ReDivia - Repositorio Digital de l'Instit Valencià d'Investigacions Agràries
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Citrus tristeza virus p23: a unique protein mediating key virus-host interactions
Get PDFThe large RNA genome of Citrus tristeza virus (CTV; ca. 20 kb) contains 12 open reading frames, with the 3′-terminal one corresponding to a protein of 209 amino acids (p23) that is expressed from an abundant subgenomic RNA. p23, an RNA-binding protein with a putative zinc-finger domain and some basic motifs, is unique to CTV because no homologs have been found in other closteroviruses, including the type species of the genus Beet yellows virus (despite both viruses having many homologous genes). Consequently, p23 might have evolved for the specific interaction of CTV with its citrus hosts. From a functional perspective p23 has been involved in many roles: (I) regulation of the asymmetrical accumulation of CTV RNA strands, (II) induction of the seedling yellows syndrome in sour orange and grapefruit, (III) intracellular suppression of RNA silencing, (IV) elicitation of CTV-like symptoms when expressed ectopically as a transgene in several Citrus spp., and (V) enhancement of systemic infection (and virus accumulation) in sour orange and CTV release from the phloem in p23-expressing transgenic sweet and sour orange. Moreover, transformation of Mexican lime with intron-hairpin constructs designed for the co-inactivation of p23 and the two other CTV silencing suppressors results in complete resistance against the homologous virus. From a cellular point of view, recent data indicate that p23 accumulates preferentially in the nucleolus, being the first closterovirus protein with such a subcellular localization, as well as in plasmodesmata. These major accumulation sites most likely determine some of the functional roles of p23
Effects of Spirotetramat on Aonidiella aurantii (Homoptera: Diaspididae) and Its Parasitoid, Aphytis melinus (Hymenoptera: Aphelinidae)
Get PDFLaboratory and field studies were conducted to measure the effects of spirotetramat on life stages of California red scale, Aonidiella aurantii (Maskell), and a primary parasitoid, Aphytis melinus DeBach. Organophosphate-resistant and -susceptible populations responded similarly to spirotetramat, suggesting there is no cross-resistance between these insecticide classes. First and second instar male and female A. aurantii were 10- and 32-fold more susceptible to spirotetramat (LC50 = 0.1-0.2 ppm) compared with early third (LC50 = 1.5 ppm) and late third instar females (LC50 = 5.3 ppm). The LC99 value indicated that late stage third instar females would not be fully controlled by a field rate of spirotetramat; however, spirotetramat would reduce their fecundity by 89%. Field applications of spirotetramat in two water volumes and using two adjuvants (oil and a nonionic spray adjuvant) showed similar reduction in A. aurantii numbers, even though the higher water volume demonstrated more complete coverage. These data suggest that this foliarly applied systemic insecticide can be applied in as little as 2,340 liters/ha of water volume, minimizing application costs, and that the two adjuvants acted similarly. The endoparasitoid, A. melinus, was unaffected by the field rate of spirotetramat when it was applied to the host when the parasitoid was in the egg or larval stage. Adult A. melinus showed 2 wk of moderate reductions in survival when exposed to leaves with field-weathered residues. Spirotetramat is an integrated pest management compatible insecticide, effective in reducing A. aurantii stages and allowing survival of its primary parasitoid A. melinus
Improving the Sterile Sperm Identification Method for Its Implementation in the Area-Wide Sterile Insect Technique Program Against Ceratitis capitata (Diptera: Tephritidae) in Spain
Get PDFThe success of sterile males in area-wide sterile insect technique (aw-SIT) programs against Ceratitis capitata (Wiedemann) is currently measured by using indirect methods as the wild: sterile male ratio captured in monitoring traps. In the past decade, molecular techniques have been used to improve these methods. The development of a polymerase chain reaction-restriction fragment-length polymorphism-based method to identify the transfer of sterile sperm to wild females, the target of SIT, was considered a significant step in this direction. This method relies on identification of sperm by detecting the presence of Y chromosomes in spermathecae DNA extract complemented by the identification of the genetic origin of this sperm: Vienna-8 males or wild haplotype. However, the application of this protocol to aw-SIT programs is limited by handling time and personnel cost. The objective of this work was to obtain a high-throughput protocol to facilitate the routine measurement in a pest population of sterile sperm presence in wild females. The polymerase chain reaction-restriction fragment-length polymorphism markers previously developed were validated in Mediterranean fruit fly samples collected from various locations worldwide. A laboratory protocol previously published was modified to allow for the analysis of more samples at the same time. Preservation methods and preservation times commonly used for Mediterranean fruit fly female samples were assessed for their influence on the correct molecular detection of sterile sperm. This high-throughput methodology, as well as the results of sample management presented here, provide a robust, efficient, fast, and economical sterile sperm identification method ready to be used in all Mediterranean fruit fly SIT programs
Metabolic responses to iron deficiency in roots of Carrizo citrange [Citrus sinensis (L.) Osbeck. x Poncirus trifoliata (L.) Raf.]
No full textThe effects of iron (Fe) deficiency on the low-molecular-weight organic acid (LMWOA) metabolism have been investigated in Carrizo citrange (CC) [Citrus sinensis (L.) Osb. x Poncirus trifoliata (L.) Raf.] roots. Major LMWOAs found in roots, xylem sap and root exudates were citrate and malate and their concentrations increased with Fe deficiency. The activities of several enzymes involved in the LMWOA metabolism were also assessed in roots. In the cytosolic fraction, the activities of malate dehydrogenase (cMDH) and phosphoenolpyruvate carboxylase (PEPC) enzymes were 132 and 100% higher in Fe-deficient conditions, whereas the activity of pyruvate kinase was 31% lower and the activity of malic enzyme (ME) did not change. In the mitochondrial fraction, the activities of fumarase, MDH and citrate synthase enzymes were 158, 117 and 53% higher, respectively, in Fe-deficient extracts when compared with Fe-sufficient controls, whereas no significant differences between treatments were found for aconitase (ACO) activity. The expression of their corresponding genes in roots of Fe-deficient plants was higher than that measured in Fe-sufficient controls, except for ACO and ME. Also, dicarboxylate-tricarboxylate carrier (DTC) expression was significantly increased in Fe-deficient roots. In conclusion, Fe deficiency in CC seedlings causes a reprogramming of the carbon metabolism that involves an increase of anaplerotic fixation of carbon via PEPC and MDH activities in the cytosol and a shift of the Krebs cycle in the mitochondria towards a non-cyclic mode, as previously described in herbaceous species. In this scheme, DTC could play an important role shuttling both malate and reducing equivalents between the cytosol and the mitochondria. As a result of this metabolic switch malate and citrate concentrations in roots, xylem sap and root exudates increase
Mechanical Biosensors in Biological and Food Area: a Review
Get PDFA review of state the art about the structure, classification and operation of biosensors applied in food and biological areas is presented. This review is focused to mechanical biosensors that use mill, micro and nanocantilevers. Basic concepts of atomic force microscopy and optical systems, used as testing platform of biosensors are described. The most funcionalized strategies and geometrical configurations are also explained. Mathematical methods for evaluating the performance in static and dynamic mode of the mechanical biosensors are reviewed and examples of application in biological and food areas are provided. An overall description of the operational effect of operation conditions and design variables on the sensitivity devices is also proposed. A brief description of the design processes and manufacturing of cantilevers based silicon technology as well as information about BioMEMS and BioNEMS are provided. Finally, overall tends in research, development and commercialization of biosensors are described briefly as well as probable areas of development in food biosensors. Thereby, this review provides an overall view of biosensors, as an exploratory guide to identify the most important aspects of this technology
¿Y por qué Cipreses?
Get PDFTodo comenzó en el otoño de 1971 cuando, unos viveros valencianos de plantas ornamentales, nos trajeron al laboratorio de Patología Vegetal del Instituto Valenciano de Investigaciones Agrarias (IVIA) unas macetas plantadas de cipreses mediterráneos (Cupressus sempervirens) que mostraban una importante pérdida foliar indicando, con ello, que se encontraban enfermos. Estudiados minuciosamente, detectamos que sus partes aéreas estaban parasitadas por un agente micótico del género Pestalotiopsis. Consultada la escasa bibliografía española y la extranjera comprobamos que esta micósis no estaba señalada en el ciprés lo que nos indujo presentarla al mundo científico mediante la publicación en el año 1972 del trabajo “Un marchitamiento y secado de hojas y ramas jóvenes de origen micológico en el ciprés” en los Anales del Instituto Nacional de Investigaciones Agrarias (INIA). Posteriormente, en el año 1976, la Commonwealth Mycological Institute utilizó los datos allí descritos para completar el sheet nº 514 de sus “Descriptions of Pathogenic Fungi and Bacteria”. Ambas referencias sirvieron para darnos a conocer en el ambiente científico como investigadores interesados en los problemas patogénicos de este interesante
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First Report of Alternaria alternata Causing Postharvest Black Spot of Fresh Date Palm Fruit in Spain
No full textSugar as nutritional supplement for the zoophytophagous predator Nesidiocoris tenuis
No full textNesidiocoris tenuis (Reuter) (Hemiptera: Miridae) is a zoophytophagous predator widely used in integrated pest management programs in both greenhouse and open-field tomato crops. Mass rearing of N. tenuis is greatly dependent on Ephestia kuehniella Zeller (Lepidoptera: Pyralidae) eggs as food source. Moreover, the addition of this factitious prey after the inoculative releases of N. tenuis under field conditions is recommended to facilitate establishment of this mirid. However, E. kuehniella eggs are expensive and availability is limited. One possible strategy to reduce the amount of E. kuehniella eggs needed is the provision of sugar. In this work, the effect of sucrose as nutritional supplement on selected life-history traits of N. tenuis was studied. The addition of sucrose (0.5 M) ad libitum to a diet of E. kuehniella eggs significantly increased the progeny of N. tenuis and did not affect survival of nymphs nor developmental time. Moreover, addition of sucrose significantly reduced the number of E. kuehniella eggs consumed. These results may have practical implications of interest in mass rearing systems of N. tenuis and its management in fields and greenhouses as a part of biological control programs
