Orígenes de la ciudad romana de Ampuria

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Características morfológícas y patogénicas de aislamientos de Septoria tritici Rob ex Desm

Se analizó el comportamiento cultural y patogénicos de 8 aislamientos de Septoria tritici obtenidos a partir de hojas de trigo colectadas en el campo e infectadas naturalmente. Los diversos aislamientos monospóricos pueden diferenciarse en cultivo artificial por su aspecto, la producción de esporas, la presencia o ausencia de micelio, y el color y la frecuencia de saltaciones observadas en las colonias. Las cepas varían tanto en la abundancia como en el tipo de las esporas producidas bajo condiciones similares. Además de las picnidiosporas de forma y tamaños típicos de la especie, algunas cepas produjeron sólo esporas libres muy pequeñas (microsporas), y otras, macro y mícrosporas dentro des picnidios. Los tipos culturales predominantes de los aislamientos fueron 5: - estromático (mayor frecuencia), - albino pulverulento, - levaduroide, - mixto y - miceliar. Estos tipos culturales, en algunos casos no se mantuvieron estables a través de 3 generaciones de subcultivos. Las inoculaciones efectuadas sobre plantas de trigo en invernáculo, revelaron diferencias altamente significativas en la patogenicidad de ciertas cepas. Se encontró una relacíón entre las características culturales de los aislamientos y la severidad de la enfermedad: los aislamientos de tipo albino y levaduroide fueron los menos virulentos, tanto sobre variedades resistentes como susceptibles. La presente, constitutuye la primer cita de la presencia de esta clase de microsporas de S tritici.This study analyzed the cultural and pathogenic behavior of S tritici isolates from wheat leaves infected and collected in the field. When cultured artificially, monosporic isolates were differenciated in aspect, spore production, presence or absence of mycelium, and in color and frequency of saltation observed in the colonies as shown in table I. The characteristics noted led to the classification of the cultures as mycelial (M), typical (stromatic-pycnidial) (T) (the most frequent), powdery albino (A), yeast-like (Y) and mixed (Mx) (figs 1 and 2). In some cases these cultural types, though pure, did not remain stable after three subculture generations. The variants from the parental type appeared patches or sectorings of the yeast-like and/or the mycelial type. Sometimes these appeared in the first generation, some others in the third generation, with a low frequency of appearance with respect to the parental type. In the greenhouse, inoculation in the form of wheat plants revealed highly significant differences in the pathogenicity of some strains. Correlation of the mean percentages of pycnidial coverage showed a significant difference in isolate pathogenicity levels in the same cultivar and within cultivars (table II). Thus, the existence of physiologic specialization in S tritici is again confirmed. A relationship was found between the isolates’ cultural characteristics and the disease severity: the albino and yeast-like isolates were the least virulent for both the resistant and susceptible cultivars. Under similar conditions the strains varied in spore abundance as in the spore type produced (fig 4). Besides pycnidiospores with shape and size characteristics of the species, some strains produced only very small free spores (microspores), and some others macro and microspores within pycnidia (table III). Microspores produced in vivo were much smaller than those obtained artificially. This is the first report regarding this type of microspore in S tritici

Potenciales agentes de biocontrol de las principales enfermedades de poscosecha del Kiwi en Argentina

El objetivo de este trabajo fue identificar enfermedades del fruto de Kiwi en poscosecha, conocer sus agentes causales y disponer de métodos de control alternativos que minimicen el uso de agroquímicos. El uso de microorganismos antagonistas ofrece una alternativa complementaria de escasos antecedentes y no explorada en Argentina. Se identificaron enfermedades fúngicas a partir de frutos enfermos y se seleccionaron potenciales antagonistas desde la micoflora asociada al filoplano, fruto y suelo del cultivo de kiwi. La capacidad antagónica se evaluó in vitro. Se identificaron como agentes causales de podredumbres a Botrytis cinerea, Alternaria alternata y Pestalotiopsis sp. Los antagonistas seleccionados fueron Epicoccum nigrum y Trichoderma harzianum. Las cepas de T. harzianum presentaron efecto antagónico reduciendo significativamente la expresión de la enfermedad. Existen hongos saprobios que pueden utilizarse en el manejo integrado de enfermedades del kiwi.There is little information about diseases of Kiwi fruit in postharvest. It is necessary to know their causal agents and alternative control methods to minimize the use of agrochemicals. Antagonistic microorganisms offer a complementary alternative to analyze. The objectives of this study were to identify postharvest diseases and select antagonists to be used as biocontrol agents. Microorganisms were isolated from diseased fruits and pathogenicity tests were performed. Potential antagonists were selected from micoflora associated to phyloplane, fruit and soil cultivation. The antagonistic capability was assessed in vitro. Botrytis cinerea, Alternaria alternata, and Pestalotiopsis sp. were identified as causal agents of kiwi rot. Epicoccum nigrum and three strains of Trichoderma harzianum were selected as antagonists to perform biocontrol bioassays under in vitro conditions. T. harzianum strains tested showed antagonistic effect when compared with the controls. This saprophytes fungi could be used into an integrated kiwi diseases management.Eje A1 Sistemas de producción de base agroecológica (Trabajos científicos

Potenciales agentes de biocontrol de las principales enfermedades de poscosecha del Kiwi en Argentina

El objetivo de este trabajo fue identificar enfermedades del fruto de Kiwi en poscosecha, conocer sus agentes causales y disponer de métodos de control alternativos que minimicen el uso de agroquímicos. El uso de microorganismos antagonistas ofrece una alternativa complementaria de escasos antecedentes y no explorada en Argentina. Se identificaron enfermedades fúngicas a partir de frutos enfermos y se seleccionaron potenciales antagonistas desde la micoflora asociada al filoplano, fruto y suelo del cultivo de kiwi. La capacidad antagónica se evaluó in vitro. Se identificaron como agentes causales de podredumbres a Botrytis cinerea, Alternaria alternata y Pestalotiopsis sp. Los antagonistas seleccionados fueron Epicoccum nigrum y Trichoderma harzianum. Las cepas de T. harzianum presentaron efecto antagónico reduciendo significativamente la expresión de la enfermedad. Existen hongos saprobios que pueden utilizarse en el manejo integrado de enfermedades del kiwi.There is little information about diseases of Kiwi fruit in postharvest. It is necessary to know their causal agents and alternative control methods to minimize the use of agrochemicals. Antagonistic microorganisms offer a complementary alternative to analyze. The objectives of this study were to identify postharvest diseases and select antagonists to be used as biocontrol agents. Microorganisms were isolated from diseased fruits and pathogenicity tests were performed. Potential antagonists were selected from micoflora associated to phyloplane, fruit and soil cultivation. The antagonistic capability was assessed in vitro. Botrytis cinerea, Alternaria alternata, and Pestalotiopsis sp. were identified as causal agents of kiwi rot. Epicoccum nigrum and three strains of Trichoderma harzianum were selected as antagonists to perform biocontrol bioassays under in vitro conditions. T. harzianum strains tested showed antagonistic effect when compared with the controls. This saprophytes fungi could be used into an integrated kiwi diseases management.Eje A1 Sistemas de producción de base agroecológica (Trabajos científicos

Pyrenophora tritici-repentis, Causal Agent of Tan Spot: A Review of Intraspecific Genetic Diversity

In some countries where the wheat is cultivated, the biological adversities are led by foliar disease. These diseases have emerged as a serious problem in many areas where the wheat is the principal crop. In the last few years, minimum tillage has been considered advantageous to soil conservation, but it leads to a loss of available nutrients and a potential increase in necrotic pathogens whose saprophytic stage lives in the straw of the crop (Annone, 1985). Establishment of the crop under this management can be affected by pathogens of this type. Leaf spotting diseases can be caused by one or a combination of leaf spotting pathogens (Table 1). Leaf spotting diseases affect wheat grown reduce the photosynthetic area of leaves resulting in reduced grain filling and lower yields; particularly when the top two leaves (penultimate and flag leaves) are severely infected. The most of these diseases are similar in host symptomatology, disease cycle, life cycles of pathogens and types of damage induced. Whitin of these pathogens the Ascomycota fungus, Pyrenophora tritici-repentis (Ptr) (Died.) Drechs. It is a facultative pathogen whose asexual stage is Drechslera tritici-repentis (Dtr) (Died.). This pathogen is the causal agent of tan spot of wheat

Option pricing under stochastic volatility: the exponential Ornstein-Uhlenbeck model

We study the pricing problem for a European call option when the volatility of the underlying asset is random and follows the exponential Ornstein-Uhlenbeck model. The random diffusion model proposed is a two-dimensional market process that takes a log-Brownian motion to describe price dynamics and an Ornstein-Uhlenbeck subordinated process describing the randomness of the log-volatility. We derive an approximate option price that is valid when (i) the fluctuations of the volatility are larger than its normal level, (ii) the volatility presents a slow driving force toward its normal level and, finally, (iii) the market price of risk is a linear function of the log-volatility. We study the resulting European call price and its implied volatility for a range of parameters consistent with daily Dow Jones Index data.Comment: 26 pages, 6 colored figure

A precise characterisation of the top quark electro-weak vertices at the ILC

Top quark production in the process $e^+e^- \to t\bar{t}$ at a future linear electron positron collider with polarised beams is a powerful tool to determine indirectly the scale of new physics. The presented study, based on a detailed simulation of the ILD detector concept, assumes a centre-of-mass energy of $\sqrt{s}=500\,$GeV and a luminosity of $\mathcal{L}=500\,{\rm fb}^{-1}$ equally shared between the incoming beam polarisations of $\mathcal{P}_{e^-}, \mathcal{P}_{e^+} =\pm0.8,\mp0.3$. Events are selected in which the top pair decays semi-leptonically and the cross sections and the forward-backward asymmetries are determined. Based on these results, the vector, axial vector and tensorial $CP$ conserving couplings are extracted separately for the photon and the $Z^0$ component. With the expected precision, a large number of models in which the top quark acts as a messenger to new physics can be distinguished with many standard deviations. This will dramatically improve expectations from e.g. the LHC for electro-weak couplings of the top quark.Comment: This work is an update of arXiv:1307.8102, minor changes w.r.t. v1 (typos, wrong grammar, incomplete sentences etc.

Entropy of the Nordic electricity market: anomalous scaling, spikes, and mean-reversion

The electricity market is a very peculiar market due to the large variety of phenomena that can affect the spot price. However, this market still shows many typical features of other speculative (commodity) markets like, for instance, data clustering and mean reversion. We apply the diffusion entropy analysis (DEA) to the Nordic spot electricity market (Nord Pool). We study the waiting time statistics between consecutive spot price spikes and find it to show anomalous scaling characterized by a decaying power-law. The exponent observed in data follows a quite robust relationship with the one implied by the DEA analysis. We also in terms of the DEA revisit topics like clustering, mean-reversion and periodicities. We finally propose a GARCH inspired model but for the price itself. Models in the context of stochastic volatility processes appear under this scope to have a feasible description.Comment: 16 pages, 7 figure

Fasting enhances pyroglutamyl peptidase II activity in tanycytes of the mediobasal hypothalamus of male adult rats

Fasting down-regulates the hypothalamus-pituitary-thyroid (HPT) axis activity through a reduction of TRH synthesis in neurons of the parvocellular paraventricular nucleus of the hypothalamus (PVN). These TRH neurons project to the median eminence (ME), where TRH terminals are close to the cytoplasmic extensions of β2 tanycytes. Tanycytes express pyroglutamyl peptidase II (PPII), the TRH-degrading ectoenzyme that controls the amount of TRH that reaches the anterior pituitary. We tested the hypothesis that regulation of ME PPII activity is another mechanism by which fasting affects the activity of the HPT axis. Semiquantitative in situ hybridization histochemistry data indicated that PPII and deiodinase 2 mRNA levels increased in tanycytes after 48 hours of fasting. This increase was transitory, followed by an increase of PPII activity in the ME, and a partial reversion of the reduction in PVN pro-TRH mRNA levels and the number of TRH neurons detected by immunohistochemistry. In fed animals, adrenalectomy and corticosterone treatment did not change ME PPII activity 72 hours later. Methimazole-induced hypothyroidism produced a profound drop in tanycytes PPII mRNA levels, which was reverted by 3 days of treatment with T4. The activity of thyroliberinase, the serum isoform of PPII, was increased at most fasting time points studied. We conclude that delayed increases in both the ME PPII as well as the thyroliberinase activities in fasted male rats may facilitate the maintenance of the deep down-regulation of the HPT axis function, despite a partial reactivation of TRH expression in the PVN