This issue of Mycological Research News features: In this issue; 2004 snapshots of AM fungi: still an endless tale …; and Host specialization and evolution in Pneumocystis.

The first paper in this number describes and experiments with a new mathematical model of hyphal growth. Molecular phylogenetic papers address the circumscription of the Agaricaceae and the population biology and relationships within Phytophthora ramorum, Phomopsis isolates from sunflower, Datronia caperata, Leptographium wingfieldii, Pandora neoaphidis, and the Penicillium brevicompactum group.

A protein toxic to locusts produced by Beauveria bassiana is reported, and the translocation of carbon in microcosms by Rhizoctonia solani described.

No new scientific names are introduced in this part.

Filamentous hyphal growth is inherently suited to kinetic analysis, and in many respects the fungal mycelium can be viewed as a very mechanical biological system, which lends itself to mathematical modelling. The mathematics of hyphal tip extension growth are well-established. However, even though a hyphal growth equation can be written with confidence, and we have a good understanding of the effects of tropisms on growth, it is not easy to form a mental picture of the behaviour of large populations of hyphal tips. What is required, and what we believe we have produced, is a mathematical model that is sufficiently sophisticated to produce a realistic visualization of fungal hyphal growth. This provides us with a cyberfungus that can be used for experimentation on the theoretical rules that might govern hyphal patterning, hyphal interactions, and tissue formation and organ development by actually visualizing the virtual hyphal growth patterns that result from different regulatory scenarios. From a series of model experiments the most significant observation is that complex fungal fruit body shapes can be simulated by applying the same regulatory functions to all of the growth points active in a structure at any specific time. No global control of fruit body geometry is necessary. No localized regulation is necessary. The shape of the fruit body emerges from the concerted response of the entire population of hyphal tips, in the same way, to the same signals.

The circumscription of the family Agaricaceae, its genera and their characters are investigated. Analyses of the ITS and LSU sequence data, separately and in combination result in exclusions and reorganization. Notholepiota areolata, a secotioid species from New Zealand, Cystoagaricus with brown, irregular-knobby spores, and Leucopholiota with gelatinized hymenophoral trama and amyloid spores, fall outside the family Agaricaceae. In the reorganization, long accepted tribe and genus definitions are amended, viz.: (1) Macrolepiota and Chlorophyllum separately are monophyletic, but not together; (2) Leucoagaricus and Leucocoprinus together form one large monophyletic clade, that also includes polyphyletic Sericeomyces; (3) Lepiota, Cystolepiota and Melanophyllum together form a monophyletic clade; (4) Secotiation has happened within several clades (e.g. Agaricus and Chlorophyllum), though not in the Leucoagaricus/Leucocoprinus clade, nor in the lineage of Macrolepiota proper; gasteroid and most secotioid species in the course of adaptation acquire coloured spores; and (5) the monovelangiocarpic Chamaemyces fracidus appears to be basal to the family and provides clues to the morphology of the ancestral Agaricaceae. Trama and developmental characters characterize the different clades, whereas spore characters play a minor role.

The genetic structure within and between USA and European populations of the emerging phytopathogen Phytophthora ramorum was examined. Four primer combinations were used for amplified fragment length polymorphism (AFLP) fingerprinting of 67 USA isolates from California and Oregon, and 18 European isolates from Belgium, Germany, The Netherlands, Spain and the UK. In addition, three DNA regions (ITS, cox II, and nad 5) of additional Phytophthora species were amplified by polymerase chain reaction, sequenced, and analysed to provide better phylogenetic understanding of P. ramorum within the genus Phytophthora. AFLP banding patterns indicate that the 85 isolates form two distinct lineages within a monophyletic group, distinct from the closely related outgroup species P. lateralis. With the exception of two isolates from an Oregon nursery, European and USA isolates clustered separately within individual clades. The AFLP profiles also indicate that a single clonal lineage dominates the North American population, while the European population consists of an array of mainly unique, closely related AFLP types. Sequences from the three DNA regions were identical among all P. ramorum isolates, and phylogenetic analysis indicates that P. ramorum is closely related to P. lateralis and P. hibernalis.

The molecular diversity of Diaporthe helianthi (anamorph Phomopsis helianthi), the causal agent of sunflower stem canker, was studied in 16 isolates of different geographic origin using nuclear and mitochondrial markers. PCR products corresponding to the internal transcribed spacers (ITS1 and ITS2) of the nuclear ribosomal RNA gene, and to the mitochondrial atp6 gene were sequenced. The ITS1 and ITS2 sequences were compared with those of Phomopsis spp. and Diaporthe spp. obtained from databases. The diversity in the region surrounding the atp6 gene was also studied by restriction analysis using four enzymes. The analyses revealed a marked diversity within the sunflower-isolated strains, which appear to belong to phylogenetically unrelated groups. Noticeably, all the isolates collected in France and in the former Yugoslavia, where severe epiphytotics of sunflower stem canker are frequently reported, showed high similarity to each other forming a clade which clearly differentiated from all other ones within the genus Phomopsis. Conversely, all the isolates collected in Italy, where, despite favourable environmental conditions, the incidence of the disease is low, were only distantly related to the former group and showed sequence similarity with other previously established phylogenetic clades within the Phomopsis/Diaporthe complex.

Datronia caperata, a basidiomycete fungus, is one of the dominant polypore species found in neotropical mangrove forest fragments, where it is locally specialized on Laguncularia racemosa. We examined the genetic structure of D. caperata populations from four Panamanian mangrove forests using AFLP markers. Using five primer pair combinations, 145 loci were detected, 98.6% of which were polymorphic. Each of the populations showed a high degree of genetic diversity (Nei's h ranging from 0.146 to 0.223). Results from minimum spanning trees and Mantel tests showed little evidence for small-scale spatial structure within sites. A significant amount of total genetic variation was partitioned among populations (ΦST=0.21) separated by 10s to 100s of km, a considerably greater amount than has been detected in other mushroom and wood-decaying fungi sampled at equal or greater geographic distances. These results suggest that despite production of copious basidiospores capable of long distance dispersal, some homobasidiomycete fungi may be susceptible to genetic isolation due to habitat fragmentation.

Leptographium wingfieldii is a well-known fungal associate of the pine shoot beetle, Tomicus piniperda, in Europe. This fungus is pathogenic to pines and is an important cause of blue-stain in the sapwood of infested trees. Tomicus piniperda was first found in a Christmas tree plantation in Ohio, USA, 1992, but isolation of the fungi associated with these intercepted insects was not attempted. Fungal strains resembling L. wingfieldii were recently isolated from pines attacked by T. piniperda, Dendroctonus valens and Ips pini in the northeastern United States. These strains were morphologically similar to the ex-type and other reference strains of L. wingfieldii. Strains were also compared based on sequences of the partial ITS ribosomal DNA operon, β-tubulin and elongation factor 1-alpha (EF-1α) genes. Based on these DNA sequence comparisons, reference strains of European L. wingfieldii were conspecific with North American strains from pines attacked by T. piniperda, D. valens and I. pini. A single strain from Canada, collected in 1993 near the Ontario border with the USA, shortly after the discovery of T. piniperda in that area and tentatively identified as L. wingfieldii, was also included in this study. Its identification was confirmed, suggesting that L. wingfieldii has been present in this region and probably over the whole range of the insect's distribution for at least a decade. This represents the first record of L. wingfieldii associated with the introduced and damaging pine shoot beetle T. piniperda in North America. It shows that the fungus is well established and can become associated with other native bark beetles that attack stressed and/or dying trees. The occurrence and spread of this highly pathogenic fungus associated with North American bark beetles should be monitored.

Studies were performed to assess the genetic variation amongst isolates of the aphid-pathogenic fungus Pandora neoaphidis (syn. Erynia neoaphidis). 37 isolates were examined, from a range of pest and non-pest aphid species, as well as 21 from eight other entomophthoralean species. Universal primers were used to amplify the ITS rDNA regions and all of the species tested produced discrete ITS groups, with the exception of Conidiobolus spp. Neighbour-joining analysis of the ITS2 regions from P. neoaphidis, P. kondoiensis and Zoophthora radicans demonstrated that these three species formed distinct groups with sequence identities of 58–82% between the groups. An ITS size of ca 1100 bp was diagnostic for P. neoaphidis, while ca 1450 bp was characteristic of P. kondoiensis. ITS-RFLP analysis failed to yield intraspecific polymorphisms in any of the P. neoaphidis isolates screened, although it was useful in distinguishing between different entomophthoralean species. Some intraspecific variation in the ITS region was detected in a number of isolates of Z. radicans and Conidiobolus spp. We propose that two isolates previously identified as P. neoaphidis based on conidia morphology, are actually P. kondoiensis based on molecular studies. Sequencing analysis of the complete ITS region from P. neoaphidis and P. kondoiensis allowed species-specific primers to be developed for P. neoaphidis and P. kondoiensis. These were used to screen aphids infected in laboratory bioassays and from field-collected samples, without prior isolation of the fungus. The primers are useful tools for quantifying the epizootiology of P. neoaphidis in aphid populations, as well as assessing competitive interactions between these two species.

Penicillium brevicompactum and other isolates with the compact, complex conidiogenous apparatus typical of the species were sequenced in one ribosomal and two protein coding regions. The aligned DNA sequences were analyzed by maximum parsimony and the data from different loci were tested for compatibility using the partition homogeneity test. Analysis of each of the three loci revealed three clades corresponding to P. brevicompactum, P. olsonii and P. biourgeianum. Using the phylogenetic species concept and the genetic isolation of the clades, P. hagemi, P. patrismei, P. stoloniferum, and P. griseobrunneum are all synonyms of P. brevicompactum. P. volgaense is a synonym of Penicillium olsonii, while P. biourgeianum is a distinct species closely related to P. brevicompactum and P. olsonii. Phenotypic distinctions between the species are mostly based on colony characteristics such as colour. P. bialowiezenze, often treated as a synonym of P. brevicompactum, is most closely related to P. polonicum.

A toxic protein, bassiacridin, was purified from a strain of the entomopathogenic fungus Beauveria bassiana isolated from a locust, using chromatographic methods. The final toxic fraction contained between 0.1 and 0.3% of the proteins of the crude extract. Bassiacridin showed no affinity for ion exchangers, was characterised as a monomer with a mol. wt of 60 kDa and an isoelectric point of 9.5, and exhibited β-glucosidase, β-galactosidase and N-acetylglucosaminidase activities. Injection of fourth instar nymphs of Locusta migratoria with the pure protein at relatively low dosage (3.3 μg toxin g body wt−1) caused a rate of mortality near to 50%. The effects of the crude and pure fractions were characterized at tissular and cellular levels. The formation of melanised spots on tracheae and air sacs and of melanised nodules in contact with the fat body was observed in injected locusts. Alterations of the fine structure of epithelial cells of tracheae, air bags, and integument were also revealed. The insecticidal protein showed a specific activity against locusts. Bassiacridin is different from the other macromolecular toxins of entomopathogenic fungi already described. Microsequencing of peptides generated by trypsic digestion of bassiacridin confirmed that it is a novel molecule and showed that it exhibits a probably limited similarity with a chitin binding protein from yeast.

Responses of Rhizoctonia solani to spatial heterogeneity in sources of carbon, and associated translocation of carbon (C), were studied in a simple microcosm system comprising two discrete domains of agar gels separated on a glass slide and overlain with a porous membrane. Two arrangements of the gel pairs were used, one containing two equally large resources (representing ‘homogeneous’ conditions) and one containing a large and a negligible resource (representing ‘heterogeneous’ conditions). The nutrient sources were a standard mineral salt medium with or without glucose as sole C source. The fungus was inoculated onto one domain and growth responses determined by direct measurement of biomass. Translocation of C was quantified by use of 13C-enriched glucose. This substrate was either added to the agar at the outset, when studying newly developing colonies, or as a pulse into already established colonies. When growing in heterogeneous conditions, the fungus actively translocated C from a glucose-containing domain to sustain growth in the adjacent region lacking such a resource. In homogeneous conditions there was evidence of passive translocation (diffusion), but the fungus preferentially used local resource to maintain growth. Active translocation was only observed in newly growing colonies, whereas passive translocation occurred in both growing and established colonies. When the fungus was pulsed with a 13C-enriched glucose solution after 10 d growth, 2.5 times more 13C was taken up by the fungus grown in heterogeneous than homogeneous conditions, suggesting uptake exceeded local demands. In heterogeneous conditions, the total amount of 13C enriched glucose taken up by the fungus was independent of the location of the enriched glucose in the underlying medium. When the nylon membrane was replaced by Cellophane (an additional C source), degradation of the membrane and an increase in biomass occurred only in the heterogeneous system. The possible implications for these results in soil systems are discussed.

Mycological Research108 (2): 189–197 (February 2004).

Growth and interspecific interactions of the rare oak polypore Piptoporus quercinus

Paul WALD, Martha CROCKATT, Victoria GRAY, and Lynne BODDY

Figures 3–17 should have been reproduced as a full colour plate. The publishers would like to apologise to the authors and their readers for this error.

Mycological Research108 (1): 5–13 (January 2004).

Presidential Address

New angles in mycology: studies in directional growth and directional motility

Neil A. R. GOW

Figures 2 and 3 should have been reproduced as full colour figures on page 9 of the January issue. Pages 9 and 10 have been reprinted as they should have appeared on the following pages so that readers may replace the pages in their January issue if so desired.

The publishers would like to apologise to the author and their readers for this error.