Characterization of Fusarium graminearum isolates recovered from wheat samples from Argentina by Fourier transform infrared spectroscopy: Phenotypic diversity and detection of specific markers of aggressiveness.

Fusarium graminearum is the primary causal agent of Fusarium head blight of wheat in Argentina. This disease affects crop yields and grain quality also reducing the wheat end-use, and causing mycotoxin contamination. The aim of this work was to analyze the phenotypic characteristics associated with phenotypic diversity and aggressiveness of 34 F. graminearum sensu stricto isolates recovered from Argentinean fields in the 2008 growing season using the Fourier Transform Infrared (FTIR) dried film technology. We applied this technique also to search for spectral specific markers associated with aggressiveness. The combination of FTIR technology with hierarchical cluster analysis allowed us to determine that this population constitutes a highly diverse and heterogeneous group of fungi with significant phenotypic variance. Still, when the spectral features of a set of these isolates were compared against their aggressiveness, as measured by disease severity, thousand grains weight, and relative yield reduction, we found that the more aggressive isolates were richer in lipid content. Therefore, we could define several spectroscopic markers (>CH stretching modes in the 3000-2800 window, >CO and CO vibrational modes of esters at 1765-1707cm-1 and 1474-900cm-1, respectively), mostly assigned to lipid content that could be associated with F. graminearum aggressiveness. All together, by the application of FTIR techniques and simple multivariate analyses, it was possible to gain significant insights into the phenotypic characterization of F. graminearum local isolates, and to establish the existence of a direct relationship between lipid content and fungal aggressiveness. Considering that lipids have a major role as mediators in the interaction between plants and fungi our results could represent an attractive outcome in the study of Fusarium pathogenesis.

Mycorrhizal fungi isolated from native terrestrial orchids of pristine regions in Cordoba (Argentina).

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 Cordoba (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 degrees 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 ITSI 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 asso- ciation 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.

Mycorrhizal fungi isolated from native terrestrial orchids of pristine regions in Córdoba (Argentina) / Hongos micorrízicos aislados de orquídeas terrestres nativas de regiones pristinas en Córdoba (Argentina)

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.

La Familia Orchidaceae se encuentra estrechamente relacionada con hongos micorrízicos que pertenecen al complejo Rhizoctonia, e incluyen los géneros Ceratorhiza, Moniliopsis, Epulorhiza y Rhizoctonia. Esta asociación es esencial para el desarrollo de nuevas plantas ya que favorecen el proceso de germinación de las semillas. Por lo tanto, el conocimiento de la naturaleza de esta interacción es importante para que los resultados de los programas de conservación de orquídeas sean efectivos. La fragmentación del bosque Chaqueño Serrano en el centro de Argentina, ha alcanzado un punto crítico en los últimos años, afectando el funcionamiento del ecosistema. El objetivo de este trabajo fue: a) aislar y caracterizar hongos micorrízicos presentes en orquídeas terrestres de la provincia de Córdoba (Argentina) y b) conocer el hábitat natural y las asociaciones fúngicas que se establecen en esta región prístina. A partir de las raíces de orquídeas terrestres, se obtuvieron 23 aislamientos de hongos micorrízicos que pertenecen al complejo Rhizoctonia. Estos aislamientos fueron caracterizados con base en caracteres morfológicos y moleculares. Las características morfológicas (color y textura de las colonias, cinética de crecimiento, diámetro y largo de la hifa y presencia de esclerocios) fueron observados en PDA y MEA a 25ºC. El número de núcleos por célula se observó en cultivos crecidos en AA (agar-agua) y teñidos con una solución de Safranine-O. La región ITS se amplificó usando los primers ITS1 e ITS4. Con base en las características morfológicas de la colonia, los aislamientos fueron agrupados en binucleados (MSGib) y multinucleados (MSGim). De acuerdo al cladograma obtenido con las secuencias de ADN, los aislamientos Q23 y Q29 están relacionados a especies de Ceratobasidium, aisladas de raíces de orquídeas. Los aislamientos Q24 y Q4 se asocian con el grupo de anastomosis de Rhizoctonia AG-C. Finalmente, se observó una alta variabilidad en el grado de especificidad existente en la simbiosis que se establece entre las raíces de estas orquídeas terrestres y los aislamientos obtenidos a partir de ellas. Este es el primer reporte de la asociación entre el grupo de anastomosis AG-C y orquídeas terrestres. Dado que estos aislamientos se obtuvieron de orquídeas terrestres nativas, podrían ser incorporados como nuevos patrones para micorrizas de orquídeas terrestres en Argentina. Este trabajo contribuye al conocimiento de la relación simbiótica que se establece entre orquídeas y hongos micorrízicos, así como también al desarrollo de estrategias de conservación de orquídeas terrestres nativas del bosque Chaco Serrano.

A species-specific method for detecting pathogenic Streptomyces species from soil and potato tubers in Argentina / A species-specific method for detecting pathogenic Streptomyces species from soil and potato tubers in Argentina.

Potato common scab is caused by several soil-inhabiting pathogenic Streptomyces species. In the present study, a species-specific PCR method was used to detect Streptomyces species in potato tuber lesions and soils. Total genomic DNA from soil samples from six locations and tuber samples from four potato cultivars (Spunta, Shepody, Innovator and Russet Burbank) were assessed. Streptomyces scabies, Streptomyces acidiscabies, and Streptomyces turgidiscabies were detected in soybean, tobacco and potato soils and in all potato varieties except Russet Burbank. The phylogenetic analysis of the sequences obtained confirmed the identification. The method proposed proved to be time-saving and cost effective for the rapid detection of Streptomyces species. This is the first report of the detection of S. acidiscabies and S. turgidiscabies in soils and potato tubers from Argentina.

A species-specific method for detecting pathogenic Streptomyces species from soil and potato tubers in Argentina.

Potato common scab is caused by several soil-inhabiting pathogenic Streptomyces species. In the present study, a species-specific PCR method was used to detect Streptomyces species in potato tuber lesions and soils. Total genomic DNA from soil samples from six locations and tuber samples from four potato cultivars (Spunta, Shepody, Innovator and Russet Burbank) were assessed. Streptomyces scabies, Streptomyces acidiscabies, and Streptomyces turgidiscabies were detected in soybean, tobacco and potato soils and in all potato varieties except Russet Burbank. The phylogenetic analysis of the sequences obtained confirmed the identification. The method proposed proved to be time-saving and cost effective for the rapid detection of Streptomyces species. This is the first report of the detection of S. acidiscabies and S. turgidiscabies in soils and potato tubers from Argentina.

A species-specific method for detecting pathogenic Streptomyces species from soil and potato tubers in Argentina. / A species-specific method for detecting pathogenic Streptomyces species from soil and potato tubers in Argentina.

Potato common scab is caused by several soil-inhabiting pathogenic Streptomyces species. In the present study, a species-specific PCR method was used to detect Streptomyces species in potato tuber lesions and soils. Total genomic DNA from soil samples from six locations and tuber samples from four potato cultivars (Spunta, Shepody, Innovator and Russet Burbank) were assessed. Streptomyces scabies, Streptomyces acidiscabies, and Streptomyces turgidiscabies were detected in soybean, tobacco and potato soils and in all potato varieties except Russet Burbank. The phylogenetic analysis of the sequences obtained confirmed the identification. The method proposed proved to be time-saving and cost effective for the rapid detection of Streptomyces species. This is the first report of the detection of S. acidiscabies and S. turgidiscabies in soils and potato tubers from Argentina.