Silver nanoparticle production by the fungus Fusarium oxysporum: nanoparticle characterisation and analysis of antifungal activity against pathogenic yeasts

The microbial synthesis of nanoparticles is a green chemistry approach that combines nanotechnology and microbial biotechnology. The aim of this study was to obtain silver nanoparticles (SNPs) using aqueous extract from the filamentous fungus Fusarium oxysporum as an alternative to chemical procedures and to evaluate its antifungal activity. SNPs production increased in a concentration-dependent way up to 1 mM silver nitrate until 30 days of reaction. Monodispersed and spherical SNPs were predominantly produced. After 60 days, it was possible to observe degenerated SNPs with in additional needle morphology. The SNPs showed a high antifungal activity against Candida and Cryptococcus , with minimum inhibitory concentration values ≤ 1.68 µg/mL for both genera. Morphological alterations of Cryptococcus neoformans treated with SNPs were observed such as disruption of the cell wall and cytoplasmic membrane and lost of the cytoplasm content. This work revealed that SNPs can be easily produced by F. oxysporum aqueous extracts and may be a feasible, low-cost, environmentally friendly method for generating stable and uniformly sized SNPs. Finally, we have demonstrated that these SNPs are active against pathogenic fungi, such as Candida and Cryptococcus .

Revisionary notes on the fungus-growing ant genus Mycetarotes Emery (Hymenoptera, Formicidae)

Mycetarotes is a small genus of the exclusively Neotropical fungus-growing ants, that includes M. parallelus (Emery), M. senticosus Kempf, M. acutus Mayhé-Nunes and M. carinatus Mayhé-Nunes. We hereby revise historical and recent information regarding Mycetarotes species for the first time, providing an identification key to workers, diagnoses, synoptic illustrated redescriptions of the species, including those of sexuals when known, updates of distributional records, and nest pictures of M. carinatus and M. parallelus. We comment the taxonomy and phylogenetic relationships among Mycetarotes and related genera, and on their geographical distribution. The available biological information on the genus is summarized.

A new species of the fungus-farming ant genus Mycetagroicus Brandão & Mayhé-Nunes (Hymenoptera, Formicidae, Attini)

The fungus-farming ant genus Mycetagroicus Brandão & Mayhé-Nunes was proposed based on three species from the Brazilian "Cerrado": M. cerradensis, M. triangularis and M. urbanus. Here we describe a new species of Attini ant of the genus Mycetagroicus, M. inflatus n. sp., based on two workers collected in eastern Pará State, Brazil. A new key for species identification, comments on differences among species and new geographical distribution data are furnished.

Total lipid and fatty acid accumulation during basidiospore formation in the ectomycorrhizal fungus Pisolithus sp.

The basidiospores of Pisolithus sp. contain large amounts of lipids, indicating provision for future germination in the host rhizosphere. However, the accumulation, composition, and mobilization of lipids during formation and germination of these spores are largely unknown. In this study, lipid storage and fatty acid composition during basidiosporogenesis were analyzed in fresh basidiocarps using bright-field microscopy and gas chromatography. Abundant lipid bodies are found in the hyphae, basidia, and basidiospores of fungal basidiocarps. This evidences a considerable C transport in the basidiocarp to meet the C demand during basidiospore formation. Fatty acid composition analysis revealed the presence of 24 compounds with chains of 9 to 18 C atoms, either saturated or insaturated, with one or two insaturations. The fatty acid composition and content varied according to the developmental stage of the peridioles. In free basidiospores, the predominant compounds were 16:0, 16:1w5c, 18:1w9c, and 18:2w6,9c/18:0ante, at concentrations of 76, 46, 192, and 51 µg g-1 dry matter, respectively. Our results indicate that oleic acid is the major constituent of lipid reserves in Pisolithus sp. basidiospores. Further studies are being conducted to determine the factors that induce lipid mobilization during spore germination.

Total fatty acid composition in the characterization and identification of orchid mycorrhizal fungi Epulorhiza spp.

Rhizoctonia-like fungi are the main mycorrhizal fungi in orchid roots. Morphological characterization and analysis of conserved sequences of genomic DNA are frequently employed in the identification and study of fungi diversity. However, phytopathogenic Rhizoctonia-like fungi have been reliably and accurately characterized and identified through the examination of the fatty acid composition. To evaluate the efficacy of fatty acid composition in characterizing and identifying Rhizoctonia-like mycorrhizal fungi in orchids, three Epulorhiza spp. mycorrhizal fungi from Epidendrum secundum, two unidentified fungi isolated from Epidendrum denticulatum, and a phytopathogenic fungus, Ceratorhiza sp. AGC, were grouped based on the profile of their fatty acids, which was assessed by the Euclidian and Mahalanobis distances and the UPGMA method. Dendrograms distinguished the phytopathogenical isolate of Ceratorhiza sp. AGC from the mycorrhizal fungi studied. The symbionts of E. secundum were grouped into two clades, one containing Epulorhiza sp.1 isolates and the other the Epulorhiza sp.2 isolate. The similarity between the symbionts of E. denticulatum and Epulorhiza spp. fungi suggests that symbionts found in E. denticulatum may be identified as Epulorhiza. These results were corroborated by the analysis of the rDNA ITS region. The dendrogram constructed based on the Mahalanobis distance differentiated the clades most clearly. Fatty acid composition analysis proved to be a useful tool for characterizing and identifying Rhizoctonia-like mycorrhizal fungi.

Variation in virulence in the rice blast fungus Magnaporthe grisea in São Paulo State

Resistant varieties have been the preferred means to control Magnaporthe grisea, the causal organism of the rice blast disease. The objective of this study was to examine the degree of diversity of the pathogen in different rice growing regions of São Paulo State, Brazil. Blast samples collected from rice varieties in three different regions (Tremembé, Mococa and José Bonifácio) were analyzed for race structure employing the Japanese rice differentials. The highest degree of virulence diversity was observed in Tremembé with 22 different races in three different varieties. Furthermore, no resistance gene in the Japanese differentials was effective to all isolates of M. grisea from São Paulo State.

Aspectos biológicos y poblacionales de Nasonovia ribisnigri y Aulacorthum solani sobre lechuga

Se estimó la influencia de los cultivares Criolla Blanca, Cuatro Estaciones y Gallega, sobre la biología y los parámetros poblacionales de Nasonovia ribisnigri y Aulacorthum solani (Homoptera: Aphidoidea) a 10±1ºC y HR de 90%. Los períodos ninfal, pre-reproductivo y post-reproductivo de N. ribisnigri fueron más largos sobre Cuatro Estaciones, no así el reproductivo. En A. solani el período ninfal fue más largo sobre Criolla Blanca y Cuatro Estaciones resultando el reproductivo mayor sobre Cuatro Estaciones. Las tasas intrínsecas de crecimiento natural (r m) de N. ribisnigri y A. solani fueron mayores sobre Criolla Blanca y Gallega, respectivamente. De acuerdo a la especie predominante convendría utilizar Cuatro Estaciones para N. ribisnigri y Criolla Blanca para A. solani, en épocas frías.

Production technology for entomopathogenic fungus using a biphasic culture system

The objective of this research was to evaluate combinations of liquid media obtained from agro-industrial residues and by-products, with solid media prepared with mixtures of grains and their derivatives, aiming to increase the production of JAB 02 and JAB 45 isolates of Lecanicillium lecanii. Sporulation, conidial viability and process yield were evaluated as well as the production costs using the JAB 45 isolate as a model system were analyzed. The production of JAB 02 was not increased using the biphasic culture. For JAB 45, some combinations provided an increase in yield, especially cheese whey with wheat bran and wheat grain, with lower production costs. Viability was not influenced by the production method, and the combinations showed no differences in the process yield. The biphasic method is suitable for the production of L. lecanii, and proves to be an appropriate technology to use in mass production by biofactories.

VARIABILIDADE GENÉTICA DE ISOLADOS DE Fusarium solani e Fusarium oxysporum f. sp.passiflorae ASSOCIADOS AO MARACUJAZEIRO

Determinou-se a variabilidade genética de 37 isolados de Fusarium solani e 13 isolados de Fusarium oxysporum f. sp. passiflorae patogênicos ao maracujazeiro por meio do uso de marcadores ISSR e RAPD. Os isolados foram obtidos de maracujazeiros com sintomas de murcha, encontrados nas principais regiões produtoras do Norte Mineiro e no município de Sebastião Laranjeira – BA. Após obtenção de culturas monospóricas, os isolados tiveram seus DNAs extraídos e submetidos à reação de PCR. Foram selecionados nove primers ISSR e nove primersRAPD, e a análise de dados foi realizada, utilizando-se do coeficiente de similaridade de Jaccard. A partir da amplificação com os primers ISSR e RAPD, foram obtidos 121 e 126 locos, respectivamente, sendo quetodos apresentaram polimorfismo entre, pelo menos, dois isolados. Demonstraram-se, por meio das análises ISSR, índice de similaridade genética interespecífica de 0,15 e índices de variabilidade intraespecífica de 0,27 a 0,92 para F. solani e de 0,30 a 0,89 para F. oxysporum. f. sp. passiflorae. Já, por meio das análises RAPD, foram gerados índice de similaridade genética interespecífica de 0,11 e índices de variabilidade intraespecífica de 0,17 a 0,79 para F. solani e de 0,21 a 0,73 para F. oxysporum f. sp. passiflorae. Os isolados de F. oxysporum f. sp. passiflorae e F. solani agruparam-se em dois clustersdistintos, e observou-se uma alta variabilidade intraespecífica nas duas espécies.

An antimicrobial alkaloid and other metabolites produced by Penicillium sp. An endophytic fungus isolated from Mauritia flexuosa L. f.

The alkaloid glandicoline B (1) and six other compounds: ergosterol (2), brassicasterol (3), ergosterol peroxide (4), cerevisterol (5), mannitol (6) and 1-O-α-D-glucopyranoside (7) were isolated from Penicillium sp. strain PBR.2.2.2, a fungus from Mauritia flexuosa roots. The structures of the isolated metabolites were established by spectral analysis. MeOH extract of the fungal mycelium at 500 µg mL-1 exhibited antimicrobial activity against Staphylococcus aureus and the compound 1 at 100 µg mL-1 was active against S. aureus, Micrococcus luteus and Escherichia coli. The relationship between the bioactive properties of the fungus PBR.2.2.2 and those achieved for glandicoline B, as well the potential of this substance as bactericide is discussed.

Biomolecules produced in liquid-state fermentation by a marine-derived fungus, Penicillium roqueforti

Screening of biomass of a new marine-derived strain of Penicillium roqueforti, as produced by liquid-state fermentation, led to the identification of several volatile organic compounds active in the fatty acid pathway as well as fragments produced by their catabolism, terpenoids, and metabolites from the shikimic acid pathway. In addition, five non-volatile organic compounds, triolein, ergosterol peroxide, 9(11)-dehydroergosterol peroxide, 4-hydroxybenzaldehyde, and d-mannitol, were isolated and identified by spectroscopy. The results showed that this fungal strain did not produce any mycotoxin in the culture conditions applied, and thus is useful for industrial applications, where high value-added biomolecules are generated.

Técnica de obtenção de filtrado de cultura de Alternaria solani

This work was developed to adapt culture filtrates of Alternaria solani to be used in vitro selection of resistant potato. Three isolates of A. solani (I1 and I2) from Eldorado do Sul and Rio Pardo were used. Two liquid media, V8 and Czapek, were used to grow each of the fungal isolate, giving six culture filtrates (I1V8, I2V8, I3V8, I1Cz, I2Cz and I3Cz). Two sterilization forms, Millipore and autoclave were tested. There was no difference in these two sterilization forms. Tissue culture and toxic filtrates of A. solani have a potential to reduce the time in selection of resistant potato.

Reaction of sorghum genotypes to the anthracnose fungus Colletotrichum graminicola

The reactions of 22 sorghum (Sorghum bicolor) genotypes to six previously identified races of the sorghum anthracnose fungus Colletotrichum graminicola, were evaluated under greenhouse and field conditions. Races were inoculated in separate tests in the greenhouse. In the field, spreader rows of a susceptible genotype were artificially inoculated with a mixture of the six races of the pathogen. In the greenhouse tests, nine genotypes showed resistance to all six races. In the field high levels of dilatory resistance was observed in the sorghum genotypes CMSXS169 and CMSXS373.

Enanismo y podredumbre basal de eustoma grandiflorum y su relación con la densidad de fusarium solani en el suelo

En cultivos comerciales de lisianthus de La Plata y alrededores (Argentina), se observó que Fusarium solani afecta al 100% de los establecimientos productivos provocando enanismo y podredumbre basal. Se realizó un ensayo para analizar la densidad de F. solani del suelo bajo el efecto de distintos tratamientos y relacionarla con la evolución de ambas patologías. Los análisis del suelo se hicieron en 3 épocas: antes del transplante (octubre), al inicio (enero) y al final (marzo) de la floración. En enero y marzo se evaluó la incidencia de cada enfermedad y se cuantificaron las plantas cosechadas. La población de F. solani no varió en las 3 épocas y se redujo significativamente con los fumigantes y el vapor. Esto determinó una incidencia del enanismo (enero) de 0 a 9,5% con los primeros y de 31,4% con el vapor. Para el testigo y los fungicidas la incidencia varió entre el 87,9 y el 100%, disminuyendo las plantas cosechadas. La podredumbre basal comenzó con el ingreso del patógeno a través de las heridas producidas por la cosecha. Ésta fue significativamente mayor con los fumigantes (90,7 a 99%) y también con el vapor (76,8%), produciéndose la mayor incidencia en marzo (15,7 a 22,2 y 10,1% respectivamente), reduciéndose el período productivo. Se destaca la importancia de disminuir la densidad de F. solani en el momento del transplante. Entre los métodos de control el Metam sodio y Dazomet podrían ser eficaces sustitutos del Bromuro de metilo, seguidos por el vapor.