ReDivia - Repositorio Digital de l'Instit Valencià d'Investigacions Agràries
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Genetic variation and evolutionary analysis of broad bean wilt virus 2
No full textThe genetic variation and evolutionary mechanisms of broad bean wilt virus 2 (BBWV-2) were studied by nucleotide sequence analysis of four genomic regions of 30 isolates from different countries. Nucleotide diversity was high (0.198) for a plant virus. Phylogenetic and genetic structure analyses showed low population subdivision, suggesting a significant gene flow between distant geographic areas. Analysis of synonymous and nonsynonymous substitutions showed different negative selection pressures for different parts of the coding regions, but no positive selection was found. Several recombination detection methods showed that some BBWV-2 genomes might have originated from recombination or reassortment
Acta Horticulturae
No full textIn the Mediterranean culture of loquat (Eriobotrya japonica Lindl.), some growers apply a summer water withholding cycle in order to achieve earlier flowering and harvest in the next season. Generally, the first fruit that reach the market have higher commercial value. It has been shown that the duration and severity of the plant water stress imposed is a determinant factor in the flowering time response. Stem water potential (Ψstem), is a useful indicator of plant water status. However, because this measurement cannot be automated it is important to look for alternatives to determine plant water status with plant sensors. In many fruit trees it has been shown that stem dendrometers could be employed as a plant water status indicator. However, in Loquat trees, the usefulness of this technique has not been yet investigated. The experiment was carried out in 2009 with ‘Cardona’ where control fully irrigated trees were compared with trees submitted to water withholding during the summer. Results showed that under mild plant water stress, daily trunk shrinkage (MDS) was a sensitive indicator of plant water status and MDS was able to detect soil water deficit even before that clear differences in Ψstem could be detected. However, when plant water stress became more severe (Ψstem lower than -1.4 MPa), MDS did not increase further. Results suggest that growers can use MDS as a sensitive indicator of the early stage of plant water stress. However, once plant water stress becomes more severe (Ψstem<-1.4 MPa), as it is required to advance flowering, Ψstem is a more useful indicator of plant water stress
Effect of beeswax content on hydroxypropyl methylcellulose-based edible film properties and postharvest quality of coated plums (Cv. Angeleno)
Get PDFThe effect of beeswax (BW) content of hydroxypropyl methylcellulose (HPMC)-BW edible coatings on stand-alone film properties and on postharvest quality of coated 'Angeleno' plums was studied. The coatings contained BW at 4 lipid content levels (0, 20,40 and 60 g/100 g, dry basis). Coated and uncoated plums were stored 4 weeks at 1 degrees C and transferred to 20 degrees C for 1-3 weeks. Addition of BW to the HPMC film matrix reduced film mechanical resistance and oxygen barrier, and improved film moisture barrier. Film mechanical properties showed a good fit with an exponential and/or linear model that could provide a useful tool to predict mechanical properties with others HPMC BW composition mixtures. Coatings with BW reduced plum weight loss compared to HPMC-based coatings with no BW. Plum weight loss decreased as BW content increased from 20 to 40 g/100 g, but above 40 g/100 g BW content, weight loss was not further reduced. Whereas, water vapor permeability of stand-alone films decreased significantly as BW content increased to 60 g/100 g. Coatings reduced plum softening and bleeding, with those with lower BW content being more effective, which could be related to the ability of coatings to create a modified atmosphere in the fruit. Flavor was not affected by coating application. Results indicate that HPMC BW coatings with 20 g/100 g BW would provide the best compromise to extend shelf life of 'Angeleno' plums. (C) 2011 Elsevier Ltd. All rights reserved
The combined use of Bacillus thuringiensis and Nesidiocoris tenuis against the tomato borer Tuta absoluta
No full textSince Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae) was first detected at the end of 2006 in the Mediterranean Basin, several endemic natural enemies have been reported to prey on this exotic pest. The predator Nesidiocoris tenuis Reuter (Hemiptera: Miridae) can regulate T. absoluta populations, because it is able to prey efficiently on T. absoluta eggs. Furthermore, previous studies have demonstrated that first-instar larvae of T. absoluta are highly susceptible to Bacillus thuringiensis (Bt) treatments. In this work, we tested the combination of both approaches under greenhouse conditions. B. thuringiensis formulations were sprayed weekly for two months, three months or throughout the growing cycle, and in all cases, one N. tenuis per plant was also released. Control plants were completely destroyed by the infestation levels reached by T. absoluta. In contrast, all treatments based on B. thuringiensis treatments and releases of N. tenuis reduced leaf damage by more than 97% when compared to the untreated control, with no significant differences among them. Furthermore, yield in the control plants was significantly reduced when compared with all Bt-N. tenuis treatments. Our results demonstrate that when B. thuringiensis treatments are applied immediately after the initial detection of T. absoluta on plants, they do not interfere with N. tenuis establishment in the crop because T. absoluta eggs are available. According to our data, treatments with B. thuringiensis later in the growing season would no longer be necessary because mirids alone would control the pest
Agroinoculation of Citrus tristeza virus Causes Systemic Infection and Symptoms in the Presumed Nonhost Nicotiana benthamiana
Get PDFCitrus tristeza virus (CTV) naturally infects only some citrus species and relatives and within these it only invades phloem tissues. Failure to agroinfect citrus plants and the lack of an experimental herbaceous host hindered development of a workable genetic system. A full-genome cDNA of CTV isolate T36 was cloned in binary plasmids and was used to agroinfiltrate Nicotiana benthamiana leaves, with or without coinfiltration with plasmids expressing different silencing-suppressor proteins. A time course analysis in agroinfiltrated leaves indicated that CTV accumulates and moves cell-to-cell for at least three weeks postinoculation (wpi), and then, it moves systemically and infects the upper leaves with symptom expression. Silencing suppressors expedited systemic infection and often increased infectivity. In systemically infected Nicotiana benthamiana plants, CTV invaded first the phloem, but after 7 wpi, it was also found in other tissues and reached a high viral titer in upper leaves, thus allowing efficient transmission to citrus by stem-slash inoculation. Infected citrus plants showed the symptoms, virion morphology, and phloem restriction characteristic of the wild T36 isolate. Therefore, agroinfiltration of Nicotiana benthamiana provided the first experimental herbaceous host for CTV and an easy and efficient genetic system for this closterovirus
The ground beetle Pseudophonus rufipes revealed as predator of Ceratitis capitata in citrus orchards
Get PDFThe Mediterranean fruit fly Ceratitis capitata (Wiedemann) is a major citrus pest in Spain. Although medfly is being controlled chemically, alternative biorational strategies should be developed, like those based on conservation biological control of polyphagous predators. The ground beetle Pseudophonus rufipes (De Geer) is the most abundant carabid inhabiting the ground of citrus orchards in eastern Spain. However, little is known about its activity-density and predatory role against C. capitata in the citrus agroecosystem. Here, we report on its predatory potential on the medfly's developmental stages that take place in the citrus ground. This carabid species preyed efficiently on C. capitata third instar larvae and especially on pupae but not on teneral adults. Moreover, predation under field conditions was evaluated by detecting C. capitata DNA remains using PCR-based gut-content analysis. Half-life DNA detectability of C. capitata was of 32.33 h. Pseudophonus rufipes specimens were field-collected after C. capitata sterilized pupae were deployed in a commercial citrus orchard. Thereafter, the carabids captured by pitfall traps were analyzed, being DNA-remains of C. capitata detected in 22.2% of them. Data reported here clearly suggest that P. rufipes could play an important role in regulating medfly populations in citrus orchards. This information is particularly useful when biological control conservation strategies are being considered to control this pest
Primary postharvest evaluation of chemicals as inducers of resistance against Penicillium digitatum and Penicillium italicum on citrus fruits
No full textGeneration of Sweet Orange Transgenic Lines and Evaluation of Citrus psorosis virus-derived Resistance against Psorosis A and Psorosis B
No full textCitrus psorosis is a widespread serious disease of citrus caused by Citrus psorosis virus (CPsV). In Argentina and Uruguay, this disease is spread by an unknown vector and there is no natural resistance or tolerance to the disease. There are two types of psorosis, described according to the symptoms observed in citrus trees, psorosis A (PsA) and psorosis B (PsB). PsA protects against the severe effects of the more aggressive type PsB. We have applied pathogen-derived resistance to create a defence mechanism against this virus disease. Sweet orange transgenic lines were obtained containing three different genes of CPsV (54k, 48k and 24k genes) taken from a PsA isolate (CPV-4). Fourteen lines were selected containing 1, 2 or 3 copies of the transgenes and evaluated for their acquired resistance against PsA (CPV 4 from USA) and PsB (CPsV 189-34 from Argentina) isolates. These lines were susceptible to both isolates when graft-infected, although one of the lines carrying the cp gene (CP-96 line) containing two copies of the transgene and expressing a low level of the coat protein showed a delay in symptom expression when inoculated with the PsB isolate
Actas de Horticultura
Get PDFLa espinaca es un cultivo que responde muy bien al aporte de N en muchos casos pero en el que el contenido de nitrato en las hojas no debe sobrepasar unos determinados niveles por razones de seguridad alimentaria. Para determinar la respuesta del cultivo a la disponibilidad de N mineral en el suelo se efectuaron dos ensayos de campo en la zona de Villena (Alicante), uno en cultivo de otoño (septiembre-octubre) y otro en cultivo de invierno-primavera (febrero-mayo). En el primer ensayo, los valores de N mineral disponible en la capa de suelo de 0–30 cm en los cuatro tratamientos aplicados oscilaron de 107 kg N/ha (T1) a 228 kg N/ha (T4), mientras que en el segundo ensayo el rango de variación fue de 146 kg N/ha (T1) a 236 kg N/ha (T4). El diseño experimental fue de bloques completos al azar con seis repeticiones. El riego fue por aspersión. En el primer ensayo, la producción entre los diferentes tratamientos de N mineral disponible no presentó diferencias estadísticamente significativas (p<0.05), mientras que en el segundo ensayo los tratamientos T3 y T4, correspondientes a 191 y 236 kg N/ha, respectivamente, tuvieron una producción significativamente mayor que el tratamiento T1. Los resultados indican que las necesidades de N mineral de la espinaca (en la capa 0-30 cm) en los cultivos de otoño y primavera son de unos 130 y 190 kg/ha, respectivamente, para esta zona y para niveles de producción de 25 t/ha en la producción de otoño y de unas 35 t/ha en la producción de primavera. El contenido de nitrato en la savia de los peciolos de las hojas estuvo muy correlacionado con el nivel de N mineral disponible y los resultados indican que en el cultivo de primavera, contenidos de nitrato en savia de 2500 mg/l o superiores, medidos 60-70 días después de la siembra, indican una nutrición nitrogenada suficiente