Patologías víricas en Ulmus laevis en el este de Alemania

Virus-like leaf symptoms and dieback were observed on elm trees in a public park near Potsdam. Infection with Cherry leaf roll virus (CLRV), Elm mottle virus (EMV), Arabis mosaic virus (ArMV) and Tobacco ringspot virus (TRSV), well known viruses to infected elm trees was excluded by bioassays and serological tests. Poty- or carlavirus- like flexible particles of approximately 750 nm in length were isolated repeatedly from diseased elms. The particles were transmissible to diverse Chenopodium species, a herbaceous indicator. The virus was not a member of the Potyviridae family, based on an ELISA and an RT-PCR assay using a potyvirus genus-specific broad-spectrum polyclonal antibody and family-specific primers, respectively. Also no potyvirus-like pinwheel inclusions were found in leaf cells of infected indicator plants in electron microscopic studies. Further molecular characterization of these virus isolates is under way.En olmos situados en un parque cercano a Postdam, se ha observado la presencia de síntomas foliares similares a los producidos por virus. Mediante bioensayos y pruebas serológicas se descartó la presencia de infecciones originados por el virus del enrollamiento de la hoja del cerezo (CLRV), el virus del moteado del olmo (EMV), el virus del mosaico de Arabis (ArMV) y el virus del anillamiento del tabaco (TRSV), todos ellos bien conocidos por afectar a los olmos. Repetidamente se aisló, en olmos enfermos, partículas flexibles de aproximadamente 750 mm de longitud similares a las de Potyvirus y Carlavirus. Las partículas fueron transmisibles a diversas especies de Chenopodium, un indicador herbáceo. Según una prueba ELISA y un ensayo RT-PCR en que se usaron, respectivamente, un anticuerpo policlonal específico de género de Potyvirus de amplio espectro, y cebadores específicos de la familia, el virus no es miembro de la familia Potyviridae. Tampoco se ha encontrado, en estudios mediante microscopía electrónica, inclusiones del tipo potyvirus en las células de las hojas de plantas indicadoras infectadas. En la actualidad se están realizando nuevas caracterizaciones moleculares de estos aislamientos víricos

Parthenium weed (Parthenium hysterophorus L.) research in Ethiopia: Investigation of pathogens as biocontrol agents

Parthenium is an exotic invasive weed that now occurs widely in Ethiopia. Surveys to determine the presence and distribution of pathogens associated with parthenium and further evaluation of the pathogens found as potential biocontrol agents were carried out in Ethiopia since 1998. Several fungal isolates of the genus Helminthosporium, Phoma, Curvularia, Chaetomium, Alternaria, and Eurotium were obtained from the seeds and other plant parts. However, all of the isolates tested were non-pathogenic except Helminthosporium isolates. The two most important diseases were the rust, Puccinia abrupta var. partheniicola and the phyllody, caused by a phytoplasma belonging to the species “Candidatus Phytoplasma aurantifolia”. Host specificity tests revealed that the rust, P. abrupta, only sporulates on parthenium while the phyllody infected parthenium, groundnut, sesame, grass pea, lentil, and chickpea. Suspected insect vectors were examined for phytoplasma infection by means of Polymerase Chain Reaction (PCR). The successful acquisition of phytoplasma’s by the leafhopper, Orosius cellulosus Lindberg (Cicadellidae), was determined by molecular detection of phytoplasma. Phytoplasma was also detected from a single bait plant after feeding by the leafhopper. Sequencing data from phytoplasma obtained from parthenium and the above mentioned crops was identical with sequence identities > 98%. The rust was commonly found at 1400 – 2500 m.a.s.l. with disease incidence up to 100% in some locations while phyllody was observed at 900 – 2300 m.a.s.l. with incidence up to 75%. Individual effects of the rust and phyllody diseases on Parthenium in different locations under field condition showed significant reduction on seed and morphological parameters. Seed production was reduced by 42 and 85% due to rust and phyllody, respectively

Fluctuation conductivity and Ginzburg-Landau parameters in high-temperature superconductors above T

Theoretical Physic