Diaporthe from walnut tree (Juglans regia) in China, with insight of the Diaporthe eres complex

New species of Diaporthe (Diaporthaceae, Diaporthales) from Bauhiniavariegata in China

Diaporthe species are known as endophytes, saprobes and pathogens infecting a wide range of plants and resulting in important crop diseases. In the present study, four strains of Diaporthe were obtained from diseased leaves of Bauhiniavariegata in Guangdong Province, China. Phylogenetic analyses were conducted to identify these strains using five gene regions: internal transcribed spacer (ITS), calmodulin (cal), histone H3 (his3), translation elongation factor 1-α (tef1) and β-tubulin (tub2). The results combined with morphology revealed two new species of Diaporthe named D.bauhiniicola in D.arecae species complex and D.guangzhouensis in D.sojae species complex.

A Phylogenetic and Taxonomic Revision of Discula theae-sinensis, the Causal Agents of Anthracnose on Camellia sinensis

Tea (Camellia sinensis (L.) Kuntze) is one of the most important economic plants in China, and has many benefits for human health. Anthracnose is one of the most serious diseases of tea in China, and control of the fungus is important since most Chinese cultivars are susceptible to it. The agent of tea anthracnose was initially described as Gloeosporium theae-sinensis I. Miyake in Japan, which was later transferred to Discula, but this taxonomic position remains problematic. To shed light on these taxonomic and phylogenetic issues, the tea anthracnose pathogens were re-studied. Combining the morphological characteristics and a multigene phylogenetic analysis of nrITS, nrLSU, rpb2, and tef1 sequence data, a new genus Sinodiscula was proposed to accommodate the causal fungi of tea anthracnose, including a new species Sinodiscula camellicola and a new combination Sinodiscula theae-sinensis. Furthermore, the pathogenicity of the pathogens was determined according to Koch's postulates. This study thoroughly resolves the long-standing taxonomic and phylogenetic problems of the tea anthracnose pathogens.

Four new endophytic species of Diaporthe (Diaporthaceae, Diaporthales) isolated from Cameroon

The genus Diaporthe (Diaporthaceae, Diaporthales) is a large group of fungi frequently reported as phytopathogens, with ubiquitous distribution across the globe. Diaporthe have traditionally been characterized by the morphology of their ana- and teleomorphic state, revealing a high degree of heterogeneity as soon as DNA sequencing was utilized across the different members of the group. Their relevance for biotechnology and agriculture attracts the attention of taxonomists and natural product chemists alike in context of plant protection and exploitation for their potential to produce bioactive secondary metabolites. While more than 1000 species are described to date, Africa, as a natural habitat, has so far been under-sampled. Several endophytic fungi belonging to Diaporthe were isolated from different plant hosts in Cameroon over the course of this study. Phylogenetic analyses based on DNA sequence data of the internal transcribed spacer region and intervening 5.8S nrRNA gene, and partial fragments of the calmodulin, beta-tubulin, histone and the translation elongation factor 1-α genes, demonstrated that these isolates represent four new species, i.e. D.brideliae, D.cameroonensis, D.pseudoanacardii and D.rauvolfiae. Moreover, the description of D.isoberliniae is here emended, now incorporating the morphology of beta and gamma conidia produced by two of our endophytic isolates, which had never been documented in previous records. Moreover, the paraphyletic nature of the genus is discussed and suggestions are made for future revision of the genus.

Profiling Walnut Fungal Pathobiome Associated with Walnut Dieback Using Community-Targeted DNA Metabarcoding

Walnut dieback can be caused by several fungal pathogenic species, which are associated with symptoms ranging from branch dieback to fruit necrosis and blight, challenging the one pathogen-one disease concept. Therefore, an accurate and extensive description of the walnut fungal pathobiome is crucial. To this end, DNA metabarcoding represents a powerful approach provided that bioinformatic pipelines are evaluated to avoid misinterpretation. In this context, this study aimed to determine (i) the performance of five primer pairs targeting the ITS region in amplifying genera of interest and estimating their relative abundance based on mock communities and (ii) the degree of taxonomic resolution using phylogenetic trees. Furthermore, our pipelines were also applied to DNA sequences from symptomatic walnut husks and twigs. Overall, our results showed that the ITS2 region was a better barcode than ITS1 and ITS, resulting in significantly higher sensitivity and/or similarity of composition values. The ITS3/ITS4_KYO1 primer set allowed to cover a wider range of fungal diversity, compared to the other primer sets also targeting the ITS2 region, namely, GTAA and GTAAm. Adding an extraction step to the ITS2 sequence influenced both positively and negatively the taxonomic resolution at the genus and species level, depending on the primer pair considered. Taken together, these results suggested that Kyo set without ITS2 extraction was the best pipeline to assess the broadest fungal diversity, with a more accurate taxonomic assignment, in walnut organs with dieback symptoms.

Studies of Diaporthe (Diaporthaceae, Diaporthales) species associated with plant cankers in Beijing, China, with three new species described

The genus Diaporthe (Diaporthaceae, Diaporthales) comprises endophytes, pathogens and saprophytes, inhabiting a wide range of woody hosts and resulting in serious canker disease. To determine the diversity of Diaporthe species associated with canker disease of host plants in Beijing, China, a total of 35 representative strains were isolated from 18 host genera. Three novel species (D.changpingensis, D.diospyrina and D.ulmina) and four known species (D.corylicola, D.donglingensis, D.eres and D.rostrata) were identified, based on morphological comparison and phylogenetic analyses using partial ITS, cal, his3, tef1-α and tub2 loci. These results provide an understanding of the taxonomy of Diaporthe species associated with canker diseases in Beijing, China.

Three New Species of Diaporthe Causing Leaf Blight on Acer palmatum in China

Diaporthe spp. are often reported as plant pathogens, endophytes, and saprobes. In this study, three new species (Diaporthe foliicola, D. monospora, and D. nanjingensis) on Acer palmatum were described and illustrated based on morphological characteristics and phylogenetic analyses. Phylogenetic relationships of the new species were determined by multilocus phylogenetic analyses based on partial sequences of the internal transcribed spacer (ITS) region, translation elongation factor 1-α (TEF), β-tubulin (TUB), histone H3 (HIS), and calmodulin (CAL) genes. Genealogical concordance phylogenetic species recognition with a pairwise homoplasy index test was used to verify the conclusions of the phylogenetic analyses. All species were illustrated and their morphology and phylogenetic relationships with other related Diaporthe spp. are discussed. In addition, the tests of Koch's postulates showed that the three new species were pathogens causing leaf blight on A. palmatum.

Two new species of Diaporthe (Diaporthaceae, Diaporthales) in China

Species of Diaporthe have been reported as plant endophytes, pathogens and saprobes on a wide range of plant hosts. Strains of Diaporthe were isolated from leaf spots of Smilax glabra and dead culms of Xanthium strumarium in China, and identified based on morphology and molecular phylogenetic analyses of combined internal transcribed spacer region (ITS), calmodulin (cal), histone H3 (his3), translation elongation factor 1-alpha (tef1) and β-tubulin (tub2) loci. As a result, two new species named Diaporthe rizhaoensis and D. smilacicola are identified, described and illustrated in the present study.

Diversity of Endophytic Fungi in Annual Shoots of Prunus mandshurica (Rosaceae) in the South of Amur Region, Russia

Prunus mandshurica is a rare species of the Russian Far East; it is cultivated for fruits and as an ornamental tree. The objective was to determine the fungi associated with young shoots of the Manchurian apricot, which is an important biotic factor for plant viability and productivity. Fungi were isolated by incubation of shoot fragments (unsterilized or surface-sterilized) on a growth medium and identified according to their cultural and morphological characteristics. Diaporthe eres and Nothophoma quercina isolates were identified by multilocus phylogenetic analysis (apn2, cal, tef1-α, tub2 for D. eres, and ITS, rpb2, tub2 for N. quercina). In total, 12 species (Alternaria alternata, A. tenuissima, Aureobasidium pullulans, Cladosporium cladosporioides, C. herbarum, D. eres, Epicoccum nigrum, Fusarium graminearum, F. oxysporum, N. quercina, Sarocladium strictum, and Tripospermum myrti) and one genus (Gliocladium sp.) were found. Alternaria alternata, N. quercina, and D. eres were the most frequent species of the shoots. Alternaria tenuissima and F. oxysporum were also frequent in some collections, while all other species were rare or occasional in occurrence. Molecular analysis of D. eres and N. quercina revealed redundancy of some species within the D. eres species complex and the genus Nothophoma. This is the first report on the fungal inhabitants of asymptomatic shoots of P. mandshurica. Nothophoma quercina was identified in Russia for the first time.

Biodiversity of Fungi Inhabiting European Blueberry in North-Western Russia and in Finland

European blueberry is a common plant in coniferous and mixed forests that grows in Russia, Northern Europe, Asia, United States, and Canada. Among the fungi that cause blueberry diseases, the most harmful are Diaporthe vaccinii and Colletotrichum acutatum. These fungi are included in the consolidated list of quarantine objects of the Eurasian Economic Union and their occurrence and spread in the territory of countries of this Union is subject to strict control. Most taxa of micromycetes, particularly, Diaporthe and Colletotrichum species, can be correctly identified to the species level based on solely molecular phylogenetic features. The aim of the present work was to assess the biodiversity of fungi associated with blueberry growing in North-Western Russia and in Finland using morphological and molecular genetic features. Altogether, the study included 17 specimens of wild blueberry exhibiting necrotic spots on leaves and stem lesions that were collected in 2017 in St. Petersburg and in five districts of Leningrad region, as well as in the Republic of Karelia and in Finland. Analysis of the morphological and molecular genetic features of the fungal strains isolated from these blueberry specimens led to identification of 11 species: Boeremia exigua, Colletotrichum salicis, Diaporthe eres, Fusarium avenaceum, F. incarnatum, F. sporotrichioides, Heterophoma sylvatica, Kalmusia longispora, Microsphaeropsis olivacea, Neocucurbitaria cava, and Sporocadus rosigena. There were also fungi representing two sections of the genus Alternaria: Alternaria and Infectoriae, and micromycetes of the genera Chaetomium, Cladosporium, Coniothyrium, Curvularia, Epicoccum, Penicillium, Pestalotiopsis, Sordaria, and Trichoderma. The species Colletotrichum salicis, Heterophoma sylvatica, Kalmusia longispora, Microsphaeropsis olivacea, and Neocucurbitaria cava were for the first time found in Russia. The species Sporocadus rosigena was for the first time detected in Finland. Fusarium avenaceum, F. incarnatum, and F. sporotrichioides were for the first time observed in association with blueberry plants. The species Diaporthe vaccinii and Colletotrichum acutatum included in the consolidated list of quarantine objects of the Eurasian Economic Union were not detected in this study.

Diaporthe Diversity and Pathogenicity Revealed from a Broad Survey of Soybean Stem Blight in China

Many species in the fungal Diaporthe (anamorph Phomopsis) genus have become a group of the most important pathogens that cause seed decay, stem and pot blight, and stem canker in soybean production worldwide, resulting in significant yield loss. Due to increased disease prevalence but a lack of research, we performed an extensive field survey to isolate and identify the Diaporthe species associated with soybean stem blight in six provinces of China between 2019 and 2020. A total of 92 Diaporthe isolates were identified based on morphological and multilocus phylogenetic analysis and classified into six species: D. longicolla, D. unshiuensis, D. sojae, D. caulivora, D. tectonigena, and an unknown Diaporthe sp. The most frequently identified species was D. longicolla with 57 isolates. High genetic diversity was observed for the D. longicolla isolates, and haplotype network analysis revealed a mixed structure among the population in the six provinces. In comparative pathogenicity assays, different virulence levels were observed among the 92 Diaporthe isolates. The results of this study provide new insights into the Diaporthe spp. associated with soybean stem blight in China and can help in the development of effective management strategies.

Morphology and phylogeny of ascomycetes associated with walnut trees (Juglans regia) in Sichuan province, China

In Sichuan province, walnuts, consisting of Juglans regia, Juglans sigillata, and the hybrid J. regia × J. sigillata, are commercially important edible nuts, and J. regia is the most widespread plant. To date, the diversity and distribution of fungi inhabiting on Juglans have not received enough attention, although there have been studies focusing on pathogens from fruit and stem. In order to update the checklist of fungi associated with Sichuan walnuts, a survey on fungi associated with the three Juglans species from 15 representative regions in Sichuan was conducted. In this article, ten fungi distributed in two classes of Ascomycota (Dothideomycetes and Sordariomycetes) were described based on morpho-molecular analyses, and two novel species, Neofusicoccum sichuanense and Sphaerulina juglandina, a known species of Ophiognomonia leptostyla, and seven new hosts or geographical records of Cladosporium tenuissimum, Diatrypella vulgaris, Helminthosporium juglandinum, Helminthosporium velutinum, Loculosulcatispora hongheensis, Periconia byssoides, and Rhytidhysteron subrufulum were included. Morphological descriptions and illustrations of these fungi are provided.

Comparative Profiling of Wood Canker Pathogens from Spore Traps and Symptomatic Plant Samples Within California Almond and Walnut Orchards

Fungi causing wood canker diseases are major factors limiting productivity and longevity of almond and walnut orchards. The goal of this study was to compare pathogen profiles from spore traps with those of plant samples collected from symptomatic almond and walnut trees and assess if profiles could be influenced by orchard type and age, rainfall amount and frequency, and/or neighboring trees. Three almond orchards and one walnut orchard with different characteristics were selected for this study. Fungal inoculum was captured weekly from nine trees per orchard using a passive spore-trapping device, during a 30-week period in the rainy season (October to April) and for two consecutive years. Fungal taxa identified from spore traps were compared with a collection of fungal isolates obtained from 61 symptomatic wood samples collected from the orchards. Using a culture-dependent approach coupled with molecular identification, we identified 18 known pathogenic species from 10 fungal genera (Ceratocystis destructans, Collophorina hispanica, Cytospora eucalypti, Diaporthe ampelina, Diaporthe chamaeropis/rhusicola, Diaporthe eres, Diaporthe novem, Diplodia corticola, Diplodia mutila, Diplodia seriata, Dothiorella iberica, Dothiorella sarmentorum, Dothiorella viticola, Eutypa lata, Neofusicoccum mediterraneum, Neofusicoccum parvum, Neoscytalidium dimidiatum, and Pleurostoma richardsiae), plus two unidentified Cytospora and Diaporthe species. However, only four species were identified with both methods (Diplodia mutila, Diplodia seriata, Dothiorella Iberica, and E. lata), albeit not consistently across orchards. Our results demonstrate a clear disparity between the two diagnostic methods and caution against using passive spore traps to predict disease risks. In particular, the spore trap approach failed to capture: insect-vectored pathogens such as Ceratocystis destructans that were often recovered from almond trunk and scaffold; Diaporthe chamaeropis/rhusicola commonly isolated from wood samples likely because Diaporthe species have a spatially restricted dispersal mechanism, as spores are exuded in a cirrus; and pathogenic species with low incidence in wood samples such as P. richardsiae and Collophorina hispanica. We propose that orchard inoculum is composed of both endemic taxa that are characterized by frequent and repeated trapping events from the same trees and isolated from plant samples, as well as immigrant taxa characterized by rare trapping events. We hypothesize that host type, orchard age, precipitation, and alternative hosts at the periphery of orchards are factors that could affect pathogen profile. We discuss the limitations and benefits of our methodology and experimental design to develop guidelines and prediction tools for fungal wood canker diseases in California orchards.

Four new species of Diaporthe (Diaporthaceae, Diaporthales) from forest plants in China

Species of Diaporthe inhabit a wide range of plant hosts as plant pathogens, endophytes and saprobes. During trips to collect forest pathogens in Beijing, Jiangxi, Shaanxi and Zhejiang Provinces in China, 16 isolates of Diaporthe were obtained from branch cankers and leaf spots. These isolates were studied by applying a polyphasic approach including morphological, cultural data, and phylogenetic analyses of the nuclear ribosomal internal transcribed spacer (ITS), calmodulin (cal), histone H3 (his3), partial translation elongation factor-1α (tef-1α) and β-tubulin (tub2) loci. Results revealed four new taxa, D.celticola, D.meliae, D.quercicola, D.rhodomyrti spp. nov. and two known species, D.eres and D.multiguttulata.

Caveats of the internal transcribed spacer region as a barcode to resolve species boundaries in Diaporthe

Species in Diaporthe are largely reported as important plant pathogens. Identification of species in this genus has been complemented by morphological and molecular features. However, one important factor delaying this process is the struggle to formulate robust species concepts to create adequate international phytosanitary measures. Regardless of the wide use of the internal transcribed spacer (ITS) rDNA region, established as the primary DNA barcode for fungi, the tendency for intraspecific variation has been reported, misleading interpretation of phylogenetic analyses. Therefore, the present study aimed to illustrate, using specific examples, how the ITS region may be problematic for species delimitation. We showed that the ITS region is highly variable, with strains of Diaporthe malorum and Diaporthe novem falling into more than one clade, which if analyzed on their own, would be likely recognized as distinct taxa. Divergent ITS paralogs were also proven to coexist within the genome of D. novem. We also suggest that ITS may have escaped from concerted evolution or has undergone a duplication event. Furthermore, this study reports for the first time the existence of a putative hybrid in the genus Diaporthe. Our findings offer new clues towards the intraspecific and intragenomic variation in the ITS region, raising questions about its value for barcoding, i.e., identifying species in the genus Diaporthe. Therefore, we recommend that the ITS region be analyzed cautiously and always compared for congruence prior to description of novel taxa.

Using Genealogical Concordance and Coalescent-Based Species Delimitation to Assess Species Boundaries in the Diaporthe eres Complex

DNA sequence analysis has been of the utmost importance to delimit species boundaries in the genus Diaporthe. However, the common practice of combining multiple genes, without applying the genealogical concordance criterion has complicated the robust delimitation of species, given that phylogenetic incongruence between loci has been disregarded. Despite the several attempts to delineate the species boundaries in the D. eres complex, the phylogenetic limits within this complex remain unclear. In order to bridge this gap, we employed the Genealogical Phylogenetic Species Recognition principle (GCPSR) and the coalescent-based model Poisson Tree Processes (PTPs) and evaluated the presence of recombination within the D. eres complex. Based on the GCPSR principle, presence of incongruence between individual gene genealogies, i.e., conflicting nodes and branches lacking phylogenetic support, was evident. Moreover, the results of the coalescent model identified D. eres complex as a single species, which was not consistent with the current large number of species within the complex recognized in phylogenetic analyses. The absence of reproductive isolation and barriers to gene flow as well as the high haplotype and low nucleotide diversity indices within the above-mentioned complex suggest that D. eres constitutes a population rather than different lineages. Therefore, we argue that a cohesive approach comprising genealogical concordance criteria and methods to detect recombination must be implemented in future studies to circumscribe species in the genus Diaporthe.

Molecular reassessment of diaporthalean fungi associated with strawberry, including the leaf blight fungus, Paraphomopsis obscurans gen. et comb. nov. (Melanconiellaceae)

Phytopathogenic fungi in the order Diaporthales (Sordariomycetes) cause diseases on numerous economically important crops worldwide. In this study, we reassessed the diaporthalean species associated with prominent diseases of strawberry, namely leaf blight, leaf blotch, root rot and petiole blight, based on molecular data and morphological characters using fresh and herbarium collections. Combined analyses of four nuclear loci, 28S ribosomal DNA/large subunit rDNA (LSU), ribosomal internal transcribed spacers 1 and 2 with 5.8S ribosomal DNA (ITS), partial sequences of second largest subunit of RNA polymerase II (RPB2) and translation elongation factor 1-α (TEF1), were used to reconstruct a phylogeny for these pathogens. Results confirmed that the leaf blight pathogen formerly known as Phomopsis obscurans belongs in the family Melanconiellaceae and not with Diaporthe (syn. Phomopsis) or any other known genus in the order. A new genus Paraphomopsis is introduced herein with a new combination, Paraphomopsis obscurans, to accommodate the leaf blight fungus. Gnomoniopsis fragariae comb. nov. (Gnomoniaceae), is introduced to accommodate Gnomoniopsis fructicola, the cause of leaf blotch of strawberry. Both of the fungi causing leaf blight and leaf blotch were epitypified. Fresh collections and new molecular data were incorporated for Paragnomonia fragariae (Sydowiellaceae), which causes petiole blight and root rot of strawberry and is distinct from the above taxa. An updated multilocus phylogeny for the Diaporthales is provided with representatives of currently known families.

Etiology of Halo Blight in Michigan Hopyards

Michigan's hop acreage ranks fourth nationally, but the state's growers contend with unique disease challenges resulting from frequent rainfall and high humidity. In August 2018, a Michigan hop grower reported necrosis and blighting of foliage and shattering of cones resulting in yield loss. Irregular-shaped lesions developed on leaves, surrounded by a halo of chlorotic tissue, and cone bracts became brown. Pycnidia were observed in symptomatic tissue. The goal of this study was to identify and characterize the causal agent of symptoms in leaf and cone tissue. In symptomatic leaves, 15 of 19 isolates recovered had 96.4% internal transcribed spacer rDNA (ITSrDNA) homology with Diaporthe nomurai. Bayesian and maximum likelihood analyses were performed on a subset of isolates using ITSrDNA, histone H3, beta-tubulin, and elongation factor 1 alpha. Bootstrap and posterior probabilities supported a unique cluster of Diaporthe sp. 1-MI isolates most closely related to the Diaporthe arecae species complex, Diaporthe hongkongensis, and Diaporthe multigutullata. Diaporthe sp. 1-MI was pathogenic in detached leaf and whole plant assays. Single-spore isolates from pycnidia originating from cones and leaves shared 100% ITSrDNA homology with Diaporthe sp. 1-MI obtained from the lesion margins of leaves collected in 2018. The distribution of Diaporthe sp. 1-MI was widespread among 347 cones collected from 15 Michigan hop yards and accounted for >38% of fungi recovered from cones in three hop yards. Diaporthe sp. 1-MI causing halo and cone blight presents a new disease management challenge for Michigan hop growers.

Phylogenetic and Haplotype Network Analyses of Diaporthe eres Species in China Based on Sequences of Multiple Loci

Diaporthe eres is considered one of the most important causal agents of many plant diseases, with a broad host range worldwide. In this study, multiple sequences of ribosomal internal transcribed spacer region (ITS), translation elongation factor 1-α gene (EF1-α), beta-tubulin gene (TUB2), calmodulin gene (CAL), and histone-3 gene (HIS) were used for multi-locus phylogenetic analysis. For phylogenetic analysis, maximum likelihood (ML), maximum parsimony (MP), and Bayesian inferred (BI) approaches were performed to investigate relationships of D. eres with closely related species. The results strongly support that the D. eres species falls into a monophyletic lineage, with the characteristics of a species complex. Phylogenetic informativeness (PI) analysis showed that clear boundaries could be proposed by using EF1-α, whereas ITS showed an ineffective reconstruction and, thus, was unsuitable for speciating boundaries for Diaporthe species. A combined dataset of EF1-α, CAL, TUB2, and HIS showed strong resolution for Diaporthe species, providing insights for the D. eres complex. Accordingly, besides D. biguttusis, D. camptothecicola, D. castaneae-mollissimae, D. cotoneastri, D. ellipicola, D. longicicola, D. mahothocarpus, D. momicola, D. nobilis, and Phomopsis fukushii, which have already been previously considered the synonymous species of D. eres, another three species, D. henanensis, D. lonicerae and D. rosicola, were further revealed to be synonyms of D. eres in this study. In order to demonstrate the genetic diversity of D. eres species in China, 138 D. eres isolates were randomly selected from previous studies in 16 provinces. These isolates were obtained from different major plant species from 2006 to 2020. The genetic distance was estimated with phylogenetic analysis and haplotype networks, and it was revealed that two major haplotypes existed in the Chinese populations of D. eres. The haplotype networks were widely dispersed and not uniquely correlated to specific populations. Overall, our analyses evaluated the phylogenetic identification for D. eres species and demonstrated the population diversity of D. eres in China.

Endophytic Diaporthe Associated With Citrus grandis cv. Tomentosa in China

Diaporthe species are associated with Citrus as endophytes, pathogens, and saprobes worldwide. However, little is known about Diaporthe as endophytes in Citrus grandis in China. In this study, 24 endophytic Diaporthe isolates were obtained from cultivated C. grandis cv. "Tomentosa" in Huazhou, Guangdong Province in 2019. The nuclear ribosomal internal transcribed spacer (ITS), partial sequences of translation elongation factor 1-α (tef1), β-tubulin (tub2), and partial calmodulin (cal) gene regions were sequenced and employed to construct phylogenetic trees. Based on morphology and combined multigene phylogeny, eleven Diaporthe species were identified including two new species, Diaporthe endocitricola and D. guangdongensis. These are the first report of D. apiculata, D. aquatica, D. arecae, D. biconispora, D. limonicola, D. masirevicii, D. passifloricola, D. perseae, and D. sennae on C. grandis. This study provides the first intensive study of endophytic Diaporthe species on C. grandis cv. tomentosa in China. These results will improve the current knowledge of Diaporthe species associated with C. grandis. The results obtained in this study will also help to understand the potential pathogens and biocontrol agents and to develop a platform in disease management.

Morphology Characterization, Molecular Phylogeny, and Pathogenicity of Diaporthe passifloricola on Citrus reticulata cv. Nanfengmiju in Jiangxi Province, China

The Nanfengmiju (Citrus reticulata cv. Nanfengmiju), a high-quality local variety of mandarin, is one of the major fruit crops in Jiangxi Province, China. Citrus melanose and stem-end rot, two common fungal diseases of Nanfengmiju, are both caused by Diaporthe spp. (syn. Phomopsis spp.). Identification of the Diaporthe species is essential for epidemiological studies, quarantine measures, and management of diseases caused by these fungi. Melanose disease was observed on Nanfengmiju fruit in Jiangxi Province of China in 2016. Based on morphological characterization and multi-locus phylogenetic analyses, three out of 39 isolates from diseased samples were identified as D. passifloricola. Since these three isolates did not cause melanose on citrus fruit in the pathogenicity tests, they were presumed to be endophytic fungi present in the diseased tissues. However, our results indicate that D. passifloricola may persist as a symptom-less endophyte in the peel of citrus fruit, yet it may cause stem-end if it invades the stem end during fruit storage. To the best of our knowledge, this is the first report of D. passifloricola as the causal agent of the stem-end rot disease in Citrus reticulata cv. Nanfengmiju.

New species and records of Diaporthe from Jiangxi Province, China

Diaporthe species have often been reported as important plant pathogens, saprobes and endophytes on a wide range of plant hosts. Although several Diaporthe species have been recorded, little is known about species able to infect forest trees in Jiangxi Province. Hence, extensive surveys were recently conducted in Jiangxi Province, China. A total of 24 isolates were identified and analysed using comparisons of DNA sequence data for the nuclear ribosomal internal transcribed spacer (ITS), calmodulin (cal), histone H3 (his3), partial translation elongation factor-1α (tef1) and β-tubulin (tub2) gene regions, as well as their morphological features. Results revealed five novel taxa, D. bauhiniae, D. ganzhouensis, D. schimae, D. verniciicola, D. xunwuensis spp. nov. and three known species, D. apiculatum, D. citri and D. multigutullata.

Three new Diaporthe species from Shaanxi Province, China

Diaporthe species (Sordariomycetes, Diaporthales) are often reported as important plant pathogens, saprobes and endophytes on a wide range of plant hosts. In this study, Diaporthe specimens were collected from symptomatic twigs and branches at the Huoditang Forest Farm in Shaanxi Province, China. Identification was done using a combination of morphology and comparison of DNA sequence data of the nuclear ribosomal internal transcribed spacer (ITS), calmodulin (cal), histone H3 (his3), partial translation elongation factor-1α (tef1) and β-tubulin (tub2) gene regions. Three new Diaporthe species are proposed: D.albosinensis, D.coryli and D.shaanxiensis. All species are illustrated and their morphology and phylogenetic relationships with other Diaporthe species are discussed.

Fungal Trunk Pathogens Associated With Juglans regia in the Czech Republic

Juglans regia L. (English walnut) trees with cankers and dieback symptoms were observed in two regions in the Czech Republic. Isolations were made from diseased branches. In total, 138 fungal isolates representing 10 fungal species were obtained from wood samples and identified based on morphological characteristics and molecular methods: Cadophora novi-eboraci, Cadophora spadicis, Cryptovalsa ampelina, Diaporthe eres, Diplodia seriata, Dothiorella omnivora, Eutypa lata, Eutypella sp., Peroneutypa scoparia, and Phaeoacremonium sicilianum. Pathogenicity tests conducted under field conditions with all species using the mycelium-plug method indicated that Eutypa lata and Cadophora spp. were highly virulent to woody stems of walnut. This is the first study to detect and identify fungal trunk pathogens associated with diseased walnut trees in Europe.

Molecular Characterization of Diaporthe Species Associated With Hazelnut Defects

Fungi of the genus Diaporthe have been reported as the main causative agent of hazelnut defects in the Caucasus area. This study aimed to define which fungal species are present in defective hazelnuts grown in Turkey and confirm the role of Diaporthe spp. Seven hazelnut orchards were selected, with each one located in a different Turkish Province (Düzce, Giresun, Ordu, Samsun, Sakarya, Trabzon, and Zonguldak), and hazelnuts were collected at early and full ripening. Fungal isolation and identification were performed at the genus level based on morphological characteristics. Several genera were isolated, with Diaporthe spp. being among the prevalent. This was the only genus with increasing incidence from early to full ripening, and incidence at full ripening was positively correlated both with internal (ρ = 0.86) and visible defects (ρ = 0.81), which confirmed its role as the key causative agent of hazelnut defects. The correlation of defect occurrence with rainfall, reported in previous study, was not confirmed, possibly due to the low defect incidence. A total of 86 Diaporthe monosporic strains isolated from Turkish hazelnut samples, together with 33 strains collected in the Caucasus region and 6 from Italy, were analyzed with a multi-locus phylogeny based on three genomic loci (ITS, EF1-α, and tub). The results showed that Diaporthe strains can be grouped into 7 distinct clades, with a majority of Turkish strains (95%) being placed into a single clade related with D. eres. These samples were organized into several sub-clades, which indicates the existence of genetically diverse sub-populations.

Diaporthalean fungi associated with canker and dieback of trees from Mount Dongling in Beijing, China

Diaporthales is a fungal order comprising important plant pathogens, saprobes and endophytes on a wide range of woody hosts. It is often difficult to differentiate the pathogens in this order, since both the morphology and disease symptoms are similar among the various species. In the current study, we obtained 15 representative diaporthalean isolates from six tree hosts belonging to plant families Betulaceae, Fagaceae, Juglandaceae, Rosaceae, and Ulmaceae from Mount Dongling in China. Six species were identified residing in four families of Diaporthales (Diaporthaceae, Erythrogloeaceae, Juglanconidaceae and Melanconidaceae). Based on morphological comparison and the phylogenetic analyses of partial ITS, LSU, cal, his3, rpb2, tef1-α and tub2 gene sequences, we identified five known species (Diaporthe betulina, D. eres, D. rostrata, Juglamconis oblonga and Melanconis stilbostoma) and one novel species (Dendrostoma donglinensis). These results represent the first study of diaporthalean fungi associated with canker and dieback symptoms from Mount Dongling in Beijing, China.

High diversity of Diaporthe species associated with dieback diseases in China, with twelve new species described

Diaporthe species have often been reported as important plant pathogens, saprobes and endophytes on a wide range of plant hosts. Although several Diaporthe species have been recorded in China, little is known about species able to infect forest trees. Therefore, extensive surveys were recently conducted in Beijing, Heilongjiang, Jiangsu, Jiangxi, Shaanxi and Zhejiang Provinces. The current results emphasised on 15 species from 42 representative isolates involving 16 host genera using comparisons of DNA sequence data for the nuclear ribosomal internal transcribed spacer (ITS), calmodulin (cal), histone H3 (his3), partial translation elongation factor-1α (tef1) and β-tubulin (tub2) gene regions, as well as their morphological features. Three known species, D.biguttulata, D.eres and D.unshiuensis, were identified. In addition, twelve novel taxa were collected and are described as D.acerigena, D.alangii, D.betulina, D.caryae, D.cercidis, D.chensiensis, D.cinnamomi, D.conica, D.fraxinicola, D.kadsurae, D.padina and D.ukurunduensis. The current study improves the understanding of species causing diebacks on ecological and economic forest trees and provides useful information for the effective disease management of these hosts in China.