This issue of Mycological Research News features: Davidiella, a new generic name for the teleomorph of Cladosporium s. str.; Will European forest fires favour Neurospora ascomata?; Programmed cell death alive and well in fungi; and Complex conidia as branched hyphal systems; An obituary for Colin Booth (1924–2003), a leading authority on Fusarium and a past-President of the British Mycological Society, is also presented.

A detailed review of chemical interactions between mycorrhizal fungi and toxic metal cations is followed by ten original research papers. These consider the molecular phylogenetics of Caloplaca and Xanthoria, Termitomyces spp. and related fungi, the separation of Linocarpon and Neolinocarpon spp. using ultrastructural features, the Leptosphaeria maculans–L. biglobosa complex, diversity within Hyaloperonospora parasitica and Thanatephoriu cucumeris (anamorph Rhizoctonia solani), the development of markers for studies within Phialocephala fortinii, host–parasite relationships in Hypomyces spp., hypovirulence in Sclerotinia sclerotiorum, and airborne mould spores in apartments.

No new scientific names are introduced in this part.

Mycorrhizal associations, including ericoid, arbuscular and ecto-mycorrhizas, are found colonising highly metal contaminated soils. How do mycorrhizal fungi achieve metal resistance, and does this metal resistance confer enhanced metal resistance to plant symbionts? These are the questions explored in this review by considering the mechanistic basis of mycorrhizal adaptation to metal cations. Recent molecular and physiological studies are discussed. The review reappraises what constitutes metal resistance in the context of mycorrhizal associations and sets out the constitutive and adaptive mechanisms available for mycorrhizas to adapt to contaminated sites.

The only direct evidence of mycorrhizal adaptation to metal cation pollutants is the exudation of organic acids to alter pollutant availability in the rhizosphere. This is not to say that other mechanism of adaptation do not exist, but conclusive evidence of adaptive mechanisms of tolerance are lacking. For constitutive mechanisms of resistance, there is much more evidence, and mycorrhizas possess the same constitutive mechanisms for dealing with metal contaminants as other organisms.

Rhizosphere chemistry is critical to understanding the interactions of mycorrhizas with polluted soils. Soil pH, mineral weathering, pollutant precipitation with plant excreted organic acids all may have a key role in constitutive and adaptive tolerance of mycorrhizal associations present on contaminated sites.

The responses of mycorrhizal fungi to toxic metal cations are diverse. This, linked to the fact that mycorrhizal diversity is normally high, even on highly contaminated sites, suggests that this diversity may have a significant role in colonisation of contaminated sites by mycorrhizas. That is, the environment selects for the fungal community that can best cope with the environment, so having diverse physiological attributes will enable colonisation of a wide range of metal contaminated micro-habitats.

A molecular phylogenetic analysis of rDNA was performed for seven Caloplaca, seven Xanthoria, one Fulgensia and five outgroup species. Phylogenetic hypotheses are constructed based on nuclear small and large subunit rDNA, separately and in combination. Three strongly supported major monophyletic groups were revealed within the Teloschistaceae. One group represents the Xanthoria fallax-group. The second group includes three subgroups: (1) X. parietina and X. elegans; (2) basal placodioid Caloplaca species followed by speciations leading to X. polycarpa and X. candelaria; and (3) a mixture of placodioid and endolithic Caloplaca species. The third main monophyletic group represents a heterogeneous assemblage of Caloplaca and Fulgensia species with a drastically different metabolite content. We report here that the two genera Caloplaca and Xanthoria, as well as the subgenus Gasparrinia, are all polyphyletic. The taxonomic significance of thallus morphology in Teloschistaceae and the current delimitation of the genus Xanthoria is discussed in light of these results.

Phylogenetic relationships of termitophilic fungi were estimated with Bayesian as well as other phylogenetic methods from partial sequences of the nuclear encoded large subunit ribosomal DNA (nLSU-rDNA) and the mitochondrial encoded small subunit ribosomal DNA (mtSSU-rDNA). Sequences were obtained from basidiomes covering the morphological, taxonomical, and geographical span of termitophilic mushroom-forming fungi, and analysed together with sequences from termite nests and termite guts from most known genera of fungus growing termites from geographically diverse regions. Topologies of trees resulting from the combined analyses of the two ribosomal genes generally show no positive conflicts with those obtained from separate analyses. We show that termitophilic fungi constitute a strongly supported monophyletic group within lyophylloid species. The genera Sinotermitomyces and Podabrella are derived within Termitomyces, and do not form monophyletic groups. Identical sequences were frequently found among samples of basidiomes from the same continents and among fungi utilized by termites from the same continent. However, only two sequences were identical between basidiome samples and termite nest/gut samples suggesting fruiting species do not form a representative sample of termitophilic fungi. No sequences were identical between samples from Asia and Africa indicating some geographic differentiation between these continents.

Leptosphaeria maculans (anamorph Phoma lingam), the ascomycete causing stem canker of crucifers, is a species complex that can be separated into at least seven distinct subgroups using a combination of biochemical and molecular criteria. In the present study sequences of the entire ITS region, including the 5.8S rDNA, of 38 isolates representing the seven subgroups, along with specimens from culture collections, were analysed, compared to those of closely related Leptosphaeria species, and the phylogeny inferred using parsimony and distance analyses. A well-supported clade encompassed all isolates of the seven subgroups along with L. conferta, a known saprobe of dried crucifer stems. The L. maculans isolates were further separated into two well-supported clades corresponding to L. maculans s. str. and the recently named L. biglobosa. Parsimony and distance analyses further separated groups within both species, usually corresponding to specific host plants or geographic origin, e.g. L. maculans ‘brassicae’ from cultivated Brassica, L. maculans ‘lepidii’, from Lepidium sp., L. biglobosa ‘brassicae’, from various Brassica species, L. biglobosa ‘thlaspii’ from Thlaspi arvense, L. biglobosa ‘erysimii’ from Erysimum sp., and L. biglobosa ‘canadensis’ mostly found in central Canada. The oldest L. maculans specimens maintained in international collections clustered with either L. maculans ‘brassicae’, L. biglobosa ‘brassicae’, or a still different group closely related to L. biglobosa ‘thlaspii’. The evolutionary relationships between the seven infraspecific groups are discussed in terms of phytopathological relevance and species isolation linked with specific life cycle, geographic isolation or host specificity.

Ascospore appendages of two species of Linocarpon and three species of Neolinocarpon are illustrated using electron microscopy. The structure of these appendages can be used to distinguish between species. The ascospore appendages of species in both genera, however, were found to have similar structure. Thus, species of Linocarpon and Neolinocarpon could not be delineated at the generic level based on ascospore appendage structure.

Sequence analysis of the ITS region of rDNA was used to investigate the level of genetic diversity occurring within Hyaloperonospora parasitica, and to show the relationship between phylogenies of these fungi and their hosts (Brassicaceae). Maximum parsimony and neighbour-joining analyses were performed using sequences from 32 isolates of Hyaloperonospora and Perofascia, which infect core brassicaceous hosts. For comparison, five isolates of Peronospora were also studied. The constructed phylogenetic trees showed trichotomy, showing that Hyaloperonospora, Perofascia, and Peronospora have different evolutionary histories. Although isolates from Peronospora and Perofascia clearly formed respective clades, the Hyaloperonospora group allowed separation of the isolates into four distinct clades, which shared significantly low sequence similarities. We suggest that H. parasitica infecting brassicaceous hosts should be divided into a number of distinct species. The comparison of the phylogeny of H. parasitica and that of the Brassicaceae suggests that this fungus is closely related with tribes Arabidae and Brassiceae within this host family, illustrating the potential of downy mildews for co-evolution with their hosts.

DNA sequence analysis of the internal transcribed spacer region 1 (ITS1) and random amplified polymorphic DNA (RAPD) markers were used to survey genetic variability in relation to agronomic and regional factors among 60 isolates of Thanatephorus cucumeris (anamorph Rhizoctonia solani) collected from lesions on potato stems or sclerotia of potato tubers. Based on comparative sequence analysis it was shown that all isolates belonged to anastomosis group 3 subgroup Potato Type (AG-3 PT). ITS1 sequence polymorphisms were found within 45 of the 60 isolates showing that different types of the ITS-region are present in individual isolates. Cloning and sequence analysis of the ITS1 region from three selected isolates with sequence polymorphism showed that two different ITS1-types were present in each isolate. RAPD analysis identified 51 RAPD-phenotypes among the 60 investigated isolates indicating a high level of diversity within the subgroup AG-3 PT. Putative clonal isolates with identical RAPD- and ITS1-types were identified within fields, and in one case the same phenotype was found in two different fields separated by several hundred kilometers. Population subdivision analysis based on phenotypic as well as genotypic diversities showed differentiation among populations from different fields when isolates were sampled from tubers, indicating restricted gene flow among soil populations. Low differentiation was seen among field populations sampled from stems, indicating that gene flow is taking place. The population structure was not influenced by the previous crop in the rotation nor by the two cultivars ‘Sava’ and ‘Bintje’.

Single-copy RFLP markers were developed for the root endophytic fungus Phialocephala fortinii. After an initial screening of 40 probes with four restriction enzymes, EcoRV and HindIII were chosen to analyse 31 strains of P. fortinii and nine strains of a closely related morphotype (Type 1) which have known ISSR-PCR or allozyme phenotypes. Type 1 isolates and a single genetically different isolate with Type 1 like morphology, a representative of a possible third taxon, showed unique alleles with several probes and both restriction enzymes. Consequently, both taxa were easily distinguishable from P. fortinii isolates. Whereas EcoRV in combination with seven probes revealed only eight multi-locus haplotypes among 17 ISSR phenotypes, HindIII in combination with 12 probes was able to distinguish all ISSR and/or allozyme phenotypes except two pairs of strains. Strains of P. fortinii showed a high gene diversity, and up to 15 alleles per locus were observed among the 31 strains of P. fortinii. The 12 probes used in combination with HindIII were (partially) sequenced and BLAST searches showed no similarities with known sequences indicating that they probably are non-coding regions of the genome. Enzyme-probe combinations suitable to indicate the genetic structure of P. fortinii and Type 1 populations were easily identified in the present study. This opens up avenues to study communities of the P. fortinii complex exposed to various environments and management intensities, and will help to promote the understanding of these extremely successful organisms.

Host specificity of the mycoparasite Hypomyces microspermus to the Xerocomus chrysenteron group has been observed, but primarily from European collections. Our objectives were to test host specificity among Hypomyces spp. associated with boletes in California oak-woodlands, investigate population biology of these parasites, and to initiate studies on host-parasite coevolution. Bolete samples were collected from four locations separated by up to 600 km. Hypomyces isolates were cultured and host tissue samples taken for molecular identification. Based on AFLP analysis, four distinct Hypomyces clades were found with little genotypic diversity within each group. ITS-rDNA regions of selected isolates from each group were sequenced and analyzed along with sequences from a previously published phylogeny. Isolates from two AFLP groups clustered with H. microspermus whereas isolates from the other two AFLP groups clustered with H. chrysospermus. ITS-RFLP followed by sequence analysis identified three bolete hosts: (1) X. dryophilus; (2) a Xerocomus species closely related to X. dryophilus with affinities to X. chrysenteron; and (3) a Xerocomus species related to the X. subtomentosus group, which is not closely related to X. dryophilus and X. chrysenteron. H. microspermus infected X. dryophilus and the species with affinities to X. chrysenteron, whereas H. chrysospermus infected the species with affinities to X. chrysenteron and the species related to the X. subtomentosus group. These results support previous observations that H. microspermus is host-specific to the X. chrysenteron group, and that H. chrysospermus is more of a generalist pathogen. We also conclude that host-parasite coevolution studies within this system will not be possible until a phylogeny of North American boletes is in place.

Spontaneously-occurring hypovirulence in the tan sclerotial isolate S10 of Sclerotinia sclerotiorum from sunflower in Canada was characterized and compared to another hypovirulent isolate Ep-1PN of S. sclerotiorum from eggplant in China. Hypovirulent isolates derived from S10 were purified by single hyphal tip isolations from colonies of S10 showing abnormal growth on potato dextrose agar (PDA) and tested for pathogenicity on leaves of canola (Brassica napus cv. ‘Westar’). These abnormal isolates differed from the virulent isolate wtS10 derived from a normal colony of S10 by the reduced hyphal growth, induced production of abnormal hyphal branches, enhanced production of brown pigments, reduced sclerotial formation on PDA, reduced oxalic acid accumulation in potato dextrose broth, and reduced pathogenicity on canola. Vegetative transfers revealed that the hypovirulence phenotype of the hypovirulent isolate S10-2A-11 was stable. This preliminary in vitro transmission test indicated that the hypovirulence in the isolate S10-2A-11 was transmissible but at a lower rate than that of the hypovirulent isolate Ep-1PN. Double-stranded ribonucleic acids (dsRNAs) were detected in isolate Ep-1PN, but not in hypovirulent and virulent isolates derived from S10. The existence of dsRNA-free hypovirulence in S10 progenies suggests that another hypovirulence mechanism may exist in S. sclerotiorum.

Indoor air contamination with mould spores currently experiences an increasing interest with respect to their relevance to health. To assess adverse health effects, epidemiological studies combine the health outcome of individuals with their concomitant exposure to airborne spores, which is observed, for example, during the current month. While the latter is representative for the studied period, health effects might also be the result of long term-exposure or emerge in consequence of a peak of pollution throughout the year. To consider such questions, additional information about the spatiotemporal distribution of airborne spores is necessary.

This paper aims at elucidating the spatial and temporal variation of spore concentrations in Leipzig, Germany. The analysis is based on 1165 matched pairs of indoor and outdoor measurements taken in the period 1998–2002. All data were collected in the frame of previous epidemiological studies and refer to apartments. The analysis comprised spore concentrations (as CFU m−3 in air) of the most important genera, such as Penicillium, Aspergillus, Alternaria, Mucorales, Cladosporium, and also for yeasts.

We found two groups of fungi differing in their spatiotemporal distribution. As this behaviour can be explained by the predominant origin and growing conditions, we call them indoor-relevant and outdoor-relevant genera. Penicillium species are a representative of the former group, while the latter is well represented by Cladosporium. In the studied period we did not observe a clear trend in the spore concentration. Outdoors there is a year-to-year variation of Cladosporium spore concentrations, which follow the prevalent climatic conditions.

For the spore concentration of the outdoor-relevant group a significant annual cycle was observed. Highest concentrations occurred during the summer months and were about 100× the winter burden. That means, for a direct comparison of measurements of spore concentrations taken during different months the season has to be considered. We summarise the findings in a seasonal model, which is fitted to our measurements. Based on the model we developed a procedure for seasonal adjustment, which enabled us to estimate the annual peak spore concentration utilising one monthly observation.

Colin Booth, Assistant Director of the Commonwealth Mycological Institute from 1969–85, Secretary of the International Mycological Association 1971–77, and President of the British Mycological Society in 1977, died in 2003, aged 78 years.

Mycological Research107 (8): 901–916 (August 2003).

In the review paper by Tehler, Little & Farris, ‘The full-length phylogenetic tree from 1551 ribosomal sequences of chitinous fungi, Fungi’, two parts of Fig. 4 were omitted and incorrectly replaced by other parts of the figure during printing after checking by the authors and Executive Editor.

The Publishers wish to apologise for this mistake, and regret the inevitable inconvenience and confusion caused by those wishing to interpret this Figure.