ReDivia - Repositorio Digital de l'Instit Valencià d'Investigacions Agràries
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Assessment of the diversity and dynamics of Plum pox virus and aphid populations in transgenic European plums under Mediterranean conditions
No full textThe molecular variability of Plum pox virus (PPV) populations was compared in transgenic European plums (Prunus domestica L.) carrying the coat protein (CP) gene of PPV and non-transgenic plums in an experimental orchard in Valencia, Spain. A major objective of this study was to detect recombination between PPV CP transgene transcripts and infecting PPV RNA. Additionally, we assessed the number and species of PPV aphid vectors that visited transgenic and non-transgenic plum trees. Test trees consisted of five different P. domestica transgenic lines, i.e. the PPV-resistant C5 'HoneySweet' line and the PPV-susceptible C4, C6, PT6 and PT23 lines, and non-transgenic P. domestica and P. salicina Lind trees. No significant difference in the genetic diversity of PPV populations infecting transgenic and conventional plums was detected, in particular no recombinant between transgene transcripts and incoming viral RNA was found at detectable levels. Also, no significant difference was detected in aphid populations, including viruliferous individuals, that visited transgenic and conventional plums. Our data indicate that PPV-CP transgenic European plums exposed to natural PPV infection over an 8 year period caused limited, if any, risk beyond the cultivation of conventional plums under Mediterranean conditions in terms of the emergence of recombinant PPV and diversity of PPV and aphid populations
Development of a sensor-controlled sprayer for applying low-volume bait treatments
No full textFruit flies that are very important pests on a large number of crops, can be controlled efficiently using low-volume applications to deposit large droplets of insecticidal bait on the exterior of the crop canopy. To meet these requirements a sensor-controlled sprayer was developed, consisting of a hydraulic system that was fitted with air induction nozzles, an ultrasonic sensor and a control unit with display and navigator keys. This sprayer was designed to apply low spray volumes as very coarse spray droplets. The nozzle with the coarsest spray was an Al11003 operated at 0.1 MPa. The sensor recognised differences in crop canopy so could adapt the application to different citrus crop systems in commercial orchards. The sensor-controlled sprayer was tested measuring the size of deposited droplets on the target and observing its performance on the field. Coverage was predominently on the outer canopy zone with little inside the canopy. This sprayer provides an alternative to cover treatments, not only from environmental but also from economic reasons. (C) 2008 Elsevier Ltd. All rights reserved
Oocyte activation procedures and influence of serum on porcine oocyte maturation and subsequent parthenogenetic and nuclear transfer embryo development
No full textThe viability of SCNT embryos is poor, with an extremely low cloned piglet production rate. In the present work, we studied the effect of three activation protocols based. on ionomycin treatment (5 mu M ionomycin for 5 min and incubated in 2 mM 6-DMAP for 3.5 h) or electric stimuli (two square wave electrical DC pulses of 1.2 kV/cm for 30 mu s) combined or not with 6-DMAP on parthenogenetic embryo development. Oocytes activated by ionomycin plus 6-DMAP showed lower cleavage (47.2 vs. 78.5-81.5; p < 0.05) and blastocyst rates (11.3 vs. 29.2-32.1; p < 0.05) than those activated by electrical and electrical plus 6-DMAP treatments. Also, we studied the effect of addition of serum to maturation medium (0% vs. 10%) on nuclear maturation and further parthenogenetic and SCNT embryo development. We observed in the parthenogenetic embryos that cleavage rates in the serum-free group were significantly higher than in the serum-supplemented group (81.8 vs. 69.6% respectively; p < 0.05), although these differences were not detected in blastocyst rates or blastocyst nuclei numbers. Regarding SCNT embryos, no significant differences were observed in cleavage or blastocyst rates between different experimental groups of SCNT embryos. In conclusion, electrical pulse followed or not by 6-DMAP was found to be an efficient procedure to artificially activate MII porcine oocytes. Moreover, the addition of serum to oocyte maturation media did not seem to improve parthenogenetic or SCNT porcine embryo development
Controlled in vivo infestation of mandarin fruit with Ceratitis capitata for development of quarantine treatments
Get PDFMovement of citrus fruit from Ceratitis capitata-infested areas requires mandatory quarantine treatments. Development of such treatments requires the use of infested fruit. The in vivo approach is the most realistic way to obtain these fruit. However, it requires previous studies to determine the optimal fruit:fly ratio to minimize the number of decayed fruit and to maximize the number of flies per fruit obtained. In this study, the optimal fruit:fly ratio for the in vivo infestation of mandarin fruit was investigated. The effect of different fruit:fly ratios from 1:5 to 1:50 for an exposure time of up to 3 days on the number of both decayed fruit and puparia per fruit was determined. Provided that an adequate fungicide treatment is applied before the infestation to avoid fruit decay, the use of a 1 :10 fruit:fly ratio for 48 h is enough to obtain almost 20 healthy puparia per fruit. These results allow the use of the in vivo approach to develop quarantine treatments against C. capitata in mandarins
Survival strategies and pathogenicity of Ralstonia solanacearum phylotype II subjected to prolonged starvation in environmental water microcosms
No full textSurvival strategies exhibited over 4 years by Ralstonia solanacearum phylotype (ph) II biovar (bv) 2 in environmental water microcosms were examined. The bacterium is a devastating phytopathogen whose ph 11 bv 2 causes bacterial wilt in solanaceous crops and ornamental plants. Outbreaks of the disease may originate from dissemination of the pathogen in watercourses, where it has to cope with prolonged nutrient limitation. To ascertain the effect of long-term starvation on survival and pathogenicity of R. solanacearum in natural water microcosms, survival experiments were conducted. Microcosms were prepared from different sterile river water samples, inoculated separately with two European strains of ph 11 at 10(6) C.f.U. ml(-1) and maintained at 24 degrees C for 4 years. In all assayed waters, starved R. solanacearum remained in a non-growing but culturable state during the first year, maintaining approximately the initial numbers. Thereafter, part of the population of R. solanacearum progressively lost the ability to form colonies, and non-culturable but metabolically active cells appeared. During the whole period, the bacterium remained pathogenic on host plants and underwent a transition from typical bacilli to small cocci which tended to aggregate. Some starved R. solanacearum cells filamented and formed buds. Starvation response, viable but non-culturable state, morphological changes and aggregation have not previously been reported for this pathogen as survival mechanisms induced in oligotrophic conditions. The potential existence of long-starved pathogenic cells in environmental waters may raise new concerns about the epidemiology of bacterial wilt disease
Importance of ground-dwelling predators on controlling 'Ceratitis capitata 'in Spanish citrus orchards
No full textThere is little information on the role of the predaceous ground arthropods in citrus crops in
Spain. In the present work we report on the activity-density of the predominant ground predators belonging to Araneae, Dermaptera, Staphylinidae and Carabidae. Four citrus groves in Valencia (Spain) were monitored by pitfall trapping across the diagonal in each orchard from August 2003 to April 2007. For the most abundant predators within Araneae (Pardosa cribata Simon), Dermaptera (Forficula auricularia L.) and Carabidae [(Pseudophonus rufipes (DeGeer)], it was assessed the capacity to prey on the Ceratitis capitata (Wiedemann) stages that can be found on the citrus ground (third instar larvae, pupae and teneral adults).
Moreover, functional response parameters against this prey were also obtained. Finally, preydetection tools (molecular markers and immuno-assays) are being developed to establish the role of those predators in the control of C. capitata under field conditions
Comportamiento agronómico de diferentes cvs. de alcachofa multiplicadas por semilla
Get PDFSe estudia el comportamiento agronómico y las características morfológicas de una
colección de 12 cultivares (cvs) de alcachofa (Cynara scolymus) multiplicadas por semilla,
comparadas con los cvs. Blanca de Tudela y Violeta de Provence, de multiplicación
vegetativa. Los cvs. multiplicados por semilla se sembraron el 14 de junio de 2005,
transplantando toda la experiencia el 1 de agosto. Todas las plantas fueron sometidas
a tres tratamientos sucesivos con ácido giberélico con una concentración de 30 ppm.
con abono foliar al 0,1%, aplicaciones que se realizaron los días 20 de septiembre, 5 y
20 de octubre.
El mayor rendimiento comercial se obtuvo con el cv. Madrigal que fue también el
más tardío. La mayor precocidad correspondió al cv. Blanca de Tudela, sin diferencias
estadísticamente significativas (e.s.) en la producción acumulada en enero respecto
a los cvs. A-106, Victoria y Lorca. El peso medio de los capítulos osciló entre los 184
y 183 g de los cvs. AR-1 y Madrigal durante el mes de marzo, frente a 97 y 99 g de
los cvs. Victoria y Lorca, en ese mismo mes
Toxoptera citricida (Kirkaldy) (Hemiptera, Aphididae) and its natural enemies in Spain
Get PDFThe aphid Toxoptera citricida (Kirkaldy) is the most efficient vector of Citrus tristeza virus (CTV) in the world, and it can transmit the more aggressive isolates of CTV. T. citricida is present in most of the zones growing citrus in the world, but it was absent from the Mediterranean Basin and North America until middle 1990’s. Nevertheless, it was detected on citrus trees in 1994 in Madeira,
in 1995 in Florida, in 2002 in Asturias, Spain (in yellow water traps), in 2003 in northern mainland Portugal, and in 2004 in southern Galicia, Spain, even though the three last detections were not published till 2005. As a consequence of its detection in Spain, several surveys and studies were undertaken from 2005. The main results are listed below. Currently, T. citricida is present on citrus along the Atlantic coast in the northwest quadrant of the Iberian Peninsula. In Asturias, it presents a minimum in winter and other one in summer, but the last one is shorter than the minimum which Mediterranean citrus aphids have too. Chaenomeles speciosa (Rosaceae) has been found as an occasional alternative host for T. citricida. No winter eggs of T. citricida have been seen. CTV spread has not been detected in northern Spain. T. citricida is attacked in the Atlantic area by several natural enemy species, most of them present in the Mediterranean zone
Comparación de la producción ecológica e integrada de hortícolas en una experiencia de ocho años: estudio de las propiedades físico-químicas, químicas y biológicas del suelo
Get PDFEn un ensayo experimental que se viene realizando desde el año 1998 en el Centro de Formación de la Fundación Ruralcaja en Paiporta (Valencia), se están comparando dos sistemas agrarios de hortícolas en Producción Ecológica versus Producción Integrada con la finalidad de comprobar los efectos de estas dos formas de manejo a largo plazo tanto sobre los cultivos como sobre el suelo. En esta comunicación se presentan los resultados correspondientes a los efectos provocados sobre las características del suelo: físico-químicas (pH y conductividad eléctrica), química (nutrientes asimilables), y biológicas (materia orgánica y actividad enzimáticas), tras ocho años de aplicación de las distintas técnicas de cultivo