Técnica simple de bioensayo con metabolítos volátiles producidos por especies fúngicas

Muchos microorganismos producen sus­tancias volátiles que pueden estimular o inhibir el crecimiento, germinación o morfogénesis de numerosas especies de hongos, incluidos algunos fitopatógenos (Batra y Baja], 1967; Bilai, 1956; Fríes, 1973; Hutchinson, 1971). Los bioensayos empleando cepas fúngicas que liberan metabolítos con efecto fungistático o fungicida, constituyen uno de los aspectos básicos en el estudio de las interacciones antagonistas. Entre esos componentes ga­seosos, han sido frecuentemente identificados el dióxido de carbono, etanol, acetaldehido, acetona, propanol e isobutanol (Buston ef al., 1966; Fries, 1973; Robinson y Garrett, 1969). Para comprobar la efectividad de los mismos como mecanismo de control biológico, se uti­lizan diversos dispositivos adaptados a una técnica común: superponer 2 cultivos que crecen en distintos envases permitiendo el contacto entre los gases provenientes de la colonia inferior y la restante, cuyo grado de afectación se quiere medir.Facultad de Ciencias Agrarias y Forestale

First report of Colletotrichum gloeosporioides causing anthracnose on Blepharocalyx salicifolius in Argentina

Anthracnose symptoms were observed on Blepharocalyx salicifolius from Entre Ríos and Buenos Aires provinces, Eastern Argentina. Colletotrichum gloeosporioides sensu lato (teleomorph Glomerella cingulata) was identified as the causal agent based on disease symptoms, the morphological characteristics of the isolated fungus and pathogenicity tests. To our knowledge, this is the first report of C. gloeosporioides causing leaf spot on Blepharocalyx salicifolius.Centro de Investigaciones de Fitopatologí

Weed diseases in La Plata area II. Identification of pathogens with potentitial for weed biocontrol programmes

En este trabajo se completa el estudio de las enfermedades halladas en un grupo de malezas del cinturón hortícola platense, Provincia de Buenos Aires, y de la capacidad potencial de los respectivos patógenos para emplearlos como biocontrol adores. Fueron registradas 21 especies fúngicas sobre los siguientes hospedantes: Anoda cristata, Baccharis medullosa, Bidens subalternaos, Cirsium vulgare,Commelina erecta, Cynodon dactylon, Datura ferox, Digitaria sanguinalis, Modiolacaroliniana, Phalaris minor, Polygonum convolvulus, Rumex crispus, Sonchusoleraceus, Urtica urens, Wedelia glauca y Xanthium cavanillesii. A partir de tos resultados que surgieron de los estudios etiosintomatológicos, como así también de las observaciones del daño producido e intensidad de ataque, pudo determinarse que los microorganismos con posibilidades de constituirse en agentes de biocontrol son: Alternaría sp sobre W. glauca; Puccinia calcitrapae sobre C. vulgare: P. heterospora sobre A. cristata: P.modiolae sobre M. multifida; P.polygoni-amphibii sobre P. convolvulus; Septoria urticae sobre U. urens: Uromycesbidenticola sobre B. subalternaos y U. commelinae sobre C. virginica.The aim of this research was to study fungal diseases found on weeds of vegetable crops of the rural belt of La Plata (Buenos Aires Province). In order to establish the poteniial of the microorganisms as biological control agenfs, the level of damage caused by the pathogens was also determined. Twenty-one species of fungi were recorded from the following hosts: Anodacristata, Baccharis medullosa, Bidens subalternaos, Cirsium vulgare, Commelinaerecta, Cynodon dactylon, Datura ferox, Digitaria sanguinalis, Modiola caroliniana,Phalaris minor, Polygonum convolvulus, Rumex crispus, Sonchus oleraceus, Urticaurens, Wedelia glauca y Xanthium cavanillesii.Facultad de Ciencias Agrarias y Forestale

Weed diseases in La Plata area II. Identification of pathogens with potentitial for weed biocontrol programmes

En este trabajo se completa el estudio de las enfermedades halladas en un grupo de malezas del cinturón hortícola platense, Provincia de Buenos Aires, y de la capacidad potencial de los respectivos patógenos para emplearlos como biocontrol adores. Fueron registradas 21 especies fúngicas sobre los siguientes hospedantes: Anoda cristata, Baccharis medullosa, Bidens subalternaos, Cirsium vulgare,Commelina erecta, Cynodon dactylon, Datura ferox, Digitaria sanguinalis, Modiolacaroliniana, Phalaris minor, Polygonum convolvulus, Rumex crispus, Sonchusoleraceus, Urtica urens, Wedelia glauca y Xanthium cavanillesii. A partir de tos resultados que surgieron de los estudios etiosintomatológicos, como así también de las observaciones del daño producido e intensidad de ataque, pudo determinarse que los microorganismos con posibilidades de constituirse en agentes de biocontrol son: Alternaría sp sobre W. glauca; Puccinia calcitrapae sobre C. vulgare: P. heterospora sobre A. cristata: P.modiolae sobre M. multifida; P.polygoni-amphibii sobre P. convolvulus; Septoria urticae sobre U. urens: Uromycesbidenticola sobre B. subalternaos y U. commelinae sobre C. virginica.The aim of this research was to study fungal diseases found on weeds of vegetable crops of the rural belt of La Plata (Buenos Aires Province). In order to establish the poteniial of the microorganisms as biological control agenfs, the level of damage caused by the pathogens was also determined. Twenty-one species of fungi were recorded from the following hosts: Anodacristata, Baccharis medullosa, Bidens subalternaos, Cirsium vulgare, Commelinaerecta, Cynodon dactylon, Datura ferox, Digitaria sanguinalis, Modiola caroliniana,Phalaris minor, Polygonum convolvulus, Rumex crispus, Sonchus oleraceus, Urticaurens, Wedelia glauca y Xanthium cavanillesii.Facultad de Ciencias Agrarias y Forestale

Volatile organic compounds released by the entomopathogenic fungus Beauveria bassiana

The composition of volatile organic compounds (VOC) released by the entomopathogenic fungus Beauveria bassiana (Hyphomycete: Deuteromycotina) utilizing two different carbon sources was investigated. Analyses were performed by solid-phase microextraction (SPME) coupled to capillary gas chromatography (CGC) and CGC-mass spectrometry (MS). Major components in glucose-grown cultures were diisopropyl naphthalenes, ethanol, and sesquiterpenes. Alkane-grown fungal VOC switched to a fingerprint with prevalence of n-decane. This is the first report on the volatiles released by entomopathogenic fungi.Instituto de Investigaciones Bioquímicas de La PlataCentro de Investigaciones de Fitopatologí

Volatile organic compounds released by the entomopathogenic fungus Beauveria bassiana

The composition of volatile organic compounds (VOC) released by the entomopathogenic fungus Beauveria bassiana (Hyphomycete: Deuteromycotina) utilizing two different carbon sources was investigated. Analyses were performed by solid-phase microextraction (SPME) coupled to capillary gas chromatography (CGC) and CGC-mass spectrometry (MS). Major components in glucose-grown cultures were diisopropyl naphthalenes, ethanol, and sesquiterpenes. Alkane-grown fungal VOC switched to a fingerprint with prevalence of n-decane. This is the first report on the volatiles released by entomopathogenic fungi.Instituto de Investigaciones Bioquímicas de La PlataCentro de Investigaciones de Fitopatologí

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

First report of Colletotrichum gloeosporioides causing anthracnose on Blepharocalyx salicifolius in Argentina

Anthracnose symptoms were observed on Blepharocalyx salicifolius from Entre Ríos and Buenos Aires provinces, Eastern Argentina. Colletotrichum gloeosporioides sensu lato (teleomorph Glomerella cingulata) was identified as the causal agent based on disease symptoms, the morphological characteristics of the isolated fungus and pathogenicity tests. To our knowledge, this is the first report of C. gloeosporioides causing leaf spot on Blepharocalyx salicifolius.Centro de Investigaciones de Fitopatologí

The entomopathogenous Beauveria bassiana as a potential biocontrol agent of Coleoptera Xanthogaleruca luteola (Müller)

Se aisló al entomopatógeno Beauveria bassiana, desde poblaciones de Xanthogaleruca luteola, recolectadas en olmos de la provincia de Buenos Aires. In vitro se evaluaron 2 métodos de inoculación sobre desoves y larvas: mediante espolvoreo e inmersión en suspensión acuosa de los conidios del hongo. Ambos resultaron efectivos (principalmente el primero), para el biocontrol de la vaquita del olmo.From adults of Xanthogaleruca luteola collected in elm trees of the Buenos Aires province (Argentina) the entomopathogenic fungus Beauveria bassiana, was isolated. Two inoculation methods in spawns and larvae were evaluated in vitro: through powdering and submersion in aqueous suspension of the conidia. Both methods were effective (specially the former) for the biocontrol of "elm leaf beetle".Facultad de Ciencias Agrarias y Forestale

Pathogenicity of Beauveria bassiana for adults of Tribolium castaneum ( Col.: Tenebrionidae ) in stored grains

Conidia ofBeauveria bassiana were evaluated for activity against adults ofTribolium castaneum, under laboratory conditions closely resembling the stored-grain conditions. Three doses of the fungus were applied in the treatments: 0.1 g, 0.5 g and 1 g per 20 insects/dose/flask. Treated insects and untreated were incubated in broken wheat. There were 5 replications for each test. A total of 1600 treated and control insects used were kept in a climatic chamber (70±5% and 27±2°C) for 45 days. Observations were performed daily and the recording of infected cadavers began when the percentage of mortality exceeded 50%. The evaluation of the efficiency of each dose ofB. bassiana was made 14, 21, 28 and 45 days after inoculation. Mortality of adults that were exposed to the beetles treated with 0.5 g and 1 g of conidia ofB. bassiana / 20 adults was 87 and 85% respectively, within 21 days of exposure. Onset of mortality was further delayed at lower dosage of the fungus; 55% after 21 days. After 28 days there were no difference in mortality between the 0.5 g and 1 g dosages ofB. bassiana. The most efficient treatment was 0.5 g/20 insects, which resulted in a control higher than 50% 14 days post treatment.Facultad de Ciencias Agrarias y ForestalesComisión de Investigaciones Científicas de la provincia de Buenos Aire