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The antimicrobial activity of six plant extracts from Ocimum basilicum, Azadirachta indica, Eucalyptus chamadulonsis, Datura stramonium, Nerium oleander, and Allium sativum was tested for controlling Alternaria solani in vitro and in vivo. In in vitro study the leaf extracts of D. stramonium, A. indica, and A. sativum at 5% concentration caused the highest reduction of mycelial growth of A. solani (44.4, 43.3 and 42.2%, respectively), while O. basilicum at 1% and 5% concentration and N. oleander at 5% concentration caused the lowest inhibition of mycelial growth of the pathogen. In greenhouse experiments the highest reduction of disease severity was achieved by the extracts of A. sativum at 5% concentration and D. stramonium at 1% and 5% concentration. The greatest reduction of disease severity was achieved by A. sativum at 5% concentration and the smallest reduction was obtained when tomato plants were treated with O. basilicum at 1% and 5% concentration (46.1 and 45.2 %, respectively). D. stramonium and A. sativum at 5% concentration increased the fruit yield by 76.2% and 66.7% compared to the infected control. All treatments with plant extracts significantly reduced the early blight disease as well as increased the yield of tomato compared to the infected control under field conditions.

Le premier roman d'Héctor Tizón, Fuego en Casabindo (1969), reste relativement méconnu alors qu'il constitue une experimentation originale dans le contexte du boom des années 1960. Encore inédite en français, sa traduction est en cours et pose de nombreuses questions. Ce récit fragmentaire, au style tres elliptique et poétique, traverse par des voix ancestrales, rnelant le passé et le présent, le reve et la réalité, repose sur un substrat culturel tres riche, celui de la culture andine du nord-ouest argentin. Le traducteur se trouve alors face â de nombreux culturemes et â plusieurs strategies possibles.

La obra narrativa de Héctor Tizón incluye, desde su primera novela publicada, Fuego en Casabindo (1969), la adscripción a la tradición homérica, cifrada en la cita del epígrafe, de un fragmento de Odisea (11. 216-224), enunciado por Anticlea, quien revela a su hijo lo que ocurre con los seres humanos cuando mueren. Al mismo tiempo, incorpora en el mundo narrado los cantares y los relatos populares tradicionales, los mitos y creencias de la región noroeste de la Argentina. La escatología es un conocimiento que articula estas culturas tan alejadas en el tiempo y el espacio. Este artículo sostiene que el motivo griego integrado en la novela no es un componente secundario, sino que constituye la matriz narrativa, da forma a la estructura novelesca y resulta significativo para la interpretación.

▪ Abstract  Suppression of the blossom-blight phase of fire blight is a key point in the management of this destructive and increasingly important disease of apple and pear. For blossom infection to occur, the causal bacterium, Erwinia amylovora, needs to increase its population size through an epiphytic phase that occurs on stigmatic surfaces. Knowledge of the ecology of the pathogen on stigmas has been key to the development of predictive models for infection and optimal timing of antibiotic sprays. Other bacterial epiphytes also colonize stigmas where they can interact with and suppress epiphytic growth of the pathogen. A commercially available bacterial antagonist of E. amylovora (BlightBan, Pseudomonas fluorescens A506) can be included in antibiotic spray programs. Integration of bacterial antagonists with chemical methods suppresses populations of the pathogen and concomitantly, fills the ecological niche provided by the stigma with a nonpathogenic, competing microorganism. Further integration of biologically based methods with conventional management of blossom blight may be achievable by increasing the diversity of applied antagonists, by refining predictive models to incorporate antagonist use, and by gaining an improved understanding of the interactions that occur among indigenous and applied bacterial epiphytes, antibiotics, and the physical environment.

Archivo histórico de Kipus: Revista Andina de Letras y Estudios Culturales, 1998.

Fluorescence in situ hybridization (FISH) is a powerful tool for physical mapping in human and other mammalian species. However, application of the FISH technique has been limited in plant species, especially for mapping single- or low-copy DNA sequences, due to inconsistent signal production in plant chromosome preparations. Here we demonstrate that bacterial artificial chromosome (BAC) clones can be mapped readily on rice (Oryza sativa L.) chromosomes by FISH. Repetitive DNA sequences in BAC clones can be suppressed efficiently by using rice genomic DNA as a competitor in the hybridization mixture. BAC clones as small as 40 kb were successfully mapped. To demonstrate the application of the FISH technique in physical mapping of plant genomes, both anonymous BAC clones and clones closely linked to a rice bacterial blight-resistance locus, Xa21, were chosen for analysis. The physical location of Xa21 and the relationships among the linked clones were established, thus demonstrating the utility of FISH in plant genome analysis.

Plant defense responses to pathogen infection involve the production of active oxygen species, including hydrogen peroxide (H2O2). We obtained transgenic potato plants expressing a fungal gene encoding glucose oxidase, which generates H2O2 when glucose is oxidized. H2O2 levels were elevated in both leaf and tuber tissues of these plants. Transgenic potato tubers exhibited strong resistance to a bacterial soft rot disease caused by Erwinia carotovora subsp carotovora, and disease resistance was sustained under both aerobic and anaerobic conditions of bacterial infection. This resistance to soft rot was apparently mediated by elevated levels of H2O2, because the resistance could be counteracted by exogenously added H2O2-degrading catalase. The transgenic plants with increased levels of H2O2 also exhibited enhanced resistance to potato late blight caused by Phytophthora infestans. The development of lesions resulting from infection by P. infestans was significantly delayed in leaves of these plants. Thus, the expression of an active oxygen species-generating enzyme in transgenic plants represents a novel approach for engineering broad-spectrum disease resistance in plants

Biotrophic invasive hyphae (IH) of the blast fungus Magnaporthe oryzae secrete effectors to alter host defenses and cellular processes as they successively invade living rice (Oryza sativa) cells. However, few blast effectors have been identified. Indeed, understanding fungal and rice genes contributing to biotrophic invasion has been difficult because so few plant cells have encountered IH at the earliest infection stages. We developed a robust procedure for isolating infected-rice sheath RNAs in which ~20% of the RNA originated from IH in first-invaded cells. We analyzed these IH RNAs relative to control mycelial RNAs using M. oryzae oligoarrays. With a 10-fold differential expression threshold, we identified known effector PWL2 and 58 candidate effectors. Four of these candidates were confirmed to be fungal biotrophy-associated secreted (BAS) proteins. Fluorescently labeled BAS proteins were secreted into rice cells in distinct patterns in compatible, but not in incompatible, interactions. BAS1 and BAS2 proteins preferentially accumulated in biotrophic interfacial complexes along with known avirulence effectors, BAS3 showed additional localization near cell wall crossing points, and BAS4 uniformly outlined growing IH. Analysis of the same infected-tissue RNAs with rice oligoarrays identified putative effector-induced rice susceptibility genes, which are highly enriched for sensor-transduction components rather than typically identified defense response genes.

Desde sus comienzos, desde los primeros pasos para lograr la independencia de la futura Nación Argentina, luchas intestinas signaron el tenor del recorrido institucional. La generación del 37, jóvenes nacidos en la primera década del siglo XIX cuando la Revolución de Mayo de 1810 exaltaba los ánimos patriotas empeñados en cortar lazos con España, enfrentaban ideológicamente a los denominados «federales» cuyo conductor, Juan Manuel de Rosas, dominaba la rica y extensa región de la Provincia de Buenos Aires. El exilio fue el camino obligado de los disidentes al régimen rosista. Los países vecinos de Chile y Uruguay fueron refugio de Domingo Faustino Sarmiento y Esteban Echeverría, dos de los principales protagonistas de esta contienda. En el exilio, ambos escribieron dos textos fundantes de la literatura argentina: Facundo, una suerte de biografía del caudillo homónimo de la región de Cuyo y el Noroeste argentino de donde era originario Sarmiento y El matadero de Esteban Echeverría cuyo título, a través de una sinécdoque, refería a la situación de violencia que reinaba en la provincia de Buenos Aires. La intolerancia política, la persecución y muerte marcaron las décadas en la Argentina de forma sistemática hasta 1983, fecha en la que se recuperó la democracia. La literatura en sus variadas manifestaciones genéricas, particularmente narrativa y dramaturgia, dejaron un testimonio elocuente y verosímil de los hechos. Paradójicamente, la ficción tuvo a su cargo la verdadera historia; la contracara de la historia oficial que se difundía en épocas de gobiernos dictatoriales donde la censura imperaba. En el siglo XX y en particular durante la dictadura del último gobierno militar acaecida entre 1976 y 1983, los textos circulaban en forma clandestina y los escritores –aquellos que pudieron huir y salvaron su vida– escribieron desde el exterior. Esta vez, España y México fueron, entre otros, países  que tendieron sus lazos solidarios; los países vecinos de Argentina, Chile, Uruguay, Paraguay, padecían sus respectivas dictaduras.

Transgenic potato and tobacco plants carrying the osmotin gene under the control of the cauliflower mosaic virus 35S promoter constitutively overexpressed osmotin to a level of approximately 2% of total cellular protein. Leaves of transgenic potato plants exhibited delayed development of disease symptoms after inoculation with spore suspensions of Phytophthora infestans, which is the cause of late blight disease of potato. In contrast, transgenic tobacco plants did not display any change in the development of disease symptoms when challenged with either spore suspensions or fungal mycelia of Phytophthora parasitica var. nicotianae. Using in vitro assays, purified osmotin was found to be more effective against P. infestans. Some inhibition of P. parasitica also was observed in vitro even though no in vivo effect could be established