ReDivia - Repositorio Digital de l'Instit Valencià d'Investigacions Agràries
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Moonlighting bacteriophage proteins derepress staphylococcal pathogenicity islands
Get PDFStaphylococcal superantigen-carrying pathogenicity islands (SaPIs) are discrete, chromosomally integrated units of similar to 15 kilobases that are induced by helper phages to excise and replicate. SaPI DNA is then efficiently encapsidated in phage-like infectious particles, leading to extremely high frequencies of intra-as well as intergeneric transfer(1-3). In the absence of helper phage lytic growth, the island is maintained in a quiescent prophage-like state by a global repressor, Stl, which controls expression of most of the SaPI genes(4). Here we show that SaPI derepression is effected by a specific, non-essential phage protein that binds to Stl, disrupting the Stl-DNA complex and thereby initiating the excision-replication-packaging cycle of the island. Because SaPIs require phage proteins to be packaged(5,6), this strategy assures that SaPIs will be transferred once induced. Several different SaPIs are induced by helper phage 80 alpha and, in each case, the SaPI commandeers a different non-essential phage protein for its derepression. The highly specific interactions between different SaPI repressors and helper-phage-encoded anti-repressors represent a remarkable evolutionary adaptation involved in pathogenicity island mobilization
The fertility of ram sperm held for 24 h at 5 degrees C prior to cryopreservation
No full textDiluted ram sperm can be held for 24 h at 5 °C prior to cryopreservation without impacting cryosurvival rates, however, the effects this storage has on subsequent fertility are unknown. These studies were conducted to evaluate the fertility of semen held for 24 h (to mimic shipping semen to a cryopreservation center), prior to freezing. Semen from Suffolk rams (n = 3 in experiment 1 and n = 6 in experiment 2) with initial motility of greater than 70%, were diluted to 200 × 106 sperm/mL, in one step, with a Tris–egg yolk–glycerol diluent. In experiment 1, diluted samples were cooled to 5 °C over 2 h, and then divided. Sperm in one fraction were loaded into 0.5 mL straws, frozen (T0) and stored in liquid nitrogen until thawing. Sperm in the second fraction were held at 5 °C for 24 h (T24) before being frozen. In experiment 2 ejaculates were collected and divided into two fractions. Sperm in one fraction were treated with cholesterol-loaded cyclodextrin (CLC) and sperm in the other served as control. Both fractions were diluted, cooled, and cryopreserved as described in experiment 1. Stage of the estrous cycle was synchronized in ewes (n = 196) using controlled internal drug releasing devices (CIDR) for 12 d and at CIDR removal each ewe was administered PMSG (500 IU in experiment 1 and 350 IU in experiment 2) immediately before insemination. Ewes were stratified by age and randomly assigned to one of the semen treatments; experiment 1: Fresh (F), T0, or T24; experiment 2: F, T24, or CLC, and inseminated laparoscopically 56 h after CIDR removal. Differences in fertility were detected between experiments, but not for treatments within experiments. Differences in fertility were also observed due to ewe age, with the 3-year-old ewes having the greatest fertility (50.7%) and 6-year-old ewes having the least fertility (9.6%; P < 0.05). Differences in the prolificacy rates due to semen treatment were also observed but differences due to ewe age were not detected. Therefore, sperm can be held at 5 °C for 24 h prior to cryopreservation without altering sperm fertilit
Dissemination of Pseudomonas savastanoi pv. savastanoi populations and subsequent appearance of olive knot disease
No full textPseudomonas savastanoi pv. savastanoi (Psv) is the causal agent of olive knot disease. The bacterium survives epiphytically and gains ingress through new wounds where infections and colonization result in knot formation. The natural spread of the bacterium and the subsequent appearance of the disease in olive orchards is poorly understood. The aim of this study was to monitor Psv epiphytic populations in inoculated plants with knots versus non-inoculated healthy trees within the same orchard over four years. Additionally, disease severity was measured in both inoculated and non-inoculated control trees. Epiphytic Psv populations moved from inoculated to non-inoculated trees, although average Psv populations were higher in inoculated trees. Olive knot severity increased over the course of the study in all treatments and cultivars, with all plants reaching a high level of disease by the end of the study. However, the delay in the onset of disease was longer in non-inoculated than in inoculated trees. Molecular typing of Psv isolates recovered from non-inoculated control trees confirmed that they were similar to the inoculated strain. These data demonstrate that Psv can move over short distances in olive orchards through dissemination of epiphytic bacteria and suggest a relationship between the presence of epiphytic Psv and the number of knots on trees
Deficit irrigation in fruit trees and vines in Spain. A review
No full textWater has become the most precious of natural resources in many areas of Spain and, since agriculture is the major consumer of water, improvements in water use efficiency are increasingly sought. Regulated deficit irrigation (RDI) is an irrigation strategy based on applying only a fraction of the plant water requirements during certain periods of plant development. The paper reviews the available information on RDI strategies, in woody tree crops and vines based on studies by Spanish research groups. Both the promising results obtained and the drawbacks are covered
The Conserved Zn Finger Domain and Adjacent Basic Motifs of the P23 Silencing Suppressor of Citrus Tristeza Virus are Required for Pathogenesis in Transgenic Mexican Lime Plants
No full textActa Horticulturae
No full textNew hydroxypropyl methylcellulose (HPMC)-lipid edible composite films and coatings containing food preservatives with antifungal properties were developed to control citrus postharvest green and blue molds, caused by the pathogens Penicillium digitatum (PD) and Penicillium italicum (PI), respectively. Tested chemicals were mainly salts of organic acids, salts of parabens, and mineral salts, all classified as food additives or generally recognized as safe (GRAS) compounds. The antifungal activity of stand-alone edible films were evaluated in vitro using disk diameter tests. Selected edible coatings containing food preservatives were tested in vivo on 'Ortanique' hybrid mandarins to determine their curative (coated 24h after fungal inoculation) and preventive (coated 24h before fungal inoculation) activity. Disease incidence and severity were determined on fruit artificially inoculated with the pathogens and incubated at 20 degrees C and 90% RH for 7 days. Film disks containing sodium salts of parabens and the organic acid salts potassium sorbate (PS) and sodium benzoate (SB) were the most effective to inhibit both PD and PI. The use of mixtures of parabens or organic acid salts did not provide any additive or synergistic effect for in vitro pathogen inhibition when compared to the use of single chemicals. On 'Ortanique' mandarins treated after fungal inoculation, paraben-, PS-, and SB-based coatings only reduced the incidence of green and blue molds by about 40 and 20%, respectively. However, HPMC-lipid coatings containing a mixture of PS and sodium propionate (PS+SP) reduced disease incidence by more than 75 and 65%, respectively. On these fruit, the severity (lesion size) of both molds was reduced by more than 90%. The incidence and severity of both green and blue molds on mandarins coated before inoculation (preventive activity) was not significantly affected by the application of any of the antifungal coatings
Vector and virus induce plant responses that benefit a non-vector herbivore
No full textThe negative cross-talk between induced plant defences against pathogens and arthropod herbivores is exploited by vectors of plant pathogens: a plant challenged by pathogens reduces investment in defences that would otherwise be elicited by herbivores. This negative cross-talk may also be exploited by non-vector herbivores which elicit similar anti-herbivore defences in the plant. We studied how damage by the thrips Frankliniella occidentalis and/or infection with Tomato spotted wilt virus (TSWV) affect the performance of a non-vector arthropod: the two-spotted spider mite Tetranychus urticae, a parenchym feeder just like F occidentalis. Juvenile survival of spider mites on plants inoculated with TSWV by thrips was higher than on control and on thrips-damaged plants. However, thrips damage did not reduce spider-mite survival as compared to the control, suggesting that the positive effect of TSWV on spider-mite survival is independent of anti-thrips defence. Developmental and oviposition rates were enhanced on plants inoculated with TSWV by thrips and on plants with thrips damage. Therefore, spider mites benefit from TSWV-infection of pepper plants, but also from the response of plants to thrips damage. We suggest that the positive effects of TSWV on this non-vector species cannot be explained exclusively by cross-talk between anti-herbivore and anti-pathogen plant defences
Cl- homeostasis in includer and excluder citrus rootstocks: transport mechanisms and identification of candidate genes
No full textTo reveal specific Cl- transport activities in the symplastic pathway, uptake, long-distance transport and distribution of Cl- have been investigated in the citrus rootstocks Carrizo citrange (CC, Cl- includer) and Cleopatra mandarin (CM, Cl- excluder). Using an external concentration of 4.5 mm Cl-, both species actively transported Cl- to levels that exceeded the critical requirement concentration by one and two orders of magnitude in the excluder and the includer rootstocks, respectively. Both CC and CM modulated Cl- influx according to the availability of the nutrient as uptake capacity was induced by Cl- starvation, but inhibited after Cl- resupply. Net Cl- uptake was higher in the includer CC, an observation that correlated with a lower root-to-shoot transport capacity in the excluder CM. The patterns of tissue Cl- accumulation indicated that chloride exclusion in the salt-tolerant rootstock CM was caused by a reduced net Cl- loading into the root xylem. Genes CcCCC1, CcSLAH1 and CcICln1 putatively involved in the regulation of chloride transport were isolated and their expression analysed in response to both changes in the nutritional status of Cl- and salt stress. The previously uncharacterized ICln gene exhibited a strong repression to Cl- application in the excluder rootstock, suggesting a role in regulating Cl- homeostasis in plants
Manual básico de agricultura ecológica
No full textLa citricultura española tiene planteados actualmente algunos problemas, que van reduciendo la rentabilidad económica y social del cultivo, tan serios como: el paulatino envejecimiento de los agricultores y su desprofesionalización; las plagas y enfermedades nuevas o recurrentes; la creciente dependencia de las empresas agroquímicas; el estancamiento y cambio de hábitos en el consumo; la entrada de empresas productoras a la vez que comercializadoras con nuevas transformaciones en un mercado muy complejo; la agrupación de las grandes distribuciones en pocas manos, en un régimen similar a oligopolios; la competencia cada vez más intensa de otros países, etc. Los residuos de fitosanitarios y de abonos químicos que contaminan los alimentos y el entorno (Domínguez Gento y Domínguez, 1999), el empobrecimiento de los suelos, su erosión y otros impactos negativos sobre el medio ambiente y sobre la salud de los consumidores complican cada vez más la situación, máxime cuando en Europa cada vez somos vez más exigentes en cuanto a estos aspectos que también se han de tener en cuenta al analizar la calidad y la sostenibilidad de la producción. Resulta, pues, evidente la necesidad de nuevos enfoques para resolver los problemas de la citricultura valenciana, y en ese sentido surge la citricultura ecológica. Así, aprovechando los innumerables cambios que afectan a nuestra agricultura, la apuesta por la citricultura ecológica en nuestro territorio parece imparable, siendo indispensable para llegar a buen puerto la mejora de las técnicas y de la transferencia de la información, mediante medios como el presente cuaderno
Artrópodos depredadores potenciales de Ceratitis capitata (Wiedemann) presentes en el suelo de cítricos
Get PDFLa mosca mediterránea de la fruta Ceratitis capitata (Wiedemann) es una de las plagas más importantes en la fruticultura mundial. En España, por su gran repercusión económica, se le considera como una de las plagas más graves de los cítricos. Tradicionalmente el control de esta especie se ha basado en la aplicación de tratamientos químicos. Sin embargo, la repercusión medio ambiental de los plaguicidas, sus efectos secundarios tanto sobre la fauna útil presente en el cultivo como sobre la salud humana, y los elevados costes de cultivo que suponen, han llevado a la búsqueda de nuevas alternativas para la gestión de esta plaga. En este contexto, el control biológico aparece como una herramienta muy poco explotada para esta plaga. Tanto las larvas de tercer estadio como las pupas y los adultos recién emergidos pueden darse en el suelo de los cítricos. Por esta razón, en la presente tesis se ha estudiado en profundidad la importancia de los depredadores polífagos que habitan el suelo de los cítricos y su influencia sobre C. capitata