Bradley R. Kropp

The Effects of Silvicultural Treatments on Occurrence of Mycorrhizal Sporocarps in a Pinus contorta Forest: A Preliminary Study

A preliminary survey was conducted to evaluate the effects of thinning and clearcutting, followed by replanting, on mycorrhizal fungi. A total of 48 species of mycorrhizal fungi was recorded for the study site. Suillus brevipes and S. tomentosus were the dominant species. Data from the survey indicate that thinning reduced the total number of species as compared to an undisturbed stand. Some fungi were adversely affected by thinning while others were positively affected. Members of the Hygrophoraceae appeared to be most susceptible to mild disturbance such as thinning. While clearcutting had a negative impact on the total number of sporocarps of mycorrhizal fungi, Suillus brevipes increased in percent abundance as severity of disturbance increased.

Population structure and mycelial phenotypic variability of the ectomycorrhizal basidiomycete Laccaria bicolor (Maire) Orton

Mating type allele distribution and phenotypic variability were investigated in field populations of Laccaria bicolor. Sporophores associated with Norway spruce (Picea abies), colonized by natural sources of inoculum and growing in a seed orchard, were sampled to obtain dikaryotic strains and assay their phenotypic variability for traits important to the symbiosis. Basid-iospores were also collected for mating type analysis of different mycelia. Four sporophore mating types were identified containing seven A and five B factors. Out-breeding efficiency was estimated at 73.8% and the population was slightly inbred. Crosses with previously characterized L. bicolor strains from two nearby populations identified in total six sporophore mating types and ten A and nine B factors, for an estimated outbreeding efficiency (85.7%) similar to previous studies of more spatially disparate Laccaria spp. populations. Dikaryotic strains were tested for mycelial growth rate, as a measure of their competitive ability, on agar media containing a soluble (NaH2PO4), or an insoluble (CaHPO4) phosphate source. Their ability to solubilize the latter was also tested to assess their relative capacity to access insoluble, inorganic phosphate. In most cases, significant variation was detected among strains from the same site for all variables. On three sites (VC4, VC5 and VC7), each determined previously to possess a uniform mycelial genotype, phenotypic variability was likely due to epigenetic variation among different strains of the same genotype. Possible evidence for dikaryon-monokaryon crosses was observed in vivo on one sample site (VC2) where adjacent mycelia shared two mating factors. The phenotypic variability of different mycelial genotypes reflected their genetic variability observed as mating type allele diversity and underlined the importance of basidiospore dispersal in introducing new genotypes into the population. The reproductive strategies of L. bicolor are discussed and compared to those of other basidiomycete species.

Athelia arachnoidea, the sexual state of Rhizoctonia carotae, a pathogen of carrot in cold storage

Athelia arachnoidea was collected during winter on dead leaves of deciduous trees in Oregon. Minute sclerotia (0.2-1.0 mm) were seen on hyme- nia, whereas in culture sclerotia were much larger (1.0-5.0 mm). The pathogenicity, morphological characteristics, and temperature growth responses of the anamorphic state, were identical to Rhizoctonia carotae. The relationship between the sclerotial ana? morph and the teleomorph was confirmed by DNA sequence of the internal transcribed spacers of the nuclear ribosomal repeat unit. The sequences were homologous among the specimens of A. arachnoidea and the sclerotial anamorph from Oregon, A. arach? noidea and R. carotae isolates from culture collec? tions, and several isolates of R. carotae from carrot cold-storage facilities. Like R. carotae, A. arachnoidea produced abundant crystals of calcium oxalate on the hyphae, was pathogenic on carrot at 3 C, and caused crater rot symptoms equivalent in severity. Sclerotia of A. arachnoidea-R. carotae did not germi? nate under conditions suitable for eruptive germi? nation in A. rolfsii. The DNA sequence of A. epiphylla from Europe was identical (within 6 bp) to A. arach? noidea-R. carotae, whereas A. epiphylla from North America varied by 34-46 independent base pair changes. Athelia epiphylla and A. arachnoidea formed similar sclerotia. Connecting the Rhizoctonia root pathogen to the Athelia teleomorph links the dispa- rate literatures on the natural history of this fungus and reveals significant insights into the epidemiology of the disease. Fibularhizoctonia gen. nov. is proposed to encompass Rhizoctonia species with clamp connec? tions, and the description of R. carotae and R. centri- fuga are emended.

Polymorphisms in the large intergenic spacer of the nuclear ribosomal repeat identify Laccaria proxima strains

A simple method for identifying strains of Laccaria proxima is presented which uses the poly- merase chain reaction (PCR) to amplify the large in- tergenic spacer region of the nuclear ribosomal re- peat. The large intergenic spacer region of L. proxi- ma is approximately 4000 base pairs long and is vari- able enough to permit clear identification of individual strains after digestion with restriction en- donucleases. This has only been partially possible with other published PCR-based identification meth- ods which use conserved primers. The method has the potential to be adapted for use in identifying iso- lates directly from roots and avoids the use of labeled probes needed for identifying Laccaria strains with techniques which are not PCR-based.

Basidiospore homoplasy and variation in the Inocybe chelanensis group in North America

We present a morphological and phylogenetic study of Inocybe chelanensis and other North American species of Inocybe that have unusually elongated nodulose spores. Taxonomy and illustrations of these species are provided, along with a key to these and similar species found in Europe and North America. The species concept of I. chelanensis is broadened to include the range of variation occurring for the species in North America. Despite similar basidiospore morphologies, I. chelanensis and I. candidipes are not closely related. Inocybe chelanensis is related more closely to I. stellatospora and I. candidipes is related to I. glabrodisca based on RPB1 and nLSU-rDNA nucleotide sequences. Distal enlongation of Inocybe basidiospores was achieved independently in at least two separate lineages of Inocybe. Inocybe candidipes and I. sierraensis are described as new.

Inheritance of the ability for ectomycorrhizal colonization of Pinus strobus by Laccaria bicolor

Ectomycorrhizal colonization of Pinus strobus by monokaryotic and dikaryotic progeny of two strains of Laccaria bicolor was studied. The mon- okaryotic progeny of one strain formed ectomycor- rhizae with between 1.5 and 80% of the available short roots. In the other case, the monokaryotic progeny formed ectomycorrhizae with between zero and 22% of the available roots. Percent ectomycor- rhizal colonization by the dikaryotic progeny of both strains was continuously distributed from 30 to 84% in one case and from zero to 80% in the other. The results indicate that percent ectomycorrhizal coloni- zation is polygenically controlled. A quantitative anal- ysis of the dikaryotic progeny of one of the strains indicates that the degree of genetic determination, under the conditions of this study, are 19.7 and 4.4%. The interactive genetic component accounted for most of the genetically determined variation in this

Establishment and Dispersal of Puccinia thlaspeos in Field Populations of Dyer's Woad

Dyers woad rust is being intensively studied as a biocontrol agent for the noxious weed dyers woad. These studies report on methods to establish this fungus in woad populations and to obtain information about disease incidence and dispersal of the rust subsequent to establishment. Inoculum dosages as low as 1 mg/plant established disease in dyers woad rosettes. Dosages higher than 1 mg/plant resulted in better levels of infection, and inoculation was equally effective when the inoculum was placed directly on the plants or on the soil adjacent to the plants. The highest incidence of infection occurred when plants were inoculated in the spring, whereas summer or fall inoculations did not result in infections. Large-scale inoculation of woad was effective and resulted in significant levels of disease. However, it was not clear if artificial inoculation was effective in changing disease incidence in populations of woad where the rust was present prior to treatment because there were no significant differences between inoculated and check plots. Woad rust is systemic but apparently it is not seed dispersed, even though some infected plants occasionally produce seed. Two years after inoculation, dyers woad rust had dispersed an average of 14.6 m from the focus of inoculation. After 3 years, the dispersal distance had not increased and infected plants averaged only 10 m from the point of inoculation. Disease was maintained naturally in woad populations after treatment, but the overall percent infection in the treated plots decreased by 3 years after inoculation.

Cryptolepiota, a new sequestrate genus in the Agaricaceae with evidence for adaptive radiation in western North America

Phylogenetic analyses based on nLSU and ITS sequence data indicate that the sequestrate genus Gigasperma is polyphyletic. Gigasperma cryptica, which is known only from New Zealand, has affinities with the Cortinariaceae whereas G. americanum and two additional undescribed taxa from western North America are derived from Lepiota within the Agaricaceae. The three North American taxa appear to be recently evolved and are closely related. They occur in similar environments and form a well supported clade indicating that adaptive radiation has occurred within this group of fungi. An independent genus with sequestrate fructifications, Cryptolepiota is proposed to accommodate the three species in this clade. Cryptolepiota microspora and C. mengei are described as new, and G. americanum is transferred to Cryptolepiota. Gigasperma cryptica is illustrated and compared with the species of Cryptolepiota.

Inocybe section Rimosae in Utah: phylogenetic affinities and new species.

Results of a study on species of Inocybe section Rimosae sensu lato in Utah are presented. Eight species, seven from the Pseudosperma clade (section Rimosae sensu stricto) and one from the Inosperma clade (section Rimosae pro parte), are documented morphologically and phylogenetically. Five of the eight species, I. aestiva, I. breviterincarnata, I. cercocarpi, I. niveivelata and I. occidentalis—all members of the Pseudosperma clade—are described as new from Utah and other western states. Two European species, I. spuria and I. obsoleta, are confirmed from Utah. Inocybe aurora, originally described from Nova Scotia, is synonymized with I. obsoleta. The only member of the Inosperma clade recorded from Utah is I. lanatodisca, a widely distributed species for which three geographical clusters were detected. The phylogenetic analyses indicate that the Pseudosperma clade includes 53 clusters or species worldwide and that the Inosperma clade includes 47 such clusters. Many of these probably correspond to undescribed species. A key to species of section Rimosae sensu lato from Utah is provided together with illustrations of the eight species found in the state.

Phylogenetic taxonomy of the Inocybe splendens group and evolution of supersection “Marginatae”

A phylogenetic and taxonomic study of the Inocybe splendens complex in western North America is presented. Our analysis indicates that western North American and European specimens referable to I. splendens sensu lato cluster into eight clades and that European and western North American representatives of this taxon are not conspecific. Section Splendentes and supersection “Marginatae” of Inocybe, smooth-spored taxa characterized by a syndrome of unique developmental characters (entirely or mostly pruinose stipe, absence of cortina, frequent presence of marginate basal bulb) are not monophyletic. The species concept for I. splendens is discussed, and a lectotype for I. splendens sensu Heim is designated. Two new species, I. monticola and I. praecox, are illustrated and described. The poorly known species I. bakeri is redescribed from type material, and a key for 22 species is provided for identification of these and other non-reddening species with smooth spores and a caulocystidiate stipe reported from North America and Europe.