Polyphasic studies of new species of Diaporthe from native forest in Chile, with descriptions of Diaporthe araucanorum sp. nov., Diaporthe foikelawen sp. nov. and Diaporthe patagonica sp. nov

Species of Diaporthe (Diaporthaceae, Diaporthales) associated with Alnusnepalensis leaf spot and branch canker diseases in Xizang, China

Alnusnepalensis is an important tree species in the Himalayas with significant ecological and economic roles. During disease surveys in Xizang, China, we observed leaf spot and branch canker symptoms on this tree. Fungal isolates associated with these diseases were collected and identified based on morphological characteristics and phylogenetic analysis of ITS, cal, his3, tef1, and tub2 sequences. As a result, Diaporthealnicola sp. nov. and D.amygdali were identified from the leaf spots, while D.linzhiensis was identified to be associated with the cankered branches. This study identifies pathogenic species from alder trees, providing a foundation for future disease management and forest health research.

Diaporthe betae sp. nov., a new species associating with sugar beet root rot in Heilongjiang Province, China

Introduction

Sugar beet (Beta vulgaris L.) is an economically important crop grown worldwide, but its production is threatened by root rot diseases caused by soil-borne fungi. This study aimed to identify and characterize a new pathogen causing root rot in sugar beet in Heilongjiang Province, China.

Methods

During 2019 and 2023, isolates were obtained from infected sugar beet roots showing symptoms of red-brown or black lesions and tissue necrosis. The pathogenicity of the causal organism was confirmed by Koch's postulates. The isolates were characterized based on morphological features and multilocus phylogenetic analyses. To evaluate potential control measures for this new pathogen in field conditions, the fungicides pyraclostrobin, boscalid, and fluconazole were tested for their efficacy in inhibiting the growth of this new pathogen in vitro.

Results

The newly discovered pathogen was found to differ from previously described taxa in conidial morphology, molecular features, and disease index. Thus, the pathogen was determined to be a new species, which we called Diaporthe betae sp. nov. All three fungicides demonstrated significant inhibitory effects, with fluconazole showing the strongest activity and pyraclostrobin the second-highest efficacy.

Discussion

The discovery of this new pathogenic fungus will help researchers elucidate the pathogenesis of sugar beet root rot and provide a theoretical basis for performing targeted monitoring, preventing diseases and implementing control measures.

Diaporthe species on palms - integrative taxonomic approach for species boundaries delimitation in the genus Diaporthe, with the description of D. pygmaeae sp. nov

The application of traditional morphological and ecological species concepts to closely related, asexual fungal taxa is challenging due to the lack of distinctive morphological characters and frequent cosmopolitan and plurivorous behaviour. As a result, multilocus sequence analysis (MLSA) has become a powerful and widely used tool to recognise and delimit independent evolutionary lineages (IEL) in fungi. However, MLSA can mask discordances in individual gene trees and lead to misinterpretation of speciation events. This phenomenon has been extensively documented in Diaporthe, and species identifications in this genus remains an ongoing challenge. However, the accurate delimitation of Diaporthe species is critical as the genus encompasses several cosmopolitan pathogens that cause serious diseases on many economically important plant hosts. In this regard, following a survey of palm leaf spotting fungi in Lisbon, Portugal, Diaporthe species occurring on Arecaceae hosts were used as a case study to implement an integrative taxonomic approach for a reliable species identification in the genus. Molecular analyses based on the genealogical concordance phylogenetic species recognition (GCPSR) and DNA-based species delimitation methods revealed that speciation events in the genus have been highly overestimated. Most IEL identified by the GCPSR were also recognised by Poisson tree processes (PTP) coalescent-based methods, which indicated that phylogenetic lineages in Diaporthe are likely influenced by incomplete lineage sorting (ILS) and reticulation events. Furthermore, the recognition of genetic recombination signals and the evaluation of genetic variability based on sequence polymorphisms reinforced these hypotheses. New clues towards the intraspecific variation in the common loci used for phylogenetic inference of Diaporthe species are discussed. These results demonstrate that intraspecific variability has often been used as an indicator to introduce new species in Diaporthe, which has led to a proliferation of species names in the genus. Based on these data, 53 species are reduced to synonymy with 18 existing Diaporthe species, and a new species, D. pygmaeae, is introduced. Thirteen new plant host-fungus associations are reported, all of which represent new host family records for Arecaceae. This study has recognised and resolved a total of 14 valid Diaporthe species associated with Arecaceae hosts worldwide, some of which are associated with disease symptoms. This illustrates the need for more systematic research to examine the complex of Diaporthe taxa associated with palms and determine their potential pathogenicity. By implementing a more rational framework for future studies on species delimitation in Diaporthe, this study provides a solid foundation to stabilise the taxonomy of species in the genus. Guidelines for species recognition, definition and identification in Diaporthe are included. Taxonomic novelties: New species: Diaporthe pygmaeae D.S. Pereira & A.J.L. Phillips. New synonyms: Diaporthe afzeliae Monkai & Lumyong, Diaporthe alangii C.M. Tian & Q. Yang, Diaporthe araliae-chinensis S.Y. Wang et al., Diaporthe australiana R.G. Shivas et al., Diaporthe australpacifica Y.P. Tan & R.G. Shivas, Diaporthe bombacis Monkai & Lumyong, Diaporthe caryae C.M. Tian & Q. Yang, Diaporthe chimonanthi (C.Q. Chang et al.) Y.H. Gao & L. Cai, Diaporthe conferta H. Dong et al., Diaporthe diospyrina Y.K. Bai & X.L. Fan, Diaporthe durionigena L.D. Thao et al., Diaporthe etinsideae Y.P. Tan & R.G. Shivas, Diaporthe eucalyptorum Crous & R.G. Shivas, Diaporthe fujianensis Jayaward. et al., Diaporthe fusiformis Jayaward. et al., Diaporthe globoostiolata Monkai & Lumyong, Diaporthe hainanensis Qin Yang, Diaporthe hongkongensis R.R. Gomes et al., Diaporthe hubeiensis Dissan. et al., Diaporthe infecunda R.R. Gomes et al., Diaporthe italiana Chethana et al., Diaporthe juglandigena S.Y. Wang et al., Diaporthe lagerstroemiae (C.Q. Chang et al.) Y.H. Gao & L. Cai, Diaporthe lithocarpi (Y.H. Gao et al.) Y.H. Gao & L. Cai, Diaporthe lutescens S.T. Huang et al., Diaporthe machili S.T. Huang et al., Diaporthe megabiguttulata M. Luo et al., Diaporthe middletonii R.G. Shivas et al., Diaporthe morindae M. Luo et al., Diaporthe nannuoshanensis S.T. Huang et al., Diaporthe nigra Brahman. & K.D. Hyde, Diaporthe orixae Q.T. Lu & Zhen Zhang, Diaporthe passifloricola Crous & M.J. Wingf., Diaporthe pimpinellae Abeywickrama et al., Diaporthe pseudoinconspicua T.G.L Oliveira et al., Diaporthe pungensis S.T. Huang et al., Diaporthe rhodomyrti C.M. Tian & Qin Yang, Diaporthe rosae M.C. Samar. & K.D. Hyde, Diaporthe rumicicola Manawas et al., Diaporthe salicicola R.G. Shivas et al., Diaporthe samaneae Monkai & Lumyong, Diaporthe subcylindrospora S.K. Huang et al., Diaporthe tectonae Doilom et al., Diaporthe tectonigena Doilom et al., Diaporthe theobromatis H. Dong et al., Diaporthe thunbergiicola Udayanga & K.D. Hyde, Diaporthe tuyouyouiae Y.P. Tan et al., Diaporthe unshiuensis F. Huang et al., Diaporthe vochysiae S.A. Noriler et al., Diaporthe xishuangbannaensis Hongsanan & K.D. Hyde, Diaporthe xylocarpi M.S. Calabon & E.B.G. Jones, Diaporthe zaobaisu Y.S. Guo & G.P. Wang, Diaporthe zhaoqingensis M. Luo et al. Citation: Pereira DS, Phillips AJL (2024). Diaporthe species on palms - integrative taxonomic approach for species boundaries delimitation in the genus Diaporthe, with the description of D. pygmaeae sp. nov. Studies in Mycology 109: 487-594. doi: 10.3114/sim.2024.109.08.

An Emerging Disease of Chickpea, Basal Stem Rot Caused by Diaporthe aspalathi in China

Chickpea (Cicer arietinum L.) is an important legume crop worldwide. An emerging disease, basal stem rot with obvious wilt symptoms, was observed in the upper part of chickpea plants during the disease survey in Qiubei County of Yunnan Province. Three fungal isolates (ZD36-1, ZD36-2, and ZD36-3) were obtained from the diseased tissue of chickpea plants collected from the field. Those isolates were morphologically found to be similar to Diaporthe aspalathi. Molecular sequence analyses of multiple gene regions (ITS, tef1, tub2, cal, and his3) indicated that the three isolates showed a high identity with D. aspalathi. Pathogenicity and host range tests of the isolates were performed on the original host chickpea and eight other legume crops. The isolates were strongly pathogenic to chickpea and appeared highly pathogenic to soybean, cowpea, and mung bean; moderated or mild pathogenic to adzuki bean and common bean; however, the isolates did not cause symptoms on grass pea (Lathyrus sativus). Diaporthe aspalathi was previously reported as a main pathogen causing the southern stem canker in soybean. To our knowledge, this is the first report of D. aspalathi inducing basal stem rot on chickpea worldwide.

Molecular Characterization and Pathogenicity of Diaporthe Species Causing Nut Rot of Hazelnut in Italy

Hazelnut (Corylus avellana), a nut crop that is rapidly expanding worldwide, is endangered by a rot. Nut rot results in hazelnut defects. A survey was conducted in northwestern Italy during 2020 and 2021 to identify the causal agents of hazelnut rots. Typical symptoms of black rot, mold, and necrotic spots were observed on hazelnuts. The prevalent fungi isolated from symptomatic hazelnut kernels were Diaporthe spp. (38%), Botryosphaeria dothidea (26%), Diplodia seriata (14%), and other fungal genera with less frequent occurrences. Among 161 isolated Diaporthe spp., 40 were selected for further analysis. Based on morphological characterization and multilocus phylogenetic analysis of the ITS, tef-1α, and tub2, seven Diaporthe species were identified as D. eres, D. foeniculina, D. novem, D. oncostoma, D. ravennica, D. rudis, and D. sojae. D. eres was the main species isolated from hazelnut rots, in particular from moldy nuts. The pathogenicity test performed on hazelnuts 'Tonda Gentile del Piemonte' using a mycelium plug showed that all the Diaporthe isolates were pathogenic on their original host. To our knowledge, this work is the first report of D. novem, D. oncostoma, and D. ravennica on hazelnuts worldwide. D. foeniculina, D. rudis, and D. sojae were reported for the first time as agents of hazelnut rot in Italy. Future studies should focus on the comprehension of epidemiology and climatic conditions favoring the development of Diaporthe spp. on hazelnut. Prevention and control measures should target D. eres, representing the main causal agents responsible for defects and nut rot of hazelnuts in Italy.

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.

Integrative Taxonomy of Novel Diaporthe Species Associated with Medicinal Plants in Thailand

During our investigations of the microfungi on medicinal plants in Thailand, five isolates of Diaporthe were obtained. These isolates were identified and described using a multiproxy approach, viz. morphology, cultural characteristics, host association, the multiloci phylogeny of ITS, tef1-α, tub2, cal, and his3, and DNA comparisons. Five new species, Diaporthe afzeliae, D. bombacis, D. careyae, D. globoostiolata, and D. samaneae, are introduced as saprobes from the plant hosts, viz. Afzelia xylocarpa, Bombax ceiba, Careya sphaerica, a member of Fagaceae, and Samanea saman. Interestingly, this is the first report of Diaporthe species on these plants, except on the Fagaceae member. The morphological comparison, updated molecular phylogeny, and pairwise homoplasy index (PHI) analysis strongly support the establishment of novel species. Our phylogeny also revealed the close relationship between D. zhaoqingensis and D. chiangmaiensis; however, the evidence from the PHI test and DNA comparison indicated that they are distinct species. These findings improve the existing knowledge of taxonomy and host diversity of Diaporthe species as well as highlight the untapped potential of these medicinal plants for searching for new fungi.

Taxonomy and Multigene Phylogeny of Diaporthales in Guizhou Province, China

In a study of fungi isolated from plant material in Guizhou Province, China, we identified 23 strains of Diaporthales belonging to nine species. These are identified from multigene phylogenetic analyses of ITS, LSU, rpb2, tef1, and tub2 gene sequence data coupled with morphological studies. The fungi include a new genus (Pseudomastigosporella) in Foliocryphiaceae isolated from Acer palmatum and Hypericum patulum, a new species of Chrysofolia isolated from Coriaria nepalensis, and five new species of Diaporthe isolated from Juglans regia, Eucommia ulmoides, and Hypericum patulum. Gnomoniopsis rosae and Coniella quercicola are newly recorded species for China.

Diaporthe species infecting sunflower (Helianthus annuus) in Russia, with the description of two new species

Phomopsis stem canker is economically important sunflower disease that caused by multiple Diaporthe species. Recent investigations resulted in the resolution that there are at least 13 Diaporthe species that can infect sunflower. A comprehensive analysis of the biodiversity and geographic distribution of Diaporthe species in Russia, particularly those that infect sunflower, has not been undertaken. For this study, 16 Diaporthe isolates were obtained from samples of stem canker and visually healthy seeds of Helianthus annuus from northwestern, central European, southern European Russia, North Caucasus, and the Urals in 2016-2019. The aim of this study was to identify these Diaporthe isolates based on morphology and sequence analyses of the nuclear ribosomal internal transcribed spacer (ITS) region, partial calmodulin (cal), DNA-lyase (apn2), histone H3 (his3), translation elongation factor-1α gene (tef1), and ß-tubulin (tub2) genes. The phylogenetic reconstruction revealed well-supported monophyletic clades corresponding to six Diaporthe species: D. eres, D. gulyae, D. helianthi, and D. phaseolorum. Two new species were described: Diaporthe monetii sp. nov. and Diaporthe vangoghii sp. nov. The isolates of D. gulyae and D. phaseolorum collected represent the first records of these species in Russia.

Two new species of Diaporthe (Diaporthaceae, Diaporthales) associated with tree cankers in the Netherlands

Diaporthe (Diaporthaceae, Diaporthales) is a common fungal genus inhabiting plant tissues as endophytes, pathogens and saprobes. Some species are reported from tree branches associated with canker diseases. In the present study, Diaporthe samples were collected from Alnusglutinosa, Fraxinusexcelsior and Quercusrobur in Utrecht, the Netherlands. They were identified to species based on a polyphasic approach including morphology, pure culture characters, and phylogenetic analyses of a combined matrix of partial ITS, cal, his3, tef1 and tub2 gene regions. As a result, four species (viz. Diaporthepseudoalnea sp. nov. from Alnusglutinosa, Diaporthesilvicola sp. nov. from Fraxinusexcelsior, D.foeniculacea and D.rudis from Quercusrobur) were revealed from tree branches in the Netherlands. Diaporthepseudoalnea differs from D.eres (syn. D.alnea) by its longer conidiophores. Diaporthesilvicola is distinguished from D.fraxinicola and D.fraxini-angustifoliae by larger alpha conidia.

Recent developments in less known and multi-resistant fungal opportunists

Fungal infections have increased in recent years due to host factors, such as oncohaematological and transplant-related disorders, immunosuppressive therapy, and AIDS. Additionally, molecular and proteomic facilities have become available to identify previously unrecognizable opportunists. For these reasons, reports on less-known and recalcitrant mycoses, such as those caused by black fungi, hyaline filamentous fungi, coelomycetes, Mucorales, and non-Candida yeasts have emerged. In this review, novel taxonomy in these groups, which often are multi-resistant to one or several classes of antifungals, is discussed. Clinical presentations, diagnosis and current treatment of some major groups are summarised.

Morphological and phylogenetic analyses reveal three new species of Diaporthe from Yunnan, China

Species of Diaporthe have often been reported as plant pathogens, endophytes or saprobes, commonly isolated from a wide range of plant hosts. Sixteen strains isolated from species of ten host genera in Yunnan Province, China, represented three new species of Diaporthe, D. chrysalidocarpi, D. machili and D. pometiae as well as five known species D. arecae, D. hongkongensis, D. middletonii, D. osmanthi and D. pandanicola. Morphological comparisons with known species and DNA-based phylogenies based on the analysis of a multigene (ITS, TUB, TEF, CAL and HIS) dataset support the establishment of the new species. This study reveals that a high species diversity of Diaporthe with wide host ranges occur in tropical rainforest in Yunnan Province, China.

Diaporthe amygdali, a species complex or a complex species?

Delimitation of species boundaries within the fungal genus Diaporthe has been challenging, but the analyses of combined multilocus DNA sequences has become an important tool to infer phylogenetic relationships and to circumscribe species. However, analyses of congruence between individual gene genealogies and the application of the genealogical concordance principle have been somehow overlooked. We noted that a group of species including D. amygdali, D. garethjonesii, D. sterilis, D. kadsurae, D. ternstroemia, D. ovoicicola, D. fusicola, D. chongqingensis and D. mediterranea, commonly known as D. amygdali complex, occupy a monophyletic clade in Diaporthe phylogenies but the limits of all species within the complex are not entirely clear. To assess the boundaries of species within this complex we employed the Genealogical Concordance Phylogenetic Species Recognition principle (GCPSR) and coalescence-based models: General Mixed Yule-Coalescent (GMYC) and Poisson Tree Processes (PTP). The incongruence detected between individual gene phylogenies, as well as the results of coalescent methods do not support the recognition of lineages within the complex as distinct species. Moreover, results support the absence of reproductive isolation and barriers to gene flow in this complex, thus providing further evidence that the D. amygdali species complex constitutes a single species. This study highlights the relevance of the application of the GCPSR principle, showing that concatenation analysis of multilocus DNA sequences, although being a powerful tool, might lead to an erroneous definition of species limits. Additionally, it further shows that coalescent methods are useful tools to assist in a more robust delimitation of species boundaries in the genus Diaporthe.

Morphological and molecular identification of Diaporthe species in south-western China, with description of eight new species

Diaporthe species have often been reported as plant pathogens, endophytes and saprophytes, commonly isolated from a wide range of infected plant hosts. In the present study, twenty strains obtained from leaf spots of twelve host plants in Yunnan Province of China were isolated. Based on a combination of morphology, culture characteristics and multilocus sequence analysis of the rDNA internal transcribed spacer region (ITS), translation elongation factor 1-α (TEF), β-tubulin (TUB), calmodulin (CAL), and histone (HIS) genes, these strains were identified as eight new species: Diaporthe camelliae-sinensis, D. grandiflori, D. heliconiae, D. heterostemmatis, D. litchii, D. lutescens, D. melastomatis, D. pungensis and two previously described species, D. subclavata and D. tectonendophytica. This study showed high species diversity of Diaporthe in tropical rain forests and its hosts in south-western China.

Unravelling Diaporthe Species Associated with Woody Hosts from Karst Formations (Guizhou) in China

Though several Diaporthe species have been reported in China, little is known about the species associated with nature reserves in Guizhou province. During a survey of fungi in six nature reserves in Guizhou province of China, thirty-one Diaporthe isolates were collected from different woody hosts. Based on morphology, culture characteristics and molecular phylogenetic analysis, these isolates were characterized and identified. Phylogenetic analysis of internal transcribed spacer region (ITS), combined with translation elongation factor 1-alpha (tef), β-tubulin (tub), calmodulin (cal) and histone H3 (his) gene regions identified five known Diaporthe species and seven distinct lineages representing novel Diaporthe species. The details of five known species: Diaporthe cercidis, D. cinnamomi, D. conica, D. nobilis and D. sackstonii are given and the seven new species D. constrictospora, D. ellipsospora, D. guttulata, D. irregularis, D. lenispora, D. minima, and D. minusculata are introduced with detailed descriptions and illustrations. This study revealed a high diversity of previously undescribed Diaporthe species associated with woody hosts in various nature reserves of Guizhou province, indicating that there is a potential of Diaporthe species remains to be discovered in this unique landform (Karst formations) in China. Interestingly, the five known Diaporthe species have been reported as pathogens of various hosts, and this could indicate that those newly introduced species in this study could be potentially pathogenic pending further studies to confirm.

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.