reinii on Salix reinii was characterized by its amphigenous telia and ellipsoid urediniospores with echinulate spines on a rugose surface. Phylogenetic results using the rDNA ITS region (complete ITS1, 5.8S rRNA gene and ITS2) supported morphological elucidation, and both morphological and molecular evidences supported M. salicis-reinii as a new species. In addition, M. ribesii-viminalis was identified on S. pet-susu and S. sachalinensis, and M. ribesii-purpureae was recognized on S. integra. These two Melampsora species were reported as new records in Japan for the first time.

Families and genera of diaporthalean fungi associated with canker and dieback of tree hosts

In this study we accept 25 families in Diaporthales based on phylogenetic analyses using partial ITS, LSU, rpb2 and tef1-α gene sequences. Four different families associated with canker and dieback of tree hosts are morphologically treated and phylogenetically compared. These include three new families (Diaporthostomataceae, Pseudomelanconidaceae, Synnemasporellaceae), and one new genus, Dendrostoma (Erythrogloeaceae). Dendrostoma is newly described from Malus spectabilis, Osmanthus fragrans and Quercus acutissima having fusoid to cylindrical, bicellular ascospores, with three new species namely D. mali, D. osmanthi and D. quercinum. Diaporthostomataceae is characterised by conical and discrete perithecia with bicellular, fusoid ascospores on branches of Machilus leptophylla. Pseudomelanconidaceae is defined by conidiogenous cells with apical collarets and discreet annellations, and the inconspicuous hyaline conidial sheath when mature on Carya cathayensis, compared to morphologically similar families Melanconidaceae and Juglanconidaceae. Synnemasporellaceae is proposed to accommodate fungi with synnematous conidiomata, with descriptions of S. toxicodendri on Toxicodendron sylvestre and S. aculeans on Rhus copallina.