Gerhard Kost

Piriformospora indica, gen. et sp. nov., a new root-colonizing fungus.

A new fungus isolate was discovered in an arbuscular mycorrhizal fungal spore from a desert soil in India. It could easily be cultivated on various synthetic media, and formed pear-shaped chlamydos...

Regulation of cell separation in the dimorphic fungus Ustilago maydis

During its haploid phase the dimorphic fungus Ustilago maydis grows vegetatively by budding. We have identified two genes, don1 and don3, which control the separation of mother and daughter cells. Mutant cells form tree‐like clusters in liquid culture and grow as ring‐like (donut‐shaped) colonies on solid medium. In wild‐type U. maydis cells, two distinct septa are formed during cytokinesis and delimit a fragmentation zone. Cells defective for either don1 or don3 display only a single septum and fail to complete cell separation. don1 encodes a guanine nucleotide exchange factor (GEF) of the Dbl family specific for Rho/Rac GTPases. Don3 belongs to the germinal‐centre‐kinase (GC) subfamily of Ste20‐like protein kinases. We have isolated the U. maydis homologues of the small GTP binding proteins Rho2, Rho3, Rac1 and Cdc42. Out of these, only Cdc42 interacts specifically with Don1 and Don3 in the yeast two‐hybrid system. We propose that Don1 and Don3 regulate the initiation of the secondary septum, which is required for proper cell separation.

DNA Sequence Analyses Reveal Abundant Diversity, Endemism and Evidence for Asian Origin of the Porcini Mushrooms

The wild gourmet mushroom Boletus edulis and its close allies are of significant ecological and economic importance. They are found throughout the Northern Hemisphere, but despite their ubiquity there are still many unresolved issues with regard to the taxonomy, systematics and biogeography of this group of mushrooms. Most phylogenetic studies of Boletus so far have characterized samples from North America and Europe and little information is available on samples from other areas, including the ecologically and geographically diverse regions of China. Here we analyzed DNA sequence variation in three gene markers from samples of these mushrooms from across China and compared our findings with those from other representative regions. Our results revealed fifteen novel phylogenetic species (about one-third of the known species) and a newly identified lineage represented by Boletus sp. HKAS71346 from tropical Asia. The phylogenetic analyses support eastern Asia as the center of diversity for the porcini sensu stricto clade. Within this clade, B. edulis is the only known holarctic species. The majority of the other phylogenetic species are geographically restricted in their distributions. Furthermore, molecular dating and geological evidence suggest that this group of mushrooms originated during the Eocene in eastern Asia, followed by dispersal to and subsequent speciation in other parts of Asia, Europe, and the Americas from the middle Miocene through the early Pliocene. In contrast to the ancient dispersal of porcini in the strict sense in the Northern Hemisphere, the occurrence of B. reticulatus and B. edulis sensu lato in the Southern Hemisphere was probably due to recent human-mediated introductions.

First Remarks on the Symbiotic Interaction Between Piriformospora indica and Terrestrial Orchids

From a desert soil in northwest India monosporic inocula of Glomus mosseae were obtained. By placing the spores on plates with minimal medium (MM1, Williams 1992), a continuously growing mycelium could be isolated. The fungus was also cultivatable on other agar media and in liquid culture. It was described as Piriformospora indica Varma, Rexer, Kost & Franken (Varma et al. 1998).

Colonization of roots of cultivated Solanum lycopersicum by dark septate and other ascomycetous endophytes

Tomato (Solanum lycopersicum L.) roots from four different crop sites in Colombia were surface sterilized and 51 fungal isolates were obtained and conserved for further analysis. Based on microscopical observations and growth characteristics, 20 fungal isolates corresponded to genus Fusarium, six presented asexual conidia different from Fusarium, eight were sterile mycelia, seven of which had dark septate hyphae and 17 did not continue to grow on plates after being recovered from conservation. Growth on different media, detailed morphological characterization and ITS region sequencing of the six sporulating and eight sterile isolates revealed that they belonged to different orders of Ascomycota and that the sterile dark septate endophytes did not correspond to the well known Phialocephala group. Interactions of nine isolates with tomato plantlets were assessed in vitro. No effect on shoot development was revealed, but three isolates caused brown spots in roots. Colonization patterns as analyzed by confocal microscopy differed among the isolates and ranged from epidermal to cortical penetration. Altogether 11 new isolates from root endophytic fungi were obtained, seven of which showed features of dark septate endophytes. Four known morphotypes were represented by five isolates, while six isolates belonged to five morphotypes of putative new unknown species.

The taxonomic foundation, species circumscription and continental endemisms of Singerocybe: evidence from morphological and molecular data

The genus Singerocybe (Tricholomataceae, Agaricales, Basidiomycota) has been the subject of controversy since its proposal in 1988. Its taxonomic foundation, species circumscription and geographical distribution have not yet been examined with molecular sequence data. In this study phylogenetic analyses on this group of fungi were conducted based on collections from Europe, eastern Asia, southern Asia, North America and Australia, with four nuclear markers, ITS, nrLSU, tef1-α and rpb2. Molecular phylogenetic analyses, together with morphological observations, strongly support Singerocybe as a monophyletic group and identify the vesicles in the pileal and stipe cuticle as a synapomorphy of this genus. Seven species are recognized in the genus, including one new species and four new combinations. Clitocybe trogioides and Clitocybe trogioides var. odorifera are synonyms of Singerocybe humilis and Singerocybe alboinfundibuliformis respectively. Most of these species are geographically restricted in their distributions. Furthermore our study expands the distribution range of Singerocybe from the North Temperate Zone to Australia (Tasmania) and tropical southern Asia.

Macrofungi on soil in coniferous forests

A survey is given about species composition of higher fungi in coniferous forest communities. Natural forest communities as weH as artificial forest stands are considered. Host range of mycorrhizal fungi, dependence of soil conditions (pH-value, nutrient content, moisture) and climate are discussed in detail. 1. Artificial spruce forests In comparison to natural Piceetum-communities the macromycetes flora of spruce plantation is reduced and varies within a wide range. It consists of frequent and ecologically unspecific species. The dominating fungal species are mostly acidophilic. A complied list of macromycetes species of spruce forests is given. It gives information about abundance, occurrence on different soil types, distribution in different altitudes and areas of Europe. Only some widespread litter decomposing and lignicolous fungi can abundantly be found in spruce plantations. The age of the forest stands distinctly influences the composition of fungal species and their abundance. Disturbances of forest stands caused by man change the natural macromycetes flora. The reduction of species in forest stands is directly dependent on the intensity of forestry management. After manuring with nitrogen or depositing chalk, the fungal flora is transformed by elimination of acidophilic species and by invasion of more neutrophilic fungi. 2. Fungi of natural Piceetum The fungal vegetation of natural spruce forests mainly consists of acidophilic macromycetes. Some neutrophilic species fructificate in Piceetum on chalkcontaining soil of deeply weathered limestone. A few species are exclusively distributed in the boreal or subalpine areas of Norway spruce (see list). Most macromycetes associated with Picea abies in natural Piceetum can also be found in spruce plantations in the lowlads. 3. Fungi in forest communities with silver fir Forest communities with silver fir, which grow in sites with good mineral sources and higher soil pH-values, have a characteristic macromycetes flora. Some of these macromycetes can also be associated with broadleaf trees (especially Fagussp.). In silver fir forests on acid soil, some acidophilic fungi commonly found in Picea-forest communities also occur. While soil inhabiting fungi of Abies are sensitive for climatical conditions. 4. Fungi in Pinus cembra — Larix decidua forests of central Alps Beside ectomycorrhizal species associated with Pinus cembra or Larix decidua, some other macromycetes, adapted to other species of the genus Pinus, can be found in these forest communities. Lists of characteristic species are given. The litter decomposing and soil-inhabiting Basidiomycetes mostly are unspecific, widespread, and common species of coniferous forests. 5. Fungi in pine forest communities Many ectomycorrhizal and saprophytical macromycetes living in pine forests are stenecously adapted to these forest communities. In may cases the ecological amplitude of Pinus sylvestris is broader than that of the associated fungi. Therefore, the fungal vegetation of certain pine forests characteristic species of several pine forest communities. Lists of important and characteristic species of several pine forest communities (pine forest on dunes, moor pine forests, Empertrum-Pinus-forests, Pinus sylvestris forests on chalky soil) are presented. The fungal species composition of pine plantations is discussed. In sandy (silicatic) pine forests a rich macromycetes flora thrives, but many pine forest associated fungi are strongly threatened. The decline of many macrofungi of pine forests on poor, acid soil is remarkable. But the fungal flora of all indigenous forest communities has to be protected. The problem is that in many cases the knowledge about composition of the fungi in forest communities is deficient. Many additional studies are necessary to elucidate the interactions between fungi and plants in forests communities.

Morphology and Ultrastructure of Piriformospora indica

A review is given about the morphological and ultrastructural characters of Piriformospora indica. The morphology of hyphal cells, mycelial, and chlamydospores are described in detail. Piriformospora is able to form different types of interactions with plant groups mosses, ferns, and gymno- and angiosperms. A survey of the tested host plants is given. The morphology of interacting hyphae and root cells depends on the plant species. Besides the mutualistic mode of life, Piriformospora indica is able to live as an endophytic fungus; under specific conditions, this species can behave as a necrotrophic fungus. All these different characters of the plant growth-promoting fungus, Piriformospora indica, indicate that this species is very valuable for basic research and a wide spectrum of applications in agriculture and horticulture.

Six newly developed microsatellite markers of Laccaria amethystina, using an improved CSSR approach

Microsatellite markers were established by an improved combined simple sequence repeat (CSSR) approach for the ectomycorrhizal basidiomycete Laccaria amethystina. Six markers delivered codominant polymorphic results, with up to six different alleles. They were tested with DNA originating from sporocarps and ectomycorrhizal root tips from silver fir (Abies alba), collected in the northern Black Forest. Sporocarps and ectoymcorrhizae exhibited similar allelic profiles, without any distorting influence of the host tree species. Results were compared to allelic profiles delivered by three published Asian markers. Allelic frequencies of the new markers showed a higher resolution of individuals within the population community, but partially a lower grade of heterozygosity. Possible reasons are discussed, and further questions addressed.

Analysis of the volatilome of Calocybe gambosa

The volatilomes of fresh and dried fruiting bodies of Calocybe gambosa were analyzed and compared in this study for the first time. Aroma compounds were extracted by means of liquid/liquid extraction, purified by solvent assisted flavor evaporation (SAFE), and identified by gas chromatography-mass spectrometry and olfactometry. An aroma extract dilution analysis (AEDA) was performed to identify the key flavor compounds, and the main volatiles were quantified by GC flame ionization detection. The key odor compound of fresh fruiting bodies of C. gambosa was (E)-non-2-enal, which, together with (E)-non-2-en-1-ol, was responsible for the characteristic flour- and cucumber-like odor. The aroma profile of commercially available dried fruiting bodies of C. gambosa showed a different pattern. In the dried fruiting bodies, odor compounds like 3-methylbutanoic acid were dominating, and (E)-non-2-enal was not detectable. Thus, the aroma quality of commercially available dried fruiting bodies of C. gambosa differs significantly from that of freshly collected specimens.