The southernmost portion of the Andes in South America hosts Nothofagaceae forests that form ectomycorrhizal (EcM) associations. We compiled all the published reports of EcM taxa from these woodlands, based on fruit-body collections and molecularly identified root tips. This resulted in 87 peer-reviewed research papers dealing with EcM associations from Nothofagaceae forests published over the past 62 years. Based on these papers the EcM richness and its association with Nothofagaceae species was analyzed. Represented by 45 genera (34 Basidiomycetes and 11 Ascomycetes), 479 EcM taxa have been recorded, plus an additional 46 EcM taxa which are potentially EcM. Cortinarius was the most frequent and diverse genus, with 64.9% of total species. Nothofagus dombeyi had the highest number of unique EcM species, followed by N. pumilio, N. antarctica and Lophozonia obliqua. The EcM community associated with Nothofagus species, except N. nitida, showed higher similarities among themselves, than with Lophozonia and Fuscospora species. Beta diversity indexes showed EcM Nothofagus species have 29–42% niche overlap, while Nothofagus—Lophozonia only had 1–16%. The assessment of the accuracy of the EcM diversity, host specificity and community structure deserve further studies combining phylogenetic analysis based on broad ecological surveys. On the basis of pre-selected criteria Austropaxillus statuum, Cortinarius fragilis, Cortinarius xiphidipus and Hallingea purpurea are proposed as candidates for nursery spore inoculations, and should be subject to scientific evaluation to determine costs and benefits.

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Since 2015, Araucaria araucana, an ecologically and economically important conifer native to Argentina and Chile, has suffered an unusual partial death of the crown throughout almost all of the distribution range in Argentina. No primary pathogen or pest was evident, associated with the phenomenon. Isolates of Mortierella, a poorly studied fungal genus in Patagonia, were obtained from the margins of necrotic phloem tissue of symptomatic trees. Five species of Mortierella were isolated from affected tissues. In inoculation tests, Mortierella alpina and M. aff. basiparvispora were pathogenic to A. araucana. These species caused necrosis of phloem, leading to chlorosis, foliar desiccation and eventually death, demonstrating that Mortierellales may play a role in the decline of the tree.

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Ponderosa pine ( Pinus ponderosa Dougl. ex P. & C. Laws.), an ectomycorrhiza (EM) dependent species, has been widely introduced in Patagonia, Argentina. This study used morphotyping, restriction analysis, and sequencing of EM root tips from ponderosa pine seedlings in two nurseries to assess the complete EM fungus (EMF) richness, to confirm doubtful identities of commonly reported morphotypes, and to evaluate the efficiency of morphotyping compared with molecular analysis. This interdisciplinary approach together with the fact that is the first study in which Patagonian nurseries EMF are genetically evaluated contributes to the general knowledge of this important group of fungi. Sequencing revealed the presence of 11 taxa. Basidiomycetes included Thelephoraceae ( Tomentella sp.), Atheliaceae ( Amphinema byssoides (Pers.) J. Erikss.), Hydnangiaceae ( Laccaria sp.), Rhizopogonaceae ( Rhizopogon roseolus (Corda) Th. Fr.), and Cortinariaceae ( Hebeloma mesophaeum (Pers.) Quel.). Ascomycetes included Pezizaceae ( Wilcoxina mikolae (Chin S. Yang & H.E. Wilcox) Chin S. Yang & Korf and Wilcoxina sp.) and Tuberaceae ( Tuber sp.). Morphotyping proved to be useful for certain EMF species (R. roseolus, H. mesophaeum, A. byssoides, and to a lesser extent Tuber sp.) in which some morphological features are conspicuous and unique. Our detection of W. mikolae and Wilcoxina sp. are new records for ponderosa pine in Patagonia. All of the EM taxa identified are common to pine plantations and nurseries around the world, and no indigenous EM associated with native Nothofagus spp. were found.

SUMMARYSeveral reports of tree planters from the Patagonian Andes region of Chubut (Argentina) have pointed out that seedlings of Pinus ponderosa, obligate ectotrophic species, produced in greenhouses with high levels of fertilization without ectomycorrhizal inoculum applications, showed low or null ectomycorrhizal infection at the end of nursery stage but had excellent performance in plantation sites during the first years. This study was planned to evaluate if those seedlings develop mycorrhizal associations once installed in plantations, and if those associations are originated from inoculums acquired in the nursery. Three evaluations were done: 1) analyses of seedlings at the end of nursery period, to evaluate their initial mycorrhizal condition, 2) analyses after 6 month, with seedlings transplanted into pots with semi-sterile substrate, to establish if there exists inoculum in the system that did not express because of the high fertilization levels and, 3) analyses after 24 month, with seedlings planted in a field distant from any source of ectomycorrhizal inoculum, to evaluate the associations developed in the planting site. Results showed that: 1) the studied nursery produced seedlings with null or very low levels of mycorrhization, with low morphotypes' richness; 2) seedlings showed very high mycorrhizal percentages after 6 months (under greenhouse conditions) and after 24 months (in field conditions); 3) different mycorrhizal fungi behave differently under fertilization. The analyzed nursery fortuitously incorporated mycorrhizal inoculum that rapidly colonized seedlings, immediately after fertilization was interrupted. This fact demonstrates that the hypothesis that ponderosa pine seedlings can establish and grow in anectotrophic environments without EM symbioses is false.Key words: inoculum, nursery, mycorrhizas, Patagonia. RESUMENRepetidos reportes de plantadores de la zona cordillerana del Chubut (Argentina) han señalado que las plántulas de Pinus ponderosa, especie ectotrófica obligada, producidas bajo invernáculo con fertirriego y sin aplicación de inoculantes ectomicorrícicos, que presentaban baja o nula infección ectomicorrícica al terminar la etapa de vivero, mostraron excelentes comportamientos en los sitios de plantación durante los primeros años. Por ello, se planteó este estudio con el objetivo de constatar si las plántulas allí producidas desarrollan asociaciones micorrícicas una vez llevadas a plantación, y si éstas se originan a partir de inóculo adquirido en el vivero. Para ello, se realizaron tres evaluaciones de las plántulas: 1) al salir del vivero de producción acelerada, para constatar el estado micorrícico inicial, 2) después de seis meses de crecimiento luego de un trasplante a macetas con sustrato semi-estéril, para constatar si existía inóculo en el sistema que no se expresaba por el fertirriego, y 3) después de 24 meses luego de implantadas en un predio alejado de cualquier fuente de inóculo ectomicorrícico, para constatar el tipo de asociaciones formadas en el sitio de planta...

Phytophthora austrocedri is a pathogen of Austrocedrus chilensis causing “Mal del Ciprés” (cypress sickness) in Patagonia and killing Juniperus communis in Britain, along with other species in the Cupressaceae. The evident association of the pathogen with members of the Cupressaceae makes it necessary to study the susceptibility of other species related to A. chilensis to prevent the emergence of new diseases. The present study tested the pathogenicity of P. austrocedri to three native and endemic conifers in South America: Fitzroya cupressoides, Pilgerodendron uviferum and Araucaria araucana. The results showed that F. cupressoides and P. uviferum were highly susceptible to P. austrocedri. Since these are endangered tree species, the outcome of this study is crucial for governmental agencies, policymakers and stakeholders.