ReDivia - Repositorio Digital de l'Instit Valencià d'Investigacions Agràries
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Development of Viral Vectors Based on Citrus leaf blotch virus to Express Foreign Proteins or Analyze Gene Function in Citrus Plants
Get PDFViral vectors have been used to express foreign proteins in plants or to silence endogenous genes. This methodology could be appropriate for citrus plants that have long juvenile periods and adult plants that are difficult to transform. We developed viral vectors based on Citrus leaf blotch virus (CLBV) by duplicating a minimum promoter (92 bp) either at the 3′ untranslated region (clbv3′pr vector) or at the intergenic region between the movement and coat protein (CP) genes (clbvINpr vector). The duplicated fragment (–42/+50) around the transcription start site of the CP subgenomic RNA (sgRNA) had the full promoter activity and induced synthesis of a new sgRNA in infected plants. Agroinoculation with these vectors resulted in systemic infection of Nicotiana benthamiana and the resulting virions systemically infected citrus plants. A clbvINpr vector carrying the green fluorescent protein (GFP) gene expressed GFP in citrus plants and triggered gfp silencing in gfp-transgenic citrus plants, and vectors carrying fragments of the phytoene desaturase or the magnesium chelatase genes incited a silencing phenotype in citrus plants. These silenced phenotypes persisted in successive flushes. Because CLBV infections are symptomless in most citrus species, the effective silencing induced by CLBV-derived vectors will be helpful to analyze citrus gene function
Does host adaptation of Tetranychus urticae populations in clementine orchards with a Festuca arundinacea cover contribute to a better natural regulation of this pest mite?
No full textTetranychus urticae Koch (Acari: Tetranychidae) is a key pest of clementine mandarins, Citrus clementina Tanaka (Rutaceae), in Spain. This mite is highly polyphagous and can be easily found in clementine orchards, both in the trees and in the associated flora. In a previous study we found that the use of a cover of Festuca arundinacea Schreber (Poaceae) offered a better regulation of T. urticae populations than either bare soil or the traditional wild cover, which included a mix of weed species. We hypothesized that the selection of two host races of T. urticae, specialized in F. arundinacea and C. clementina, could partly explain the results obtained (bottom-up regulation). Reciprocal transplant experiments show that sympatric deme x host combinations had higher mean fitness values than the allopatric combinations in clementine, but not in F. arundinacea, for most of the fitness parameters evaluated in our study. Because local adaptation implies mean deme fitness to be systematically higher for the sympatric deme x habitat combinations than for the allopatric ones, these results can be taken as indicative of occurrence of local adaptation in T. urticae. Molecular genetic analyses with microsatellite markers support this conclusion and indicate that local adaptation of T. urticae found in our system may indeed contribute to a better natural regulation of this mite
In-line sorting of irregular potatoes by using automated computer-based machine vision system
No full textThis study was conducted to develop a fast and accurate computer-based machine vision system for detecting irregular potatoes in real-time. Supported algorithms were specifically developed and programmed for image acquisition and processing, controlling the whole process, saving the classification results and monitoring the progress of all operations. A database of images was first formulated from potatoes with different shapes and sizes, and then some essential geometrical features such as perimeter, centroid, area, moment of inertia, length and width were extracted from each image. Also, eight shape parameters originated from size features and Fourier transform were calculated for each image in the database. All extracted shape parameters were entered in a stepwise linear discriminant analysis to extract the most important parameters that most characterized the regularity of potatoes. Based on stepwise linear discriminant analysis, two shape features (roundness and extent) and four Fourier-shape descriptors were found to be effective in sorting regular and irregular potatoes. The average correct classification was 96.5% for a training set composed of 228 potatoes and then the algorithm was validated in another testing set composed of 182 potatoes in a real-time operation. The experiments showed that the success of in-line classification of moving potatoes was 96.2%. Concurrently, the well-shaped potatoes were classified by size achieving a 100% accuracy indicating that the developed machine vision system has a great potential in automatic detection and sorting of misshapen products. (c) 2012 Elsevier Ltd. All rights reserved
Comparative use of InDel and SSR markers in deciphering the interspecific structure of cultivated citrus genetic diversity: a perspective for genetic association studies
No full textGenetic stratification associated with domestication history is a key parameter for estimating the pertinence of genetic association study within a gene pool. Previous molecular and phenotypic studies have shown that most of the diversity of cultivated citrus results from recombination between three main species: C. medica (citron), C. reticulata (mandarin) and C. maxima (pummelo). However, the precise contribution of each of these basic species to the genomes of secondary cultivated species, such as C. sinensis (sweet orange), C. limon (lemon), C. aurantium (sour orange), C. paradisi (grapefruit) and recent hybrids is unknown. Our study focused on: (1) the development of insertion-deletion (InDel) markers and their comparison with SSR markers for use in genetic diversity and phylogenetic studies; (2) the analysis of the contributions of basic taxa to the genomes of secondary species and modern cultivars and (3) the description of the organisation of the Citrus gene pool, to evaluate how genetic association studies should be done at the cultivated Citrus gene pool level. InDel markers appear to be better phylogenetic markers for tracing the contributions of the three ancestral species, whereas SSR markers are more useful for intraspecific diversity analysis. Most of the genetic organisation of the Citrus gene pool is related to the differentiation between C. reticulata, C. maxima and C. medica. High and generalised LD was observed, probably due to the initial differentiation between the basic species and a limited number of interspecific recombinations. This structure precludes association genetic studies at the genus level without developing additional recombinant populations from interspecific hybrids. Association genetic studies should also be affordable at intraspecific level in a less structured pool such as C. reticulata
Predatory Mite, Amblyseius Swirskii (Acari: Phytoseiidae), for Biological Control of Asian Citrus Psyllid, Diaphorina Citri (Hemiptera: Psyllidae)
Get PDFThe Asian Citrus Psyllid (ACP), Diaphorina citri Kuwayama (Hemiptera: Psyllidae) is a serious pest of citrus in many citrus-producing regions. It vectors the bacterium 'Candidatus Liberibacter asiaticus' thought to be the causal agent of the devastating "Huanglongbing" (HLB) or citrus greening disease. Both pest and the disease are well established in Florida. Several insect predators, particularly lady beetles and the parasitoid Tamarixia radiata (Waterston) (Hymenoptera: Eulophidae), are known to cause significant mortality to ACP immatures. However, there are no reports on the effectiveness of predatory mites against ACP. We evaluated the suitability of D. citri eggs and nymphs as prey for the predatory mite Amblyseius swirskii Athias-Henriot (Acari: Phytoseiidae) in laboratory arenas, and its potential to reduce psyllid populations in the glasshouse on caged Murraya paniculata (L.) Jack plants. Mortality of D. citri eggs on M. paniculata shoots exposed to A. swirskii in plastic arenas was 4 times greater after 6 d compared to unexposed control plants. Mites were also observed sucking out body fluids of first instar nymphs. In the glasshouse, total number of D. citri adults collected over 8 wk from infested plants in ventilated cylinders with A. swirskii present averaged 80% less than the control without mites. These findings showed a significant negative impact of A. swirskii on D. citri under controlled conditions. Further research needs to focus on rates and frequency of release, impact of A. swirskii on D. citri populations in citrus and other hosts under field conditions, and interactions of A. swirskii and D. citri with native predatory mites
Evaluación de la resistencia a Phytophthora capsici y Phytophthora nicotianae var. parasitica de tres portainjertos comerciales de pimiento
Get PDFLos problemas que se plantean con Phytophthora capsici y Phytophthora nicotianae var. parasitica (Phytophthora parasitica) para su control, utilizando distintos procedimientos de desinfección del suelo, han motivado la evaluación de vías alternativas utilizando plantas injertadas sobre porta-injertos resistentes. Esta técnica goza de un éxito importante para el control de otros patógenos del suelo y es una técnica compatible con la producción ecológica. Por ejemplo, en el control del virus del cribado (MNSV) en melón y sandía o en el control de P. parasitica en tomate. Siguiendo esas orientaciones existen en
el mercado, actualmente, patrones que se preconizan con resistencias a patógenos que, a veces, no están suficientemente evaluados. Este hecho ha motivado el trabajo que se resume en esta comunicación
How far may rabbit cage’s space recommendations reach: the gap between science and regulations
Get PDFAnimal welfare is a major concern in livestock production. The impact of housing conditions on animal well-being is under study in several species such as chickens, laying hens, or pigs and, some European Directives have been developed in order to protect animal welfare. In these Directives aspects related to housing conditions have been regulated. Several attempts have been done to propose a European Directive for rabbit farming in terms of welfare protection, but any agreement have been reached for now. One of the main hot spots is related to cages design. Strong efforts are being made nowadays in order to reach a compromise to define cages characteristics which really benefit rabbits’ welfare. In this context, the main aim of this work is to develop a critical review about rabbit does space needs in relation to cages design. It becomes necessary to determine the behavioural needs of
rabbits in terms of welfare, so that the space requirements can be known. This might lead to define appropriate housing conditions, although the needs of the animal can change according to age, learning, diurnal rhythm, season and genetic relations. In general, regarding the height of the cages (as well as width), few papers have been found and a European Food Safety Authorities’ report
recognises, that in the absence of scientific evidence concerning these needs of rabbits, it may be important for growing rabbits to be able to sit and stand with ears erect, as well as rear up occasionally. Regarding the use of platforms, enriching the cage with raised platforms aims at satisfying the doe’s need for isolation from the litter, rather than stimulating exercise. Nevertheless,
the use of platforms may cause hygiene problems which have to be solved. Therefore, elevated platforms might be considered as environmental enrichment elements and not as structural needs. The patent general lack of information in the topic must be considered when new housing conditions are being proposed, and only those aspects which could lead to real improvement of rabbit’s welfare have to be taken into account. The authors propose a cage size for lactating does of 45×75×38 cm (height,
length and width) with a minimum surface of 3,500 cm2 (nest-box not included)
First report of Alternaria alternata causing postharvest black spot of persimmon in Spain
No full textThe use of integrative taxonomy in determining species limits in the convergent pupa coloration pattern of Aphytis species
No full textCorrect species identification in field surveys determines the success of natural enemies in biological control programmes. For such surveys, short-keys, mainly based on one or two morphological characters, are used as a quick-tool to ascertain species identification. However, when the whole character plasticity (the one used in the short-keys) has not been covered or is shared between species, some misidentifications could occur. Aphytis (Hymenoptera: Aphelinidae) are one of the most important natural enemies of armoured scales around the world. Pupa pigmentation pattern is the main character used in short-keys for species identification in field surveys in citrus production areas. However, field surveys in the Iberian Peninsula since 1998 have led to the misidentification of an increasing number of specimens that do not fit with the alpha-taxonomical keys for the described Aphytis species. Integrative taxonomy has recently been used as a helpful tool in solving species limits and/or species assignments. In this study, we present the unification of molecular taxonomy (based on DNA barcodes) and traditional taxonomy, including biological studies, to clarify the species status of unidentified field-collected individuals of Aphytis lingnanensis group and Aphytis chrysomphali group, which parasitize California Red Scale Aonidiella aurantii (Maskell) (Hemiptera: Diaspididae). Our results (molecular, morphological and biological) show that these specimens belong to either Aphytis melinus DeBach or A. chrysomphali (Mercet) species, despite their differences in pupa pigmentation. We propose an integrative taxonomic key for assignment to the correct species for the use in field surveys on CRS in the Iberian Peninsula which takes into account the plasticity of pupa characters and a DNA barcode key for its use with damaged or immature specimens. (C) 2011 Elsevier Inc. All rights reserved
In planta recovery of Erwinia amylovora viable but nonculturable cells
No full textLittle is known about the survival mechanisms of Erwinia amylovora outside its hosts. It has been demonstrated that it enters the viable but nonculturable state (VBNC) when exposed to different types of stress. In the VBNC state, bacterial cells remain viable but unable to grow on the solid general media where they usually do, and are thus undetectable by conventional culture-dependent methods. In this work, we have evaluated the recovery of E. amylovora VBNC cells by passage through pear plantlets, in comparison with other recovery methods commonly used for this pathogen: incubation in KB broth and inoculation of immature fruits. VBNC cells were obtained by exposure of bacterial cells to different types of stress (oligotrophy, nutrient deprivation and chlorine), and recovery assays were performed at 26 degrees C. In all cases, the recovery of VBNC cells was more effective in plantlets than in liquid KB or immature fruits. In fact, when cells were exposed to chlorine for more than 30 min, only passage through host plant gave positive result, enabling recovery of E. amylovora cells few days after inoculation of plants. These results suggest a higher effectiveness of in planta recovery than those performed with liquid KB or detached fruits. Our results support the hypothesis of the VBNC state being part of the E. amylovora life cycle. The potential existence of this physiological state in nature should be taken in consideration in epidemiological studies of fire blight, with the aim to optimize the management and control of this disease