Phylogeny and taxonomy of Erysiphe spp. on Rhododendron, with a special emphasis on North American species.

The genus Rhododendron comprises over 1000 evergreen and deciduous species. In the Pacific Northwest Coast region of North America (PNWC), powdery mildews infecting deciduous Rhododendron spp. are well documented but less so on evergreen Rhododendron spp. Infections of both groups of hosts historically have been attributed to Erysiphe azaleae or E. vaccinii. No formal characterizations of powdery mildew fungi infecting either deciduous or evergreen Rhododendron spp. in the PNWC have been completed. The objectives of this study were to identify the powdery mildew pathogens infecting evergreen Rhododendron spp. in the PNWC and to assess the phylogenetic position of these fungi within the Erysiphaceae. To ascertain valid taxonomic conclusions, and to determine whether potential introductions of exotic Rhododendron powdery mildews in North America have occurred, it was necessary to put the new North American phylogenetic data into a worldwide context. Therefore, available phylogenetic data from all Erysiphe spp. on Rhododendron have been included in our analyses.Based on analyses of numerous new internal transcribed spacer (ITS) and 28S rDNA sequences and already available sequences deposited in GenBank retrieved from evergreen and deciduous Rhododendron spp., the following Erysiphe spp. could be phylogenetically confirmed (all belonging to Erysiphe sect. Microsphaera): Erysiphe azaleae nom. cons. (Oidium ericinum could be verified as a synonym), E. digitata (holotype sequenced), E. izuensis, and E. vaccinii. Erysiphe azaleae and E. vaccinii are epitypified with sequenced specimens, and an ex-neotype sequence has been obtained for Oidium ericinum. Erysiphe rhododendri (Erysiphe sect. Erysiphe), only known from two collections in India (Himalayan region), was not available for phylogentic analyses.

Fusicoccum arbuti sp. nov. causing cankers on pacific madrone in western North America with notes on Fusicoccum dimidiatum, the correct name for Scytalidium dimidiatum and Nattrassia mangiferae.

Pacific madrone (Arbutus menziesii) is a broadleaf evergreen tree native to western North America that has been in decline for the past 30 years. A fungus has been isolated and was verified as the cause of cankers on dying trees. It was determined to belong in the genus Fusicoccum, an asexual state of Botryosphaeria. This genus in both its sexual and asexual states commonly causes canker diseases of deciduous woody plants. Using morphological and molecular data the fungus causing cankers on Pacific madrone is characterized, described and illustrated as a new species of Fusicoccum, F. arbuti D.F. Farr & M. Elliott sp. nov. No sexual state is known for F. arbuti. Evidence from the literature, cultures and specimens suggests that F. arbuti, often mistakenly identified as Nattrassia mangiferae, has been causing madrone canker since at least 1968. Authentic isolates of Nattrassia mangiferae as the synanamorph Scytalidium dimidiatum were sequenced and determined to be different from Fusicoccum arbuti and to belong in Botryosphaeria/Fusicoccum. In addition to molecular sequence data, the morphology of the pycnidial and arthric conidial states of Nattrassia mangiferae/ Scytalidium dimidiatum resembles that of Fusicoccum. Therefore the correct name for Nattrassia mangiferae and its numerous synonyms (Dothiorella mangiferae, Torula dimidata, Scytilidium dimidiatum, Fusicoccum eucalypti, Hendersonula toruloidea, H. cypria, Exosporina fawcetii, H. agathidia, and S. lignicola) is Fusicoccum dimidiatum (Penz.) D.F. Farr, comb. nov.

Nitrogen and carbon stable isotope abundances support the myco-heterotrophic nature and host-specificity of certain achlorophyllous plants.

• Over 400 species of achlorophyllous vascular plants are thought to obtain all C from symbiotic fungi. Consequently, they are termed 'myco-heterotrophic.' However, direct evidence of myco-heterotrophy in these plants is limited. • During an investigation of the patterns of N and C stable isotopes of various ecosystem pools in two old-growth conifer forests, we sampled six species of myco-heterotrophic achlorophyllous plants to determine the ability of stable isotope ratios to provide evidence of myco-heterotrophy and host-specificity within these symbioses. • Dual-isotope signatures of the myco-heterotrophic plants differed from those of all other pools. They were most similar to the signatures of ectomycorrhizal fungi, and least like those of green plants. δ15 N values of the myco-heterotrophic plants correlated strongly and positively with those of putative mycobionts. • Used in conjunction with other techniques, N and C stable isotope ratios can be used to demonstrate myco-heterotrophy and host-specificity in these plants when other ecosystem pools are well characterized. They also appear promising for estimating the degree of heterotrophy in photosynthetic, partially myco-heterotrophic plants.

Patterns of nitrogen and carbon stable isotope ratios in macrofungi, plants and soils in two old-growth conifer forests.

• To further assess the usefulness of stable isotope ratios for understanding elemental cycling and fungal ecology, we measured δ15 N and δ13 C in ectomycorrhizal and saprotrophic macrofungi, plants, woody debris and soils from two old-growth conifer forests in Olympic National Park, Washington, USA. • Ecosystem isotope patterns were similar at the two forests, but differences existed that appear to reflect soil nitrogen availability and C allocation within the ectomycorrhizal symbioses. δ15 N and δ13 C of ectomycorrhizal and saprotrophic fungi differed in both forests, and a dual δ15 N/δ13 C plot provided the best means of distinguishing them. Within both groups, δ15 N and δ13 C differed among genera and species, and the difference in species composition was an important determinant of the different overall δ15 N of the ectomycorrhizal fungi at the two forests. • Variation in multiple ecophysiological traits such as organic N use, mycelial morphology and transfer of N to phytobionts appears to underlie the variation in the isotope signatures of ectomycorrhizal fungi. • The varied isotope signatures of ectomycorrhizal fungi suggest considerable functional diversity among them. Life-history strategies could provide a framework for interpreting these patterns.

Biomass and nutrient concentrations of sporocarps produced by mycorrhizal and decomposer fungi in Abies amabilis stands.

Sporocarps and sclerotia were collected for a one-year period in 23- and 180-year-old Abies amabilis stands in western Washington. All sporocarps were classified and chemically analyzed for N, P, K, Ca, Mg, Na and Fe. Lactarius sp. and Cortinarius sp. contributed the largest proportion of the total annual epigeous sporocarp production in both stands. Annual epigeous production was 34 kg/ha in the young stand and 27 kg/ha in the mature stand. Hypogeous sporocarp production increased from 1 kg ha-1 yr-1 to 380 kg ha-1 yr-1 with increasing stand age. High sclerotia biomass occurred in the young (2,300 kg/ha) and mature (3,000 kg/ha) stands. Peak sclerotia and epigeous sporocarp biomass in the young stand and epigeous and hypogeous sporocarp biomass in the mature stand coincided with the fall peak of mycorrhizal root biomass.In the young stand, sporocarps produced by decomposer fungi concentrated higher levels of Ca and Mn than those produced by mycorrhizal fungi. In the mature stand, sporocarps of decomposer fungi concentrated higher levels of N, P, Mn, Ca and Fe than sporocarps of mycorrhizal fungi. Epigeous and hypogeous sporocarps concentrated higher levels of N, P, and K than sclerotia or mycelium. The highest concentration of N (4.36%), P (0.76%), K (3.22%) and Na (1,678 ppm) occurred in epigeous sporocarps. Highest Mn (740 ppm) and Ca (20,600 ppm) concentrations occurred in mycelium, while highest Mg (1,929 ppm) concentrations were in hypogeous sporocarps and highest Fe (4,153 ppm) concentrations were in sclerotia.