ReDivia - Repositorio Digital de l'Instit Valencià d'Investigacions Agràries
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Symptoms induced by transgenic expression of p23 from Citrus tristeza virus in phloem-associated cells of Mexican lime mimic virus infection without the aberrations accompanying constitutive expression
Get PDFCitrus tristeza virus (CTV) is phloem restricted in natural citrus hosts. The 23-kDa protein (p23) encoded by the virus is an RNA silencing suppressor and a pathogenicity determinant. The expression of p23, or its N-terminal 157-amino-acid fragment comprising the zinc finger and flanking basic motifs, driven by the constitutive 35S promoter of cauliflower mosaic virus, induces CTV-like symptoms and other aberrations in transgenic citrus. To better define the role of p23 in CTV pathogenesis, we compared the phenotypes of Mexican lime transformed with p23-derived transgenes from the severe T36 and mild T317 CTV isolates under the control of the phloem-specific promoter from Commelina yellow mottle virus (CoYMV) or the 35S promoter. Expression of the constructs restricted to the phloem induced a phenotype resembling CTV-specific symptoms (vein clearing and necrosis, and stem pitting), but not the non-specific aberrations (such as mature leaf epinasty and yellow pinpoints, growth cessation and apical necrosis) observed when p23 was ectopically expressed. Furthermore, vein necrosis and stem pitting in Mexican lime appeared to be specifically associated with p23 from T36. Phloem-specific accumulation of the p23158-209(T36) fragment was sufficient to induce the same anomalies, indicating that the region comprising the N-terminal 157 amino acids of p23 is responsible (at least in part) for the vein clearing, stem pitting and, possibly, vein corking in this host
Sugar provisioning maximizes the biocontrol service of parasitoids
No full textThere is increasing interest in the use of food supplements in agriculture to enhance the performance of parasitoids as part of conservation biological control. Nevertheless, there is limited evidence demonstrating the effectiveness of this approach, and this shortage of successful examples raises doubt regarding the validity of this approach. The use of sugar sources relies on tiered premises that: (i) parasitoids are sugar limited and (ii) this limitation is alleviated through the provision of sugar sources, thereby increasing both (iii) parasitoid fitness and (iv) the population density, which together lead to (v) an increase in parasitism. In the present study, we address these five premises through experiments examining the release of the parasitoid Aphytis melinus DeBach (Hymenoptera: Aphelinidae) into the citrus agroecosystem with and without sugars. The results demonstrated that A.melinus is sugar limited when honeydew producers are scarce in the field. The provision of sugars did not increase the sugar contents in A.melinus females but rather increased the realized fecundity in these parasitoids, suggesting that females use energy for foraging and oviposition. Sugar sources increased the parasitoid population density twofold, and this increase most likely reflects the enhanced parasitoid longevity. Higher population densities and the increased realized fecundity of A.melinus obtained from trees with sugars were reflected in a twofold increase of parasitized hosts. Synthesis and applications. This study provides the first evidence supporting the five premises underlying sugar provisioning for parasitoids and demonstrates the potential value of sugar provisioning to enhance natural pest control in agricultural systems. This study provides the first evidence supporting the five premises underlying sugar provisioning for parasitoids and demonstrates the potential value of sugar provisioning to enhance natural pest control in agricultural systems
Acta Horticulturae
No full textGamma irradiation is widely used to obtain seedless citrus fruits. Herein, different new clones obtained by bud irradiation of several seedy citrus cultivars grown in the Mediterranean were studied to assess seedlessness, pollen germination, fruit characteristics and quality attributes. Findings indicate that irradiation altered aspects other than seedlessness, such as pollen germination, and some of the clones presented fruits with different weight, size, acidity and maturity index. Fruit quality and nutritional bio-components also were affected. Our results indicated high contents in natural antioxidants as vitamin C and phenolic compounds in these citrus varieties, and provide a qualitative and quantitative survey of the fruit taste and organoleptic quality. High-performance liquid chromatographic methods were used to identify and quantify these bioactive compounds. These aspects are important for the consumer that demands the prevention of health problems through nutrition and certain fruit quality traits, including fruit size, internal quality, good rind colour and easy peeling. All irradiated clones studied presented lower seed numbers and reduced pollen germination compared to the corresponding controls, and some of these clones, which ripen late in the season and whose fruit quality is maintained or improved, are in the process of protection. In conclusion, budwood irradiation is a suitable technique to improve cultivars, produce seedless cultivars, adjust ripening time or raise the content of health-promoting compounds
Acta Horticulturae
No full textIn the Mediterranean area, citrus fruits are primarily produced for the fresh fruit market and Spain is the principal producer of the area. Seedlessness is one of the most important characteristics for mandarin fresh fruits. Triploid hybrids allow implementing this trait in commercial cultivars. In this work we described 'Alborea' and 'Albir', two new triploid hybrids originated from the IVIA triploid breeding program, which will be soon released to growers. 'Alborea' was obtained from an open pollinated 'Fortune' mandarin. Fruits reach optimum maturity at the beginning of January, although they can be harvested from December until the end of January. Fruits are easy-to-peel, with a diameter of 50-60 mm, and rind is deep orange red in color. 'Albir' was obtained from a cross between 'Fortune' and 'Kara' mandarins. Fruits reach optimum maturity at the beginning of February, although they can be harvested from January until second half of February. Fruits are easy-to-peel with a diameter of 60-70 mm and fruit rind is orange red in color. This variety has the same origin as 'Safor', a previously released triploid hybrid. The fruits of the two varieties are somewhat similar, but 'Albir' matures one month earlier. With these cultivars, 'Albir' and 'Safor', it will be possible to supply similar fruits to the market from January to the end of March
Acta Horticulturae
No full textIt is believed that Citrus medica, C. maxima, C. reticulata and C. micrantha have generated all cultivated citrus species. Depending on the classification, lemons and limes are classified either into two species, C. limon and C. aurantifolia (Swingle and Reece, 1967) or into more than 30 (Tanaka, 1977). In order to study the molecular phylogeny of this citrus group, we analyzed 23 targeted sequenced nuclear genes and used three mitochondrial and five chloroplastic markers for 15 lemons and limes compared with representatives of the four basic taxa. We observed three main groups, each one derived from direct interspecific hybridizations: (1) the Mexican lime group (C. aurantifolia), including C. macrophylla, arising from hybridizations between papeda (C. micrantha) and citron (C. medica); (2) the yellow lemon group (C. limon) that are hybrids between sour orange (C. aurantium, which is believed to be a hybrid between C. maxima and C. reticulata) and citron; and (3) a rootstock lemon/lime group (Rough lemon and Rangpur lime) that are hybrids between an acid mandarin and a citron. We also identified different probable backcrosses and genotypes with more complex origin. None of the analyzed limes and lemons shared the C. medica cytoplasm, while this taxon is the common nuclear contributor of all limes and lemons. Limes and lemons appear to be a very complex citrus varietal group with the contribution of the 4 basic taxa. Neither the Swingle and Reece classification nor the Tanaka fit with the genetic evidence
Short and long-term efficacy and phytotoxicity of phosphine against Rhynchophorus ferrugineus in live Phoenix canariensis palms
Get PDFThe red palm weevil, Rhynchophorus ferrugineus, is a palm borer native to South Asia which has spread mainly due to the unintended movement of infested planting material. As a result, this species has become the most destructive palm pest in the world. The difficulty of detecting the early stages of infestation due to its cryptic life cycle has led many countries to implement, strict pre- and post-entry quarantine regulations to prevent further spread. However, there are no quarantine protocols to ensure that palm material for planting is free of R. ferrugineus. The aim of this study has been to determine the efficacy of aluminium phosphide as a safe quarantine treatment against different stages of R. ferrugineus and the possible phytotoxic effects on live Phoenix canariensis palms. Our results confirm that a dose of 1.14 g/m(3) for 2 days is enough to kill all stages of R. ferrugineus in live palms with no phytotoxic effects on treated palms for up to one year after the treatment. This procedure, which could be easily applied in sealed containers used for palm trade, could drastically reduce risks associated to palm movement worldwide
Assessment of cluster yield components by image analysis
No full textBackground:
Berry weight, berry number and cluster weight are key parameters for yield estimation for wine and tablegrape industry. Current yield prediction methods are destructive, labour-demanding and time-consuming. In this work, a new methodology, based on image analysis was developed to determine cluster yield components in a fast and inexpensive way.
Results:
Clusters of seven different red varieties of grapevine (Vitis vinifera L.) were photographed under laboratory conditions and their cluster yield components manually determined after image acquisition. Two algorithms based on the Canny and the logarithmic image processing approaches were tested to find the contours of the berries in the images prior to berry detection performed by means of the Hough Transform. Results were obtained in two ways: by analysing either a single image of the cluster or using four images per cluster from different orientations. The best results (R-2 between 69% and 95% in berry detection and between 65% and 97% in cluster weight estimation) were achieved using four images and the Canny algorithm. The model's capability based on image analysis to predict berry weight was 84%.
Conclusion:
The new and low-cost methodology presented here enabled the assessment of cluster yield components, saving time and providing inexpensive information in comparison with current manual methods. (c) 2014 Society of Chemical Industr
Acta Horticulturae
No full textCitrus reticulata is considered one of the four main ancestral taxa of cultivated citrus and is widely associated with the mandarin horticultural group. However, several studies suggest introgressions of other taxa and the precise structure of the mandarin group is not known. To analyse the structuration of mandarin germplasm and the potential interspecific introgressions, 208 accessions were genotyped by the KASPar method, with sixty-seven single nucleotide polymorphism (SNP) markers mined in 27 nuclear genes and in clementine BAC-ends. These SNP markers were employed for the study of 208 genotypes comprised of 169 ` mandarin-like' genotypes and 39 genotypes belonging to ancestral taxa. Structure software was used to identify groups within the mandarin germplasm. Six mandarin groups were identified, some of them in agreement with the species defined by Tanaka. Many mandarins were located between these mandarin groups, indicating a high level of admixture between the identified parental groups. New insights in the organization of mandarin germplasm and its structure are presented in this work, which will be useful for better management of citrus germplasm collections
Use of "ChemSensor" as an early discrimination tool of Iberian pig semen according to their freezability
Get PDFPara favorecer el uso de dosis de inseminación de semen de porcino congelado-descongelado a nivel comercial, sería interesante conocer de antemano si el semen de verraco congelará bien o mal. El objetivo de este estudio fue evaluar el 'ChemSensor' (cromatógrafo de gases-masas unido a un software de análisis quimiométrico) como herramienta precoz de discriminación entre eyaculados según su congelabilidad. Para ello se utilizaron 33 eyaculados de verracos de raza Ibérica de los cuales se cogió una alícuota de 1 ml de semen y se analizó con el 'ChemSensor', el resto del eyaculado fue congelado-descongelado usando un protocolo estandarizado, para determinar su congelabilidad (buenos y malos congeladores) en función del porcentaje de espermatozoides con la membrana plasmática intacta y el porcentaje de espermatozoides móviles totales post-descongelación. Para el análisis con el 'ChemSensor', las muestras se volatilizaron e ionizaron descomponiéndolas en diferentes iones con un tamaño determinado, que se usaron como variables de discriminación, para separar los eyaculados en función de su congelabilidad. El 'ChemSensor' fue capaz de discriminar todos los eyaculados de los buenos congeladores; y dentro del grupo de los malos congeladores solamente una muestra fue clasificada erróneamente. Debido al reducido número de muestras, la distancia obtenida entre grupos (2,62), aunque no muy elevada, podría considerarse como significativa, aunque sería necesario un mayor número de muestras para poder crear un modelo matemático más robusto. En conclusión, el 'ChemSensor' es una posible herramienta adecuada para la discriminación precoz de eyaculados de cerdo Ibérico en función de su congelabilidad
Annual Review of Entomology
No full textParasitoids of the hymenopterous family Encyrtidae are one of the most important groups of natural enemies of soft scale insects and have been used extensively in biological control. We summarize existing knowledge of the biology, ecology, and behavior of these parasitoids and how it relates to biological control. Soft scale stage/size and phenology are important determinants of host range and host utilization, which are key aspects in understanding how control by these parasitoids is exerted. Furthermore, the nutritional ecology of encyrtids and their physiological interactions with their hosts affect soft scale insect population dynamics. Lastly, the interactions among encyrtids, heteronomous parasitoids, and ants shape parasitoid species complexes and consequently have a direct impact on the biological control of soft scale insects