La podredumbre del ajo causada por Fusarium proliferatum

La producción anual de ajo en España es de 154.587 t y su cultivo ocupa unas 15.900 ha distribuidas principalmente en Castilla La Mancha (53,1%), Andalucía (27,4%) y Castilla y León (9,1%). En Castilla La Mancha, la principal Comunidad productora, se ha cultivado en la presente campaña un 7 % más que en la campaña 2009/2010, siendo Albacete la provincia con mayor superficie cultivada de ajos con 4.750 ha, seguida de Cuenca con 2.200 ha. Las plagas y enfermedades en el cultivo del ajo suponen elevadas pérdidas económicas cada año en nuestro país. En 2008, distintos agricultores de varios municipios de Castilla y León detectaron bulbos de ajo del cultivar “Blancomor de Vallelado” que presentaban síntomas de podredumbre húmeda durante el almacenamiento. Posteriormente, en el año 2009, esta misma podredumbre se observó también en las provincias de Albacete y Cuenca en el cultivar “Morado de Pedroñeras”. Estudios sobre esta nueva enfermedad se están llevando a cabo en colaboración con productores castellanomanchegos pertenecientes a Coopaman SCL

Divergence of the IGS rDNA in Fusarium proliferatum and Fusarium globosum reveals two strain specific non-orthologous types

A phylogenic analysis of Fusarium proliferatum and closely related species was performed using the most variable part within the intergenic spacer of the nuclear ribosomal DNA (IGS) and compared with a previously reported phylogeny performed in the same group of samples with a partial region of the nuclear single copy gene encoding the elongation factor 1α (EF-1α). The phylogenies from both genomic sequences were not concordant and revealed the presence of two nonorthologous IGS types, named types I and II, in F. proliferatum and Fusarium globosum. Two specific PCR assays designed to amplify either IGS type I or type II revealed that only one IGS type was present in each individual in these two species. The presence of both IGS types at the species level indicates that homogenization has not been achieved yet. This might be retarded if panmictic sexual reproduction was affected by certain levels of clonal reproduction and/or by the diverse hosts that these species are able to colonize. This study indicates that taxonomic studies carried out with the IGS rDNA, which has been widely used in Fusarium, should be undertaken with caution.

Fusarium proliferatum isolated from garlic in Spain: Identification, toxigenic potential and pathogenicity on related Allium species

Fusarium proliferatum has been reported on garlic in the Northwest USA, Spain and Serbia, causing water-soaked tan-colored lesions on cloves. In this work, Fusarium proliferatum was isolated from 300 symptomatic garlic bulbs. Morphological identification of Fusarium was confirmed using species-specific PCR assays and EF-1α sequencing. Confirmation of pathogenicity was conducted with eighteen isolates. Six randomly selected F. proliferatum isolates from garlic were tested for specific pathogenicity and screened for fusaric acid production. Additionally, pathogenicity of each F. proliferatum isolate was tested on healthy seedlings of onion (Allium cepa), leek (A. porrum), scallions (A. fistulosum), chives (A. schoenoprasum) and garlic (A. sativum). A disease severity index (DSI) was calculated as the mean severity on three plants of each species with four test replicates. Symptoms on onion and garlic plants were observed three weeks after inoculation. All isolates tested produced symptoms on all varieties inoculated. Inoculation of F. proliferatum isolates from diseased garlic onto other Allium species provided new information on host range and pathogenicity. The results demonstrated differences in susceptibility with respect to host species and cultivar. The F. proliferatum isolates tested all produced fusaric acid (FA); correlations between FA production and isolate pathogenicity are discussed. Additionally, all isolates showed the presence of the FUM1 gene suggesting the ability of Spanish isolates to produce fumonisins.

The effects of storage duration, temperature and cultivar on the severity of garlic clove rot caused by Fusarium proliferatum.

Diseases that affect garlic during storage can lead to severe economic losses for farmers worldwide. One causal agent of clove rot is Fusarium proliferatum. Here, the progress of clove rot caused by F. proliferatum and its dependence on different storage conditions and cultivar type were studied. The effect of temperature on mycelial growth, conidial viability, and fungal survival during garlic commercial storage was documented. Samples of 50 bulbs from a randomized field trial with three different clonal generations for purple garlic (F3, F4 and F5) and the F4 clonal generation for white garlic were labeled and stored for two months (short-term storage). In addition, another sample of the F5 clonal generation of purple garlic was stored for 6 months after harvest (long-term storage). The presence of the pathogen and the percentage of symptomatic cloves were evaluated. A notable difference in the rot severity index (RSI) of different garlic varieties was observed. In all studied cases, clove rot increased with storage time at 20 ◦ C, and the white garlic variety had a higher index of rot severity after two months of storage. Additionally, there were clear differences between the growth rates of F. proliferatum isolates. Studies conducted on the temperature responses of the pathogen propagules showed that expo- sure for at least 20 min at 50 ◦ C was highly effective in significantly reducing the viability of fungal conidia. Pathogenicity studies showed that the fungus is pathogenic in all commercial varieties. However, there were significant differences in varietal susceptibility between Chinese and white garlic type cultivars (81.84 ± 16.44% and 87.5 ± 23.19% symptomatic cloves, respectively) and purple cultivars (49.06 ± 13.42% symptomatic cloves)

Identificação, caracterização e avaliação da patogenicidade de diferentes isolados de fusarium spp. para o controle de thaumastocoris peregrinus (hemiptera: thaumastocoridae)

Pós-graduação em Agronomia (Proteção de Plantas) - FCA

Controle biológico de thaumastocoris peregrinus (Hemiptera: thaumastocoridae) com fungos entomopatogênicos

Pós-graduação em Agronomia (Proteção de Plantas) - FCA

Biological control of the bronze bug, Thaumastocoris peregrinus, in eucalyptus plantations in Brazil

The bronze bug Thaumastocoris peregrinus (Hemiptera: Thaumastocoridae) was detected in Brazil in 2008 and infested >180 000 ha of eucalyptus plantations in 2011. The bronze bug can cause a reduction of 10–15% in wood productivity after 2 years of heavy infestation. Although there is not an effective control method known, biological control is the main control strategy studied. An exotic egg parasitoid, Cleruchoides noackae (Hymenoptera: Mymaridae), was imported from Australia in 2012, reared in a laboratory and released in three Brazilian regions. Parasitoids were recovered at release points after 20–30 d. In 2013, preliminary evaluations demonstrated parasitoid establishment in these areas, and the parasitoid was recovered in adjacent areas after 1 year of release. Bioassays confi rmed egg parasitism of 15–20% by C. noackae. Other native natural enemies were studied. We found green lacewing Chrysoperla externa and predatory bugs Supputius cincticeps and Atopozelus opsimus preying on nymphs and/or adults of T. peregrinus. Another promising possibility is entomopathogenic fungi. Commercial formulations of Beauveria bassiana were tested with success in lab and fi eld conditions. Fusarium proliferatum and Paecilomyces cateniannulatus caused mortality of T. peregrinus in natural epizooties. After 5 years of research, it is possible to develop an integrated pest management system (IPM) for eucalyptus plantations based on biocontrol strategy for bronze bug.

Microbiota asociada a la enfermedad de la punta negra del trigo duro. Efectos del riego, el abonado nitrogenado y la variedad cultivada en la incidencia de la enfermedad

La enfermedad fúngica de la punta negra del trigo se caracteriza por provocar en las semillas afectadas un oscurecimiento de la zona del embrión que en ocasiones puede extenderse hacia la hendidura central dejando el grano completamente ennegrecido. Su incidencia en el cultivo de trigo es extremadamente variable y depende en gran medida de las condiciones ambientales, así pues, condiciones de alta humedad pueden incrementar a punta negra. Su presencia en el trigo duro repercute en el rendimiento semolero. Además la pasta elaborada a partir de semilla enferma presenta manchas negras y adquiere color y olor desagradable. Esta enfermedad es poco conocida a nivel europeo, sin embargo existen numerosos estudios para conocer su etiología y los factores que afectan a su aparición en países como Nueva Zelanda, Australia, Estados Unidos o Canadá. El presente trabajo pretende dar a conocer esta patología en España, determinando la influencia del riego, el abonado nitrogenado y la variedad cultivada en la incidencia de la enfermedad. Para ello se ha contado con un diseño experimental basado en 10 cultivares sembrados en parcelas con dos tratamientos de riego y dos de abonado nitrogenado. El análisis de las semillas infectadas en cámara húmeda y medios de cultivo PDA y K reveló 12 géneros fúngicos diferentes, de los cuales Alternaria alternata y Fusarium proliferatum estaban presentes en todas las muestras. El estudio del riego y abonado nitrogenado mostró diferencias significativas en la incidencia de punta negra pero fueron los 10 cultivares incluidos en el ensayo los que mayor importancia cobraron desde el punto de vista de la aparición de la enfermedad. El genotipo resultó determinante a la hora de establecer los niveles de afectación ya que las muestras encuadradas botánicamente como Triticum turgidum subsp. Turgidum convar. Turgidum presentaron una mayor susceptibilidad. las prueas de patogenicidd con los tres principales hongos asociados a la punta negra dieron resultados negativos para la germinación-nascencia de las plántulas de trigo duro inoculadas.

Enfermedades y fisiopatías que afectan a la calidad del ajo en postcosecha

Las enfermedades y fisiopatías que afectan al ajo pueden llegar a ocasionar importantes pérdidas en postcosecha, de vital importancia cuando el producto se destina a la exportación a mercados que cada día son más exigentes. En 2008, distintos agricultores de varios municipios de Castilla y León detectaron bulbos de ajo que presentaban síntomas de podredumbre húmeda durante el almacenamiento. Posteriormente, en el año 2009, esta misma podredumbre se observó también en las provincias de Albacete y Cuenca y en muestras procedentes de Córdoba. Hasta la fecha se ha identificado a Fusarium proliferatum como el agente causal de la podredumbre del diente.

Structure Variation And Dynamics of the Nuclear Ribosomal Intergenic Spacer Region in Key Gibberella Fujikuroi Complex Species

The intergenic spacer (IGS) region of the ribosomal DNA was cloned and sequenced in eight species within the Gibberella fujikuroi species complex with anamorphs in the genus Fusarium , a group that includes the most relevant toxigenic species. DNA sequence analyses revealed two categories of repeated elements: long repeats and short repeats of 125 and 8 bp, respectively. Long repeats were present in two copies and were conserved in all the species analyzed, whereas different numbers of short repeat elements were observed, leading to species-specific IGS sequences with different length. In Fusarium subglutinans and Fusarium nygamai , these differences seemed to be the result of duplication and deletion events. Here, we propose a model based on unequal crossing over that can explain these processes. The partial IGS sequence of 22 Fusarium proliferatum isolates was also obtained to study variation at the intraspecific level. The results revealed no differences in terms of number or pattern of repeated elements and detected frequent gene conversion events. These results suggest that the homogenization observed at the intraspecific level might not be achieved primarily by unequal crossing-over events but rather by processes associated with recombination such as gene conversion events.

Carbon and nitrogen limitation increase chitosan antifungal activity in Neurospora crassa and fungal human pathogens

Chitosan permeabilizes plasma membrane and kills sensitive filamentous fungi and yeast. Membrane fluidity and cell energy determine chitosan sensitivity in fungi. A five-fold reduction of both glucose (main carbon (C) source) and nitrogen (N) increased 2-fold Neurospora crassa sensitivity to chitosan. We linked this increase with production of intracellular reactive oxygen species (ROS) and plasma membrane permeabilization. Releasing N. crassa from nutrient limitation reduced chitosan antifungal activity in spite of high ROS intracellular levels. With lactate instead of glucose, C and N limitation increased N. crassa sensitivity to chitosan further (4-fold) than what glucose did. Nutrient limitation also increased sensitivity of filamentous fungi and yeast human pathogens to chitosan. For Fusarium proliferatum, lowering 100-fold C and N content in the growth medium, increased 16-fold chitosan sensitivity. Similar results were found for Candida spp. (including fluconazole resistant strains) and Cryptococcus spp. Severe C and N limitation increased chitosan antifungal activity for all pathogens tested. Chitosan at 100 μg ml-1 was lethal for most fungal human pathogens tested but non-toxic to HEK293 and COS7 mammalian cell lines. Besides, chitosan increased 90% survival of Galleria mellonella larvae infected with C. albicans. These results are of paramount for developing chitosan as antifungal.

Fungal microbiota from rain water and pathogenicity of Fusarium species isolated from atmospheric dust and rainfall dust

In order to determine the presence of Fusarium spp. in atmospheric dust and rainfall dust, samples were collected during September 2007, and July, August, and October 2008. The results reveal the prevalence of airborne Fusarium species coming from the atmosphere of the South East coast of Spain. Five different Fusarium species were isolated from the settling dust: Fusarium oxysporum, F. solani, F. equiseti, F. dimerum, and F. proliferatum. Moreover, rainwater samples were obtained during significant rainfall events in January and February 2009. Using the dilution-plate method, 12 fungal genera were identified from these rainwater samples. Specific analyses of the rainwater revealed the presence of three species of Fusarium: F. oxysporum, F. proliferatum and F. equiseti. A total of 57 isolates of Fusarium spp. obtained from both rainwater and atmospheric rainfall dust sampling were inoculated onto melon (Cucumis melo L.) cv. Piñonet and tomato (Lycopersicon esculentum Mill.) cv. San Pedro. These species were chosen because they are the main herbaceous crops in Almeria province. The results presented in this work indicate strongly that spores or propagules of Fusarium are able to cross the continental barrier carried by winds from the Sahara (Africa) to crop or coastal lands in Europe. Results show differences in the pathogenicity of the isolates tested. Both hosts showed root rot when inoculated with different species of Fusarium, although fresh weight measurements did not bring any information about the pathogenicity. The findings presented above are strong indications that long-distance transmission of Fusarium propagules may occur. Diseases caused by species of Fusarium are common in these areas. They were in the past, and are still today, a problem for greenhouses crops in Almería, and many species have been listed as pathogens on agricultural crops in this region. Saharan air masses dominate the Mediterranean regions. The evidence of long distance dispersal of Fusarium spp. by atmospheric dust and rainwater together with their proved pathogenicity must be taken into account in epidemiological studies.

Growth of Fusarium species as affected by temperature and osmotic potential (NaCl and KCl) interactions.

Myceliar growth of 90 Fusarium strains os F. acuminatum, F. chlamydosporum, F. culmorum, F. equiseti, F.verticillioides, F. oxysporum, F. proliferatum, F. solani an F. sambucinum isolated from fluvial channels and sea beds of the south-eastern coast of Spain was tested on potato-dextrose-agar adjusted to different matric potentials with either KCl or NaCl (from - 1.50 to - 144.54 bars).

Effects of water potential on spore germination and viability of Fusarium species

Germination of macroconidia and/or microconidia of 24 strains of Fusarium solani, F. chlamydosporum, F. culmorum, F. equiseti, F. verticillioides, F. sambucinum, F. oxysporum and F. proliferatum isolated from fluvial channels and sea beds of the south-eastern coast of Spain, and three control strains (F. oxysporum isolated from affected cultures) was studied in distilled water in response to a range of water potentials adjusted with NaCI. (0, -13.79, -41.79, -70.37, -99.56 and -144.54 bars). The vialibility (UFC/ml) of suspension was also tested in three time periods (0,24 and 48h). Conidia always germinated in distilled water. The pattern of conidial germination obseved of F. verticillioides, F. oxysporum, F. proliferatum, F. chlamydosporum and F. culmorum was similar. A great diminution of spore germination was found in -13.79 bars solutions. Spore germination percentage for F. solani isolates was maximal at 48 h. and -13.79 bars with 21.33% spore germination, 16% higher than germination in distilled water. F. equiseti shows the maximum germination percentage in -144.54 bars solution in 24 h time with 12.36% germination. These results did not agree with those obtained in the viability test where maximum germination was found in distilled water. The viability analysis showed the great capacity of F. verticilloides strains to form viable colonies, even in such extreme conditions as -144,54 bars after 24 h F. proliferatum colony formation was prevented in the range of -70.37 bars. These results show the clear affectation of water potential to conidia germination of Fusaria. The ability of certain species of Fusarium to develop a saprophytic life in the salt water of the Mediterraneam Sea could be certain. Successful germination, even under high salty media conditions, suggests taht Fusarium spp. could have a competitive advantage over other soil fungi in crops irrigated with saline water. In the specific case of F. solani, water potential of -13.79 bars affected germination positively. It could indicate that F. solani has an special physiological mechanism of survival in low water potential environments.