Papers by Viviana Barrera
Journal of Plant Pathology, 2011
Field trials were conducted in commercial plots over two consecutive years in order to determine ... more Field trials were conducted in commercial plots over two consecutive years in order to determine the effect of wild oat used as green manure and biocontrol agents, alone or combined, on potato yield, number of tubers and scab incidence. The biomass of green manure was added to the soil one and a half months before sowing. Potato seeds were dipped in liquid suspensions containing either Bacillus subtilis B-235 or Trichoderma harzianum Th-1, or a combination of both. Green manure was effective in promoting potato yield and reducing scab incidence. The combination of green manure and the liquid formulation of B-235 provided significantly improved results with a higher number of potato tubers and lower potato scab incidence. The combination of wild oat green manure and B-235 is thus a promising alternative to improve potato yield and reduce scab incidence.
Revista De La Facultad De Agronomia De La Universidad Del Zulia, 2015
En Argentina, la “podredumbre basal” y el “mal de almacigos” causados por el complejo Fusarium sp... more En Argentina, la “podredumbre basal” y el “mal de almacigos” causados por el complejo Fusarium spp. constituyen uno de los problemas mas serios en cebolla. En este trabajo se estudio el uso de especies del genero Trichoderma como agentes de control biologico (ACB) de F. oxysporum, causal del “mal de almacigos” en cebolla. Se identificaron y caracterizaron morfologica, cultural y fisiologicamente a 10 aislamientos de Trichoderma spp. del cepario de Fitopatologia. Por secuenciacion del gen TEF-1α se identificaron las especies de Trichoderma harzianum s.l. (7), T. atroviride (1), T. koningiopsis (1) y T. longibrachiatum (1). Los aislamientos nativos se compararon con una cepa de un biofungicida comercial (PHCTM T22, Root Shield/Plant Shield) en su capacidad antagonista de aislamientos de F. oxysporum. Se estudio in vitro el potencial antagonico en cultivos duales y enfrentados. Ademas, se determino la velocidad de crecimiento en placa y la tolerancia a metabolitos volatiles producidos ...
Revista Argentina de Microbiología, 2013
How to cite Complete issue More information about this article Journal's homepage in redalyc.org ... more How to cite Complete issue More information about this article Journal's homepage in redalyc.org Scientific Information System Network of Scientific Journals from Latin America, the Caribbean, Spain and Portugal Non-profit academic project, developed under the open access initiative
Revista Argentina de microbiología
A phenol-degrading fungus was isolated from crop soils. Molecular characterization (using interna... more A phenol-degrading fungus was isolated from crop soils. Molecular characterization (using internal transcribed spacer, translation elongation factor and beta-tubulin gene sequences) and biochemical characterization allowed to identify the fungal strain as Penicillium chrysogenum Thom ERK1. Phenol degradation was tested at 25 degrees C under resting mycelium conditions at 6, 30, 60, 200, 350 and 400 mg/l of phenol as the only source of carbon and energy. The time required for complete phenol degradation increased at different initial phenol concentrations. Maximum specific degradation rate (0.89978 mg of phenol/day/mg of dry weight) was obtained at 200 mg/l. Biomass yield decreased at initial phenol concentrations above 60 mg/l. Catechol was identified as an intermediate metabolite by HPLC analysis and catechol dioxygenase activity was detected in plate assays, suggesting that phenol metabolism could occur via ortho fission of catechol. Wheat seeds were used as phytotoxicity indicato...
Revista de Biología Tropical, 2015
Orchidaceae is a highly dependent group on the Rhizoctonia complex that includes Ceratorhiza, Mon... more Orchidaceae is a highly dependent group on the Rhizoctonia complex that includes Ceratorhiza, Moniliopsis, Epulorhiza and Rhizoctonia, for seed germination and the development of new orchid plants. Thus, the isolation and identification of orchid mycorrhizal fungi are important to understand the orchid-fungus relationship, which can lead to the development of efficient conservation strategies by in vivo germination of seeds from endangered orchid plants. The aim of our work was to isolate and characterize the different mycorrhizal fungi found in roots of terrestrial orchids from Córdoba (Argentina), and, to learn about the natural habit and fungal associations in the Chaco Serrano woodland pristine region. In this study, bloomed orchid root and rhizosphere soil samples were obtained in two times from Valle de Punilla during spring of 2007; samples were kept in plastic bags until processed within 48 hours, and mycorrhizal condition confirmed assessing peloton presence. A total of 23 isolates of the orchideous mycorrhizal Rhizoctonia complex were obtained. The isolates were studied based on morphological characters and ITS-rDNA sequences. Morphological characteristics as color of colonies, texture, growth rate, hyphal diameter and length and presence of sclerotia were observed on culture media. To define the number of nuclei per cell, the isolates were grown in Petri dishes containing water-agar (WA) for three days at 25°C and stained with Safranine-O solution. The mycorrhizal fungi were grouped into binucleate (MSGib, 10 isolates) and multinucleate (MSGim, 13 isolates) based on morphological characteristics of the colonies. We obtained the ITS1-5.8s-ITS4 region that was amplified using primers ITS1 and ITS4. Based on DNA sequencing, isolates Q23 and Q29 were found to be related to species of Ceratobasidium. Isolates Q24 and Q4 were related to the binucleated anastomosis group AG-C of Rhizoctonia sp. The rest of the isolates grouped in the Ceratobasidium clade without grouping. From our knowledge this is the first report of the association of the AG-C testers with terrestrial orchids. A high specificity was observed in the symbiotic relationship. As the mycorrhizal fungal isolates were obtained from native orchids, they could be incorporated in conservation programes of endangered orchids in Argentina.
The genus Cladorrhinum constitutes a fungal group of prime importance for agriculture and livesto... more The genus Cladorrhinum constitutes a fungal group of prime importance for agriculture and livestock, since some species have biocontrol potential or were shown to promote plant growth and to produce phytases, which are enzymes useful for processing animal feed. We assessed the species diversity of Cladorrhinum in Argentina. Strains were identified at the species level by analysis of morphological and physiological characters, as well as by using molecular characters and by sequencing three nuclear DNA loci: internal transcribed spacer regions (ITS), and the 28S ribosomal subunit and β-tubulin genes. C. bulbillosum and C. samala were detected, and a new species is described as C. australe.
Mycotaxon
Artificial thermal shock conducted on 50 soil samples from a semi-arid geographic region (Catamar... more Artificial thermal shock conducted on 50 soil samples from a semi-arid geographic region (Catamarca and La Rioja provinces) in northern Argentina yielded 34 heat-resistant fungal strains. These strains were assigned to seventeen taxa in ten ascomycete genera: Arthrinium (1), Aspergillus (3), Epicoccum (1), Gilmaniella (1), Hamigera (2), Leiothecium (1), Penicillium (2), Talaromyces (4), Trichocladium (1), and Trichoderma (1). All strains were identified by phenotypic features, with molecular data additionally obtained for eleven strains. Five species are reported for the first time in Argentina.
Revista Argentina de Microbiología
Fungi from the genus Cladorrhinum (Ascomycota) are promising agents in the biocontrol of phytopat... more Fungi from the genus Cladorrhinum (Ascomycota) are promising agents in the biocontrol of phytopathogens, in the promotion of plant growth, and in the production of enzymes with technological application. We analyzed comparatively the ability of 5 native strains of Cladorrhinum samala and Cladorrhinum bulbillosum with reference strains belonging to the same genus. We used 95 individual carbon sources available in microplates from the Biolog ® FF system. Although most of the strains mainly used soluble carbohydrates, the metabolic profile was highly dependent upon each isolate and it revealed intraspecific physiological variability in Cladorrhinum species.
Phytotaxa
Aspergillus fuscicans, a new species within Aspergillus section Usti from Argentinean semi-arid s... more Aspergillus fuscicans, a new species within Aspergillus section Usti from Argentinean semi-arid soil is introduced. Molecular, morphological and physiological studies were conducted, based on sequence analysis of partial β-tubulin and calmodulin sequence data. Aspergillus fuscicans formed a distinct, well-defined clade related to A. calidoustus and A. pseudodeflectus. In addition, A. fuscicans was able to grow and sporulate at 37 ºC, and had a negative Ehrlich reaction. Morphological and physiological features could be used to differentiate the new species from its phylogenetically related taxa.
Http Digital Bl Fcen Uba Ar, 2012
Revista Argentina de Microbiología, 2015
In order to determine the behavior of mycotoxin-producing fungal populations linked with silobags... more In order to determine the behavior of mycotoxin-producing fungal populations linked with silobags stored corn grains with a moisture content greater at the recommended as safe, 270 samples taken in three times (beginning, 90 days, final) over a five month period of storage were evaluated. The fungal biota was quantified and identified and the contamination with fumonisin and aflatoxin was determined. Extrinsic factors (environment), intrinsic factors (grains) and technological factors (location of the grains in the profile of silobag) were taken into account to evaluate the presence and quantity of total and mycotoxigenic fungal populations. The pH of grains and O2 levels were significantly reduced after five months, while CO2 concentration increased in the same period. The total counts of mycobiota were significantly higher in grains located in the top layer of silobag. Mycotoxigenic species of Fusarium, Aspergillus, Penicillium and Eurotium were identified. The frequency of isolation of Fusarium verticillioides decreased at the end of storage and Aspergillus flavus was isolated only at the beginning of storage. The counts of the Penicillium spp. and Eurotium spp. were increased at the end of storage. Fumonisin contamination was found in all the samples (100%) with maximum levels of 5.707mg/kg whereas aflatoxin contaminated only 40% with maximum levels of 0.0008mg/kg. The environmental and substrate conditions generated during the storage limited the development of mycotoxigenic fungi and mycotoxin production.
Mycological Progress, 2015
The genus Cladorrhinum constitutes a fungal group of prime importance for agriculture and livesto... more The genus Cladorrhinum constitutes a fungal group of prime importance for agriculture and livestock, since some species have biocontrol potential or were shown to promote plant growth and to produce phytases, which are enzymes useful for processing animal feed. We assessed the species diversity of Cladorrhinum in Argentina. Strains were identified at the species level by analysis of morphological and physiological characters, as well as by using molecular characters and by sequencing three nuclear DNA loci: internal transcribed spacer regions (ITS), and the 28S ribosomal subunit and β-tubulin genes. C. bulbillosum and C. samala were detected, and a new species is described as C. australe.
Tropical Plant Pathology, 2015
In Argentina, more than 60 % of the tobacco crops are grown in the northwestern part of the count... more In Argentina, more than 60 % of the tobacco crops are grown in the northwestern part of the country and where Rhizoctonia solani leads to a reduction in crop yield and quality. In this study, 35 isolates of Rhizoctonia were obtained from 32 tobacco fields in northwestern Argentina and characterized by both morphological and molecular approaches. Based on the variability in the ITS region, isolates were identified as R. solani (80 %), Waitea circinata var. zeae (Rhizoctonia zeae) (8 %) and binucleate Rhizoctonia (8 %). Most isolates of R. solani belonged to the anastomosis groups (AGs) AG 4 HG-I (44 %), AG 2-1 (41 %) and AG 4 HG-III (13 %). Isolates of binucleate Rhizoctonia belonged to AG-F and AG-P of Ceratobasidium sp. Morphological variability was higher within isolates of AG 2-1 and AG 4 HG-III than within those of AG 4 HG-I. Aggressiveness of the isolates towards tobacco seedlings was assessed in the greenhouse. Isolates of AG 2-1 were the most aggressive on leaves, causing target spot, whereas isolates of AG 4 HG-I were the most aggressive on stems and roots, causing damping-off.
Revista Argentina de Microbiología, 2015
Mycopathologia, 2005
Many filamentous fungi produce an array of extracellular enzymes that acting in cell walls releas... more Many filamentous fungi produce an array of extracellular enzymes that acting in cell walls release elicitors of the plant defense response These enzymes may therefore be important in biocontrol applications. The aim of this study was to characterize extracellular degradative enzymes produced by a non-pathogenic binucleate isolate of Rhizoctonia AG-G. The fungus was grown in liquid culture supplemented with pectin, polygalacturonic acid or glucose as a carbon sources and filtrates of the culture media were analyzed for the detection of pectinolytic and glucan hydrolytic enzymes. Using only pectin as a carbon source, secretion of polygalacturonases and methylesterases was found. When the liquid medium was supplemented with polygalacturonic acid, only polygalacturonase activity was detected. However, when glucose was used as carbon source b-1,3 and b-1,6 glucanases activities were detected, using laminarin and pustulan as substrates, but none of the pectinolytic activities were found. These enzymes were partially purified and characterized. The b-(1,3)(1,6) glucanase and polygalacturonase enzymes showed to be active against cell wall polysaccharides from potato sprouts. These enzymes may have an important role in fungus-plant cell wall interaction. This is the first study about the production of extracellular enzymes by non-pathogenic binucleate Rhizoctonia AG-G.
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Papers by Viviana Barrera