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Alternaria is one of the main fungal genera affecting the quality of barley grains. In this study, a polyphasic approach was carried out to characterise the Alternaria population infecting different cultivars of barley grains from the major producing regions of Argentina in the 2014 and 2015 seasons. Its relationship with Fusarium and correlations between predominant species, barley cultivars, and climatic conditions in the growing regions were evaluated. Alternaria incidence exceeded that of Fusarium in all the barley samples and was higher in the drier season (21% in 2014 and 42% in 2015 vs. 6% and 4%, respectively). The main Alternaria species-groups identified were present in both growing seasons in similar frequencies (A. tenuissima sp.-grp., 83.4% in 2014 and 81.7% in 2015; A. infectoria sp.-grp., 11.7% in 2014 and 11.3% in 2015). The dominant Alternaria species-group isolated and identified based on morphological characteristics, DNA sequencing, and metabolite profile was A. tenuissima (72.9%), followed by A. infectoria (14.6%). An association between their frequency and field temperature was observed; A. tenuissima sp.-grp. was more frequent in northern localities, where higher temperatures were registered, while the opposite was observed for A. infectoria sp.-grp. A smaller percentage of A. arborescens sp.-grp. (5%), A. alternata sp.-grp. (3.9%) and A. vaccinii (1.4%) were also identified. Both secondary metabolite profiles and phylogenetic analysis were useful to distinguish isolates from Alternaria section Alternaria and section Infectoriae. Regarding metabolite profiles, alternariol was the most frequent compound produced by isolates of the section Alternaria. Infectopyrones and novae-zelandins were produced by most of the isolates from section Infectoriae. The barley cultivars analysed in this study did not show a particular susceptibility regarding the Alternaria population composition, except for Andreia, which presented the highest frequency of contamination with A. tenuissima sp.-grp. The rest of the cultivars, when grown in different regions, showed different proportion of the Alternaria sp.-grps., suggesting that other factors were determinant in their distribution. The results obtained in the present study will be a valuable tool for health authorities to assess the need for regulations on Alternaria mycotoxins, given the high incidence of Alternaria spp. in barley and the diversity of metabolites that might contaminate the grains.

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BACKGROUND: Wheat is the most important winter crop in the world, being affected by the presence of fungal, mainly those belonging to the Fusarium genus. Fusarium head blight (FHB) is a serious disease that causes important economic damage and quantitative/qualitative losses, with Fusarium graminearum and Fusarium poae being two of the most isolated species worldwide. The present study aimed to evaluate the interaction between F. graminearum and F. poae and the effects on disease parameters, grain quality and mycotoxin contamination on five wheat genotypes under field conditions during three growing seasons. RESULTS: Statistical differences between Fusarium treatments were found for disease parameters, grain quality and mycotoxin contamination during the 2014/2015 growing season. High values of incidence (58.00 ± 8.00%), severity (6.28 ± 1.51%) and FHB index (4.72 ± 1.35) were observed for F. graminearum + F. poae treatment. Regarding grain quality, the results showed that the degradation of different protein fractions depends on each Fusarium species: glutenins were degraded preferably by F. graminearum (-70.82%), gliadins were degraded preferably by F. poae (-29.42%), whereas both protein fractions were degraded when both Fusarium species were present (-60.91% and -16.51%, respectively). Significant differences were observed for mycotoxin contamination between genotypes, with Proteo being the most affected (DON = 12.01 ± 3.67 µg g-1 ). In addition, we report that 3-ADON predominated over 15-ADON in the three seasons evaluated. CONCLUSION: Variations in plant-pathogen interaction (Fusarium-wheat pathosystem) should be considered at least in years with favorable climatic conditions for FHB development, as a result of the potential impact of this disease on grain quality and mycotoxin contamination. © 2019 Society of Chemical Industry.

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BACKGROUND: Barley (Hordeum vulgare L.) is one of the most important cereals worldwide, and its quality is affected by fungal contamination such as species of the genus Alternaria. No information is available about the occurrence of Alternaria mycotoxins in Argentinean barley grains, which is of concern, because they can be transferred into malt and beer. The aim of this study was to analyze the occurrence of alternariol (AOH), alternariol monomethyl ether (AME) and tenuazonic acid (TeA) in malting barley grains from the main producing region of Argentina during the 2014 and 2015 growing seasons. RESULTS: The most frequent mycotoxin was AOH (64%), which was detected at higher levels (712 µg kg-1 ) compared with other studies, followed by TeA (37%, 1522 µg kg-1 ), while AME was present in five samples in the 2015 growing season only, with a mean of 4876 µg kg-1 . A similar frequency of mycotoxin occurrence was observed in both years (80.8 vs 85.3%), but more diverse contamination was found in 2015, which was characterized by lower accumulated precipitation. Nevertheless, AOH was more frequently found in 2014 than in 2015 (80.8 and 47.1% respectively). A negative correlation between AOH concentration and temperature was observed. The susceptibility of different barley varieties to mycotoxin accumulation varied with the mycotoxin, geographical location and meteorological conditions. CONCLUSION: The results obtained in the present work represent a tool for risk assessment of exposition to these mycotoxins and could be used by food safety authorities to determine the need for their regulation. Furthermore, the establishment of a hazard analysis and critical control point (HACCP) system to minimize fungal and mycotoxin contamination in barley from farm to processing could be apply to ensure food safety. © 2019 Society of Chemical Industry.

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In this work, we present a novel biostimulant for sustainable crop disease management, PSP1, based on the plant defense-elicitor AsES, an extracellular protease produced by the strawberry fungal pathogen Acremonium strictum. Fungal fermentation conditions and downstream processing were determined to maximize extracellular protein production, product stability and a high plant defense-eliciting activity, as monitored by anthracnose resistance in supernatant-treated strawberry plants subsequently infected with a virulent strain of Colletotrichum acutatum. Fermentation batches were shown to reduce anthracnose development by 30-60% as compared to infected non-treated plants. Product formulation was shown to be stable for 6 months when stored at temperatures up to 45°C and toxicological tests showed that PSP1 was harmless to beneficial organisms and non-toxic to mammalian species at concentrations 50 times higher than those used in plant experiments. Furthermore, disease protection studies using dilutions of PSP1 indicated that there is a minimum threshold protease activity needed to induce pathogen defense in strawberry and that this induction effect is dose-independent. A significant characteristic of PSP1 is its broad-range protection against different diseases in various crop species. In soybean, PSP1 reduced the symptomatology by 70% of Corynespora cassiicola, etiological agent of the target spot. This protection effect was similar to the commercial inducer BION 500 WG based on BTH, and both products were shown to induce an oxidative burst and up-regulated PR1-gene expression in soybean. Furthermore, a double PSP1-treatment on greenhouse-grown sugarcane plants provided protection against bacterial red stripe disease caused by Acidovorax avenae and a double foliar application of PSP1 on field-grown wheat plants significantly increased resistance against Fusarium graminearum, causal agent of head blight disease, manifested mainly in an increased seed germination rate. In summary, these disease protection studies demonstrated an effective control against both bacterial and fungal pathogens in both monocot and dicot crop species, which together with its low production cost, effectiveness at low concentrations, long shelf-life, tolerance to high temperatures, harmlessness to non-target organisms and simple handling and application, make PSP1 a very promising candidate for effective and sustainable disease management in many crop species.

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Rachiplusia nu (Guenée) (Lepidoptera: Noctuidae) is one of the major lepidopteran pests defoliating soybeans (Glycine max Merrill) in Argentina. The combined use of chemical insecticides and entomopathogenic fungi is a promising pest-control option to minimize adverse chemical effects. In this work, we evaluated the interactions between five insecticides-two being considered biorational-and five fungal entomopathogenic strains under laboratory conditions in order to determine the possible usefulness of combinations of these agents against R. nu. The insecticides were tested for compatibility at four doses by in vitro bioassay and for the lethality of R. nu by inoculations at three doses. Fungal strains were applied at 1 x 10(8), 1 x 10(6), and 1 x 10(4) conidia/ml. The combinations of those insecticides with Beauveria bassiana (LPSc 1067, LPSc 1082, LPSc 1098), Metarhizium anisopliae (LPSc 907), and Metarhizium robertsii (LPSc 963) caused higher R. nu-larval mortalities than any of the individual agents alone. We observed significant differences in the in vitro conidial viability, vegetative growth, and conidia production of the five strains of entomopathogenic fungi exposed to different doses of the chemical insecticides. The combination gamma-cyhalothrin-LPSc-1067 caused the highest percent mortality of R. nu larvae, with synergism occurring between the two agents at 50% and 25% of the maximum field doses.

Rachiplusia nu (Guenée) (Lepidoptera: Noctuidae) es una de las principales plagas de lepidópteros defoliadores del cultivo de soja (Glycine max Merrill) en Argentina. El uso combinado de insecticidas químicos y hongos entomopatógenos es una opción de control de plagas prometedora para minimizar los efectos químicos adversos. En este trabajo se evaluaron las interacciones entre 5 insecticidas -2 de ellos considerados biorracionales-- y 5 cepas fúngicas entomopatógenas en condiciones de laboratorio, para determinar la posible utilidad de combinaciones de estos agentes frente a R. nu. Se evaluó la compatibilidad de los insecticidas a 4 dosis mediante bioensayos in vitro y la letalidad de aquellos sobre R. nu mediante inoculaciones a 3 dosis. Las cepas fúngicas se evaluaron a concentraciones de 1 x 10(8), 1 x 10(6) y 1 x 10(4) conidios/ml. Las combinaciones de estos insecticidas con Beauveria bassiana (LPSc1067, LPSc 1082, LPSc 1098), Metarhizium anisopliae (LPSc 907) y Metarhizium robertsii (LPSc 963) causaron una mayor mortalidad de larvas de R. nu que cualquiera de los agentes individuales. Asimismo, se observaron diferencias significativas en la viabilidad de los conidios in vitro, el crecimiento vegetativo y la producción de conidios de las 5 cepas de hongos entomopatógenos expuestos a diferentes dosis de los insecticidas químicos. La combinación gamma-cialotrina-LPSc-1067 causó el mayor porcentaje de mortalidad de larvas de R. nu, con un efecto de sinergismo entre los 2 agentes al 50 y el 25% de las dosis de campo recomendadas por el fabricante.

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Rachiplusia nu (Guenée) (Lepidoptera: Noctuidae) is one of the major lepidopteran pests defoliating soybeans (Glycine max Merrill) in Argentina. The combined use of chemical insecticides and entomopathogenic fungi is a promising pest-control option to minimize adverse chemical effects. In this work, we evaluated the interactions between five insecticides-two being considered biorational-and five fungal entomopathogenic strains under laboratory conditions in order to determine the possible usefulness of combinations of these agents against R. nu. The insecticides were tested for compatibility at four doses by in vitro bioassay and for the lethality of R. nu by inoculations at three doses. Fungal strains were applied at 1×108, 1×106, and 1×104conidia/ml. The combinations of those insecticides with Beauveria bassiana (LPSc 1067, LPSc 1082, LPSc 1098), Metarhizium anisopliae (LPSc 907), and Metarhizium robertsii (LPSc 963) caused higher R. nu-larval mortalities than any of the individual agents alone. We observed significant differences in the in vitro conidial viability, vegetative growth, and conidia production of the five strains of entomopathogenic fungi exposed to different doses of the chemical insecticides. The combination gamma-cyhalothrin-LPSc-1067 caused the highest percent mortality of R. nu larvae, with synergism occurring between the two agents at 50% and 25% of the maximum field doses.

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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.

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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.

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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.

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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.

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One of the most important diseases in cereal crops is Fusarium head blight, being Fusarium graminearum the main etiological agent. This fungus has the ability to produce a wide spectrum and quantity of toxins, especially deoxynivalenol (DON). During the last crop season (2012-2013) the climatic conditions favored Fusarium colonization. The objective of this work was to determine the presence of this fungus as well as the DON content in 50 wheat grain samples. Our results showed that 80% of the samples were contaminated with Fusarium graminearum. Twenty four percent (24%) of the samples contained ≥ 1µg/g DON, 26% ranged from 0,5 and 0,99µg/g, and the remaining 50% had values lower than 0,5µg/g. Correlation was found between the presence of Fusarium graminearum and DON. It is necessary to establish DON limit values in wheat grains for human consumption.

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La fusariosis es una de las enfermedades más importantes de los cereales, Fusarium graminearum es su principal agente etiológico. Este hongo posee la capacidad de producir distintos tipos y niveles de toxinas, en especial deoxinivalenol (DON). En la campaña 2012-2013 se dieron condiciones ambientales predisponentes para el desarrollo de esta enfermedad. El objetivo de este trabajo fue evaluar la presencia del hongo y el contenido de DON en 50 muestras de trigo. Los resultados demostraron la presencia de Fusarium graminearum en el 80 % de las muestras analizadas. El 24 % de las muestras presentó valores de DON ≥ 1µg/g, el 26 % varió entre 0,5 y 0,99µg/g, mientras que el 50 % restante mostró valores inferiores a 0,5µg/g. Se observó correlación entre la presencia de Fusarium graminearum y de DON. Es necesario establecer valores límites de DON en granos de trigo destinados al consumo humano

One of the most important diseases in cereal crops is Fusarium head blight, being Fusarium graminearum the main etiological agent. This fungus has the ability to produce a wide spectrum and quantity of toxins, especially deoxynivalenol (DON). During the last crop season (2012-2013) the climatic conditions favored Fusarium colonization. The objective of this work was to determine the presence of this fungus as well as the DON content in 50 wheat grain samples. Our results showed that 80% of the samples were contaminated with Fusarium graminearum. Twenty four percent (24%) of the samples contained ≥ 1µg/g DON, 26% ranged from 0,5 and 0,99µg/g, and the remaining 50% had values lower than 0,5µg/g. Correlation was found between the presence of Fusarium graminearum and DON. It is necessary to establish DON limit values in wheat grains for human consumption

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Fusarium poae is a relatively weak pathogen with increasing importance in cereal grains, principally due to its capacity to produce several mycotoxins. In this study, we evaluated the pathogenicity and toxin accumulation of individual F. poae isolates on wheat and barley under natural conditions for 3 years. Analysis of variance demonstrated significant differences for year-genotype, year-isolate, genotype-isolate, and year-genotype-isolate interactions for both incidence and disease severity. Based on contrast analysis, 'Apogee' was more susceptible than the other wheat genotypes, wheat genotypes were more susceptible than barley genotypes, durum wheat genotypes were more susceptible than bread wheat genotypes, and barley genotype 'Scarlett' had greater symptom development per spike than the other barley genotypes. Neither HT-2 nor T-2 toxins were detected in the grain samples. However, high levels of nivalenol were found in both wheat and barley samples. The increased reported isolation of F. poae from wheat and barley and the high capacity of this fungus to produce nivalenol underlie the need for more studies on F. poae-host interactions, especially for barley.

RESUMO

One of the most important diseases in cereal crops is Fusarium head blight, being Fusarium graminearum the main etiological agent. This fungus has the ability to produce a wide spectrum and quantity of toxins, especially deoxynivalenol (DON). During the last crop season (2012-2013) the climatic conditions favored Fusarium colonization. The objective of this work was to determine the presence of this fungus as well as the DON content in 50 wheat grain samples. Our results showed that 80

of the samples were contaminated with Fusarium graminearum. Twenty four percent (24

) of the samples contained  1Ag/g DON, 26

ranged from 0,5 and 0,99Ag/g, and the remaining 50

had values lower than 0,5Ag/g. Correlation was found between the presence of Fusarium graminearum and DON. It is necessary to establish DON limit values in wheat grains for human consumption.

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Some producers of dry fermented sausages use fungal starter cultures with the aim to achieve a desirable surface appearance and avoid the growth of mycotoxigenic fungi. These commercial cultures are mainly composed of Penicillium nalgiovense biotype 6. In contrast, in the case of producers who do not use starters, sausages are spontaneously colonized by the house mycobiota, which generally consists of heterogeneous molds corresponding to different genera and species. In this work, the surface mycobiota of dry fermented sausages produced in Colonia Caroya (Córdoba, Argentina) was determined in both summer and winter seasons. All the sausages sampled had been made without the use of surface fungal starters. In the 57 sausages analyzed in the two winter seasons studied (2010 and 2012), we found a total of 95 isolates of filamentous fungi belonging to six genera (Penicillium, Aspergillus, Mucor, Cladosporium, Scopulariopsis and Eurotium) and ten fungal species, whereas in the 36 sausages analyzed in the two summer seasons studied (2011 and 2012), we found 89 isolates belonging to five genera (Penicillium, Aspergillus, Mucor, Cladosporium and Geotrichum) and ten fungal species. Although 16 different species were found in both winter and summer seasons, only 2 of them predominated completely. P. nalgiovense was found in almost 100% of the sausages analyzed, where biotype 4 was the most frequent. This species gives a whitish gray coloration to the sausages. Considering that the factories sampled do not use fungal starter cultures, this predominance is very interesting since mycotoxin production by this fungus has not been reported. Aspergillus ochraceus was isolated with a frequency of 80-90% in the summer seasons, but in none of the winter samples. The presence of this fungus in sausages produced in the summer was attributed to the high environmental temperatures and the uncontrolled temperature in the ripening rooms during the night. In all cases, A. ochraceus was responsible for the undesirable yellowish gold color of the casing. This fungus thus causes significant economic losses to the producers of Colonia Caroya during the months of high temperatures.

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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.

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Fusarium species can produce mycotoxins, which can contaminate cereal-based food producing adverse effects for human and animal health. In recent years, the importance of Fusarium poae has increased within the Fusarium head blight complex. Fusarium poae is known to produce trichothecenes, especially nivalenol, a potent mycotoxin able to cause a variety of toxic effects. In this study, a specific primer pair was designed based on the tri7 gene to detect potential nivalenol-producing F. poae isolates. A total of 125 F. poae, four F. cerealis, two F. culmorum, one F. langsethiae, one F. sporotrichioides and seven F. graminearum, plus F. austroamericanum, F. meridionale, F. graminearum sensu stricto and F. cortaderiae from the NRRL collection were analysed, and only F. poae isolates gave a positive result for the presence of a 296-bp partial tri7 DNA fragment. Moreover, the primer set was tested from cereal seed samples where F. poae and other Fusarium species with a negative result for the specific reaction ( F. graminearum, F. oxysporum, F. chlamydosporum, F. sporotrichioides, F. equiseti and F. acuminatum) were isolated, and the expected fragment was amplified. We developed a rapid and reliable PCR assay to detect potential nivalenol-producing F. poae isolates.

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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.

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RESUMO

Pseudocercospora griseola is the causal agent of angular leaf spot of common bean (ALS). It has undergone parallel coevolution with its host and two major groups have been defined, "Andean" (P. griseola f. griseola) and "Mesoamerican" (P. griseola f. mesoamericana). The aim of this study was to analyze the nature and the level of the dark pigment synthesized by the representatives of each group. After 21 days of incubation on potato dextrose agar medium, P. griseola f. griseola isolate S3b developed colonies with diameters of 17.5 +/- 1.3 mm and concentric rings of pigmentation. Isolate T4 of P. griseola f. mesoamericana presented smaller colonies (9.9 +/- 0.3 mm) with a uniform dark-gray color. Both isolates, S3b and T4, produced the same pigment, a 1,8-dihydroxynaphthalene-melanin, although different in quantity and structural features as suggested by the IR spectrum. The P. griseola f. griseola isolate S3b had a higher growth rate and melanin content as well as smaller sensitivity to melanin synthesis inhibitors compared to the isolate T4 of P. griseola f. mesoamericana. These results suggest a possible link between melanin and growth in P. griseola.

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