Intraspecific competition is the basis for biological control of aflatoxins, but there is little understanding of the mechanism(s) by which competing strains inhibit toxin production. Evidence is presented that demonstrates a relationship between strength of the vegetative compatibility reaction and aflatoxin production in Aspergillus flavus and A. parasiticus using the suspended disk culture method. Combining wild-type aflatoxin-producing isolates belonging to different vegetative compatibility groups (VCGs) resulted in a substantial reduction in aflatoxin yield. Pairs of aflatoxin-producing isolates within the same VCG, but showing weak compatibility reactions using complementary nitrate-nonutilizing mutants, also were associated with reduced levels of aflatoxin B₁. In contrast, pairings of isolates displaying a strong compatibility reaction typically produced high levels of aflatoxins. These results suggest that interactions between vegetatively compatible wild-type isolates of A. flavus and A. parasiticus are cooperative and result in more aflatoxin B₁ than pairings between isolates that are incompatible. Successful hyphal fusions among spore germlings produce a common mycelial network with a larger resource base to support aflatoxin biosynthesis. By comparison, vegetative incompatibility reactions might result in the death of those heterokaryotic cells composed of incompatible nuclei and thereby disrupt the formation of mycelial networks at the expense of aflatoxin biosynthesis.

During an extended search in Western Canada for fungal root endophytes useful as biocontrol agents against soil-borne pathogens, we isolated Heteroconium chaetospira, as well as Phialocephala fortinii or similar taxa, from seven samples of forest soil using herbaceous seedlings of four different species (i.e., barley, Chinese cabbage, eggplant, and melon) as bait plants. Our results support a previous observation that eggplant is a particularly effective species for baiting H. chaetospira from soil and confirm the ability of this fungus to grow as an endophyte in the roots of axenically reared host plants. Cultural characters show that this species is similar to P. fortinii and other melanized fungi in the dark septate endophyte (DSE) group (e.g., Leptodontidium orchidicola, P. sphaeroides, and Cadophora finlandica) in that it produces darkly pigmented colonies on agar media. Heteroconium chaetospira differs from P. fortinii and other melanized members of the Leotiomycetes in the DSE group in that its conidia are fusiform and develop in blastic acropetal chains. Heteroconium chaetospira is phylogenetically distant from most DSE taxa because DNA sequences for the nuclear small subunit (SSU) ribosomal RNA gene (rDNA) indicate that the taxon is affiliated with the Herpotrichiellaceae of the Chaetothyriales rather than with the Leotiomycetes.

A new clitocyboid genus of Agaricales, Cleistocybe, is described to accommodate the isolated evolutionary position of the new species Cleistocybe vernalis inferred by a previously published multigene phylogenetic study. Cleistocybe is distinguished from other clitocyboid lineages by a combination of morphological characters, including lamellae that become gray in age, an interwoven hymenophoral trama with divergent elements when young, strongly interwoven pileipellis with pigmented and encrusted hyphae, white spore deposit, a distinct or ephemeral fibrillose to submembranous partial veil, and smooth, inamyloid basidiospores that are inequilateral in profile view. Cleistocybe encompasses two species, C. vernalis and Clitocybe gomphidioides, based on morphological comparisons with C. vernalis. Clitocybe subvelosa is confirmed as conspecific with C. gomphidioides based on morphological and ITS sequence comparisons of type collections. Cleistocybe is known only from western North America in coniferous forests and appears most closely related to the ectomycorrhizal genus Catathelasma and the saprotrophic genera Callistosporium, Macrocybe, and Pleurocollybia based on nLSU-rDNA phylogenetic analysis. Together these lineages constitute the Catathelasma clade.

This article describes two new anamorphic fungi from freshwater habitats, Dictyosporium tetrasporum sp. nov. and Exserticlava yunnanensis sp. nov., based on morphological characters. Both species are illustrated with light micrographs and compared with similar taxa. Pseudofuscophialis lignicola and Pseudobotrytis terrestris are reported as new records from freshwater habitats.

Amplified fragment length polymorphism (AFLP) analysis was used to examine genetic differences in Agaricus blazei cultivated strains and their single-spore isolates (SSIs). AFLP analysis with five primer combinations identified a total of 267 AFLP bands from nine cultivated strains (one from Brazil and eight from Japan), of which 165 were polymorphic between the nine strains. An AFLP data dendrogram grouped the eight Japanese strains, with the Brazilian strain acting as an outlier, suggesting that the Brazilian and Japanese strains are genetically quite different. Twelve SSIs derived from each of four cultivated strains were subjected to AFLP analysis. All the AFLP bands detected in the cultivated strains were also found in at least one SSI, but some unique bands were detected in SSIs. The total number of AFLP bands from individual SSIs was clearly less than those from their parental strains, and many of polymorphic AFLP bands from the parental strains segregated in SSIs at a ratio of 1 : 1, suggesting that the SSIs are homokaryotic. Distance values based on presence or absence of individual AFLP bands among SSIs from different strains were clearly higher than those among SSIs from a single strain. In addition, AFLP analysis was shown to be useful in confirming hybrid formation in crosses between SSIs.

Spores of the arbuscular mycorrhizal fungus, Gigaspora margarita, were placed near the root tip, the middle of the root (equal distance from root base and root tip), or the root base (close to the shoot) of the first primary root of 9-day-old onion. Two weeks later, the number and position of appressoria and the appressoria with penetrating hyphae were determined in the first and the newly formed second primary roots. The total number of appressoria was not significantly different among the treatments. Inoculation near the root tip of the first primary root resulted in the formation of a large number of appressoria on the first primary root and the formation of about three times fewer appressoria on the second primary root. Inoculation near the base of the first primary root resulted in the formation of no appressoria on the first primary root, whereas many appressoria were formed on the second primary root. Our results suggest that the root age is a determinant of the appressorium formation.

Aseroë coccinea, an invalid name for a Japanese phalloid, is formally validated. Morphological features of A. coccinea are described and illustrated. This fungus is well distinguishable from the other known species of Aseroë by 7–9 bright red arms dispersed radially on the apex of the receptacle, not bifurcating but simple, and consisting of a single tubulate chamber.

We collected Cordyceps brongniartii from the wild associated with coleopteran larvae for the first time in Japan. Morphological comparisons of C. brongniartii with the type specimen showed slight morphological difference, whereas it showed considerable differences from those collected in the wild in China. PCR-RFLP and ITS sequence analyses corroborated the teleomorph–anamorph relationship between C. brongniartii and Beauveria brongniartii.

The ITS region of ectomycorrhizal fungi was analyzed, and species-specific PCR primers were designed for 8 ectomycorrhizal Tricholoma species. Although a high degree of intraspecific homology was observed, interspecific variation was sufficient to design species-specific primers based on sequence of the ITS region. PCR amplification with the specific primers generated fragments of the expected sizes from DNA extracted from the strains of each species but gave no amplified products from the strains of the other 16 species in eight genera. These results suggest that sequence of the ITS region is appropriate to be used for species-level identification of ectomycorrhizal fungi.

Pluteus chrysophaeus is described as a new record for Japanese mycobiota. Pluteus leoninus, reported for the first time from Japan by Imai (1938), probably represents P. chrysophaeus. The new Japanese specimens of P. leoninus is redescribed and illustrated.