Mycobiota on exoskeleton debris of Neohelice granulata in an alkaline-sodic salt marsh: in vitro enzyme ability at different temperatures and pH.

This study analysed the mycobiota on exoskeleton debris of the crab Neohelice granulata collected from an alkaline salt marsh and assessed the in vitro enzyme ability of selected isolates at different temperatures and pH. Exoskeleton fragments were incubated in moist chambers on paper and on agar medium. Growth and enzyme ability of selected fungi were also evaluated in agar media with 0.5 % casein, 1% Tween®20, and Chitin-Azure® by the production of a halo/growth ratio. We identified 22 fungal species using both methods. Since the two isolation methods added information to one another, both ones are necessary to recover the cultivable mycobiota associated with the exoskeleton debris. All fungi showed greater levels of enzyme activity in alkaline than acid medium with Tween®20. The halo diameter on casein and chitin varied according to the fungal isolate and pH. Most fungi had a larger halo at 4°C than at the other temperatures tested. Clonostachys rosea showed the greatest activity in all media at 4ºC. We conclude that exoskeletons of the N. granulata are a source of fungi able to produce enzyme activities that show differences upon incubation conditions to which they are cultivated such as ones including specific temperatures and pH values.

[Combination of phosphorus solubilizing and mobilizing fungi with phosphate rocks and volcanic materials to promote plant growth of lettuce (Lactuca sativa L.)]. / Combinación de hongos movilizadores y solubilizadores de fósforo con rocas fosfóricas y materiales volcánicos para la promoción del crecimiento de plantas de lechuga (Lactuca sativa L.).

Arbuscular mycorrhizal fungi (AMF) increase the uptake of soluble phosphates, while phosphorus solubilizing fungi (S) promote solubilization of insoluble phosphates complexes, favoring plant nutrition. Another alternative to maintaining crop productivity is to combine minerals and rocks that provide nutrients and other desirable properties. The aim of this work was to combine AMF and S with pyroclastic materials (ashes and pumices) from Puyehue volcano and phosphate rocks (PR) from Rio Chico Group (Chubut) - to formulate a substrate for the production of potted Lactuca sativa. A mixture of Terrafertil®:ashes was used as substrate. Penicillium thomii was the solubilizing fungus and Rhizophagus intraradices spores (AMF) was the P mobilizer (AEGIS® Irriga). The treatments were: 1) Substrate; 2) Substrate+AMF; 3) Substrate+S; 4) Substrate+AMF+S; 5) Substrate: PR; 6) Substrate: PR+AMF; 7) Substrate: PR+S and 8) Substrate: PR+AMF+S. Three replicates were performed per treatment. All parameters evaluated (total and assimilable P content in substrate, P in plant tissue and plant dry biomass) were significantly higher in plants grown in substrate containing PR and inoculas with S and AMF. This work confirms that the combination of S/AMF with Puyehue volcanic ashes, PR from the Río Chico Group and a commercial substrate promote the growth of L. sativa, thus increasing the added value of national geomaterials.

First record of Talaromyces udagawae in soil related to decomposing human remains in Argentina.

The morphologic features of Talaromyces udagawae Stolk and Samson are here described and illustrated. This teleomorphic Ascomycota fungus was isolated from soil obtained in Buenos Aires province (Argentina) from beneath a human cadaver in an advanced state of decomposition. After washing and serial dilution of the soil along with moist-chamber techniques for fungal cultivation, T. udagawae formed very restricted colonies of bright yellow color on different growth media with 8-ascospored asci. The ascospores were ellipsoidal and ornamented. The anamorphic state was not observed. Molecular-genetic techniques identified the species. The present record is the first of the species in Argentina, pointing it as a tool to identify soils where cadaver decomposition occurs.

Endophytic fungi from selected varieties of soybean (Glycine max L. Merr.) and corn (Zea mays L.) grown in an agricultural area of Argentina.

Endophytic fungi are ubiquitous and live within host plants without causing any noticeable symptoms of disease. Little is known about the diversity and function of fungal endophytes in plants, particularly in economically important species. The aim of this study was to determine the identity and diversity of endophytic fungi in leaves, stems and roots of soybean and corn plants and to determine their infection frequencies. Plants were collected in six areas of the provinces of Buenos Aires and Entre Ríos (Argentina) two areas were selected for sampling corn and four for soybean. Leaf, stem and root samples were surface-sterilized, cut into 1cm(2) pieces using a sterile scalpel and aseptically transferred to plates containing potato dextrose agar plus antibiotics. The species were identified using both morphological and molecular data. Fungal endophyte colonization in soybean plants was influenced by tissue type and varieties whereas in corn plants only by tissue type. A greater number of endophytes were isolated from stem tissues than from leaves and root tissues in both species of plants. The most frequently isolated species in all soybean cultivars was Fusarium graminearum and the least isolated one was Scopulariopsis brevicaulis. Furthermore, the most frequently isolated species in corn plants was Aspergillus terreus whereas the least isolated one was Aspergillus flavus. These results could be relevant in the search for endophytic fungi isolates that could be of interest in the control of agricultural pests.

Escovopsis trichodermoides sp. nov., isolated from a nest of the lower attine ant Mycocepurus goeldii.

Currently, five species are formally described in Escovopsis, a specialized mycoparasitic genus of fungus gardens of attine ants (Hymenoptera: Formicidae: tribe Attini). Four species were isolated from leaf-cutting ants in Brazil, including Escovopsis moelleri and Escovopsis microspora from nests of Acromyrmex subterraneus molestans, Escovopsis weberi from a nest of Atta sp. and Escovopsis lentecrescens from a nest of Acromyrmex subterraneus subterraneus. The fifth species, Escovopsis aspergilloides was isolated from a nest of the higher attine ant Trachymyrmex ruthae from Trinidad. Here, we describe a new species, Escovopsis trichodermoides isolated from a fungus garden of the lower attine ant Mycocepurus goeldii, which differs from the five other species by highly branched, trichoderma-like conidiophores lacking swollen vesicles, with reduced conidiogenous cells and distinctive conidia morphology. Phylogenetic analyses based on partial tef1 gene sequences support the distinctiveness of this species. A portion of the internal transcribed spacers of the nuclear rDNA was sequenced to serve as a DNA barcode. Future molecular and morphological studies in this group of fungi will certainly unravel the taxonomic diversity of Escovopsis associated with fungus-growing ants.

Composition and structure of arbuscular-mycorrhizal communities in El Palmar National Park, Argentina.

The arbuscular-mycorrhizal-fungal (AMF) communities from the El Palmar National Park of Entre Ríos Province, Argentina, were investigated and characterized. The species of AMF present in five distinct vegetation types-gallery forest, grassland, marsh, palm forest, and scrubland-were isolated, identified and quantified over 2 y. Forty-six AMF morphotaxa were found. The composition of the AMF communities differed between the seasons, soil and vegetation types. Seasonal variations were observed in members of the Acaulosporaceae, Archaeosporaceae, Claroideoglomeraceae, Gigasporaceae and Pacisporaceae. Depending on soil type, the AMF-spore communities were dominated by members of one of the two main orders of the Glomeromycota. AMF communities from grassland and palm forest, which occur on sandy soils, comprised primarily members of the Diversisporales, with a high percentage of species of Acaulospora and of Gigasporaceae. Communities from the gallery forest, marsh and scrubland, which occur on loam-clay soils, were composed of members of the Glomerales, with a high percentage of spores from species of Glomus. Thus, both AMF and plant communities would appear to be strongly and similarly influenced by edaphic conditions.

Pathogenic and enzyme activities of the entomopathogenic fungus Tolypocladium cylindrosporum (Ascomycota: Hypocreales) from Tierra del Fuego, Argentina.

Tolypocladium cylindrosporum is an entomopathogenic fungi that has been studied as a biological control agent against insects of several orders. The fungus has been isolated from the soil as well as from insects of the orders Coleoptera, Lepidoptera, Diptera and Hymenoptera. In this study, we analyzed the ability of a strain of T cylindrosporum, isolated from soil samples taken in Tierra del Fuego, Argentina, to produce hydrolytic enzymes, and to study the relationship of those activities to the fungus pathogenicity against pest aphids. We have made the traditional and molecular characterization of this strain of T cylindrosporum. The expression of hydrolase activity in the fungal strain was estimated at three incubation temperatures (4 degreeC, 12 degreeC and 24 degreeC), on different agar media supplemented with the following specific substrates: chitin azure, Tween 20, casein, and urea for chitinase, lipase, protease, and urease activity, respectively. The hydrolytic-enzyme activity was estimated qualitatively according to the presence of a halo of clarification through hydrolase action, besides was expressed semi-quantitatively as the ratio between the hydrolytic-halo and colony diameters. The pathogenicity of the fungus was tested on adults of the aphid Rhopalosiphum padi at three temperatures of incubation (4 degree C, 12 degree C and 24 degree C). The suspension was adjusted to a concentration of 1x10(7) conidia/ml. In pathogenicity assays at seven days post-inoculation, the fungus caused the mortality of adults of Ropalosiphum padi at different temperatures also showed a broad ability to grow on several agar-culture media, supplemented with different carbon sources at the three incubation temperatures tested. Although, the growth was greater with higher incubation temperatures (with maximum levels at 24 degreeC), the fungus reached similar colony diameters after 15 days of incubation on the medium supplemented with Tween 20 at the lower two incubation temperatures of 4 degreeC or 12 degreeC. In accordance with the results on colony diameters, the fungus revealed an ability to degrade casein, chitin derivatives, Tween 20, and urea as evidenced by the appearance of a halo around the fungal colony. Because of its origin and temperature tolerance, this Argentine strain has great potential for use as a biocontrol agent for insect pest control in cold and temperate environments.

Native arbuscular mycorrhizal fungi in the Yungas forests, Argentina.

The arbuscular mycorrhizal fungal (AMF) communities from the Yungas forests of Argentina were studied. The AMF species present in the rhizosphere of some dominant native plants (one tree: Alnus acuminata; three herbaceous species: Duchesnea indica, Oxalis conorrhiza, Trifolium aff. repens; and one shrub: Sambucus peruviana) from two sites (Quebrada del Portugués and Narváez Range) of the Yungas forests were isolated, identified and quantified during the four seasons of the year. Twenty-two AMF morphotaxa were found. Spore density of some AMF species at each site varied among seasons. The genera that most contributed to the biodiversity index were Acaulospora for Quebrada del Portugués and Glomus for Narváez Range. High diversity values were observed in the Yungas forests, particularly in the spring (rainy season). We concluded AMF differed in species composition and seasonal sporulation dynamics in the Yungas forests.

Pathogenic ability and saline stress tolerance of two Fusarium isolates from Odontesthes bonariensis eggs.

BACKGROUND: Several fungal species represent a potential risk to embryos of Odontesthes bonariensis (Cuvier and Valenciennes, 1835), a euryhaline freshwater fish that lives in the Pampean inland waters and has potential economic relevance. AIMS: To identify two fungi isolated from O. bonariensis eggs exposed to saline conditions and to characterize their pathogenicity and tolerance to sodium chloride solutions. METHODS: The isolates were identified by morphological features, and a preliminar phylogenetic analysis using sequences of translation elongation factor 1-alpha (EF-1α) and calmodulin (CAM) was performed. Koch's postulates were tested to identify the causative agent of fungal infection. The influence of NaCl on the fungal growth was evaluated in in vitro assays. RESULTS: The isolates LPSC 1001 and 1002 were identified as representatives of the genus Fusarium, and belonging to the Fusarium incarnatum-Fusarium equiseti species complex (FIESC) and the Fusarium solani species complex (FSSC), respectively. Histological observations on eggs exposed in vitro to both isolates in infectivity assays confirmed the ability of the fungal isolates to penetrate to egg's chorionic membrane, leading to the death of embryos. Increasing NaCl concentration in the culture medium reduced the growth of the isolates LPSC 1001 and 1002, being completely inhibited at 160 and 120g/l NaCl respectively. CONCLUSIONS: The isolates LPSC 1001 (FIESC) and 1002 (FSSC) were identified as fungal pathogens to O. bonariensis eggs. The use of NaCl solutions as antifungal treatment was not effective to control the infection with these strains.

Preliminary data on growth and enzymatic abilities of soil fungus Humicolopsis cephalosporioides at different incubation temperatures.

BACKGROUND: Nothofagus pumilio (Poepp & Endl.) Krasser, known as "lenga" is the most important timber wood species in southernmost Patagonia (Argentina). Humicolopsis cephalosporioides Cabral & Marchand is a soil fungus associated with Nothofagus pumilio forests, which has outstanding cellulolytic activity. However, there is no information about the ability of this fungus to use organic substrates other than cellulose, and its ability to produce different enzyme systems, as well as its response to temperature. AIMS: The aim of this study was to examine the role of H. cephalosporioides in degradation processes in N. pumilio forests in detail by evaluating the in vitro ability of four isolates of this fungus to grow and produce different lytic enzyme systems, and their response to incubation temperature. METHODS: The ability of the fungi to grow and produce enzyme systems was estimated by inoculating them on agar media with specific substrates, and the cultures were incubated at three temperatures. RESULTS: A differential behavior of each strain in levels of growth and enzyme activity was found according to the medium type and/or incubation temperature. CONCLUSIONS: A intra-specific variability was found in H. cephalosporioides. Likewise a possible link between the saprotrophic role of this fungus in N. pumilio forests and the degradation of organic matter under stress conditions, such as those from frosty environments, was also discussed.

A Cladistic Analysis of the Genus Cyttaria (Fungi-Ascomycotina).

Abstract-Cyttaria Berkeley (Cyttariaceae, Cyttariales, Class Discomycetes), is a genus of eleven species, seven from South America and four from Australasia (Australia, Tasmania, and New Zealand). Cyttaria is a monophyletic genus defined by the following synapomorphies: fleshy to gelatinous stromata with endostromatic apothecia; and complete lack of fungal chitin in the cell walls, having instead ß-1-3-glucan. All Cyttaria are exclusive parasites of Nothofagus species. A cladistic analysis of the genus was performed using 18 characters from macromorphology, micro-morphology, and phenology. Polarity of characters is based on the outgroup comparison method (using the Class Discomycetes as a whole) and on the ontogenetic criterion. A hypothetical outgroup was constructed using all plesiomorphic states. Two equally parsimonious cladograms were produced, each with 40 steps and a consistency index of 0.70. These differed in the position of the South American species C. hookeri and C. johowii. In one cladogram, C. hookeri is the sister group to the rest of the genus, and in the other, both species form a monophyletic group (ascospores ovoid) that is the sister group of the rest of the genus. Our analysis of the two characters causing this difference (position of apothecia on stroma, and shape of ascospores) supports the latter hypothesis. In both cladograms, all of the Australasian species form a monophyletic group (thick ectostroma), and, within that, two subgroups are defined: C. gunnii-C. pallida (papillae present), and C. nigra-C. septentrionalis (ectostroma with black incrustations). The Australasian species form a monophyletic group (spermatangia absent) with C. berteroi, and this last group forms a monophyletic group (conidia absent) with C. espinosae. Cytlaria darwimi and C. exigua form another monophyletic group (very thick ectostroma). Excluding C. hookeri and C. johowii, C. hariotii is the sister group to the remaining eight species.

Native arbuscular mycorrhizal fungi (AMF) from mountain grassland (Cordoba, Argentina) I. Seasonal variation of fungal spore diversity.

Arbuscular mycorrhizal fungi (AMF) were studied in the rhizosphere of 3 Poaceae with metabolic pathway C(3) (Briza subaristata Lam., Deyeuxia hieronymi (Hack.) Türpe and Poa stuckertii (Hack.) Parodi), 2 Poaceae with C(4) metabolic type (Eragrostis lugens Nees and Sorghastrum pellitum (Hack.) Parodi.), and a Rosaceae (Alchemilla pinnata Ruíz & Pav.) from a natural mountain grassland in Central Argentina (South America). Host species, their metabolic type, seasonal changes, and grazing effects over AM fungal diversity were analyzed. Seventeen mycorrhizal fungi taxa were found, widespread in all families of Glomales. Density of endomycorrhizal fungi was found to be strongly influenced with seasons and host metabolic pathway, although biodiversity (H), richness (S) and evenness (E) did not change. In most cases grazing did not affect these variables.

Arbuscular mycorrhizal fungi in a mountain grassland II: Seasonal variation of colonization studied, along with its relation to grazing and metabolic host type.

The relationships among seasons, host metabolic type, grazing and arbuscular mycorrhizal colonization were analyzed in a high South American native grassland. This study investigated seasonal changes and grazing effects on the symbiotic endomycorrhizal interaction in 5 Poaceae [C(3) metabolic pathway: Briza subaristata Lam., Deyeuxia hieronymi (Hack.) Türpe and Poa stuckertii (Hack.) Parodi; with C(4) metabolic pathway: Eragrostis lugens Nees and Sorghastrum pellitum (Hack.) Parodi; and a Rosaceae (Alchemilla pinnata Ruíz & Pav.)]. All hosts were dominant species in the mountain grassland in central Argentina. It was found that the seasons markedly influenced endomycorrhizal colonization, whereas grazing did not affect this interaction. C(4) grasses presented the highest root colonization. Hosts Briza subaristata (C(3) metabolic pathway) and Sorghastrum pellitum (C(4) metabolic pathway) showed Arum- and Paris-type colonization and intermediate forms.

Soil fungi: their potential use as a forensic tool.

As a grave is an anomalous environment and differs from its surroundings, criminal investigators employ different techniques for locating, recovering, and analyzing clandestine graves. In this study were identified the fungi found in the soil under corpses in decomposition with an aim at relating the copresence of human remains and different fungal species. Were isolated the fungi in three ways: soil washing, serial dilutions, and moist chamber growth. Dichotomomyces cejpii, Talaromyces trachyspermus, Talaromyces flavus, and Talaromyces sp. were the representative species found--with those belonging to the ammonia group, whose fungi are the first in the succession of cadaver decomposition directly in the ground. The mycobiota found at the present study area clearly differs to mycobiota identified in control sample and from previously described species for other areas of Buenos Aires Province, Argentina. Further forensic examples of this type are needed to develop fully the detailed use of mycology as a forensic tool.

Primer registro de Talaromyces udagawae relacionado con cuerpos humanos en descomposición, en suelo de la Argentina / First record of Talaromyces udagawae in soil related to decomposing human remains in Argentina

The morphologic features of Talaromyces udagawae Stolk and Samson are here described and illustrated. This teleomorphic Ascomycota fungus was isolated from soil obtained in Buenos Aires province (Argentina) from beneath a human cadaver in an advanced state of decomposition. After washing and serial dilution of the soil along with moist-chamber techniques for fungal cultivation, T. udagawae formed very restricted colonies of bright yellow color on different growth media with 8-ascospored asci. The ascospores were ellipsoidal and ornamented. The anamorphic state was not observed. Molecular-genetic techniques identified the species. The present record is the first of the species in Argentina, pointing it as a tool to identify soils where cadaver decomposition occurs.

Se describen e ilustran las características morfológicas de Talaromyces udagawae Stolk y Samson. Se aisló el estado teleomórfico de este hongo Ascomycota de suelo obtenido en la provincia de Buenos Aires (Argentina), por debajo de un cadáver humano en avanzado estado de descomposición. Las muestras de suelo fueron analizadas mediante lavado, dilución seriada y cámaras húmedas, técnicas ampliamente usadas para el estudio de hongos de suelo. T. udagawae formó colonias muy restringidas de color amarillo brillante en diferentes medios de cultivo, con ascos con 8 ascosporas. Las ascosporas eran elipsoidales y ornamentadas. No fue hallado el estado anamórfico. La especie también fue identificada mediante técnicas moleculares. El presente registro es el primero de la especie en la Argentina y el único que la postula como herramienta para identificar suelos donde ocurre una descomposición cadavérica.

Pathogenic ability and saline stress tolerance of two Fusarium isolates from Odontesthes bonariensis eggs / Patogenicidad y tolerancia al estrés salino de dos aislamientos de Fusarium aislados de huevos de Odontesthes bonariensis

Background. Several fungal species represent a potential risk to embryos of Odontesthes bonariensis (Cuvier and Valenciennes, 1835), a euryhaline freshwater fish that lives in the Pampean inland waters and has potential economic relevance. Aims. To identify two fungi isolated from O. bonariensis eggs exposed to saline conditions and to characterize their pathogenicity and tolerance to sodium chloride solutions. Methods. The isolates were identified by morphological features, and a preliminar phylogenetic analysis using sequences of translation elongation factor 1-alpha (EF-1α) and calmodulin (CAM) was performed. Koch's postulates were tested to identify the causative agent of fungal infection. The influence of NaCl on the fungal growth was evaluated in in vitro assays. Results. The isolates LPSC 1001 and 1002 were identified as representatives of the genus Fusarium, and belonging to the Fusarium incarnatum-Fusarium equiseti species complex (FIESC) and the Fusarium solani species complex (FSSC), respectively. Histological observations on eggs exposed in vitro to both isolates in infectivity assays confirmed the ability of the fungal isolates to penetrate to egg's chorionic membrane, leading to the death of embryos. Increasing NaCl concentration in the culture medium reduced the growth of the isolates LPSC 1001 and 1002, being completely inhibited at 160 and 120 g/l NaCl respectively. Conclusions. The isolates LPSC 1001 (FIESC) and 1002 (FSSC) were identified as fungal pathogens to O. bonariensis eggs. The use of NaCl solutions as antifungal treatment was not effective to control the infection with these strains (AU)

Antecedentes. Diversas especies de hongos pueden representar un riesgo importante para los embriones de Odontesthes bonariensis (Cuvier & Valenciennes 1835), un pez de agua dulce eurihalino que vive en las aguas interiores pampeanas y tiene una relevancia económica potencial. Objetivos. Identificar dos especies de hongos de huevos de O. bonariensis expuestos a condiciones salinas y caracterizar su patogenicidad y tolerancia a las soluciones de cloruro de sodio. Métodos. Se identificaron los aislamientos por sus características morfológicas, y se realizó un análisis filogenético preliminar utilizando secuencias de traslación del factor 1 alfa elongación (EF- 1α) y calmodulina (CAM). Se llevaron a cabo los postulados de Koch para identificar el agente causante de la infección fúngica. La influencia de NaCl sobre el crecimiento fúngico se evaluó en ensayos in vitro. Resultados. Se identificaron los aislamientos LPSC 1001 y 1002 como representantes del género Fusarium, y pertenecientes al complejo de especies Fusarium incarnatum-Fusarium equiseti (FIESC) y al complejo de especies de Fusarium solani (FSSC), respectivamente. Las observaciones histológicas en los huevos expuestos in vitro a ambos aislamientos en los ensayos de infectividad confirmaron la capacidad de estos para penetrar en la membrana coriónica, lo que condujo a la muerte de los embriones. El aumento de la concentración de NaCl en el medio de cultivo redujo el crecimiento de los aislamientos LPSC 1001 y 1002, quedando completamente inhibidos a 160 y 120 g/l de NaCl, respectivamente. Conclusiones. Se identificaron los aislamientos LPSC 1001 (FIESC) y 1002 (FSSC) como hongos patógenos para los huevos de O. bonariensis; el uso de soluciones de NaCl como tratamiento antifúngico no resultó eficaz para el control de la infección con estas cepas (AU)

Endophytic fungi from selected varieties of soybean (Glycine max L. Merr.) and corn (Zea mays L.) grown in an agricultural area of Argentina / Hongos endófitos aislados de cultivares de soja (Glycine max L. Merr) y maíz (Zea mays L.) presentes en áreas agrícolas argentinas

Endophytic fungi are ubiquitous and live within host plants without causing any noticeable symptoms of disease. Little is known about the diversity and function of fungal endophytes in plants, particularly in economically important species. The aim of this study was to determine the identity and diversity of endophytic fungi in leaves, stems and roots of soybean and corn plants and to determine their infection frequencies. Plants were collected in six areas of the provinces of Buenos Aires and Entre Ríos (Argentina) two areas were selected for sampling corn and four for soybean. Leaf, stem and root samples were surface-sterilized, cut into 1 cm² pieces using a sterile scalpel and aseptically transferred to plates containing potato dextrose agar plus antibiotics. The species were identified using both morphological and molecular data. Fungal endophyte colonization in soybean plants was influenced by tissue type and varieties whereas in corn plants only by tissue type. A greater number of endophytes were isolated from stem tissues than from leaves and root tissues in both species of plants. The most frequently isolated species in all soybean cultivars was Fusarium graminearum and the least isolated one was Scopulariopsis brevicaulis. Furthermore, the most frequently isolated species in corn plants was Aspergillus terreus whereas the least isolated one was Aspergillus flavus. These results could be relevant in the search for endophytic fungi isolates that could be of interest in the control of agricultural pests.

Los hongos endófitos son ubicuos y se encuentran en el interior de los tejidos de las plantas de manera asintomática. Se sabe muy poco acerca de la diversidad y la función de estos hongos, particularmente en especies de importancia económica. El objetivo de este trabajo fue determinar la diversidad y la frecuencia de colonización de hongos endófitos en raíces, tallos y hojas de 2 variedades de maíz y de 4 variedades de soja; las muestras se tomaron de 6 áreas diferentes ubicadas en las provincias de Buenos Aires y Entre Ríos (Argentina). Con un bisturí estéril se obtuvieron porciones de 1 cm² de raíz, tallo y hoja, que fueron colocados en placas con agar papa dextrosa más antibiótico. Las especies de hongos fueron identificadas a partir de características morfológicas y moleculares. La colonización de hongos endófitos en soja estuvo influenciada por la variedad y por el tipo de tejido, en tanto que en el maíz solo hubo influencia del tipo de tejido. El mayor número de endófitos se encontró en los tallos de ambas especies. El aislamiento más frecuente en todas las variedades de soja fue Fusarium graminearum y el menos frecuente Scopulariopsis brevicaulis. En ambas variedades de maíz la especie con mayor frecuencia de aislamiento fue Aspergillus terreus y la de menor fue Aspergillus flavus. Estos resultados son relevantes para la búsqueda de especies de hongos endófitos que podrían ser de interés en el control de plagas agrícolas.

Preliminary data on growth and enzymatic abilities of soil fungus Humicolopsis cephalosporioides at different incubation temperatures / Datos preliminares sobre el crecimiento y la capacidad enzimática del hongo de suelo Humicolopsis cephalosporioides a diferentes temperaturas de incubación

Background. Nothofagus pumilio (Poepp & Endl.) Krasser, known as 'lenga' is the most important timber wood species in southernmost Patagonia (Argentina). Humicolopsis cephalosporioides Cabral & Marchand is a soil fungus associated with Nothofagus pumilio forests, which has outstanding cellulolytic activity. However, there is no information about the ability of this fungus to use organic substrates other than cellulose, and its ability to produce different enzyme systems, as well as its response to temperature. Aims. The aim of this study was to examine the role of H. cephalosporioides in degradation processes in N. pumilio forests in detail by evaluating the in vitro ability of four isolates of this fungus to grow and produce different lytic enzyme systems, and their response to incubation temperature. Methods. The ability of the fungi to grow and produce enzyme systems was estimated by inoculating them on agar media with specific substrates, and the cultures were incubated at three temperatures. Results. A differential behavior of each strain in levels of growth and enzyme activity was found according to the medium type and/or incubation temperature. Conclusions. A intra-specific variability was found in H. cephalosporioides. Likewise a possible link between the saprotrophic role of this fungus in N. pumilio forests and the degradation of organic matter under stress conditions, such as those from frosty environments, was also discussed (AU)

Antecedentes. Nothofagus pumilio (Poepp & Endl) Krasser (N. pumilio), conocido como «lenga», es la especie maderable más importante en el extremo sur de Patagonia (Argentina). Humicolopsis cephalosporioides Cabral & Marchand es un hongo del suelo asociado a bosques de N. pumilio, que tiene una actividad celulolítica excepcional. Sin embargo, no hay información acerca de la capacidad de este hongo para utilizar otros sustratos orgánicos distintos de la celulosa, o para producir diferentes sistemas enzimáticos, así como su respuesta a la temperatura. Objetivos. El objetivo de este estudio fue profundizar en el rol que Humicolopsis cephalosporioides tiene en los procesos de degradación en los bosques de N. pumilio a través de la evaluación de la capacidad in vitro de 4 aislamientos de este hongo para crecer y producir diferentes sistemas enzimáticos líticos y su respuesta a la temperatura de incubación. Métodos. La capacidad de los hongos para crecer y producir sistemas enzimáticos se estimó a través de su inoculación sobre medios de agar con sustratos específicos, siendo incubados a 3 temperaturas. Resultados. Se observó un comportamiento diferencial de cada cepa en el crecimiento y la actividad enzimática de acuerdo con el tipo de medio o la temperatura de incubación. Conclusiones. Se observó variabilidad intraespecífica en Humicolopsis cephalosporioides. Asimismo, se discutió la posible relación entre el rol saprotrófico de este hongo en los bosques de N. pumilio y la degradación de la materia orgánica en condiciones estresantes, como las existentes en ambientes fríos (AU)

Pathogenic and enzyme activities of the entomopathogenic fungus Tolypocladium cylindrosporum (Ascomycota: Hypocreales) from Tierra del Fuego, Argentina

Tolypocladium cylindrosporum is an entomopathogenic fungi that has been studied as a biological control agent against insects of several orders. The fungus has been isolated from the soil as well as from insects of the orders Coleoptera, Lepidoptera, Diptera and Hymenoptera. In this study, we analyzed the ability of a strain of T. cylindrosporum, isolated from soil samples taken in Tierra del Fuego, Argentina, to produce hydrolytic enzymes, and to study the relationship of those activities to the fungus pathogenicity against pest aphids. We have made the traditional and molecular characterization of this strain of T. cylindrosporum. The expression of hydrolase activity in the fungal strain was estimated at three incubation temperatures (4ºC, 12ºC and 24ºC), on different agar media supplemented with the following specific substrates: chitin azure, Tween ® 20, casein, and urea for chitinase, lipase, protease, and urease activity, respectively. The hydrolytic-enzyme activity was estimated qualitatively according to the presence of a halo of clarification through hydrolase action, besides was expressed semi-quantitatively as the ratio between the hydrolytic-halo and colony diameters. The pathogenicity of the fungus was tested on adults of the aphid Rhopalosiphum padi at three temperatures of incubation (4ºC, 12ºC and 24ºC). The suspension was adjusted to a concentration of 1x10 7 conidia/ml. In pathogenicity assays at seven days post-inoculation, the fungus caused the mortality of adults of Ropalosiphum padi at different temperatures also showed a broad ability to grow on several agar-culture media, supplemented with different carbon sources at the three incubation temperatures tested. Although, the growth was greater with higher incubation temperatures (with maximum levels at 24°C), the fungus reached similar colony diameters after 15 days of incubation on the medium supplemented with Tween® 20 at the lower two incubation temperatures of 4°C or 12°C. In accordance with the results on colony diameters, the fungus revealed an ability to degrade casein, chitin derivatives, Tween® 20, and urea as evidenced by the appearance of a halo around the fungal colony. Because of its origin and temperature tolerance, this Argentine strain has great potential for use as a biocontrol agent for insect pest control in cold and temperate environments. Rev. Biol. Trop. 60 (2): 833-841. Epub 2012 June 01.

El hongo entomopatógeno Tolypocladium cylindrosporum ha sido estudiado como un agente de control biológico contra insectos de varios órdenes. Esta especie fue aislada del suelo, así como de insectos de los órdenes Coleoptera, Lepidoptera, Diptera e Hymenoptera. En el presente trabajo hemos analizado la capacidad de una cepa de T. cylindrosporum (LPSC Nº1065) aislada del suelo en Tierra del Fuego, Argentina, para producir enzimas hidrolíticas y determinar la relación de esta actividad con la patogenicidad del hongo para combatir la plaga de los áfidos en diferentes temperaturas (4º, 12º y 24ºC). En los ensayos de patogenicidad, siete días posteriores a la inoculación, se registró mortalidad en los adultos del áfido Ropalosiphum padi a diferentes temperaturas y también se demostró una amplia capacidad de crecer en varios medios de cultivos complementados con diferentes fuentes de carbono bajo las tres temperaturas de incubación ensayadas. Debido a su origen y a la tolerancia que tiene a bajas temperaturas esta cepa, presenta un gran potencial para su uso como agente de control biológico para las plagas de insectos de ambientes fríos y templados.