Tick pathogenicity, thermal tolerance and virus infection in Tolypocladium cylindrosporum

10 páginas, 5 tablas, 5 figurasTolypocladium cylindrosporum is a fungus which has been isolated from soil, from asymptomatic plants as an endophyte, and has been shown to be pathogenic to several species of arthropods. The objective of the present work was to study a collection of T. cylindrosporum strains in order to evaluate the characteristics of this fungus as a bioacaricide. The pathogenicity of five different strains of T. cylindrosporum was tested against two tick species, Ornithodoros erraticus and Ornithodoros moubata. Both tick species were susceptible to all the fungal strains. Mortality was greater for O. erraticus, and differed among the five developmental stages of the ticks tested, and among the fungal treatments. Mean mortality rates were close to 60% for O. erraticus, similar to those reported for other entomopathogenic fungi used for this purpose. The responses of eleven different strains of the fungus to 22ºC and 30ºC were also studied. Significant differences in temperature tolerance occurred among the strains, and growth inhibition was observed at 30ºC. Several mycoviruses were found infecting five of the eleven strains. However, no clear relationship was found between the presence of viruses and fungal growth or pathogenicity.This work was financed with research grants AGL2008-01159AGR, awarded by the Spanish Government,and CSI07A08, awarded by the Regional Government of Castilla y León (Spain).Peer reviewe

Potencial del hongo endofíto epichloë festucae para la mejora del cesped.

{ESP} Algunas especies de gramíneas forrajeras o cespitosas de importancia económica como Festuca arundinacea, Festuca rubra y Lolium perenne son huéspedes de hongos endofíticos de los géneros Neotyphodiumy Epichloë. Estos hongos tienen la capacidad de infectar las plantas sin inducir síntomas, se transmiten eficientemente por semilla y producen alcaloides tóxicos que pueden afectar a herbívoros que consumen plantas infectadas. Festuca rubra es una gramínea que se cultiva para formar céspedes deportivos y ornamentales. En España lamayoría de las plantas de Festuca rubra en poblaciones naturales están infectadas por el hongo Epichloë festucae. Varios estudios han mostrado que la asociación con Epichloë festucae es beneficiosa para las plantas, cuya tolerancia a situaciones de estrés causado por factores bióticos (herbívoros, hongos patógenos) o abióticos (exceso o deficiencia de nutrientes, sequía) esmayor al estar asociadas a Epichloë festucae. Esta especie fúngica tiene un buen potencial como factor útil para la mejora de variedades de Festuca rubra destinadas a céspedes. El hongo posee características que facilitan la producción industrial de variedades de F. rubra infectadas. Estas variedades podrían ser cultivadas con un coste económico ymedioambiental inferior al de las variedades no infectadas.{ENG} Some economically important turf and forage grasses are hosts of Epichloë and Neotyphodium fungal endophytes. These fungi can asymptomatically infect their plant hosts, are vertically transmitted by seed, and produce toxic alkaloids which are toxic to herbivores. Festuca rubra is cultivated as an sports and ornamental turfgrass. In Spain, about 70% of the plants in wild populations are infected by Epichloë festucae. Several studies have shown that the association with this fungal endophyte is beneficial for the plants whose tolerance to biotic (herbivore and fungal pathogen attack) and abiotic stress (nutrient deficiency or excess, drought) is greater when infected. Epichloë festucae has an important potential as an useful factor for turfgrass cultivar improvement. Large scale production of infected seeds is feasible because of several characteristics of the fungal life cycle. Endophyte infected cultivars are likely to perform better than non infected ones in situations of low maintenance lawns, and to require less economic input for theirmaintenance

The symbiosis with the fungal endophyte Epichloe festucae affects the phosphorus content of Festuca rubra.

XLIV Reunión Científica de la Sociedad Española para el Estudio de los Pastos. 10-14 de mayo de 2004, Salamanca (España){ESP}En los pastos de dehesas de Salamanca cerca del 70%. de las plantas de Festuca rubra están permanentemente infectadas por el hongo endofítico Epichloe festucae. Se realizó un experimento de campo en el cual se comparó el contenido de fósforo en cinco líneas de F. rubra, cada una de las cuales estaba compuesta por una versión endofítica y otra no infectada. En plantas en estado vegetativo se detectó un aumento estadísticamente significativo del contenido de P en las plantas infectadas de todas las líneas. Este efecto también se observó en plantas en estado reproductivo, pero en este caso no hubo diferencias tan pronunciadas debidas a la infección. También se ha observado una tendencia a una mayor producción de biomasa por parte de las plantas infectadas por Epichloe festucae.{ENG}In the dehesa grasslands of the province of Salamanca, close to 70% of the Festuca rubra plants are infected by the fungal endophyte Epichloe festucae. An experiment was done to compare the phosphorus content in five half-sib families of Festuca rubra. Each family was composed by an endophyte infected and an endophyte free version of the half-sib plants. In plants in vegetative state, the P content was significantly higher for infected plants in analyses conducted at two different years. During the reproductive state of the plants, a non-significant similar trend was observed. Biomass production was also higherin infected that in non-infected plants.Este trabajo se ha financiado con el proyecto AGL 2002-02766 del Plan Nacional 1 +D. Agradecemos la colaboración de María Romo, Yolanda Arnaiz y Carlos Estévez

Lucha frente a la Varroosis en colmenas Layens

111 páginas, 89 figuras, 17 tablas . -- Con la colaboración de: Mª Sonia Rodríguez Cruz, José Manuel Ordax de Castro, Raquel Arroyo Palomares, Yolanda Picó García, Juan Manuel Andrés Sánchez, Francisco Javier Fernández Santiago, Miguel Ángel Santos Oliva, Fernando Sánchez-Montejo Álvarez y Aurelio Pérez Sánchez.Actualmente la varroosis es el principal problema de la apicultura a nivel sanitario, tratándose de la enfermedad de las colonias de abejas más importante, y la única que obliga a realizar un tratamiento sistemático de la colmena para que los efectos del parásito no influyan negativamente en el rendimiento o incluso la viabilidad de la misma. Como consecuencia de la importancia de la actividad apícola en Castilla y León y dada la problemática sanitaria a la que se enfrenta el sector apícola, se justifica perfectamente la ejecución de un estudio de lucha frente a la varroosis, realizado en colmena Layens, colmena utilizada por el 80% de los apicultores españoles y mayoritaria en Salamanca. El estudio se ha ejecutado en esta provincia, que dispone del mayor número de apicultores profesionales y de colmenas y persigue que los resultados permitan a los apicultores mejorar la lucha contra esta parasitosis en sus explotaciones apícolas y mantener su viabilidad.Diputación de Salamanca. Organismo Autónomo de Empleo y Desarrollo Rural.N

Hongos endófitos epichloë en pastos de la Península Ibérica

13 páginas, 11 figuras, 3 tablasEpichloë fungal endophytes infect asymptomatically several grass species. Infected plants produce alkaloids toxic to herbivores and are more resistant to several biotic and abiotic stress factors. In this paper, we review the incidence of Epichloë endophytes in grasses from pastures of the Iberian Peninsula and their alkaloid contents. In addition, we address the main effects of Epichloë in the host grass Festuca rubra (increase in nutrient content, effect on germination, effect on allelopathic potential and pathogen resistance).Los hongos endofíticos del género Epichloë infectan de forma asintomática numerosas especies de gramíneas. Las plantas infectadas por estos hongos contienen alcaloides tóxicos para herbívoros, y además son más resistentes a diversos factores de estrés biótico y abiótico. Este trabajo es una revisión sobre la incidencia de endófitos Epichloë y producción de alcaloides en gramíneas de pastos de la península Ibérica. Además, se consideran los principales efectos que produce Epichloë en Festuca rubra como gramínea hospedadora (incremento del contenido de nutrientes, efecto en la germinación, efecto en el potencial alelopático y resistencia a patógenos).Este trabajo se ha realizado en el marco de los proyectos del Plan Nacional I+D+i (AGL2011-22783) y del Plan Regional de la Junta de Castilla y León (CSI231U14).Peer reviewe

Epichloë Endophyte-Promoted Seed Pathogen Increases Host Grass Resistance Against Insect Herbivory

Plants host taxonomically and functionally complex communities of microbes. However, ecological studies on plant–microbe interactions rarely address the role of multiple co-occurring plant-associated microbes. Here, we contend that plant-associated microbes interact with each other and can have joint consequences for higher trophic levels. In this study we recorded the occurrence of the plant seed pathogenic fungus Claviceps purpurea and aphids (Sitobion sp.) on an established field experiment with red fescue (Festuca rubra) plants symbiotic to a seed transmitted endophytic fungus Epichloë festucae (E+) or non-symbiotic (E−). Both fungi are known to produce animal-toxic alkaloids. The study was conducted in a semi-natural setting, where E+ and E− plants from different origins (Spain and Northern Finland) were planted in a randomized design in a fenced common garden at Kevo Subarctic Research Station in Northern Finland. The results reveal that 45 % of E+ plants were infected with Claviceps compared to 31 % of E- plants. Uninfected plants had 4.5 times more aphids than Claviceps infected plants. By contrast, aphid infestation was unaffected by Epichloë symbiosis. Claviceps alkaloid concentrations correlated with a decrease in aphid numbers, which indicates their insect deterring features. These results show that plant mutualistic fungi can increase the infection probability of a pathogenic fungus, which then becomes beneficial to the plant by controlling herbivorous insects. Our study highlights the complexity and context dependency of species–species and multi-trophic interactions, thus challenging the labeling of species as plant mutualists or pathogens.</p

Genetic Diversity of the Symbiotic Fungus Epichloë festucae in Naturally Occurring Host Grass Populations

Epichloë festucae is a common symbiont of the perennial and widely distributed cool season grass, Festuca rubra. The symbiosis is highly integrated involving systemic growth of the fungus throughout above-ground host parts and vertical transmission from plant to its offspring via host seeds. However, the nature of symbiosis is labile ranging from antagonistic to mutualistic depending on prevailing selection pressures. Both the loss of fungus in the maternal host lineage and horizontal transmission through sexual spores within the host population may partly explain the detected variation in symbiosis in wild grass populations. Epichloë species are commonly considered as pathogens when they produce sexual spores and partly castrate their host plant. This is the pathogenic end of the continuum from antagonistic to mutualistic interactions. Here we examined the population genetic structure of E. festucae to reveal the gene flow, importance of reproduction modes, and alkaloid potential of the symbiotic fungus in Europe. Epichloë-species are highly dependent on the host in survival and reproduction whilst benefits to the host are largely linked to defensive mutualism attributable to fungal-origin bioactive alkaloids that negatively affect vertebrate and/or invertebrate herbivores. We detected decreased genetic diversity in previously glaciated areas compared to non-glaciated regions during the last glacial maximum period and found three major genetic clusters in E. festucae populations: southern, northeastern and northwestern Europe. Sexual reproduction may have a higher role than expected in Spanish E. festucae populations due to the predominance of unique genotypes and presence of both mating types in the region. In contrast, asexual reproduction via host seeds predominates in the Faroe Island and Finland in northern Europe due to the presence of biased mating-type ratios and large dominant genotypes in the E. festucae populations within the region. A substantially larger variation of alkaloid genotypes was observed in the fungal populations than expected, although the variability of the alkaloid genotypes within populations is considerably lower in northern than Spanish populations in southern Europe. E. festucae populations consist of different combinations of alkaloid classes from the gene clusters of ergot alkaloid and indole-terpenes, and from pyrrolopyrazine alkaloid gene. We suggest that the postglacial distribution history of the host grass, prevailing reproduction strategies of E. festucae, and local selection pressures likely explain a large part of the genetic variation observed in fungal populations among geographic regions. The identified alkaloid genotypes can be used by turfgrass breeders to improve resistance against herbivores in red fescue varieties and to develop new sustainable cultivars in Europe.Peer reviewe