Plant-associated Fungi Research Articles

A novel plant-fungal association reveals fundamental sRNA and gene expression reprogramming at the onset of symbiosis

Abstract Background Beneficial associations between plants and microbes are widespread in nature and have been studied extensively in the microbial-dominant environment of the rhizosphere. Such associations are highly advantageous for the organisms involved, benefiting soil microbes by providing them access to plant metabolites, while plant growth and development are enhanced through the promotion of nutrient uptake and/or protection against (a)biotic stresses. While the establishment and maintenance of mutualistic associations have been shown to require genetic and epigenetic reprogramming, as well as an exchange of effector molecules between microbes and plants, whether short RNAs are able to effect such changes is currently unknown. Here, we established an interaction between the model grass species Brachypodium distachyon (Bd, Pooideae) and the beneficial fungal root endophyte Serendipita indica (Si, syn. Piriformospora indica, Sebacinales) to elucidate RNA interference-based regulatory changes in gene expression and small (s)RNA profiles that occurred during establishment of a Sebacinalean symbiosis. Results Colonization of Bd roots with Si resulted in higher grain yield, confirming the mutualistic character of this interaction. Resequencing of the Si genome using the Oxford Nanopore technique, followed by de novo assembly yielded in 57 contigs and 9441 predicted genes, including putative members of several families involved in sRNA production. Transcriptome analysis at an early stage of the mutualistic interaction identified 2963 differentially expressed genes (DEG) in Si and 317 in Bd line 21-3. The fungal DEGs were largely associated with carbohydrate metabolism, cell wall degradation, and nutrient uptake, while plant DEGs indicated modulation of (a)biotic stress responses and defense pathways. Additionally, 10% of the upregulated fungal DEGs encode candidate protein effectors, including six DELD proteins typical for Sebacinales. Analysis of the global changes in the sRNA profiles of both associated organisms revealed several putative endogenous plant sRNAs expressed during colonization belonging to known micro (mi)RNA families involved in growth and developmental regulation. Among Bd- and Si-generated sRNAs with putative functions in the interacting organism, we identified transcripts for proteins involved in circadian clock and flowering regulation as well as immunity as potential targets of fungal sRNAs, reflecting the beneficial activity of Si. Conclusions We detected beneficial effects of Si colonization on Bd growth and development, and established a novel plant-mutualist interaction model between these organisms. Together, the changes in gene expression and identification of interaction-induced sRNAs in both organisms support sRNA-based regulation of defense responses and plant development in Bd, as well as nutrient acquisition and cell growth in Si. Our data suggests that a Sebacinalean symbiosis involves reciprocal sRNA targeting of genes during the interaction.

New Cytotoxic Cytochalasans from a Plant-Associated Fungus Chaetomium globosum kz-19.

Four new cytochalasans, phychaetoglobins A–D (1–4), together with twelve known cytochalasans (5–16), were isolated from a mangrove-associated fungus Chaetomium globosum kz-19. The new structures were elucidated on the basis of extensive 1D and 2D NMR, HR ESIMS spectroscopic analyses, and electronic circular dichroism (ECD) calculations. The absolute configuration of 2 was established by application of Mosher’s method. Compounds 4–8 exhibited moderate cytotoxicities against A549 and HeLa cell lines with the IC50 values less than 20 μM.

The Interspecific Fungal Hybrid Verticillium longisporum Displays Subgenome-Specific Gene Expression.

ABSTRACTHybridization is an important evolutionary mechanism that can enable organisms to adapt to environmental challenges. It has previously been shown that the fungal allodiploid species Verticillium longisporum, the causal agent of verticillium stem striping in rapeseed, originated from at least three independent hybridization events between two haploid Verticillium species. To reveal the impact of genome duplication as a consequence of hybridization, we studied the genome and transcriptome dynamics upon two independent V. longisporum hybridization events, represented by the hybrid lineages “A1/D1” and “A1/D3.” We show that V. longisporum genomes are characterized by extensive chromosomal rearrangements, including between parental chromosomal sets. V. longisporum hybrids display signs of evolutionary dynamics that are typically associated with the aftermath of allodiploidization, such as haploidization and more relaxed gene evolution. The expression patterns of the two subgenomes within the two hybrid lineages are more similar than those of the shared A1 parent between the two lineages, showing that the expression patterns of the parental genomes homogenized within a lineage. However, as genes that display differential parental expression in planta do not typically display the same pattern in vitro, we conclude that subgenome-specific responses occur in both lineages. Overall, our study uncovers genomic and transcriptomic plasticity during the evolution of the filamentous fungal hybrid V. longisporum and illustrates its adaptive potential.

Aspochalasin H1: A New Cyclic Aspochalasin from Hawaiian Plant-Associated Endophytic Fungus Aspergillus sp. FT1307.

Aspergillus is one of the most diverse genera, and it is chemically profound and known to produce many biologically active secondary metabolites. In the present study, a new aspochalasin H1 (1), together with nine known compounds (2–10), were isolated from a Hawaiian plant-associated endophytic fungus Aspergillus sp. FT1307. The structures were elucidated using nuclear magnetic resonance (NMR) (1H, 1H-1H COSY, HSQC, HMBC, ROESY and 1D NOE), high-resolution electrospray ionization mass spectroscopy (HRESIMS), and comparisons with the reported literature. The absolute configuration of the new compound was established by electronic circular dichroism (ECD) in combination with NMR calculations. The new compound contains an epoxide moiety and an adjacent trans-diol, which has not been reported before in the aspochalasin family. The antibacterial screening of the isolated compounds was carried out against pathogenic bacteria (Staphylococcus aureus, Methicillin-resistant S. aureus and Bacillus subtilis). The antiproliferative activity of compounds 1–10 was evaluated against human breast cancer cell lines (MCF-7 and T46D) and ovarian cancer cell lines (A2780).

Sampling Volatile Organic Compounds from Individual Cotton Leaves to Test Effects of Fungal Endophyte Treatments

Facultative fungal endophytes are unspecialized plant-associated fungi capable of colonizing plant tissues without causing symptoms of disease. Studies suggest facultative fungal endophytes enhance cotton (Gossypium hirsutum L.) plant defense against insect herbivores and might alter emissions of volatile organic compounds. We tested for changes in emissions of volatile organic compounds using cotton plants treated with facultative fungal endophtytes Beauveria bassiana (Balsamo-Crivelli) Vuillemin strain GHA and Phialemonium inflatum (Burnside) strain TAMU490 in the presence and absence of herbivory. Solid-phase micro-extraction was used to sample static headspace of individual leaves in collection chambers designed specifically for the experiment. Relative abundance of volatile organic compounds was significantly affected by herbivory, but differences caused by treatment with B. bassiana or P. inflatum were not significant. Findings showed our sampling method can be used to assess constitutive and herbivore-induced volatile organic compound profiles from individual leaves, but further studies need to investigate mechanisms underlying facultative fungal endophyte-mediated herbivore resistance in cotton.

Forest plant cover and mineral type determine the diversity and composition of mineral-colonizing fungal communities

Soil fungi play a fundamental role in the cycling of nutrients and tree nutrition in forests. As mycorrhizal fungi are closely associated with their host trees and provide them essential base cations and phosphorus, we hypothesize that they actively mine soil minerals and transfer their nutritive content to their host. Therefore, mycorrhizal fungi are expected to be important colonizers of soil mineral surfaces relative to other fungal trophic guilds. To test this hypothesis, 50 μm nylon mesh bags were filled with three different mineral types (i.e. calcite, apatite and obsidian) and buried in the same soil colonized by three forest stands (i.e. beech, Corsican pine and coppice with standards). After an in situ incubation period of 29 months in the topsoil, mineral dissolution was detectable in the mesh bags, and the analysis of the fungal communities was therefore undertaken. Minerals presented a lower fungal biomass than the surrounding bulk soil and no difference between the three mineral types tested was observed. The high-throughput sequencing (HTS) approach showed that the fungal communities differed among the three forest stands, but in each case, mineral associated fungal taxa differed significantly from those in the bulk soil. To a lesser extent, fungal communities further varied between the three mineral types. Overall, trophic inference analyses suggested that two groups of plant-associated fungi, namely the ectomycorrhizal and endophytic fungi, were the major fungal mineral colonizers. Saprophytes also appeared significantly enriched on minerals comparatively to the surrounding bulk soil. Together, our data reveal at local scale that the mineral-associated fungal communities are first determined by the forest plant cover and then by the type of mineral.

A Sesquiterpene Synthase from the Endophytic Fungus Serendipita indica Catalyzes Formation of Viridiflorol.

Interactions between plant-associated fungi and their hosts are characterized by a continuous crosstalk of chemical molecules. Specialized metabolites are often produced during these associations and play important roles in the symbiosis between the plant and the fungus, as well as in the establishment of additional interactions between the symbionts and other organisms present in the niche. Serendipita indica, a root endophytic fungus from the phylum Basidiomycota, is able to colonize a wide range of plant species, conferring many benefits to its hosts. The genome of S. indica possesses only few genes predicted to be involved in specialized metabolite biosynthesis, including a putative terpenoid synthase gene (SiTPS). In our experimental setup, SiTPS expression was upregulated when the fungus colonized tomato roots compared to its expression in fungal biomass growing on synthetic medium. Heterologous expression of SiTPS in Escherichia coli showed that the produced protein catalyzes the synthesis of a few sesquiterpenoids, with the alcohol viridiflorol being the main product. To investigate the role of SiTPS in the plant-endophyte interaction, an SiTPS-over-expressing mutant line was created and assessed for its ability to colonize tomato roots. Although overexpression of SiTPS did not lead to improved fungal colonization ability, an in vitro growth-inhibition assay showed that viridiflorol has antifungal properties. Addition of viridiflorol to the culture medium inhibited the germination of spores from a phytopathogenic fungus, indicating that SiTPS and its products could provide S. indica with a competitive advantage over other plant-associated fungi during root colonization.

Drivers and implications of distance decay differ for ectomycorrhizal and foliar endophytic fungi across an anciently fragmented landscape.

Fungal communities associated with plants often decrease in similarity as the distance between sampling sites increases (i.e., they demonstrate distance decay). In the southwestern USA, forests occur in highlands separated from one another by warmer, drier biomes with plant and fungal communities that differ from those at higher elevations. These disjunct forests are broadly similar in climate to one another, offering an opportunity to examine drivers of distance decay in plant-associated fungi across multiple ecologically similar yet geographically disparate landscapes. We examined ectomycorrhizal and foliar endophytic fungi associated with a dominant forest tree (Pinus ponderosa) in forests across ca. 550 km of geographic distance from northwestern to southeastern Arizona (USA). Both guilds of fungi showed distance decay, but drivers differed for each: ectomycorrhizal fungi are constrained primarily by dispersal limitation, whereas foliar endophytes are constrained by specific environmental conditions. Most ectomycorrhizal fungi were found in only a single forested area, as were many endophytic fungi. Such regional-scale perspectives are needed for baseline estimates of fungal diversity associated with forest trees at a landscape scale, with attention to the sensitivity of different guilds of fungal symbionts to decreasing areas of suitable habitat, increasing disturbance, and related impacts of climate change.

Comparative transcriptomics reveal different mechanisms for hyphal growth across four plant-associated dimorphic fungi

Fungal dimorphism is a phenomenon by which a fungus can grow both as a yeast form and a hyphal form. It is frequently related to pathogenicity as different growth forms are more suitable for different functions during a life cycle. Among dimorphic plant pathogens, the corn smut fungus Ustilago maydis serves as a model organism to understand fungal dimorphism and its effect on pathogenicity. However, there is a lack of data on whether mechanisms elucidated from model species are broadly applicable to other fungi. In this study, two non-model plant-associated species in the smut fungus subphylum (Ustilaginomycotina), Tilletiopsis washingtonensis and Meira miltonrushii, were selected to compare dimorphic mechanisms in these to those in U. maydis. We sequenced transcriptomic profiles during both yeast and hyphal growth in these two species using Tween40, a lipid mimic, as a trigger for hyphal growth. We then compared our data with previously published data from U. maydis and a fourth but unrelated dimorphic phytopathogen, Ophiostoma novo-ulmi. Comparative transcriptomics was performed to identify common genes upregulated during hyphal growth in all four dimorphic species. Intriguingly, T. washingtonensis shares the least similarities of transcriptomic alteration (hyphal growth versus yeast growth) with the others, although it is closely related to M. miltonrushii and U. maydis. This suggests that phylogenetic relatedness is not correlated with transcriptomic similarity under the same biological phenomenon. Among commonly expressed genes in the four species, genes in cell energy production and conversion, amino acid transport and metabolism and cytoskeleton are significantly enriched. Considering dimorphism genes characterized in U. maydis, as well as hyphal tip-associated genes from the literature, we found only genes encoding the cell end marker Tea4/TeaC and the kinesin motor protein Kin3 concordantly expressed in all four species. This suggests a divergence in species-specific mechanisms for dimorphic transition and hyphal growth.

Benefits to Plant Health and Productivity From Enhancing Plant Microbial Symbionts.

Plants exist in close association with uncountable numbers of microorganisms around, on, and within them. Some of these endophytically colonize plant roots. The colonization of roots by certain symbiotic strains of plant-associated bacteria and fungi results in these plants performing better than plants whose roots are colonized by only the wild populations of microbes. We consider here crop plants whose roots are inhabited by introduced organisms, referring to them as Enhanced Plant Holobionts (EPHs). EPHs frequently exhibit resistance to specific plant diseases and pests (biotic stresses); resistance to abiotic stresses such as drought, cold, salinity, and flooding; enhanced nutrient acquisition and nutrient use efficiency; increased photosynthetic capability; and enhanced ability to maintain efficient internal cellular functioning. The microbes described here generate effects in part through their production of Symbiont-Associated Molecular Patterns (SAMPs) that interact with receptors in plant cell membranes. Such interaction results in the transduction of systemic signals that cause plant-wide changes in the plants’ gene expression and physiology. EPH effects arise not only from plant-microbe interactions, but also from microbe-microbe interactions like competition, mycoparasitism, and antibiotic production. When root and shoot growth are enhanced as a consequence of these root endophytes, this increases the yield from EPH plants. An additional benefit from growing larger root systems and having greater photosynthetic capability is greater sequestration of atmospheric CO2. This is transferred to roots where sequestered C, through exudation or root decomposition, becomes part of the total soil carbon, which reduces global warming potential in the atmosphere. Forming EPHs requires selection and introduction of appropriate strains of microorganisms, with EPH performance affected also by the delivery and management practices.

Interkingdom plant-microbial ecological networks under selective and clear cutting of tropical rainforest

Recent studies have revealed that interkingdom relationships in below-aboveground metacommunity may contribute to ecosystem functions more than species diversity. While effects of deforestation on aboveground interactions have been well studied, the responses of interactions among plant, soil bacterial and fungal communities to deforestation are pooly understood and their effects on vegetation restoration remain unknown. We sequenced soil 16S rRNA and ITS genes from the primary forest without logging history and secondary forests that had been clear cut or selective cut and left to recover for up to 50 years in the typical tropical rainforest in Hainan Island. Soil bacterial-fungal, plant-bacterial and plant-fungal associations were illustrated via ecological network analysis, and their correlations with plant composition, soil and litter properties were examined to explore the links to ecosystem functions.A higher negative proportion of bacterial-fungal interactions was found in selective cut sites while a higher positive proportion presented in clear cut sites. The changes after selective cut was related to tree composition and reductions in nitrogen and phosphorus content from soil and litter, indicating increased competition for nutrients, decoupling of communities and niche differentiation. The bacterial-fungal interaction changes after clear cut was associated with decrease in tree biomass and soil carbon content while increase in litter carbon content, implying increased co-operation in nutrient strategies and community homogenization. This ecological implications of bacterial-fungal interaction after clear cut was also applicable to plant-microbial interaction showing modular structure and strong across-module associations and significant correlations with litter carbon and soil nitrogen availability, which was indicative of a particular collection of microbial members under given plant species driving by changes in carbon and nitrogen content. Overall, the responses of bacterial-fungal and plant–microbe interactions to selective cut may in term promote the recovery of plant diversity during forest restoration, whereas these responses to clear cut may hinder the recovery of plant community diversity, and more costly restoration approaches based on different tree species planting will be required. This study suggested that the interkingdom interactions in below-aboveground metacommunity are indicative of changes in tree composition and soil fertility during the restoration of logged forest, and changes in such interkingdom interactions could in turn influence plant diversity and soil nutrients transformation.

Take-All Disease: New Insights into an Important Wheat Root Pathogen.

Take-all disease, caused by the fungal root pathogen Gaeumannomyces tritici, is considered to be the most important root disease of wheat worldwide. Here we review the advances in take-all research over the last 15 years, focusing on the identification of new sources of genetic resistance in wheat relatives and the role of the microbiome in disease development. We also highlight recent breakthroughs in the molecular interactions between G. tritici and wheat, including genome and transcriptome analyses. These new findings will aid the development of novel control strategies against take-all disease. In light of this growing understanding, the G. tritici-wheat interaction could provide a model study system for root-infecting fungal pathogens of cereals.

Unraveling the AM fungal community for understanding its ecosystem resilience to changed climate in agroecosystems

The changing global climate affects the agroecosystem making it challenging to achieve the world’s sustainable development goals. Among the facets of belowground microbial communities, the arbuscular mycorrhizal fungi (AMF) hold an important place. They represent the most common symbiont phylum colonizing more than 80% of the plant families and are likely to be affected by global climate change. These fungi facilitate plant’s mineral acquisition, improving growth and protecting them from biotic and abiotic stresses. The elevated carbon dioxide (eCO2) level, temperature, increased nitrogen and phosphorus deposition influences the plant phenology and AMF functioning through changes in diversity and community composition of AMF. The interaction effects of soil management practices due to climate change affect the system productivity and perturb mineral cycling. Understanding the carbon and nitrogen cycling of an agro-ecosystem and its associated AMF communities concerning ecosystem productivity is the need of the hour. Plant-fungal associations require a more environment resilient approach to ameliorate the effect of anthropogenic changes in carbon and nitrogen cycles. Since AMF communities alter due to local environmental conditions and land-use changes, the most adapted community may help in predicting the mycorrhizal responses to chemical fertilizers, eCO2, temperature and drought. In this review, we aimed at investigating (i) the diversity and community composition of AMF in relation to the change in crop and soil management practices, and (ii) how the adapted AMF communities may perform in maintaining the ecosystem resilience of these agroecosystems under climate change conditions. Hence, AMF-plant symbiosis can be effectively integrated into global climate change models. Eventually, the ecosystem resilience will be better understood to exploit the resident AMF communities to offset some of the detrimental effects of anthropogenic environmental change.

Bioactive metabolites from the desert plant-associated endophytic fungus Chaetomium globosum (Chaetomiaceae)

Globosumin, an undescribed chromene-4,7(4aH)-dione-tetramic acid PKS-PKS-NRPS hybrid, and globosumone, an undescribed azaphilone, together with ten known metabolites, were isolated from the desert plant-associated endophytic fungus Chaetomium globosum (Chaetomiaceae). The planar structures and relative configurations of globosumin and globosumone were determined by high-resolution ESI-MS and NMR data, and the absolute configurations of these two metabolites were determined by electronic circular dichroism (ECD) and circular dichroism (CD) combined with time-dependent density functional theory (TDDFT)-based quantum-chemical calculations. Chaetoglobosin A displayed biological effects against the seedling growth of Arabidopsis thaliana (Brassicaceae) in a dose-dependent manner, and this compound also exhibited biological activity against two cancer cell lines, A549 and HepG2, with IC50 values of 6.82 ± 2.34 and 38.62 ± 7.44 μM, respectively.

Idiosyncratic responses to simulated herbivory by root fungal symbionts in a subarctic meadow

ABSTRACT Plant-associated fungi have elementary roles in ecosystem productivity. There is little information on the interactions between arbuscular mycorrhizal (AM) fungal symbiosis, fine endophytic (FE) and dark septate endophytic (DSE) fungi, and their host plants in cold climate systems. In particular, the environmental filters potentially driving the relative abundance of these root symbionts remain unknown. We investigated the interlinkage of plant and belowground fungal responses to simulated herbivory (clipping, fertilization, and trampling) in a subarctic meadow system. AM and FE frequency in the two target plant roots, Potentilla crantzii and Saussurea alpina, was unaffected by simulated herbivory, highlighting the importance and resilience of arbuscule forming mycorrhizas in a range of environmental conditions. Fertilization and trampling increased DSE colonization in P. crantzii roots although generally P. crantzii performance was reduced in these plots. The idiosyncratic responses by DSE fungal frequency in the two host plants in our experiment indicate that the host plant identity has a pivotal role in the DSE fungus–plant outcome. DSE fungal frequency did not respond to environmental manipulations in a manner similar to arbuscular mycorrhizas, suggesting that they have a different role in plant ecology.

A New Chromene Derivative and a New Polyalcohol Isolated From the Fungus Xylaria sp. 111A Associated With Garcinia polyantha Leaves

From the crude extract of the plant-associated fungus Xylaria sp. collected in Cameroon, a new 2 H-chromene derivative, hexacycloxylariolone (1), and a new polyalcohol, xylatriol (2), were isolated, in addition to 3 known compounds, 2,3-furandiol (3), 1,8-dimethoxynaphthalene (4), and 1-palmitoyl-rac-glycerol (5). Their chemical structures were established on the basis of the interpretation of spectroscopic data. Hexacycloxylariolone (1), 1,8-dimethoxynaphthalene (4), and 1-palmitoyl-rac-glycerol (5) showed antiproliferative activity by inhibiting the growth of Raw 264.7 and THP-1 cancer cell lines.

Investigating the Smuts: Common Cues, Signaling Pathways, and the Role of MAT in Dimorphic Switching and Pathogenesis.

The corn smut fungus Ustilago maydis serves as a model species for studying fungal dimorphism and its role in phytopathogenic development. The pathogen has two growth phases: a saprobic yeast phase and a pathogenic filamentous phase. Dimorphic transition of U. maydis involves complex processes of signal perception, mating, and cellular reprogramming. Recent advances in improvement of reference genomes, high-throughput sequencing and molecular genetics studies have been expanding research in this field. However, the biology of other non-model species is frequently overlooked. This leads to uncertainty regarding how much of what is known in U. maydis is applicable to other dimorphic fungi. In this review, we will discuss dimorphic fungi in the aspects of physiology, reproductive biology, genomics, and molecular genetics. We also perform comparative analyses between U. maydis and other fungi in Ustilaginomycotina, the subphylum to which U. maydis belongs. We find that lipid/hydrophobicity is a potential common cue for dimorphic transition in plant-associated dimorphic fungi. However, genomic profiles alone are not adequate to explain dimorphism across different fungi.

Evaluation of foliar fungus-mediated interactions with below and aboveground enemies of the invasive plant Ageratina adenophora.

Plant–fungal associations are frequently key drivers of plant invasion success. Foliar fungi can benefit their invasive hosts by enhancing growth promotion, disease resistance and environmental stress tolerance. However, the roles of foliar fungi may vary when a given invasive plant faces different stresses. In this study, we designed three independent experiments to evaluate the effects of a foliar fungus, Colletotrichum sp., on the growth performance of the invasive plant Ageratina adenophora under different soil conditions, as well as the responses of A. adenophora to the foliar fungal pathogen Diaporthe helianthi and to herbivory. We found that the soil type was the most influential factor for the growth of A. adenophora. The role of the foliar fungus Colletotrichum sp. varied in the different soil types but generally adversely affected leaf development in A. adenophora. Colletotrichum sp. may be a weak latent foliar pathogen that can enhance the pathogenicity of D. helianthi on leaves of A. adenophora and marginally reduce signs of herbivory by natural insects in the wild on A. adenophora seedlings. In general, the benefits of the foliar fungus Colletotrichum to the fitness of A. adenophora are not significant in the context of this experimental design. However, our data highlight the need to consider both aboveground and belowground biota in different soil habitats when evaluating the effects of foliar fungi.

Antifungal meroterpenes and dioxolanone derivatives from plant-associated endophytic fungus Phyllosticta sp. WGHL2

Four new meroterpenes named as guignardones U-X (1–4), along with eleven known meroterpenes (5–15) and three known dioxolanone derivatives (16–18), were obtained from the endophytic fungus Phyllosticta sp. WGHL2. The structural elucidation was conducted by HRESIMS, NMR, single crystal X-ray diffraction, along with ECD calculations and comparison. In antifungal tests, compound 16 possessed broad-spectrum antifungal activities against Rhizoctonia solani, Fusarium graminearum and Botrytis cinerea with inhibition ratio of 48.43%, 40.98%, and 49.53% at 50 μg/mL, respectively. Moreover, compound 16 showed moderate protective effect against B. cinerea in vivo at 200 μg/mL and exhibited effective inhibition on the spore germination of B. cinerea.

Morphological and molecular characterization of two graminicolous <i>Exserohilum</i> species associated with cultivated rice and early barnyard grass from Sri Lanka

The genus Exserohilum (Order Pleosporales, Class Dothideomycetes) comprises plant pathogenic hyphomycetous fungi, associated with poaceous hosts. Although numerous pathogenic species of Exserohilum are known globally, only E. turcicum and E. rostratum have been reported from Sri Lanka. In the present study, samples showing the symptoms of leaf blight of Oryza sativa (cultivated rice) and sheath blight of Echinochloa oryzoides (early barnyard grass) were collected and causal agents were primarily identified as Exserohilum spp. based on morphological characters. Molecular phylogenetic analyses based on three loci namely, nuclear ribosomal internal transcribed spacer (ITS), partial glyceraldehyde 3-phosphate dehydrogenase (GPDH) and translational elongation factor (TEF-1α) were used to infer evolutionary relationships and accurate identification. These isolates from O. sativa and Echinochloa oryzoides were identified as Exserohilum rostratum and E. oryzicola respectively. Both records are novel plant-fungal associations from Sri Lanka based on available data. This study suggests the need for morphological and molecular reassessments of emerging and poorly known species of fungi associated with cereals, their wild relatives and other economically important hosts in Sri Lanka.