Effect of Huntiella decorticans and drought on Nothofagus dombeyi seedlings.

In the temperate forests of Patagonia, Argentina, Nothofagus dombeyi, commonly known as Coihue, has shown sensitivity to intense drought events, leading to mortality. Studies have been conducted on Coihue decline and mortality using a variety of approaches, including the role of extreme heat waves and drought, pests and pathogens, particularly the fungus Huntiella decorticans. This work aimed to evaluate survival, vitality, necrosis extension and growth response of inoculated and non-inoculated Coihue seedlings from different provenances exposed to different soil moisture levels. To achieve this goal, 96 Coihue seedlings from 2 different provenances were assigned to 8 different experimental treatments. Treatments were composed of the presence or absence of H. decorticans and different soil moisture content conditions, dry, wet and the exposure to dry condition at different times of the experiment. Both dry conditions and H. decorticans had negative effects on the survival and growth rate of Coihue. The combination of both factors resulted in 100 % mortality, regardless of the plants' geographical provenances. Mortality began to be observed 3 months after pathogen inoculation, during the warmest month. Necrosis extension produced by the pathogen was similar for most of the inoculated treatments. The treatment under wet condition during the experiment but subjected to dry condition in the previous growing season presented lower necrosis extension (8.4 ±â€…3.2 %), than the other treatments. The radial increase was also affected by the treatments and geographical provenance, being those plants exposed to dry conditions which grew less (0.19 ±â€…0.21 mm). This study enhances our understanding of the plant-pathogen interaction. According to our results, Coihue may become more susceptible to mortality, when H. decorticans and water deficit conditions act synergistically.

Sapwood mycobiome varies across host, plant compartment and environments in Nothofagus forests from Northern Patagonia.

Global forests are increasingly being threatened by altered climatic conditions and increased attacks by pests and pathogens. The complex ecological interactions among pathogens, microbial communities, tree hosts and the environment are important drivers of forest dynamics. Little is known about the ecology of forest pathology and related microbial communities in temperate forests of the southern hemisphere. In this study, we used next-generation sequencing to characterize sapwood-inhabiting fungal communities in North Patagonian Nothofagus forests and assessed patterns of diversity of taxa and ecological guilds across climatic, site and host variables (health condition and compartment) as a contribution to Nothofagus autecology. The diversity patterns inferred through the metabarcoding analysis were similar to those obtained through culture-dependent approaches. However, we detected additional heterogeneity and greater richness with culture-free methods. Host species was the strongest driver of fungal community structure and composition, while host health status was the weakest. The relative impacts of site, season, plant compartment and health status were different for each tree species; these differences can be interpreted as a matter of water availability. For Nothofagus dombeyi, which is distributed across a wide range of climatic conditions, site was the strongest driver of community composition. The microbiome of N. pumilio varied more with season and temperature, a relevant factor for forest conservation in the present climate change scenario. Both species carry a number of potential fungal pathogens in their sapwood, whether they exhibit symptoms or not. Our results provide insight into the diversity of fungi associated with the complex pathobiome of the dominant Nothofagus species in southern South America.

Los bosques del mundo están cada vez más amenazados por las condiciones climáticas alteradas y el aumento de los ataques de plagas y patógenos. Las complejas interacciones ecológicas entre los patógenos, las comunidades microbianas, los árboles hospedantes y el medio ambiente son impulsores importantes de la dinámica forestal. Poco se sabe sobre la ecología de la patología forestal y las comunidades microbianas relacionadas en los bosques templados del hemisferio sur. En este estudio, utilizamos la secuenciación Illumina para caracterizar las comunidades de hongos que habitan en la albura en los bosques de Nothofagus de la Patagonia Norte y evaluamos los patrones de diversidad de taxones y gremios ecológicos a través de variables climáticas, de sitio y de hospedante (identidad, condición de salud y compartimento) como una contribución a la autoecología de los Nothofagus. Los patrones de diversidad inferidos a través del análisis metabarcoding fueron similares a los obtenidos a través de enfoques dependientes de cultivo. Sin embargo, detectamos mayor heterogeneidad y mayor riqueza con métodos independientes de cultivo. La especie hospedante fue el modelador más fuerte de la estructura y composición de la comunidad fúngica, mientras que el estado de salud del hospedante fue el más débil. El impacto relativo del sitio, la estación, el compartimento y el estado de salud fueron diferentes para cada especie de árbol; estas diferencias pueden interpretarse en clave de disponibilidad de agua. Para N. dombeyi, que se distribuye a lo largo de una amplia gama de condiciones climáticas, el sitio fue el principal modelador de la composición de la comunidad. El micobioma de Nothofagus pumilio varió más con la estación y la temperatura, un factor relevante para la conservación de los bosques en el escenario actual de cambio climático. Ambas especies portan una serie de patógenos fúngicos potenciales en su albura, ya sea que muestren síntomas o no. Nuestros resultados brindan una idea de la diversidad de hongos asociados con el complejo patobioma de las especies dominantes de Nothofagus en el sur de América del Sur.

Species and genera in Aleurodiscus sensu lato as viewed from the Southern Hemisphere.

Phylogenetic relationships of 12 species in Aleurodiscus sensu lato (Stereaceae, Russulales) described from the Patagonian forests of Chile and Argentina were investigated based on sequences of nuc rDNA internal transcribed spacer region ITS1-5.8S-ITS2 (ITS) and the D1-D2 domains of nuc 28S rDNA (28S). A new genus and a new species are presented, and 10 new combinations proposed. The genus Gloeosoma is shown to be phylogenetically well supported and morphologically circumscribed; it includes G. vitellinum (type species), G. mirabile, comb. nov., G. zealandicum, comb. nov., and Gloeosoma decorticans, sp. nov., which is newly described from Chile. The new genus Stereodiscus is proposed to accommodate a group of taxa characterized by an austral distribution and morphologically by smooth, thin-walled, amyloid basidiospores and a lack of gloeocystidia and acanthocystidia; three species develop Stereum-like basidiomata and two species present discoid ones. The new genus includes the species formerly known as Aleurodiscus antarcticus, A. limonisporus, A. parmuliformis, A. patagonicus, and A. triviale. Specimens of Stereodiscus parmuliformis (A. parmuliformis) from New Zealand (where it was originally described) and southern Chile are shown to be phylogenetically conspecific, which confirms its presence in Patagonia. Gloeosoma and Stereodiscus are shown to be distantly related to Aleurodiscus s. str. and other genera in Stereaceae. The new combinations Aleurocystidiellum bernicchiae, Aleurocystidiellum hallenbergii, and Acanthobasidium quilae are proposed based on morphology and phylogenetic analyses, and Aleurodiscus cerussatus is shown to be a cryptic species complex.