New and Interesting Fungi. 5.

Nine new genera, 17 new species, nine new combinations, seven epitypes, three lectotypes, one neotype, and 14 interesting new host and / or geographical records are introduced in this study. New genera: Neobarrmaelia (based on Neobarrmaelia hyphaenes), Neobryochiton (based on Neobryochiton narthecii), Neocamarographium (based on Neocamarographium carpini), Nothocladosporium (based on Nothocladosporium syzygii), Nothopseudocercospora (based on Nothopseudocercospora dictamni), Paracamarographium (based on Paracamarographium koreanum), Pseudohormonema (based on Pseudohormonema sordidus), Quasiphoma (based on Quasiphoma hyphaenes), Rapidomyces (based on Rapidomyces narthecii). New species: Ascocorticium sorbicola (on leaves of Sorbus aucuparia, Belgium), Dactylaria retrophylli (on leaves of Retrophyllum rospigliosii, Colombia), Dactylellina miltoniae (on twigs of Miltonia clowesii, Colombia), Exophiala eucalyptigena (on dead leaves of Eucalyptus viminalis subsp. viminalis supporting Idolothrips spectrum, Australia), Idriellomyces syzygii (on leaves of Syzygium chordatum, South Africa), Microcera lichenicola (on Parmelia sulcata, Netherlands), Neobarrmaelia hyphaenes (on leaves of Hyphaene sp., South Africa), Neobryochiton narthecii (on dead leaves of Narthecium ossifragum, Netherlands), Niesslia pseudoexilis (on dead leaf of Quercus petraea, Serbia), Nothocladosporium syzygii (on leaves of Syzygium chordatum, South Africa), Nothotrimmatostroma corymbiae (on leaves of Corymbia henryi, South Africa), Phaeosphaeria hyphaenes (on leaves of Hyphaene sp., South Africa), Pseudohormonema sordidus (on a from human pacemaker, USA), Quasiphoma hyphaenes (on leaves of Hyphaene sp., South Africa), Rapidomyces narthecii (on dead leaves of Narthecium ossifragum, Netherlands), Reticulascus parahennebertii (on dead culm of Juncus inflexus, Netherlands), Scytalidium philadelphianum (from compressed air in a factory, USA). New combinations: Neobarrmaelia serenoae, Nothopseudocercospora dictamni, Dothiora viticola, Floricola sulcata, Neocamarographium carpini, Paracamarographium koreanum, Rhexocercosporidium bellocense, Russula lilacina. Epitypes: Elsinoe corni (on leaves of Cornus florida, USA), Leptopeltis litigiosa (on dead leaf fronds of Pteridium aquilinum, Netherlands), Nothopseudocercospora dictamni (on living leaves of Dictamnus albus, Russia), Ramularia arvensis (on leaves of Potentilla reptans, Netherlands), Rhexocercosporidium bellocense (on leaves of Verbascum sp., Germany), Rhopographus filicinus (on dead leaf fronds of Pteridium aquilinum, Netherlands), Septoria robiniae (on leaves of Robinia pseudoacacia, Belgium). Lectotypes: Leptopeltis litigiosa (on Pteridium aquilinum, France), Rhopographus filicinus (on dead leaf fronds of Pteridium aquilinum, Netherlands), Septoria robiniae (on leaves of Robinia pseudoacacia, Belgium). Neotype: Camarographium stephensii (on dead leaf fronds of Pteridium aquilinum, Netherlands). Citation: Crous PW, Begoude BAD, Boers J, Braun U, Declercq B, Dijksterhuis J, Elliott TF, Garay-Rodriguez GA, Jurjevic Z, Kruse J, Linde CC, Loyd A, Mound L, Osieck ER, Rivera-Vargas LI, Quimbita AM, Rodas CA, Roux J, Schumacher RK, Starink-Willemse M, Thangavel R, Trappe JM, van Iperen AL, Van Steenwinkel C, Wells A, Wingfield MJ, Yilmaz N, Groenewald JZ (2022) New and Interesting Fungi. 5. Fungal Systematics and Evolution 10: 19-90. doi: 10.3114/fuse.2022.10.02.

Redefining genera of cereal pathogens: Oculimacula, Rhynchosporium and Spermospora.

The taxonomy of Oculimacula, Rhynchosporium and Spermospora is re-evaluated, along with that of phylogenetically related genera. Isolates are identified using comparisons of DNA sequences of the internal transcribed spacer ribosomal RNA locus (ITS), partial translation elongation factor 1-alpha (tef1), actin (act), DNA-directed RNA polymerase II largest (rpb1) and second largest subunit (rpb2) genes, and the nuclear ribosomal large subunit (LSU), combined with their morphological characteristics. Oculimacula is restricted to two species, O. acuformis and O. yallundae, with O. aestiva placed in Cyphellophora, and O. anguioides accommodated in a new genus, Helgardiomyces. Rhynchosporium s. str. is restricted to species with 1-septate conidia and hooked apical beaks, while Rhynchobrunnera is introduced for species with 1-3-septate, straight conidia, lacking any apical beak. Rhynchosporium graminicola is proposed to replace the name R. commune applied to the barley scald pathogen based on nomenclatural priority. Spermospora is shown to be paraphyletic, representing Spermospora (type: S. subulata), with three new species, S. arrhenatheri, S. loliiphila and S. zeae, and Neospermospora gen. nov. (type: N. avenae). Ypsilina (type: Y. graminea), is shown to be monophyletic, but appears to be of minor importance on cereals. Finally, Vanderaaea gen. nov. (type: V. ammophilae), is introduced as a new coelomycetous fungus occurring on dead leaves of Ammophila arenaria. Citation: Crous PW, Braun U, McDonald BA, Lennox CL, Edwards J, Mann RC, Zaveri A, Linde CC, Dyer PS, Groenewald JZ (2020). Redefining genera of cereal pathogens: Oculimacula, Rhynchosporium and Spermospora. Fungal Systematics and Evolution 7: 67-98. doi: 10.3114/fuse.2021.07.04.

Evolutionary relationships among pollinators and repeated pollinator sharing in sexually deceptive orchids.

The mechanism of pollinator attraction is predicted to strongly influence both plant diversification and the extent of pollinator sharing between species. Sexually deceptive orchids rely on mimicry of species-specific sex pheromones to attract their insect pollinators. Given that sex pheromones tend to be conserved among related species, we predicted that in sexually deceptive orchids, (i) pollinator sharing is rare, (ii) closely related orchids use closely related pollinators and (iii) there is strong bias in the wasp lineages exploited by orchids. We focused on species that are pollinated by sexual deception of thynnine wasps in the distantly related genera Caladenia and Drakaea, including new field observations for 45 species of Caladenia. Specialization was extreme with most orchids using a single pollinator species. Unexpectedly, seven cases of pollinator sharing were found, including two between Caladenia and Drakaea, which exhibit strikingly different floral morphology. Phylogenetic analysis of pollinators using four nuclear sequence loci demonstrated that although orchids within major clades primarily use closely related pollinator species, up to 17% of orchids within these clades are pollinated by a member of a phylogenetically distant wasp genus. Further, compared to the total diversity of thynnine wasps within the study region, orchids show a strong bias towards exploiting certain genera. Although these patterns may arise through conservatism in the chemical classes used in sex pheromones, apparent switches between wasp clades suggest unexpected flexibility in floral semiochemical production. Alternatively, wasp sex pheromones within lineages may exhibit greater chemical diversity than currently appreciated.

Population structure of an orchid mycorrhizal fungus with genus-wide specificity.

Fundamental life history processes of mycorrhizal fungi with inconspicuous fruiting bodies can be difficult to elucidate. In this study we investigated the species identities and life history of the orchid mycorrhizal Tulasnella fungi, which associate with the south eastern Australia orchid genus Chiloglottis. Tulasnella prima was the primary partner and was found to be associated with all 17 Chiloglottis species across a range of >1000 km, and to occur in the two edaphic conditions investigated (soil and sphagnum hammocks). Another Tulasnella species (T. sphagneti) appears to be restricted to moist conditions of alpine sphagnum hammocks. The population genetic structure of the widespread species T. prima, was investigated at 10 simple sequence repeat (SSR) markers and at four cross-amplified SSR loci for T. sphagneti. For both taxa, no sharing of multilocus genotypes was found between sites, but clones were found within sites. Evidence for inbreeding within T. prima was found at 3 of 5 sites. Significant genetic differentiation was found within and between taxa. Significant local positive spatial genetic autocorrelation was detected among non-clonal isolates at the scale of two metres. Overall, the population genetic patterns indicated that in Tulasnella mating occurs by inbreeding and dispersal is typically restricted to short-distances.

A Global Perspective on the Population Structure and Reproductive System of Phyllosticta citricarpa.

The citrus pathogen Phyllosticta citricarpa was first described 117 years ago in Australia; subsequently, from the summer rainfall citrus-growing regions in China, Africa, and South America; and, recently, the United States. Limited information is available on the pathogen's population structure, mode of reproduction, and introduction pathways, which were investigated by genotyping 383 isolates representing 12 populations from South Africa, the United States, Australia, China, and Brazil. Populations were genotyped using seven published and eight newly developed polymorphic simple-sequence repeat markers. The Chinese and Australian populations had the highest genetic diversities, whereas populations from Brazil, the United States, and South Africa exhibited characteristics of founder populations. The U.S. population was clonal. Based on principal coordinate and minimum spanning network analyses, the Chinese populations were distinct from the other populations. Population differentiation and clustering analyses revealed high connectivity and possibly linked introduction pathways between South Africa, Australia, and Brazil. With the exception of the clonal U.S. populations that only contained one mating type, all the other populations contained both mating types in a ratio that did not deviate significantly from 1:1. Although most populations exhibited sexual reproduction, linkage disequilibrium analyses indicated that asexual reproduction is important in the pathogen's life cycle.

Pollination by sexual deception promotes outcrossing and mate diversity in self-compatible clonal orchids.

The majority of flowering plants rely on animals as pollen vectors. Thus, plant mating systems and pollen dispersal are strongly influenced by pollinator behaviour. In Australian sexually deceptive orchids pollinated by male thynnine wasps, outcrossing and extensive pollen flow is predicted due to floral deception, which minimizes multiple flower visitations within patches, and the movement of pollinators under mate-search rather than foraging behaviours. This hypothesis was tested using microsatellite markers to reconstruct and infer paternity in two clonal, self-compatible orchids. Offspring from naturally pollinated Chiloglottis valida and C. aff. jeanesii were acquired through symbiotic culture of seeds collected over three seasons. In both species, outcrossing was extensive (tm  = 0.924-1.00) despite clone sizes up to 11 m wide. The median pollen flow distance based on paternity for both taxa combined was 14.5 m (n = 18, range 0-69 m), being larger than typically found by paternity analyses in other herbaceous plants. Unexpectedly for orchids, some capsules were sired by more than one father, with an average of 1.35 pollen donors per fruit. This is the first genetic confirmation of polyandry in orchid capsules. Further, we report a possible link between multiple paternity and increased seed fitness. Together, these results demonstrate that deceptive pollination by mate-searching wasps enhances offspring fitness by promoting both outcrossing and within-fruit paternal diversity.

Genetic diversity and mating type distribution of Tuber melanosporum and their significance to truffle cultivation in artificially planted truffieres in Australia.

Tuber melanosporum is a truffle native to Europe and is cultivated in countries such as Australia for the gastronomic market, where production yields are often lower than expected. We assessed the genetic diversity of T. melanosporum with six microsatellite loci to assess the effect of genetic drift on truffle yield in Australia. Genetic diversity as assessed on 210 ascocarps revealed a higher allelic diversity compared to previous studies from Europe, suggesting a possible genetic expansion and/or multiple and diverse source populations for inoculum. The results also suggest that the single sequence repeat diversity of locus ME2 is adaptive and that, for example, the probability of replication errors is increased for this locus. Loss of genetic diversity in Australian populations is therefore not a likely factor in limiting ascocarp production. A survey of nursery seedlings and trees inoculated with T. melanosporum revealed that <70% of seedlings and host trees were colonized with T. melanosporum and that some trees had been contaminated by Tuber brumale, presumably during the inoculation process. Mating type (MAT1-1-1 and MAT1-2-1) analyses on seedling and four- to ten-year-old host trees found that 100% of seedlings but only approximately half of host trees had both mating types present. Furthermore, MAT1-1-1 was detected significantly more commonly than MAT1-2-1 in established trees, suggesting a competitive advantage for MAT1-1-1 strains. This study clearly shows that there are more factors involved in ascocarp production than just the presence of both mating types on host trees.

Expansion of genetic diversity in randomly mating founder populations of Alternaria brassicicola infecting Cakile maritima in Australia.

Founder populations of fungal plant pathogens are expected to have low levels of genetic diversity coupled with further genetic drift due to, e.g., limited host availability, which should result in additional population bottlenecks. This study used microsatellite markers in the interaction between Cakile maritima and the fungal pathogen Alternaria brassicicola to explore genetic expectations associated with such situations. The host, C. maritima, was introduced into Australia approximately 100 years ago, but it is unknown whether the pathogen was already present in Australia, as it has a wide occurrence, or whether it was introduced to Australia on brassicaceous hosts. Eleven A. brassicicola populations were studied, and all showed moderate levels of gene and genotypic diversity. Chi-square tests of the frequencies of mating type alleles, a large number of genotypes, and linkage equilibrium among microsatellite loci all suggest A. brassicicola reproduces sexually. Significant genetic differentiation was found among populations, but there was no evidence for isolation by distance effects. Bayesian analyses identified eight clusters where the inferred clusters did not represent geographical populations but instead consisted of individuals admixed from all populations. Further analysis indicated that fungal populations were more likely to have experienced a recent population expansion than a population bottleneck. It is suggested that A. brassicicola has been introduced into Australia multiple times, potentially increasing the diversity and size of any A. brassicola populations already present there. Combined with its ability to reproduce sexually, such processes appear to have increased the evolutionary potential of the pathogen through recent population expansions.

Molecular evidence for recent founder populations and human-mediated migration in the barley scald pathogen Rhynchosporium secalis.

Rhynchosporium secalis is an important pathogen of barley globally. Fourteen polymorphic microsatellites were analyzed for 1664 R. secalis isolates sampled from 37 field populations to infer their demographic history. The results falsified the hypothesis that R. secalis co-evolved with its barley host in the Middle East. Populations from Scandinavia had significantly higher allelic diversities, the greatest number of private alleles and the highest genotypic diversities. All but three of the analyzed populations had an excess of gene diversity compared to the number of alleles, consistent with a recent population bottleneck. The remaining populations had a gene diversity deficit consistent with a population expansion following a recent population bottleneck in the last +/-100 years. A coalescent analysis revealed that the effective population sizes based on theta, of the analyzed populations were small relative to their ancestral population sizes, indicating that only a fraction of the diversity present in the ancestral populations was transmitted into current populations. These findings are consistent with the hypothesis that the pathogen population on barley experienced a selection bottleneck imposed by the host and/or are founder populations. The mean estimate of migration rates was 2.2 (avg 90% confidence interval=1.3-3.1). Major migration routes were identified among populations separated by long distances, eg between South Africa and Australia, as well as among North Africa, the Middle East and California, suggesting contemporary exchange of infected barley seed. In contrast with earlier findings, most populations exhibited significant gametic disequilibrium, probably as a result of genetic drift. We conclude that the majority of R. secalis populations have experienced human-mediated migration that led to numerous and relatively recent founder events around the world.

Variation for neutral markers is correlated with variation for quantitative traits in the plant pathogenic fungus Mycosphaerella graminicola.

We compared genetic variation and population differentiation at RFLP marker loci with seven quantitative characters including fungicide resistance, temperature sensitivity, pycnidial size, pycnidial density, colony size, percentage of leaves covered by pycnidia (PLACP) and percentage of leaves covered by lesions (PLACL) in Mycosphaerella graminicola populations sampled from four regions. Wide variation in population differentiation was found across the quantitative traits assayed. Fungicide resistance, temperature sensitivity, and PLACP displayed a significantly higher Q(ST) than G(ST), consistent with selection for local adaptation, while pycnidial size, pycnidial density and colony size displayed a lower or significantly lower Q(ST) than G(ST), consistent with constraining selection. There was not a statistical difference between Q(ST) and G(ST) in PLACL. We also found a positive and significant correlation between genetic variation in molecular marker loci and quantitative traits at the multitrait scale, suggesting that estimates of overall genetic variation for quantitative traits in M. graminicola could be derived from analysis of the molecular genetic markers.

Population Structure of Mycosphaerella graminicola: From Lesions to Continents.

ABSTRACT The genetic structure of field populations of Mycosphaerella graminicola was determined across a hierarchy of spatial scales using restriction fragment length polymorphism markers. The hierarchical gene diversity analysis included 1,098 isolates from seven field populations. Spatial scales ranged from millimeters to thousands of kilometers, including comparisons within and among lesions, within and among fields, and within and among regions and continents. At the smallest spatial scale, microtransect sampling was used to determine the spatial distribution of 15 genotypes found among 158 isolates sampled from five individual lesions. Each lesion had two to six different genotypes including both mating types in four of the five lesions, but in most cases a lesion was composed of one or two genotypes that occupied the majority of the lesion, with other rare genotypes interspersed among the common genotypes. The majority (77%) of gene diversity was distributed within plots ranging from approximately 1 to 9 m(2) in size. Genotype diversity (G / N) within fields for the Swiss, Texas, and Israeli fields was high, ranging from 79 to 100% of maximum possible values. Low population differentiation was indicated by the low G(ST) values among populations, suggesting a corresponding high degree of gene flow among these populations. At the largest spatial scale, populations from Switzerland, Israel, Oregon, and Texas were compared. Population differentiation among these populations was low (G(ST) = 0.05), and genetic identity between populations was high. A low but significant correlation between genetic and geographic distance among populations was found (r = -0.47, P = 0.012), suggesting that these populations probably have not reached an equilibrium between gene flow and genetic drift. Gene flow on a regional level can be reduced by implementing strategies, such as improved stubble management that minimize the production of ascospores. The possibility of high levels of gene flow on a regional level indicates a significant potential risk for the regional spread of mutant alleles that enable fungicide resistance or the breakdown of resistance genes.