First Report of Fusarium Wilt of Basil Caused by Fusarium oxysporum f. sp. basilici in Argentina

ArgentinaAnnually, ~20 ha of sweet basil (Ocimum basilicumL.) are cultivated in greenhouses in the green belt area surrounding LaPlata, Argentina, mainly for fresh consumption. In 2004 to 2007, basil plants of cv. Genovese showed wilt symptoms,necrosis of leaves and stems, asymmetrical growth, and discolored vascular tissue in greenhouses in La Plata. In 2007, thesame symptoms were observed on plants of cv. Morada grown from seeds that were produced in Italy. Isolations werecompleted from root, crown, and stem sections of diseased plants of cv. Genovese from three greenhouses in 2004 to 2007,and from commercial seeds, stem sections, flowers, and seeds of diseased plants of cv. Morada in 2007. Seeds andportions of symptomatic tissues were surface­disinfested with 0.5% NaOCl for 1 min, rinsed in sterilized distilled water, airdried, and plated on 2% potato dextrose agar (PDA). Twenty­seven isolates were identified asFusarium oxysporumSchltdl.based on morphological characteristics (4), and the species identification confirmed by PCR assay using aF. oxysporumf.sp.basilici­specific primer pair, Bik 1 and Bik 2 (1). Vegetative compatibility groups (VCGs) were determined for the 27isolates through complementation of nitrate­nonutilizing mutants generated from these isolates (2) and paired with twoItalian tester strains from an international collection (PVS­Fu 220 and PVS­Fu 125, provided by V. Balmas, Univeristà degliStudi di Sassari, Italy). All 27 isolates from Argentina belonged to VCG 0200. This is a unique VCG forF. oxysporumf.sp.basiliciand has been identified in Israeli, American, and Italian isolates of the fungus (3). To fulfill Koch's postulates,pathogenicity tests were conducted with 12 isolates selected to reflect the multiple sources of fungal recovery, includingroot, crown, and stem sections, and leaves of diseased plants of cv. Genovese and commercial seeds, stem sections,flowers, and seeds of cv. Morada. Isolates were each grown on moistened (40% w/w), autoclaved, polished rice for 10days, dried, and ground in a grinder. The number of CFU/g rice was determined by serial dilution plating onto PDA plates.The inoculum was added to autoclaved soil at 104CFU/g dry soil. For each isolate, 8 healthy basil seedlings of each of cvs.Genovese and Morada were planted in pots, each containing 1 liter of inoculated soil. The control treatment consisted of 8basil seedlings of each of the same cultivars planted in autoclaved soil mixed with sterilized, ground, polished rice. Plantswere grown in a greenhouse with natural daylight for 45 to 50 days after inoculation. All inoculated plants showed the samesymptoms described for the original basil plants. No symptoms were observed on the control plants.F. oxysporumf.sp.basiliciwas re­isolated from the vascular tissue of stems of symptomatic plants but not from control plants, and speciesidentification confirmed by PCR assay as previously described. The presence of the pathogen was verified in the seed lotproduced in Italy, suggesting that this could have been a source of inoculum that introduced the pathogen into La Plata,Argentina, as supported by the hypothesis that infested seed resulted in spread of a clonal population ofF. oxysporumf.sp.basiliciinternationally (1). To our knowledge, this is the first report ofF. oxysporumf. sp.basiliciinfecting sweet basilin Argentina.Fil: Lori, Gladys. Universidad Nacional de la Plata. Facultad de Ciencias Agrarias y Forestales. Departamento de Ciencias Biológicas. Centro de Investigaciones de Fitopatología. Provincia de Buenos Aires. Gobernación. Comision de Investigaciones Científicas. Centro de Investigaciones de Fitopatología; ArgentinaFil: Malbrán, Ismael. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de la Plata. Facultad de Ciencias Agrarias y Forestales. Departamento de Ciencias Biológicas. Centro de Investigaciones de Fitopatología. Provincia de Buenos Aires. Gobernación. Comision de Investigaciones Científicas. Centro de Investigaciones de Fitopatología; ArgentinaFil: Mourelos, Cecilia Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de la Plata. Facultad de Ciencias Agrarias y Forestales. Departamento de Ciencias Biológicas. Centro de Investigaciones de Fitopatología. Provincia de Buenos Aires. Gobernación. Comision de Investigaciones Científicas. Centro de Investigaciones de Fitopatología; Argentin

Agresividad, producción de micotoxinas y diversidad en las poblaciones de Fusarium graminearum de la región triguera argentina

La fusariosis de la espiga de trigo (FET)o golpe blanco, ocasionada por Fusarium graminearum Schwabe, es una enfermedad que afecta al cultivo de trigo (Triticum aestivum L. en todo el mundo, incluyendo la Argentina. La enfermedad ocasiona disminuciones del rendimiento, perjuicios sobre la calidad del trigo y la contaminación del grano con micotoxinas, que constituyen un riesgo para la salud y comprometen su utilización en la alimentación. Estos metabolitos, principalmente el deoxinivalenol (DON), han sido indicados como posibles factores de patogenicidad. La principal alternativa para el manejo de la enfermedad la constituye la resistencia genética. El conocimiento de la diversidad a nivel genético de las poblaciones de F. graminearum así como de la variabilidad en la agresividad presente en ellas y su relación con la producción de toxinas es información indispensable para la búsqueda de genotipos resistentes a la FET. En el presente trabajo, 112 aislamientos de F. graminearum de 28 poblaciones de la Provincia de Buenos Aires fueron analizados en su variabilidad genética, agresividad y capacidad de producción de micotoxinas. Una significativa heterogeneidad genética fue observada en las poblaciones, la mayor parte de la cual correspondió a diferencias dentro de las poblaciones antes que entre las poblaciones. La agresividad de los aislamientos, ensayada mediante la inoculación artificial de espigas de plantas de trigo cultivadas a campo, resultó un rasgo altamente heredable, variable y no estructurado geográficamente. La desecación de la porción superior de las espigas sintomáticas, probablemente debida a deficiencias de agua y nutrientes resultantes de la invasión vascular del patógeno, resultó ser una función de la agresividad de los aislamientos. Todos los aislamientos analizados presentaron quimiotipo genético DON. Se encontró una correlación significativa entre la severidad de los síntomas de la FET y la acumulación de toxina en los granos, pero no entre la producción de DON in vitro e in vivo. Los resultados obtenidos constituyen un significativo aporte al conocimiento de la dinámica de una enfermedad tan importante para la producción como constituye la FE

First report of Fusarium oxysporum f. sp. lycopersici Race 3 Causing Fusarium Wilt of Tomato in Argentina

More than 15,000 ha of tomato (Solanum lycopersicum L.) are annually cultivated under greenhouse and field conditions in Argentina. From December 2013 to December 2016, plants of cultivar ‘Elpida’ showing wilting and stunting were observed in commercial fields from Goya, Corrientes. This province concentrates the largest area of greenhouses dedicated to tomato production in the country. Symptoms began as a yellowing of the lower leaves, which frequently was confined to one side of the plant at first and then spread to the rest of it. When stems of diseased plants were cut lengthwise, necrosis of the vascular tissue was observed, whereas the medulla remained healthy. Isolations were made from surface-sterilized sections of the vascular tissue, and a total of 14 monosporic isolates were obtained and identified as Fusarium oxysporum Schltdl. based on morphology and species-specific PCR (Hirano and Arie 2006). To identify the formae speciales and races of these isolates, pathogenicity tests were conducted on differential cultivars: ‘IPA-5’ (resistant to race 1), ‘Floradade’ and Elpida (resistant to races 1 and 2), ‘BHRS-2,3’ (resistant to races 1, 2 and 3), and ‘Ponderosa’ (susceptible to all races) (Reis et al. 2005). Isolates were incubated at 25 ± 2°C in 12 h light and 12 h dark on potato dextrose agar medium for 10 days. The obtained conidia were washed with autoclaved distilled water, and their concentration was adjusted to ≈106 microconidia/ml. For every isolate, four healthy seedlings of each cultivar showing the first two pairs of true leaves fully opened were removed from 35-cell germination trays, and the substrate was gently washed. The apical sector of the root was cut up to a length of 2 cm, and the remains were dipped in the spore suspension of one of the isolates for 1 min. To prepare the controls, roots were cut from four plants of each cultivar and dipped in sterilized distilled water. Afterward, the seedlings were transferred to 0.5-liter pots containing a mixture of tindalized soil, compost, and perlite (5:4:1 v/v) and grown in a greenhouse under natural daylight. Plants were evaluated 28 days postinoculation. All isolates induced typical symptoms of Fusarium wilt of tomato on cultivars Ponderosa, IPA-5, Elpida, and Floradade but not on cultivar BHRS-2,3 and hence were identified as F. oxysporum f. sp. lycopersici (Sacc.) W.C. Snyder & H.N. Hansen race 3. The pathogen was reisolated from vascular tissues of symptomatic plants from the three susceptible cultivars but not from control plants. To our knowledge, this is the first formal report of F. oxysporum f. sp. lycopersici race 3 in Corrientes, Argentina. The pathogen constitutes a potential threat to tomato production in this important area of production, and the knowledge of its presence might aid farmers in the selection of cultivars.Fil: Malbrán, Ismael. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Agrarias y Forestales. Departamento de Ciencias Biológicas. Centro de Investigaciones de Fitopatología. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Investigaciones de Fitopatología; ArgentinaFil: Mourelos, Cecilia Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; Argentina. Universidad Nacional de La Plata. Facultad de Ciencias Agrarias y Forestales. Departamento de Ciencias Biológicas. Centro de Investigaciones de Fitopatología. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Investigaciones de Fitopatología; ArgentinaFil: Lori, Gladys. Universidad Nacional de La Plata. Facultad de Ciencias Agrarias y Forestales. Departamento de Ciencias Biológicas. Centro de Investigaciones de Fitopatología. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Investigaciones de Fitopatología; Argentin

Aggressiveness and genetic variability of <i>Fusarium graminearum</i> populations from the main wheat production area of Argentina

Objectives: Differences in aggressiveness and mycotoxin production were previously found among isolates of Fusarium graminearum, the main incitant of Fusarium head blight (FHB) of wheat, from Argentina. This study aims at evaluating the genetic diversity present in these isolates and its relationship with their aggressiveness. Methods: Inter-simple sequence repeats polymerase chain reaction (ISSR-PCR) was used to asses the genetic variability present in 112 F. graminearum isolates from 28 localities of Buenos Aires Province, Argentina. The analysis of molecular variance (AMOVA) was performed to examine the population structure. Results: F. graminearum populations from Argentina showed a large genotypic variability. Seventy seven percent of the isolates included in the analysis were identified as a unique haplotype. The largest part of this variation resulted from genetic differences within (89%) rather than between populations (11%). The constructed dendrogram showed no genotype clustering according to geographic origin or aggressiveness of the isolates. Conclusions: A high genetic heterogeneity was found in the F. graminearum populations from Argentina. This diversity can possibly reflect the occurrence of high frequencies of sexual outcrosses in the field and gene flow.Centro de Investigaciones en FitopatologíaComisión de Investigaciones Científicas de la provincia de Buenos AiresConsejo Nacional de Investigaciones Científicas y Técnica

Aggressiveness and genetic variability of <i>Fusarium graminearum</i> populations from the main wheat production area of Argentina

Objectives: Differences in aggressiveness and mycotoxin production were previously found among isolates of Fusarium graminearum, the main incitant of Fusarium head blight (FHB) of wheat, from Argentina. This study aims at evaluating the genetic diversity present in these isolates and its relationship with their aggressiveness. Methods: Inter-simple sequence repeats polymerase chain reaction (ISSR-PCR) was used to asses the genetic variability present in 112 F. graminearum isolates from 28 localities of Buenos Aires Province, Argentina. The analysis of molecular variance (AMOVA) was performed to examine the population structure. Results: F. graminearum populations from Argentina showed a large genotypic variability. Seventy seven percent of the isolates included in the analysis were identified as a unique haplotype. The largest part of this variation resulted from genetic differences within (89%) rather than between populations (11%). The constructed dendrogram showed no genotype clustering according to geographic origin or aggressiveness of the isolates. Conclusions: A high genetic heterogeneity was found in the F. graminearum populations from Argentina. This diversity can possibly reflect the occurrence of high frequencies of sexual outcrosses in the field and gene flow.Centro de Investigaciones en FitopatologíaComisión de Investigaciones Científicas de la provincia de Buenos AiresConsejo Nacional de Investigaciones Científicas y Técnica

Inducción de resistencia a la Fusariosis de la espiga en líneas recombinantes de cebada, una estrategia adecuada para un manejo sustentable de cultivos extensivos

La cebada aument&oacute; su superficie sembrada en Argentina en los &uacute;ltimos a&ntilde;os y simult&aacute;neamente, la incidencia de la Fusariosis de la espiga (FE) en el cultivo ha pasado a ser una enfermedad de importancia econ&oacute;mica. Un grupo de l&iacute;neas recombinantes, portadoras de Resistencia Sist&eacute;mica Adquirida (SAR) frente a poblaciones de &aacute;fidos, mostraron en el campo variaci&oacute;n, bajo condiciones de infecci&oacute;n natural con Fusarium graminearum. Por esa raz&oacute;n, fueron probadas por su respuesta a FE con y sin pretratamientos de inductores hormonales en antesis, durante 2013 y 2014. A la cosecha se evalu&oacute; el n&uacute;mero total de granos por espiga (GE), el n&uacute;mero de granos da&ntilde;ados (GD) y el &Iacute;ndice de fusarium (IF= GD/GE). La l&iacute;nea tolerante pre-tratada con &aacute;cido jasm&oacute;nico (AJ), present&oacute;, en ambos a&ntilde;os, mayor GE, con menores GD e IF. En cebada es posible seleccionar genotipos con mecanismos inducibles de defensas, cuyo uso permitir&aacute; un manejo de la enfermedad m&aacute;s amigable con el medio ambiente, con reducci&oacute;n del uso de pesticidas y a un costo menor.Barley is one of the crops that greatly increased its sown area in Argentina in the last years. With this increment, the incidence of Fusarium head blight (FHB) became of economic importance. Several lines of a set of recombinant lines were found to provide SAR type of aphid resistance. Since these lines showed variation on the field under natural infection with Fusarium graminearum, during the last two years several lines were tested for their responses to FHB with and without pre-treatments of hormonal inductors during anthesis. At harvest the total number of grains per spike (GS), the number of damaged kernels (DK) and the Fusarium index (FI= DK/GS) were calculated. Tolerant line showed higher GS after jasmonic acid (JA) treatment, with lower DK and FI in both years. These preliminary results may imply the possibility to select barley lines tolerant to FHB carrying induced resistance genes that allow a more sustainable management of the disease with a decrease in pesticide use and at a lower cost.Eje A1 Sistemas de producción de base agroecológica (Trabajos científicos

First report of Fusarium sambucinum sensu stricto causing postharvest fruit rot of tomato in Argentina

Tomato (Solanum lycopersicum L.) is among the most important horticultural crops in Argentina. The green belt area surrounding the city of La Plata (Buenos Aires, Argentina) represents around 30% of the horticultural production of the province. Annually, an average of 408 ha of tomato is harvested in this region, of which 70% is for fresh consumption and 30% for processing. During the summer of 2013 to 2014, postharvest fruit rot was found in 20% of the storage facilities from the horticultural area of La Plata on fresh market tomato fruits cv. Elpida. Symptoms started as small circular lesions of watery aspect that increased in size over time. Lesions destroyed subepidermal tissue, causing ruptures in the epidermis and the emergence of abundant white mycelium. Fruits would eventually collapse. Surface disinfested pieces of symptomatic fruit were placed on potato dextrose agar (PDA) medium and incubated at 23 ± 2°C with a cycle of 12/12 h light/dark for 9 days in a growth chamber. Fusarium colonies with abundant white mycelia and ruby red pigments, which reached 5.1 cm in diameter in 4 days of growth, were obtained. A single conidia culture was originated of each isolate. Abundant curved, slender, 3 to 5-septate macroconidia with a constrained and pointed apical cell (3-septate: 30 to 45 × 4 to 5 µm; 5-septate: 40 to 53 × 5 µm), and a foot-shaped basal cell were produced from monophialides. Microconidia were not observed and chlamydospores were produced both singly and in chains. According to these morphological characters, the pathogen was identified as Fusarium sambucinum Fuckel sensu stricto (Nirenberg 1995). Identification was confirmed by sequencing of internal transcribed spacer (ITS) (White et al. 1990) and translation elongation factor (TEF) 1-α (O’Donnell et al. 1998) genes. Identities of the resulting sequences (accession nos. KX023900 and KX023899) were confirmed using BLAST analysis in the NCBI database. Analysis revealed 99% identity with F. sambucinum (Gibberella pulicaris isolates F153N10 and IBT1744). Similar symptomatology is induced by this fungus in potato, causing significant yield losses (Secor and Sala 2001). To fulfill Koch’s postulates, pathogenicity tests were conducted for the three isolates obtained. Symptomless tomato fruits from cv. Elpida were disinfected in 5% NaOCl, rinsed with sterile distilled water, and inoculated with macroconidia from pure cultures of the isolates using a sterile needle. A control treatment was inoculated with sterile water. After inoculation, fruits were placed in a sterile plastic container and incubated for 24 h in a moist chamber and then at 23 ± 2°C in a growth chamber. Each fruit constituted a single replicate and each treatment was replicated five times. All inoculated fruits showed symptoms identical to those observed in the field 5 days after inoculation. The control-inoculated fruits did not show symptoms of infection. F. sambucinum was reisolated from symptomatic fruits, confirming Koch’s postulates. To our knowledge, this study constitutes the first report of F. sambucinum causing symptoms of postharvest soft rot in tomato fruits in Argentina.Centro de Investigaciones en Fitopatologí

Enterobacterias aisladas de suelos agrícolas de Argentina con efecto promotor del crecimiento de plantas y biocontrol sobre fitopatógenos

Bacteria promote growth by different mechanisms like phosphate (Pi) solubilization, Indol Acetic Acid (IAA) synthesis and siderophores production. The purpose of this study was to isolate bacteria that promote the growth of plants and may also act as antagonistic organisms of plant pathogens. Pi solubilizing microorganisms that were isolated from the soils of Tres Arroyos, Buenos Aires; were also able to synthesize IAA and produce siderophores. The ability of these bacteria to solubilize Pi was directly related with the synthesis of organic acids that lowered the pH and was not related with phosphatase activity. The ability of the organisms to solubilize Pi was indirectly related with the amount of soluble Pi present in the media. Though Pi solubilizing microorganisms are mainly associated with the rhizoplane exudates, in this case did not induce Pi solubilization. In addition to promote plant growth, these bacteria proved to be antagonistic of plant pathogens such as Fusarium graminearum and F. solani.Las bacterias que promueven el crecimiento vegetal lo hacen por diferentes mecanismos como la solubilización de fósforo, la síntesis de ácido indolacético y la producción de sideróforos. El objetivo de este trabajo fue aislar bacterias que promuevan el crecimiento de plantas y que también puedan actuar como organismos antagónicos de los hongos fitopatógenos. Los microorganismos fueron aislados de suelos de Tres Arroyos, pcia de Bs As y se encontraron bacterias solubilizadoras de fosfato inorgánico, que también sintetizan ácido indol acético y sideróforos. La capacidad de estas bacterias para solubilizar fosfatos (Pi) podría estar directamente relacionada con la síntesis de ácidos orgánicos que disminuyen el pH y no guardan relación con la actividad de la fosfatasa. La capacidad de los organismos para solubilizar Pi se relacionó indirectamente con la cantidad de Pi soluble presente en los medios. La capacidad de los microorganismos solubilizadores de Pi está principalmente asociada con el efecto de los exudados presentes en el rizoplano, sin embargo, esto no ocurrió en el caso de las bacterias evaluadas en el presente trabajo. Además de promover el crecimiento de las plantas, estas bacterias demostraron ser antagónicas de patógenos de plantas como Fusarium graminearum y F. solani.Facultad de Ciencias Agrarias y Forestale

First Report of Fusarium Wilt of Basil Caused by <i>Fusarium oxysporum</i> f. sp. basilici in Argentina

Annually, ~20 ha of sweet basil (Ocimum basilicum L.) are cultivated in greenhouses in the green belt area surrounding La Plata, Argentina, mainly for fresh consumption. In 2004 to 2007, basil plants of cv. Genovese showed wilt symptoms, necrosis of leaves and stems, asymmetrical growth, and discolored vascular tissue in greenhouses in La Plata. In 2007, the same symptoms were observed on plants of cv. Morada grown from seeds that were produced in Italy. Isolations were completed from root, crown, and stem sections of diseased plants of cv. Genovese from three greenhouses in 2004 to 2007, and from commercial seeds, stem sections, flowers, and seeds of diseased plants of cv. Morada in 2007. Seeds and portions of symptomatic tissues were surfacedisinfested with 0.5% NaOCl for 1 min, rinsed in sterilized distilled water, air dried, and plated on 2% potato dextrose agar (PDA). Twentyseven isolates were identified as Fusarium oxysporum Schltdl. based on morphological characteristics, and the species identification confirmed by PCR assay using a F. oxysporum f. sp. basilicispecific primer pair, Bik 1 and Bik 2.Facultad de Ciencias Agrarias y Forestale

Diseño de péptidos antifúngicos a partir de dos defensinas de flores de cardo : síntesis y actividad contra fusarium graminearum

Las defensinas vegetales son péptidos básicos ricos en cisteína de 45 a 54 aminoácidos y estructura conservada. A pesar de su similitud estructural presentan diversidad de secuencias, lo cual puede dar cuenta de las diferentes funciones atribuidas (actividad antibacteriana, antifúngica, etc). Se han identificado dos regiones muy conservadas entre las defensinas vegetales, las cuales son importantes en relación con la actividad que exhiben: el -core ubicado en la región C-terminal y el α-core localizado en la región N-terminal. En este trabajo se diseñaron péptidos potecialmente antifúngicos a partir de estas regiones, a través del uso de herramientas bioinformáticas y empleando como plantilla la secuencia de dos defensinas de Silybum marianum (L.) Gaertn. previamente clonadas (DefSm1D y DefSm2). Cinco péptidos fueron sintetizados, purificados y caracterizados: tres derivados de DefSm1D, llamados 3243, 3245 y 3246; y dos a partir de la secuencia de DefSm2, denominados 3248 y 3250. Se evaluó su actividad contra el hongo fitopatógeno Fusarium graminearum Schwabe y dos de ellos, 3248 y 3250, resultaron activos en concentraciones micromolares. El presente trabajo contribuye al conocimiento de las defensinas, las cuales son proteínas de defensa ricas en cisteína presentes en la especie en estudio, que crece en forma silvestre en Argentina y que naturalmente presenta una significativa resistencia a patógenos fúngicosFil: Fernandez, Agustina. Universidad Nacional de La PlataFil: Malbrán, Ismael. Universidad Nacional de La PlataFil: Vairo Cavalli, Sandra Elizabeth. Universidad Nacional de La Plat