Suchergebnisse

We investigated the identity and genetic diversity of more than 100 isolates belonging to Phyllosticta (teleomorph Guignardia), with particular emphasis on Phyllosticta citricarpa and Guignardia mangiferae s.l. occurring on Citrus. Phyllosticta citricarpa is the causal agent of Citrus Black Spot and is subject to phytosanitary legislation in the EU. This species is frequently confused with a taxon generally referred to as G. mangiferae, the presumed teleomorph of P. capitalensis, which is a non-pathogenic endophyte, commonly isolated from citrus leaves and fruits and a wide range of other hosts. DNA sequence analysis of the nrDNA internal transcribed spacer region (ITS1, 5.8S nrDNA, ITS2) and partial translation elongation factor 1-alpha (TEF1), actin and glyceraldehyde-3-phosphate dehydrogenase (GPDH) genes resolved nine clades correlating to seven known, and two apparently undescribed species. Phyllosticta citribraziliensis is newly described as an endophytic species occurring on Citrus in Brazil. An epitype is designated for P. citricarpa from material newly collected in Australia, which is distinct from P. citriasiana, presently only known on C. maxima from Asia. Phyllosticta bifrenariae is newly described for a species causing leaf and bulb spots on Bifrenaria harrisoniae (Orchidaceae) in Brazil. It is morphologically distinct from P. capitalensis, which was originally described from Stanhopea (Orchidaceae) in Brazil; an epitype is designated here. Guignardia mangiferae, which was originally described from Mangifera indica (Anacardiaceae) in India, is distinguished from the non-pathogenic endophyte, P. brazilianiae sp. nov., which is common on M. indica in Brazil. Furthermore, a combined phylogenetic tree revealed the P. capitalensis s.l. clade to be genetically distinct from the reference isolate of G. mangiferae. Several names are available for this clade, the oldest being P. capitalensis. These results suggest that endophytic, non-pathogenic isolates occurring on a wide host range would be more correctly referred to as P. capitalensis. However, more genes need to be analysed to fully resolve the morphological variation still observed within this clade. ; We investigated the identity and genetic diversity of more than 100 isolates belonging to Phyllosticta (teleomorph Guignardia), with particular emphasis on Phyllosticta citricarpa and Guignardia mangiferae s.l. occurring on Citrus. Phyllosticta citricarpa is the causal agent of Citrus Black Spot and is subject to phytosanitary legislation in the EU. This species is frequently confused with a taxon generally referred to as G. mangiferae, the presumed teleomorph of P. capitalensis, which is a non-pathogenic endophyte, commonly isolated from citrus leaves and fruits and a wide range of other hosts. DNA sequence analysis of the nrDNA internal transcribed spacer region (ITS1, 5.8S nrDNA, ITS2) and partial translation elongation factor 1-alpha (TEF1), actin and glyceraldehyde-3-phosphate dehydrogenase (GPDH) genes resolved nine clades correlating to seven known, and two apparently undescribed species. Phyllosticta citribraziliensis is newly described as an endophytic species occurring on Citrus in Brazil. An epitype is designated for P. citricarpa from material newly collected in Australia, which is distinct from P. citriasiana, presently only known on C. maxima from Asia. Phyllosticta bifrenariae is newly described for a species causing leaf and bulb spots on Bifrenaria harrisoniae (Orchidaceae) in Brazil. It is morphologically distinct from P. capitalensis, which was originally described from Stanhopea (Orchidaceae) in Brazil; an epitype is designated here. Guignardia mangiferae, which was originally described from Mangifera indica (Anacardiaceae) in India, is distinguished from the non-pathogenic endophyte, P. brazilianiae sp. nov., which is common on M. indica in Brazil. Furthermore, a combined phylogenetic tree revealed the P. capitalensis s.l. clade to be genetically distinct from the reference isolate of G. mangiferae. Several names are available for this clade, the oldest being P. capitalensis. These results suggest that endophytic, non-pathogenic isolates occurring on a wide host range would be more correctly referred to as P. capitalensis. However, more genes need to be analysed to fully resolve the morphological variation still observed within this clade.

Abstract
The literature review focuses on the effect of forest soil properties on infection of coniferous trees and stumps by Heterobasidion spores and further growth of mycelium from tree to tree. Spread of the fungus is greater in alkaline soil. Forest plantations on former agricultural lands have an increased risk of infection, due to lack of antagonistic soil microorganisms. In Latvia, severe infection of spruce stands by Heterobasidion root rot has been observed on peat soils.

Fusarium root rot in a common pathogen of sweet potato, with a wide range of host plants. In the current study six new isolates of Fusarium sp., collected from infected sweet potato plants, along with a reference strain of Fusarium oxysporum, had their growth behavior studied in various pH and saline conditions. In vitro studies showed that salinity higher than 6% NaCl in the PDA substrate significantly reduces the fungal growth. At 12% NaCl, four of seven strains revealed complete mycelia inhibition. However, for the other two isolates, and for the reference strain, 12% salinity only reduced the growth with 77.4%. Regarding the fungal growth at different pH values, it was noticed that tested fusaria were not perturbed at up to 8.5 alkalinity. However, at a pH of 4.5, the growth rate was reduced, although the growth differences were diminished during prolonged incubation time. Considering the in vitro results, saline water should be tested as preventive immersion treatment on the sweet potato sprouts, before their planting, in order to reduce the incidence of Fusarium infection.

Sugar beet is extensively grown in Konya province of Turkey and about one third of production of Turkey is obtained from this region. Recently root rots have been observed at all the growth stages of sugar beet especially at later stages near the harvest. During 2015–2017 growing years, 866 fields were visited and diseased samples having root rot symptoms were collected. Various root rot pathogens were isolated from 691 fields; Rhizoctonia solani being the most common (15% of the fields) followed by Fusarium oxysporum, F. solani, Phoma betae, Aphanomyces cochlioides and Pythium spp. Apart from these pathogens, Fusarium culmorum, F. equiseti, F. sambucinum, F. verticillatum, unidentified Fusarium spp., Macrophomina phaseolina and Phytophthora spp. were also determined. All the fungal pathogens were isolated from both of the sugar beet growing stages of 0–12 BBCH and 31–49 BBCH, some of them being high ratios at the late stages. Some isolates of A. cochlioides, P. betae, Pythium spp., Phytophthora spp., and R. solani were highly aggressive when tested by a soil inoculum layer technique. Effects of twelve fungicides, in sixteen different combination and rate, on the most virulant and common four pathogens, A. cochlioides P. betae, Py. ultimum var. ultimum, Rhizoctonia solani, were investigated by the same technique. None of the fungicide mixes inhibited all four pathogens. Thiram + metalaxyl + hymexazol + pyraclastrobin mix sufficiently prevented disease development of the first three pathogens but not R. solani.

Spain is the highest avocado producer country in the European Union. White root rot caused by the ascomycete Rosellinia necatrix is one of the most important diseases of this crop in the southern coastal area of Iberian Peninsula due to its difficult management. We studied different integrated control methods of this disease and its possible combinations. First, we detected and identified mycoviruses in R. necatrix isolates and their relation with the hypovirulence factor as a future virocontrol method. As well we obtained novel antagonistic fungi (Entoleuca sp. isolates) in which we analyzed mycoviruses presence, their growth under different temperatures, their vegetative compatibility groups and their biocontrol effect against the disease. We improved a qPCR technique for the detection and quantification of this pathogen from avocado orchards soil samples, thus we used this novel technique to assess the inoculum quantity of R. necatrix in the soil after the treatments of the fungicide fluazinam that we carried out in commercial orchards. Furthermore we performed an integrated control of this disease combining low concentrations of fluazinam with antagonist organisms such as rhizobacteria strains and/or non-pathogenic R. necatrix isolates. In this work we have studied all possible chemical and biological control methods against this disease nowadays, even some of them can be applied directly in field conditions. ; España es el mayor productor de aguacate en la Unión Europea. La podredumbre blanca radicular causada por el hongo ascomiceto Rosellinia necatrix Prill. es una de las enfermedades más importantes de este cultivo en la zona costera sur de la península Ibérica por su difícil manejo. Estudiamos diferentes métodos de control integrado de esta enfermedad y sus posibles combinaciones. Primero detectamos e identificamos micovirus infectando aislados de R. necatrix y su relación con el factor de hipovirulencia como un futuro método de virocontrol. También obtuvimos novedosos hongos antagonistas (aislados de Entoleuca sp.) en los que analizamos la presencia de micovirus, su crecimiento a diferentes temperaturas, sus grupos de compatibilidad vegetativa y su efecto de biocontrol contra la enfermedad. Mejoramos una técnica de qPCR para la detección y cuantificación de este patógeno en suelo a partir de muestras procedentes de fincas de aguacate, que fue utilizada como novedosa técnica para evaluar la cantidad de inóculo de R. necatrix presente en el suelo tras los tratamientos del fungicida fluazinam que realizamos en fincas comerciales para el control de la enfermedad. Además realizamos un control integrado de esta, combinando dosis bajas de fluazinam con organismos antagonistas como cepas de rizobacterias y/o aislados no patogénicos de R. necatrix. En este trabajo se han estudiado todos los posibles métodos de controles biológicos y químicos utilizables contra esta enfermedad hoy en día, pudiendo ser alguno de ellos de aplicación inmediata en campo.

Tesis Doctoral.-- Universidad de Córdoba. Programa de Doctorado: Ingeniería Agraria, Agroalimentaria, Forestal y de Desarrollo Rural Sostenible. ; [EN] Spain is the highest avocado producer country in the European Union. White root rot caused by the ascomycete Rosellinia necatrix is one of the most important diseases of this crop in the southern coastal area of Iberian Peninsula due to its difficult management. We studied different integrated control methods of this disease and its possible combinations. First, we detected and identified mycoviruses in R. necatrix isolates and their relation with the hypovirulence factor as a future virocontrol method. As well we obtained novel antagonistic fungi (Entoleuca sp. isolates) in which we analyzed mycoviruses presence, their growth under different temperatures, their vegetative compatibility groups and their biocontrol effect against the disease. We improved a qPCR technique for the detection and quantification of this pathogen from avocado orchards soil samples, thus we used this novel technique to assess the inoculum quantity of R. necatrix in the soil after the treatments of the fungicide fluazinam that we carried out in commercial orchards. Furthermore we performed an integrated control of this disease combining low concentrations of fluazinam with antagonist organisms such as rhizobacteria strains and/or non-pathogenic R. necatrix isolates. In this work we have studied all possible chemical and biological control methods against this disease nowadays, even some of them can be applied directly in field conditions. ; [ES] España es el mayor productor de aguacate en la Unión Europea. La podredumbre blanca radicular causada por el hongo ascomiceto Rosellinia necatrix Prill. es una de las enfermedades más importantes de este cultivo en la zona costera sur de la península Ibérica por su difícil manejo. Estudiamos diferentes métodos de control integrado de esta enfermedad y sus posibles combinaciones. Primero detectamos e identificamos micovirus infectando aislados de R. necatrix y su relación con el factor de hipovirulencia como un futuro método de virocontrol. También obtuvimos novedosos hongos antagonistas (aislados de Entoleuca sp.) en los que analizamos la presencia de micovirus, su crecimiento a diferentes temperaturas, sus grupos de compatibilidad vegetativa y su efecto de biocontrol contra la enfermedad. Mejoramos una técnica de qPCR para la detección y cuantificación de este patógeno en suelo a partir de muestras procedentes de fincas de aguacate, que fue utilizada como novedosa técnica para evaluar la cantidad de inóculo de R. necatrix presente en el suelo tras los tratamientos del fungicida fluazinam que realizamos en fincas comerciales para el control de la enfermedad. Además realizamos un control integrado de esta, combinando dosis bajas de fluazinam con organismos antagonistas como cepas de rizobacterias y/o aislados no patogénicos de R. necatrix. En este trabajo se han estudiado todos los posibles métodos de controles biológicos y químicos utilizables contra esta enfermedad hoy en día, pudiendo ser alguno de ellos de aplicación inmediata en campo.

Forest decline is nowadays a major challenge to management and sustainability of natural ecosystems worldwide. This syndrome is a multifactorial disease influenced by several biotic and abiotic agents such as alien invasive pathogens, changes in land use and management policies, population dynamics driven by economic and politic changes, and climatic perturbations. All these factors changing due to anthropogenic influence, together with others, conformed the so-called global change. Since the 1990's decade, the oak decline has been identified as one of the most important ecological problems in Europe, affecting deciduous and evergreen Quercus species from the continental forests on Central and North Europe, to temperate forests of the Mediterranean basin. In the case of Iberian Peninsula, holm oak (Quercus ilex L.) and cork oak (Quercus suber L.) decline has been detected since the 1980's decade. These two species covered most of the forest surface of the south and central part of the Iberian Peninsula, mainly through "dehesas" and "montados" formations. This area is considered to be one of the worst affected regions in the world by climate change, worsening the effects and the consequences of oak decline in "dehesas". "Dehesas" are Mediterranean savanah-like ecosystems, which provide several economic yields and ecological services. In turn, the holm oak is the most representative tree in the Iberian Peninsula, and the main species conforming the tree layer on the Spanish "dehesas". The loss of this tree layer is a major ecological and economical constraint. The holm oak decline is mainly associated to the action of soil-borne pathogens, especially Phytophtora cinnamomi. Despite the influence of other factors in the decline, there is a strong association between root rot caused by oomycetes and the death of trees. Phytophtora cinnamomi is an aggressive alien plant pathogen widely widespread worldwide, which has been associated with the disease, die-off and death in a large list of different plant hosts. It is able to change trophic relationships with their hosts, becaming biotroph in asymptomatic hosts and hemibiotroph or necrotroph in susceptible hosts. It is considered that holm oak is the most susceptible Quercus sp. to the action of this pathogen. Additionally, other Phytophthora spp. and Pythium spp. have been recorded associated with the holm oak decline in Spain, Portugal, Italy and France. Many scientific efforts have focused to study this important hostpathogen system, obtaining great results and increasing the knowledge of the causes and effects of the interaction, improving management techniques to limit the spread and the symptoms. However, most of the reviewed works are based on empirical approaches, being the underlying mechanisms regulating the interaction between both species mostly unknown. This PhD Thesis covers part of this lack of basic knowledge, focusing on the host-pathogen interaction at histological and physiological level, and exploring the influence of the soil biota in the severity of the disease symptoms. For this purpose, the work was structured in seven chapters. Chapter 1 provides the framework in which the present PhD Thesis has been developed, and the general and specific objectives. Chapter 2 presents the methodology developed to evaluate the colonization and infection of Phytophthora cinnamomi in Quercus ilex seedling through the semi-automated quantification of pathogen structures present in histological sections of fine roots. A workflow was tuned-up testing different fixing solutions, embedding substances and staining methods, and the results allowed the clear differentiation of pathogen structures from host tissues. Furthermore, different indices based on structure location, host tissue classification and specificity of pathogen structures were evaluated to find the easiest and statistically robust indices that are able to explain the progress of the oomycete into the root. In chapter 3, inoculation experiments in growth chamber were carried out to describe the pathogenesis of the Quercus ilex-Phytophthora cinnamomi interaction. Longitudinal sections were analysed for epidermal, cortex, parenchymatous tissue of central cylinder and vascular tissue after 1, 3, 7 and 14 days after inoculation. Total oomycete structures area, intracellular structures area, extracellular structures area, and specific structures area of the pathogen were quantified. The analysis of these data results in the description of the colonization/infection cycle of the pathogen, classified in three different stages related with their trophic behaviour. Moreover, histological changes of the root tissues as a result of the presence of defence responses and the action of the pathogen were described. In Chapter 4, the differential responses of holm oak seedlings to the inoculation with P. cinnamomi, the acute drought and combination of both stressors were assessed. Six-months old seedlings were inoculated and mock-inoculated, and half of each inoculation treatment plans were subjected to acute drought meanwhile the others were well irrigated. Photosynthesis, stomatal conductance and fluorescence were measured weekly, and total biomass and biomass allocation parameters were quantified at the end of the experiment. The resulting data showed differences in the response of seedlings to drought and inoculation, and the influence of the additive effect of both stressors in the seedlings die-off. In Chapter 5, soil samples of "dehesas" were collected and total DNA was extracted and analysed through metabarcoding techniques, to evaluate the specific composition and diversity of the fungal and oomycete communities, and to study their relationship with the disease symptoms. The fungal community included a wide range of pathogens and abundance of ectomycorrhizal key taxa. Phytophthora spp. dominated the oomycete community, but the species related to root rot did not appear as the most abundant, nor were they related directly to defoliation levels. A particular Operational Taxonomic Unit (OTU) belonging to the genus Trichoderma was strongly correlated with the scarcity of pathogenic Phytophthora spp. The differences in defoliation were related to changes in the functionality of soil microbiota and diversity levels of pathogenic species. Chapter 6 presents the general discussion of the Thesis, including some aspects limiting the results of the works carried out, ad new work lines deriving from this Thesis, and finally Chapter 7 contains the conclusions of the work. Changes in roots as a consequence of P. cinnamomi inoculation, including defence responses, and the differential response identified with pathogen colonization/inoculation, leads to new insights about the causes of tree death. Holm oak responds to the attack of the pathogen, and their physiological changes differ from the ones caused by water stress, allowing the recovery of plants if no additional stress is present. Moreover, the study of soil microbiome in declined "dehesas" showed the influence of the microbial diversity in the health status of trees, and also presented new species of oomycetes and fungi that must be considered in the management of holm oak decline in Andalusian "dehesas". ; El decaimiento forestal es hoy en día uno de los mayores desafíos para el manejo y la sostenibilidad de los ecosistemas naturales en todo el mundo. Dicho síndrome es una enfermedad multifactorial en la que intervienen diversos agentes bióticos y abióticos como los patógenos invasores, los cambios en los usos del territorio y las políticas de recursos, o las perturbaciones climáticas. El cambio producido en todos estos factores debido a la influencia del hombre entre otros motivos es lo que se ha dado en llamar cambio global. Desde la década de los 90 del siglo XX, el decaimiento de los robles se ha identificado como uno de los problemas ecológicos más relevantes en Europa, afectando a masas de Quercus caducifolios y perennifolios desde los bosques continentales de Centro Europa y Norte Europa, hasta los bosques templados de la cuenca mediterránea. En el caso de la Península Ibérica, el decaimiento de la encina (Quercus ilex L.) y el alcornoque (Quercus suber L.) se identificó en los años 80 del siglo XX. Estas dos especies cubren la mayor parte de la superficie forestal del sur y centro de la Península Ibérica, principalmente formando sistemas de dehesa y "montados". Dicha área geográfica está considerada como una de las regiones a nivel mundial que se verán peor afectadas por el cambio climático, lo que agravaría las consecuencias y los efectos del decaimiento de la encina en las dehesas. Las dehesas son ecosistemas mediterráneos semejantes a la sabana, que proveen de diversos beneficios económicos y servicios ambientales. Por su parte, la encina es el árbol más representativo de la Península Ibérica, y la especie principal del estrato arbóreo de las dehesas. La pérdida de este estrato es un problema ecológico y económico de gran relevancia. El decaimiento de la encina está asociado principalmente a la acción de patógenos de suelo, especialmente Phytophthora cinnamomi. Sin olvidar la influencia de otros factores en el síndrome, existe una fuerte asociación entre la podredumbre radicular causada por los oomicetos y la muerte del arbolado. Phytophthora cinnamomi es un patógeno invasor muy agresivo, ampliamente distribuido por todo el mundo, que ha sido asociado con la enfermedad, la decadencia y la mortalidad de una larga lista de diferentes especies vegetales. Es una especie capaz de cambiar su relación trófica con el huésped, comportándose como un organismo biótrofo en huéspedes asintomáticos, y como hemibiótrofo ó necrótrofo en huéspedes susceptibles. Se considera que la encina es la especie del género Quercus más susceptible a la acción del patógeno. De forma adicional, otras especies de los géneros Phytophthora y Pythium se han encontrado asociadas con el decaimiento de la encina en España, Portugal, Italia y Francia. Para estudiar este sistema patógeno-huésped se han llevado a cabo grandes esfuerzos científicos, que han obtenido resultados muy meritorios y han incrementado el conocimiento de las causas y los efectos de la interacción, mejorando las técnicas de gestión para limitar la dispersión y los síntomas del decaimiento. Sin embargo, la mayoría de los trabajos revisados se basaron en aproximaciones empíricas, desconociéndose gran parte de los mecanismos subyacentes que controlan la interacción entre las dos especies. Esta Tesis cubre parte de esta falta de conocimiento básico, centrándose en la interacción entre el huésped y el patógeno a nivel histológico y fisiológico, así como explorando la influencia de la biota del suelo en la severidad de los síntomas de la enfermedad. Para dicho propósito, el trabajo se estructuró en 7 capítulos. El Capítulo 1 proporciona el marco teórico en el que se desarrolla esta Tesis Doctoral, así como los objetivos generales y específicos. El Capítulo 2 muestra la metodología desarrollada para evaluar la colonización e infección de Phytophthora cinnamomi en plántulas de Quercus ilex a través de la cuantificación semiautomática de las estructuras del patógeno presentes en secciones histológicas de raíces finas. El flujo de trabajo fue puesto a punto probando diferentes soluciones de fijación, sustancias de inclusión y métodos de tinción, y los resultados permitieron la diferenciación clara de las estructuras del patógeno y de los tejidos del huésped. Además, distintos índices basados en la localización y especificidad de las estructuras del patógeno y en el tejido del huésped, se evaluaron con el fin de buscar la manera más sencilla y estadísticamente robusta de explicar el progreso del oomiceto en la raíz a través de índices. En el capítulo 3, se llevaron a cabo experimentos en cámara de crecimiento para describir la patogénesis de la interacción entre P. cinnamomi y Q. ilex. Se analizaron secciones longitudinales de epidermis, córtex, tejido parenquimático del cilindro central y tejido vascular, a los 1, 3, 7 y 14 días después de la inoculación. Se cuantificó el área total de estructuras, estructuras intracelulares, estructuras extracelulares y estructuras específicas del patógeno. El análisis de estos datos proporcionó una descripción del ciclo de colonización/infección del patógeno, clasificada en tres etapas diferentes relacionadas con su comportamiento trófico. Asimismo se describieron los cambios histológicos resultantes de la presencia del patógeno o de las respuestas desencadenadas por la planta. En el capítulo 4 se analizó la respuesta diferencial de plántulas de encina ante la inoculación con P. cinnamomi, ante la sequía severa y ante ambos estreses combinados. Plántulas de seis meses de edad fueron inoculados y sometidos a falsa inoculación, y la mitad de cada uno de estos tratamientos fue sometida a sequía severa, mientras que el resto fue regada de manera óptima. Semanalmente se midieron los valores de fotosíntesis, conductancia estomática y fluorescencia, y la biomasa total así como la compartimentación de la biomasa fueron cuantificadas al final del experimento. Los datos resultantes mostraron la existencia de diferencias en la respuesta de las plántulas ante la sequía y la inoculación, así como el efecto aditivo de ambos estreses en la muerte de las plántulas. En el Capítulo 5 se colectaron muestras de suelo de dehesas y se extrajo el ADN total, que se analizó a través de técnicas de metabarcoding, con el fin de evaluar la composición específica y la diversidad de las comunidades fúngica y de oomicetos, y para estudiar sus relaciones con los síntomas de la enfermedad. La comunidad fúngica presentó una gran variedad de patógenos y abundancia de taxones clave de ectomicorrizas. Phytophthora spp. apareció como el taxón dominante dentro de la comunidad de oomicetos, pero las principales especies relacionadas con la podredumbre radicular no fueron las más abundantes, ni presentaron relación directa con los niveles de defoliación. Una unidad taxonómica operacional (OTU) particular, perteneciente al género Trichoderma, presentó correlaciones significativas con la escasez de especies patógenas de Phytophthora spp. Las diferencias en defoliación se correlacionaron con cambios en la funcionalidad de la microbiota del suelo y con los niveles de diversidad de las especies patógenas. El Capítulo 6 presenta la discusión general de la Tesis, incluyendo algunos aspectos que limitan los resultados de los trabajos realizados, y nuevas líneas de trabajo que se derivan de esta Tesis, y finalmente, el Capítulo 7 contiene las conclusiones del trabajo. Los cambios que se producen en la raíz a consecuencia de la inoculación con P. cinnamomi, incluyendo las respuestas defensivas, así como la respuesta diferencial identificada con la colonización/infección, conducen a nuevas apreciaciones sobre la causa de la muerte del arbolado. La encina responde al ataque del patógeno, presentando variaciones en la fisiología diferentes de las causadas por el estrés hídrico, las cuales permiten la recuperación de las plantas si no se superpone un estrés adicional a la inoculación. Adicionalmente, el estudio del microbioma del suelo en dehesas con decaimiento del encinar mostró la influencia de la diversidad microbiana en el estado sanitario del arbolado, así como mostró nuevas especies de oomicetos y hongos que deben tenerse en consideración en el manejo del decaimiento de las dehesas de encina en Andalucía.