Toyozo Sato

Phylogeny of Discosia and Seimatosporium, and introduction of Adisciso and Immersidiscosia genera nova

Discosia (teleomorph unknown) and Seimatosporium (teleomorph Discostroma) are saprobic or plant pathogenic, coelomycetous genera of so-called ‘pestalotioid fungi’ within the Amphisphaeriaceae (Xylariales). They share several morphological features and their generic circumscriptions appear unclear. We investigated the phylogenies of both genera on the basis of SSU, LSU and ITS nrDNA and β-tubulin gene sequences. Discosia was not monophyletic and was separated into two distinct lineages. Discosia eucalypti deviated from Discosia clade and was transferred to a new genus, Immersidiscosia, characterised by deeply immersed, pycnidioid conidiomata that are intraepidermal to subepidermal in origin, with a conidiomatal beak having periphyses. Subdividing Discosia into ‘sections’ was not considered phylogenetically significant at least for the three sections investigated (sect. Discosia, Laurina, and Strobilina). We recognised Seimatosporium s.l. as a monophyletic genus. An undescribed species belonging to Discosia with its associated teleomorph was collected on living leaves of Symplocos prunifolia from Yakushima Island, Japan. We have therefore established a new teleomorphic genus, Adisciso, for this new species, A. yakushimense. Discostroma tricellulare (anamorph: Seimatosporium azaleae), previously described from Rhododendron species, was transferred to Adisciso based on morphological and phylogenetic grounds. Adisciso is characterised by relatively small-sized ascomata without stromatic tissue, obclavate to broadly cylindrical asci with biseriate ascospores that have 2 transverse septa, and its Discosia anamorph. Based on these features, it can easily be distinguished from Discostroma, a similar genus within the Amphisphaeriaceae.

Taxonomic re-examination of several Japanese Stemphylium strains based on morphological and molecular phylogenetic analyses

Most of the many Stemphylium species on record as plant pathogens in Japan have been identified by morphology. Using molecular phylogenetic analysis of four loci (rDNA-ITS, EF-1α, GPD, and vmaA-vpsA) combined, we re-examined the taxonomy of 31 Stemphylium strains that had been identified morphologically before or after their deposit in the NIAS Genebank, Japan. In the present study, these Japanese strains were separated into three groups (Groups A, C, and E). Sixteen Japanese strains formed a new subgroup (designated Subgroup C2) that contained no type or ex-type strains of existing species. Four of the strains had been identified correctly, whereas the other 27 strains appear to have been misidentified based on our phylogenetic analysis. We examined the conidial morphology of four representative misidentified strains selected from each clade. While the morphological characteristics of a strain isolated from Welsh onion resembles those of the S. vesicarium type, this strain belongs to Subgroup C2 rather than Subgroup C1 and, therefore, could not be identified at the species level. Conversely, three pathogenic strains isolated from aster, asparagus, and Chinese chive were re-identified based on our combined morphological and phylogenetic data. We propose the scientific names of the aster leaf spot pathogen as S. lycopersici, and the asparagus Stemphylium leaf spot and Chinese chive brown leaf blight pathogens as S. herbarum.

Pathogenicity of Stemphylium lycopersici isolated from rotted tobacco seeds on seedlings and leaves

A preemergence damping-off of tobacco (Nicotiana tabacum L.) was found in Fukuoka, Japan, in 2009. A fungus repeatedly isolated from the black-rotted seeds reproduced the symptoms in tobacco seeds, and the preemergence damping-off developed after flower and soil inoculation with the fungus. Brown spots and blight developed on leaves of tobacco seedlings after inoculation with the isolate. The fungus was reisolated from the rotted seeds and blighted leaves. The causal fungus was identified as Stemphylium lycopersici based on morphology and phylogenetic analysis. This is the first report to confirm the pathogenicity of S. lycopersici in tobacco in the world.

Black leaf spot of Japanese persimmon (Diospyros kaki), a new disease caused by Adisciso kaki sp. nov.

A new defoliating disease with severe leaf spot of Japanese persimmon (Diospyros kaki) was found in Shimane Prefecture. A fungus, isolated from the ascospores that had formed on the leaf spot, was demonstrated to reproduce the symptoms on leaves and described as a new species, Adisciso kaki, based on morphological and molecular phylogenetic analyses. This fungus is characterized by small ascomata without clypeus, obclavate to broadly cylindrical asci with an amyloid apical apparatus, and hyaline ascospores with a submedian septum. We coined the name black leaf spot (Kurohoshi-rakuyo-byo, in Japanese) for the new disease.

Phylogenetic relationship and fungicide sensitivity of members of the Colletotrichum gloeosporioides species complex from apple

The members of the Colletotrichum gloeosporioides species complex (CGSC), the dominant pathogens of apple bitter rot in Nagano prefecture, Japan, were reidentified and the relationship between the species and fungicide sensitivity was revealed. Based on phylogenetic analysis of the ApMat locus with the neighbor-joining (NJ) method, isolates from apple contained three species of the CGSC; C. fructicola, C. aenigma, C. siamense, and three clades of the CGSC: Clade V, S and K. Colletotrichum fructicola and Clade S dominated in Nagano Prefecture. Isolates of C. siamense, C. aenigma and Clade V, S and K remained sensitive to benomyl and quinone outside inhibitor (QoI) fungicides, while C. fructicola often developed resistance to benomyl and QoI fungicides. These results suggest that the development of fungicide resistance differs among members of the CGSC.

Studies on the taxonomy and identification of plant pathogenic fungi, based on morphology and phylogenetic analyses, and fungal pathogenicity focused on host specificity

Of the approximately 5400 plant pathogenic organisms, over 4600 species are filamentous fungi, which cause threequarters of all plant diseases recorded in Japan (NARO Genebank 2016). The accurate identification of plant pathogenic fungi is essential to both precise diagnosis and effective disease control. Recently, more exact diagnosis using the DNA sequences of pathogenic fungi and/or molecular biological methods has become available for some pathogens, accompanied by the development of fungal classification, taxonomy and identification based on molecular phylogenetic analyses. However, the taxonomic identities of many pathogenic fungi reported in Japan have not yet been reexamined by these analyses; therefore, they are still identified only by morphology. Additionally, even if molecular biological diagnostic methods were developed for these fungi, they may prove impractical for use in daily agricultural production because of the need for prompt diagnosis and concerns of cost and/or labor. I and my colleagues, therefore, have reidentified plant pathogenic strains of fungi collected in Japan based on molecular phylogenetic analyses and the latest taxonomic system, as well as clarified the interspecific morphological differences among these strains to establish a simple taxonomic key useful for practitioners engaged in disease control. In addition, we found numerous new diseases and pathogenic fungi or newly identified them in Japan, then clarified the pathogenic traits of these pathogens, including host specificity, host range and pathogenic differentiation. The main outcomes of these studies on anthracnose fungi and other plant pathogenic fungi are summarized in this article.

Brown root rot caused by phellinus noxius in the Ogasawara (Bonin) islands, southern Japan - current status of the disease and its host plants

An unusual mortality of several woody plant species was recently found in the Ogasawara Islands. Here, we show that brown root rot caused by Phellinus noxius was the primary cause of this unusual tree death. Typical symptoms of the disease were confirmed on 41 plant species in 29 plant families. Among them, 23 were novel hosts of P. noxius, including 15 species endemic to the Ogasawara Islands. Six species were new host records in Japan.

Brevicollum, a new genus in Neohendersoniaceae, Pleosporales

ABSTRACT A new genus, Brevicollum, is established for two new species, B. hyalosporum on Syzygium samarangense and B. versicolor on Volkameria inermis, in Japan. This genus is characterized by the presence of immersed ascomata with an excentric to central, short cylindrical ostiolar neck, thin ascomatal wall, clavate asci with a shallow ocular chamber, and broadly fusiform, hyaline to pale brown ascospores with a sheath. Molecular phylogenetic analyses based on a combined data set of sequences of 18S and 28S nuc rDNA genes and the second largest subunit of RNA polymerase II (RPB2) revealed that Brevicollum is a member of Neohendersoniaceae (Pleosporales, Dothideomycetes). The genera Brevicollum, Crassiparies, Medicopsis, and Neohendersonia are accepted in Neohendersoniaceae. Revised descriptions of Crassiparies and its type species, C. quadrisporus, are provided based on the holotype and a newly obtained specimen and isolate. An asexual morph of C. quadrisporus is reported for the first time. The nuc rDNA internal transcribed spacer (ITS1-5.8S-ITS2 = ITS) phylogenetic tree of the newly collected species (B. hyalosporum, B. versicolor, and C. quadrisporus), and the unnamed or provisionally identified endophytic species, suggests a broader distribution of Brevicollum and Crassiparies species.

First report of flyspeck of mango caused by Stomiopeltis sp. in Japan

Flyspeck symptoms were found on mango (Mangifera indica L.) in Okinawa Prefecture, Japan in June 2014. Just before harvest, surfaces of fruits and green branches developed groups of tiny black dots within dark smudges. A fungus was isolated from the dots on both fruits and branches. The isolates were identified as Stomiopeltis sp. based on pathogenicity, morphology and molecular phylogenetic analyses with rDNA-ITS and LSU sequences. This is the first report of flyspeck (susuten-byo in Japanese) on mango caused by Stomiopeltis sp. in Japan.