Phytophthora austrocedri Elicitates Changes in Diterpene Profile of Austrocedrus chilensis.

The populations of the Andean Cupressaceae Austrocedrus chilensis have been severely affected by a disease caused by the phytopathogenic fungus Phytophthora austrocedri. A study was undertaken to disclose changes in the resin composition of P. austrocedri-infected individuals, including naturally infected and artificially inoculated trees, compared with healthy A. chilensis trees. GC-MS and (1)H-NMR studies showed a clear differentiation among healthy and infected resins, with the diterpene isopimara-8(9),15-dien-19-ol as a relevant constituent in resins from infected trees. The effect of resin fractions from P. austrocedri infected trees on the pathogen was assessed by measuring the mycelial growth in agar plates. The most active fractions from resin obtained from infected trees inhibited fungal growth by nearly 50% at 1 mg/dish (35.37 µg/cm(2)). The main constituent in the active fractions were 18-hydroxymanool and the aldehyde torulosal. Both compounds are oxidation products of manool and can be a chemical response of the tree to the pathogen or be formed from the pathogen as a biotransformation product of manool by microbial oxidation. While the diterpene profiles from A. chilensis tree resins can easily differentiate healthy and P. austrocedri infected individuals, the possible conversion of manool to the antifungal derivatives 4 and 6 by the microorganism remains to be established.

Fungal biogeography. Global diversity and geography of soil fungi.

Fungi play major roles in ecosystem processes, but the determinants of fungal diversity and biogeographic patterns remain poorly understood. Using DNA metabarcoding data from hundreds of globally distributed soil samples, we demonstrate that fungal richness is decoupled from plant diversity. The plant-to-fungus richness ratio declines exponentially toward the poles. Climatic factors, followed by edaphic and spatial variables, constitute the best predictors of fungal richness and community composition at the global scale. Fungi show similar latitudinal diversity gradients to other organisms, with several notable exceptions. These findings advance our understanding of global fungal diversity patterns and permit integration of fungi into a general macroecological framework.

Phytophthora austrocedrae sp. nov., a new species associated with Austrocedrus chilensis mortality in Patagonia (Argentina).

Phytophthora austrocedrae is a new species isolated from necrotic lesions of stem and roots of Austrocedrus chilensis. It is a homothallic species characterized by semipapillate sporangia, oogonia with amphigynous antheridia, and very slow growth (1-2 mm d(-1) on V-8 agar at 17.5 degrees C optimum temperature). Phylogenetic analysis of ITS rDNA sequence indicates that its closest relative is Phytophthora syringae, another species frequently isolated from soil and streams in A. chilensis forests.

Parenthesome structure of some corticioid fungi.

The parenthesome structure of seven corticioid species, traditionally referred to the family Corticiaceae (Basidiomycota), were studied in order to better understand their taxonomic position: Phanerochaete velutina, Phlebia radiata, P. rufa, Rhizochaete americana (syn. Ceraceomyces americana), R. brunnea, R. filamentosa (syn. Phanerochaete filamentosa) and R. radicata (syn. Phanerochaete radicata). All possessed the perforate type of parenthesome that is commonly encountered in homobasidiomycetes. This feature excludes the above taxa from both the hymenochaetoid and the cantharelloid clades which are the only groups that have imperforate parenthesomes in the homobasidiomycetes.

Phytophthora species from declining Austrocedrus chilensis forests in Patagonia, Argentina.

A survey of Phytophthora spp. in declining and healthy Austrocedrus chilensis forest was conducted to obtain an overview of the species that inhabit these forests. Seventeen declining and three healthy stands plus 11 associated streams were surveyed. Five Phytophthora species were recovered. P. syringae was the most common species isolated from soil and/or streams at nine declining sites and one healthy site. P. gonapodyides was isolated from streams only, at five declining sites. P. cambivora was isolated from soil and the undescribed taxa 'P. taxon Pgchlamydo' and 22 'P taxon Raspberry' were isolated from streams at one declining site each. The species were identified by ITS rDNA sequences and morphological features. Brief descriptions of each species and a discussion of their possible relationship with "mal del ciprés" are presented.

Rhizochaete, a new genus of phanerochaetoid fungi.

A new basidiomycete genus, Rhizochaete (Phanerochaetaceae, Polyporales), is described. Rhizochaete is characterized by a smooth to tuberculate, pellicular hymenophore and hyphal cords that turn red or violet in potassium hydroxide, monomitic hyphal system of simple or nodose septate hyphae, cystidia, and small, cylindrical to subglobose basidiospores. It morphologically is most similar to Phanerochaete. Analyses of nuclear ribosomal and internal-transcribed spacer region sequence data support a close relationship between Rhizochaete and Phanerochaete. The new taxon R. brunnea, from southern Argentina, is described and illustrated. In addition, the new combinations R. americana, R. borneensis, R. filamentosa, R. fouquieriae and R. radicata are proposed. A key to the species of Rhizochaete is provided.