Bark-inhabiting fungal communities of European chestnut undergo substantial alteration by canker formation following chestnut blight infection.

Background: Chestnut forests are severely threatened by chestnut blight caused by the fungal pathogen Cryphonectria parasitica and the infected trees exhibit bark canker in the later stage of the disease. European chestnut (Castanea sativa) is further infected by Gnomoniopsis smithogilvyi, another canker-causing fungal pathogen. We explored whether and how chestnut blight is reflected in bark-inhabiting fungal communities of European chestnut and also assessed the co-occurrence of C. parasitica and G. smithogilvyi. Materials and methods: We initially investigated the fungal communities of European chestnut bark tissues and further monitored changes in these fungal communities with regard to disease progression from infection to canker formation by analyzing bark samples from asymptomatic trees, asymptomatic trees with latent C. parasitica infection, and infected trees with canker tissues, using amplicon sequencing of the ITS2 region of rDNA. Results: The results showed that fungal community composition and diversity differed between the sample types. The fungal community composition was substantially reshaped by canker formation, whereas latent C. parasitica infection and more specifically pre-canker infection period per se had a weak effect. Fungal communities of canker samples was less diverse and more dissimilar to those of other sample types. C. parasitica dominated the mycobiome of canker samples, whereas G. smithogilvyi was found in only 9% of canker samples at very low abundances. However, G. smithogilvyi was a dominant fungus in the bark of healthy plants. Conclusion: This study highlights that canker formation is the principal driver of decreasing diversity and altered composition of the mycobiome in bark tissues of European chestnut infected by C. parasitica infection. It additionally emphasizes the scarce co-occurrence of C. parasitica and G. smithogilvyi on European chestnut.

Palm Foliage as Pathways of Pathogenic Botryosphaeriaceae Fungi and Host of New Lasiodiplodia Species from Mexico.

Tropical palm foliage is increasingly imported to satisfy the steady growing demand in European floristry. This palm foliage presumably carries along diverse fungi whose taxonomic and functional diversity have not been addressed so far. The present study investigated Botryosphaeriaceae fungi associated with the foliage of palm species Chamaedorea elegans, C. metallica, C. seifrizii, Dypsis lutescens and Lodoicea maldivica imported from Mexico. Five species were identified using combined morphological characterisation and multilocus phylogenetic analyses based on ITS, TEF-1α, TUB2 and RPB2. In addition to Endomelanconiopsis endophytica, Lasiodiplodia brasiliensis and L. euphorbicola, two new species, namely, L. lodoiceae sp. nov. and L. mexicanensis sp. nov, are proposed. Apart from E. endophytica, mostly known as endophyte, L. brasiliensis and L. euphorbicola are responsible for different rot diseases and the dieback of important tropical crop plants. In pathogenicity tests on the temperate pome fruits apple (Malus domestica) and pear (Pyrus communis), all six Botryosphaeriaceae species induced necrotic lesions at different degrees of severity, with highest the aggressiveness from L. euphorbicola and L. mexicanensis on apple and from L. mexicanensis on pear. The results indicate that tropical palm foliage can be a pathway of potentially pathogenic fungi that may give rise to concerns with regard to plant health in the destination countries.

Transferability of PCR-based diagnostic protocols: An international collaborative case study assessing protocols targeting the quarantine pine pathogen Fusarium circinatum.

Fusarium circinatum is a harmful pathogenic fungus mostly attacking Pinus species and also Pseudotsuga menziesii, causing cankers in trees of all ages, damping-off in seedlings, and mortality in cuttings and mother plants for clonal production. This fungus is listed as a quarantine pest in several parts of the world and the trade of potentially contaminated pine material such as cuttings, seedlings or seeds is restricted in order to prevent its spread to disease-free areas. Inspection of plant material often relies on DNA testing and several conventional or real-time PCR based tests targeting F. circinatum are available in the literature. In this work, an international collaborative study joined 23 partners to assess the transferability and the performance of nine molecular protocols, using a wide panel of DNA from 71 representative strains of F. circinatum and related Fusarium species. Diagnostic sensitivity, specificity and accuracy of the nine protocols all reached values >80%, and the diagnostic specificity was the only parameter differing significantly between protocols. The rates of false positives and of false negatives were computed and only the false positive rates differed significantly, ranging from 3.0% to 17.3%. The difference between protocols for some of the performance values were mainly due to cross-reactions with DNA from non-target species, which were either not tested or documented in the original articles. Considering that participating laboratories were free to use their own reagents and equipment, this study demonstrated that the diagnostic protocols for F. circinatum were not easily transferable to end-users. More generally, our results suggest that the use of protocols using conventional or real-time PCR outside their initial development and validation conditions should require careful characterization of the performance data prior to use under modified conditions (i.e. reagents and equipment). Suggestions to improve the transfer are proposed.

Phylogenetic study of the Colletotrichum species on imported citrus fruits uncovers a low diversity and a new species in the Colletotrichum gigasporum complex.

Colletotrichum species associated with citrus fruits are fragmentarily known and it lacks accordingly accurate information on the diversity carried alongside the trade of these commodities from producer countries to Europe. In this study, we investigated the molecular phylogenetic diversity, colonisation, and prevalence of Colletotrichum isolated from asymptomatic and diseased tissues of nine citrus fruit species from 17 geographically diverse countries. Totally 454 isolates were morphoculturally characterised, and multilocus analyses (ACT, ApMat, CHS-1, GAPDH, ITS, TUB2) was performed on a subset of representative morphotype isolates. Results led to the identification of three previously known species (Colletotrichum gloeosporioides, Colletotrichum karstii, Colletotrichum siamense) and one novel lineage comprising endophytic isolates from Citrus maxima. Based on this lineage, Colletotrichum citri-maximae is described as a new species in the Colletotrichum gigasporum complex, and is characterised by a long deletion in the GAPDH sequence, a character shared with three of its phylogenetic sister taxa. Prevalence of Colletotrichum varied among citrus species and was greatest on Citrus sinensis fruits. C. gloeosporioides was the most common species followed by C. siamense. Except for the new species, all other isolated Colletotrichum spp. also colonise citrus leaves, but the overall diversity on fruits may be lower than that of leaves.

Antiplasmodial and cytotoxic dibenzofurans from Preussia sp. harboured in Enantia chlorantha Oliv.

Two unusual dibenzofurans, preussiafurans A-B (1-2), together with six known compounds have been isolated from the fungus Preussia sp. occurring in Enantia chlorantha Oliv. The structures were established on the basis of 1D and 2D NMR spectroscopy and MS analysis. Compounds 1-4 showed antiplasmodial activity against erythrocytic stages of chloroquine-resistant Plasmodium falciparum (NF54) and moderate cytotoxicity on L6 cell lines with IC50 values of 8.67 and 14.8 µM, respectively.

Paeciloside A, a new antimicrobial and cytotoxic polyketide from Paecilomyces sp. strain CAFT156.

Paeciloside A (1) and eight known compounds, acremoauxin A (2), farinosones A (3) and B (4), 1,5-dideoxy-3-C-methyl-arabitol (5), ergosterol, ergosterol peroxide, cerebroside C, and adenosine, were isolated from cultures of Paecilomyces sp. CAFT156, an endophytic fungus occurring in Enantia chlorantha Oliv (Annonaceae) leaves. The structure of the new compound 1 was elucidated using MS, UV, 1D and 2D NMR experiments, while its absolute configuration was established by subsequent single-crystal X-ray diffraction analysis using copper Kα radiation and invariom nonspherical scattering factors. Paeciloside A (1) and compounds 2, 4, and 5 displayed inhibitory effects on two gram-positive bacteria, Bacillus subtilis and Staphylococcus aureus at a concentration of 40 µg per paper disk and moderate cytotoxicity towards brine shrimp larvae (Artemia salina). This study presents the first report on an endophytic fungus isolated from E. chlorantha Oliv and its natural products.

Hypochnella verrucospora (Basidiomycota, Atheliales), a neotropical new species with ornamented basidiospores.

Hypochnella verrucospora sp. nov. is described and illustrated from material collected in Brazil and Argentina. The new species is characterized by dark purplish, violaceous to dark lilaceous, resupinate and membranous basidiomes and ellipsoid to subcylindrical, pale brown, slightly thick-walled, amyloid and delicately ornamented basidiospores. The monotypic genus Hypochnella was represented so far by H. violacea, which is distinctly characterized by smooth basidiospores, and is restricted to temperate regions in the northern hemisphere, whereas H. verrucospora seems to be Neotropical. Morphological comparison of the two species and a discussion of the genus description of Hypochnella are provided.

Phylogenetic relationship of Marasmius mbalmayoensis sp. nov. to the tropical African Marasmius bekolacongoli complex based on nuc-LSU rDNA sequences.

Marasmius mbalmayoensis (Basidiomycotina, Marasmiaceae) growing on decayed leaves of Canarium schweinfurthii in the Mbalmayo Forest Reserve, Cameroon, is described. The species is remarkable due to the large basidiomata with shallow orange yellow umbilicus, long central stipe accompanied by similar long rhizomorphs on thickened basal mycelium and large lacrymiform to sigmoid basidiospores. The coarsely plicate pilei with lilac, violet to dark violaceous tints, and large distant adnate lamellae are reminiscent macroscopically of the tropical African species M. bekolacongoli. The phylogenetic relationship among M. mbalmayoensis and M. bekolacongoli was assessed, extended to other species of sects. Globulares and Sicci based on DNA sequences. Phylogenetic analysis based on nuc-LSU rDNA sequence data of selected Marasmiaceae taxa confirmed the placement of M. mbalmayoensis within the Marasmius spp. and its phylogenetic separation from M. bekolacongoli. Amyloflagellula inflata, which a BLAST analysis closely related to M. mbalmayoensis, clustered in the same clade with M. mbalmayoensis and M. bekolacongoli. The findings also indicated the complexity of M. bekolacongoli.