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Optimización de la eficiencia de uso del nitrógeno en cítricos para el desarrollo de una agricultura Sostenible. I. Obtención de fertilizantes orgánicos solubles marcados con 15N
Get PDFEn la actualidad se están modificando las prácticas agrícolas actuales orientándolas hacia sistemas alternativos de producción agrícola asumiendo, por tanto, compromisos de respeto medioambiental. Así, la agricultura ecológica se presenta como alternativa a la agricultura tradicional. Los residuos generados por las zonas agrícolas y las granjas agropecuarias, mediante un adecuado manejo, podrían ser fuente importante de nutrientes para las plantas. El propósito de este estudio consistió en la obtención de dos abonos orgánicos solubles, obtenidos de subproductos vegetales y estiércol animal, que puedan ser utilizados en riego localizado. Ambos abonos se marcaran con el isótopo estable 15N con el fin de conocer el aprovechamiento del N presente en ellos aplicado a plantas de cítricos. Para la obtención del abono orgánico de origen vegetal se marcaron plantas de maíz forrajero. Esta misma materia prima se utilizó como alimentación de ganado ovino, cuyas deyecciones sólidas marcadas se utilizaron para la obtención del abono orgánico de origen animal. Ambos abonos obtenidos presentaron una concentración elevada de nitrógeno total, con una pequeña cantidad en forma mineral (nitrato y amonio). El enriquecimiento en 15N fue de 2,62 y 2,17 %, en el abono de origen vegetal y animal respectivamente, suficiente para ser usado como fertilizante en plantas de cítricos. Ambos fertilizantes presentaron concentraciones elevadas de macro y micronutrientes, valores superiores en el de origen animal
Chloride Nutrition: Impact in Plant Development and Water Relations
Get PDFAlthough Cl- has been characterized as a micronutrient, we have observed that when available in the millimolar range (e.g. 1-5 mM), higher plants accumulate Cl- to levels that are typical of the content of a macronutrient (Plant Cell Env. 2010, 33: 2012-27). Since this requires a considerable cost of energy, we speculate whether Cl- might play a poorly understood function in plants when accumulated to macronutrient levels. Given that Cl- is a major osmotically active solute in the plant vacuole, we propose that this element improves osmoregulatory and plant water relation mechanisms. To elucidate this hypothesis, tobacco plants
were grown for 9 weeks with a basal nutrient solution (BS) and subjected to different treatments: 5 mM Clsolution (Cl); 5 mM NO3 - (N); and 5 mM SO4 2- and PO3 3- (SP). Compared to BS and SP plants, chloride nutrition in the millimolar range promoted plant growth in terms of dry weight and total leaf area. This, together with the observation that Cl- was preferentially included in growing and reproductive organs, suggested a role in plant development. In addition, compared to BS, SP and N plants, Cl plants exhibited the best water parameters
The position of the major QTL for Citrus tristeza virus resistance is conserved among Citrus grandis, C. aurantium and Poncirus trifoliata
Get PDFCitrus tristeza virus, CTV, is one of the most important citrus pathogens. Although CTV-resistant citrus rootstocks derived from Poncirus trifoliata are common, useful genetic resistance within the genus Citrus for scion improvement is very limited and no CTV-resistant sweet orange cultivar is yet available. Quantitative trait locus (QTL) analysis of the accumulation and distribution of CTV was carried out in a segregating population of 201 C. grandis x C. clementina hybrids derived from a reciprocal cross between two commercial varieties, Chandler (Ch) and Fortune (F), to genetically study the CTV resistance response. Chandler and 13 of its hybrids were found resistant to T-346 CTV isolate. The mortality of C. grandis x C. clementina hybrids, as well as CTV-challenged C. aurantium x P. trifoliata hybrids, was found to be related to the CTV resistance response. The type of cytoplasm (F or Ch) was not associated with the CTV resistance. A major QTL contributing around 24% of the total variance for CTV accumulation and spatial distribution was detected on linkage group 4b. Its position is conserved among C. grandis, C. aurantium and P. trifoliata. Seventy candidate genes of the CTV resistance response were obtained by transcriptomic bulk segregant analysis of resistant versus susceptible CTV-inoculated hybrids. Thirteen out of 28 of those candidates could be mapped on the C. grandis and/or C. clementina linkage maps. None was located on linkage group 4b, but four of them were found to be associated with CTV resistance through a minor QTL (CTVCh14) or epistatic interactions (CTVCh15, CTVCh17 and VIC)
Superparasitism in Laboratory rearing of Spalangia cameroni (Hymenoptera: Pteromalidae), a parasitoid of medfly (Diptera: Tephritidae)
No full textThe frequency of superparasitism and its effects on the quality of laboratory-reared Spalangia cameroni (Hymenoptera: Pteromalidae) parasitoids were investigated under laboratory conditions. Numerous variables were measured, such as the number of ‘ovip holes’ per host as a measure of superparasitism. Adult emergence and sex ratio, as well as female size, emergence ability from soil and longevity were also measured. Finally, an assessment was made of fertility and survival of adult parasitoids emerging from the medfly Ceratitis capitata (Diptera: Tephritidae) pupae with different levels of superparasitism. A high frequency and prevalence of superparasitism under laboratory rearing conditions was observed. The number of ‘ovip holes’ per host ranged from one to 17, with an average (±SD) of 2.8±3.4. Sex ratios became increasingly female-biased with increasing levels of superparasitism, although overall levels of wasp emergence (male, female) declined. Nevertheless, no relationship was discerned between female size and level of superparasitism. The ‘emergence ability from the soil’ was higher in those parasitoids that emerged from strongly superparasitized hosts, but not related to the type of substrate in which the host pupae were buried. The level of superparasitism did not have a significant effect on the longevity, fertility and survival of female parasitoids. Our results support the hypothesis that superparasitism in S. cameroni might be adaptive, since attributes such as ‘emergence ability from the soil’, longevity, fertility and survival were not affected by the level of superparasitism or the presumably detrimental effects derived from physical combats among conspecific larvae. Our findings are relevant to recommendations for rearing S. cameroni for biological control releases, as well as shedding light on superparasitism under both laboratory and field conditions
Structure-function analysis of the SaPIbov1 replication origin in Staphylococcus aureus
Get PDFThe SaPIs and their relatives are phage satellites and are unique among the known bacterial pathogenicity islands in their ability to replicate autonomously. They possess a phage-like replicon, which is organized as two sets of iterons arrayed symmetrically to flank an AT-rich region that is driven to melt by the binding of a SaPI-specific initiator (Rep) to the flanking iterons. Extensive deletion analysis has revealed that Rep can bind to a single iteron, generating a simple shift in a gel mobility assay; when bound on both sides, a second retarded band is seen, suggesting independent binding. Binding to both sites of the on is necessary but not sufficient to melt the AT-rich region and initiate replication. For these processes, virtually the entire origin must be present. Since SaPI replication can be initiated on linear DNA, it is suggested that bilateral binding may be necessary to constrain the intervening DNA to enable Rep-driven melting. (C) 2012 Elsevier Inc. All rights reserved
Mating disruption for the control of Aonidiella aurantii Maskell (Hemiptera: Diaspididae) may contribute to increased effectiveness of natural enemies
Get PDFBACKGROUND: New directives on sustainable use of pesticides have encouraged research on efficient alternative pest control methods. In the case of the California red scale (CRS), Aonidiella aurantii (Maskell), this imperative, along with the many difficulties in controlling this pest, have led to the investigation of new approaches. Previously developed mating disruption (MD) dispensers, together with the augmentative releases of the parasitoid Aphytis melinus DeBach, are here considered as a combined strategy for use against A. aurantii. RESULTS: Efficacy of MD was demonstrated by a mean reduction of 80% in CRS male catches and a mean fruit damage reduction of 83% compared with the control. A delay in the development of A. aurantii instars was observed in the MD plot. This delay increased the period of exposure of the susceptible instars to natural enemies, which resulted in higher predation and parasitism levels in the MD plot. Under laboratory conditions, A. melinus mating behaviour and effects on A. aurantii were not significantly altered in a CRS-pheromone-saturated environment. CONCLUSION: Mating disruption pheromone did not affect the behaviour or level of parasitism by A. melinus or the incidence of other generalist predators. Therefore, A. aurantii pheromone appears to be compatible with augmentative releases and biological control, making its use a good strategy for CRS management
Efficacy of sulphur on Tuta absoluta and its side effects on the predator Nesidiocoris tenuis
No full textThe South American tomato pinworm, Tuta absoluta (Meyrick), is one of the major pests of tomato crop. Since its detection in the Mediterranean basin, it has been commonly controlled using chemical insecticides. However, inoculation and conservation of predatory mirids, integrated with sprays of selective insecticides, has been demonstrated to be a cost-effective strategy for controlling this pest. In this work, we tested the efficacy of two sulphur formulations, dustable and wettable powder, for controlling T. absoluta on tomato under greenhouse and open-field conditions. In addition, the side effects of both sulphur formulations on the predator, Nesidiocoris tenuis (Reuter), were evaluated under laboratory conditions. Dustable sulphur, applied weekly on tomato seedlings artificially infested with T. absoluta in greenhouse conditions, significantly reduced the infestation levels and was demonstrated to have a repellent effect on oviposition. Wettable sulphur was not effective for controlling T. absoluta populations in both greenhouse and open-field experim
ents. In the side effect trials conducted with N. tenuis, only dustable sulphur resulted in being moderately harmful as a fresh residue and slightly harmful as a 7-day-old residue; no effects were recorded exposing the predator to 14-day-old sulphur residues. In contrast, wettable sulphur was classified as harmless to N. tenuis. Our results suggest that the use of sulphur, especially as dustable powder, could be considered as a tool in T. absoluta management strategies, although its side effects on N. tenuis should be taken into account. The implications of these results for the use of sulphur formulations in pest and disease management programmes in tomato crops are discussed
Effect of glycerol level on quality and fertilizing ability of cryopreserved rooster sperm
No full textShort Exposure to High CO2 and O-2 at Curing Temperature to Control Postharvest Diseases of Citrus Fruit
No full textCuring of citrus fruit at 30 to 37°C and 90 to 98% relative humidity for 65 to 72 h is an effective alternative to fungicides to control postharvest green and blue molds caused by Penicillium digitatum and P. italicum, respectively. However, commercial adoption is limited because treatment is long and it may harm fruit quality. In order to improve the feasibility of curing, short CO2 or O2 exposures at curing temperature were evaluated on ‘Nadorcott’, ‘Clemenules’, and ‘Ortanique’ mandarin fruit and ‘Valencia’ orange. Fruit were artificially inoculated, exposed 24 h later to air (control); CO2 at 15, 30, 50, or 95 kPa; or O2 at 30 or 45 kPa at 20 or 33°C for 8, 24, or 48 h and incubated at 20°C for 4, 7, or 15 days. Exposure at 33°C with CO2 at 15 kPa for 24 h or O2 at 30 kPa for 48 h effectively controlled both green and blue molds after 7 days of incubation at 20°C; however, control of both diseases was minimal after 15 days. To assess potential induction of disease resistance, fruit were treated as described above, then inoculated after 1, 2, or 5 days at 20°C and evaluated after 3 and 6 more days at 20°C. All of the treatments were ineffective in inducing fruit resistance. Short exposures of citrus fruit to high CO2 or O2 at curing temperatures may be part of a control program alternative to synthetic fungicides, especially for organic fruit market
Process performance of anaerobic co-digestion of raw and acidified pig slurry
No full textThe effect of incorporating different ratios of acidified pig slurry on methane yield was evaluated in two scales of anaerobic digesters: Thermophilic (50 degrees C) pilot scale digester (1201), operating with an average hydraulic retention time of 20 days and thermophilic (52 degrees C) full-scale digesters (10 and 30 m(3)), operating with an average hydraulic retention time of 30 days. In the lab-scale digester, different inclusion levels of acidified slurry (0-60%) were tested each 15 days, to determine the maximum ratio of acidified to non-acidified slurry causing inhibition and to find process state indicators helping to prevent process failure. In the full-scale digesters, the level of inclusion of the acidified slurry was chosen from the ratio causing methane inhibition in the pilot scale experiment and was carried on in a long-term process of 100 days. The optimal inclusion level of acidified pig slurry in anaerobic co-digestion with conventional slurry was 10%, which promoted anaerobic methane yield by nearly 20%. Higher inclusion levels caused methane inhibition and volatile fatty acids accumulations in both experiments. In order to prevent process failure, the most important traits to monitor in the anaerobic digestion of acidified pig slurry were found to be: sulfate content of the slurry, alkalinity parameters (especially partial alkalinity and the ratio of alkalinity) and total volatile fatty acids (especially acetic and butyric acids). (C) 2012 Elsevier Ltd. All rights reserved