ReDivia - Repositorio Digital de l'Instit Valencià d'Investigacions Agràries
Not a member yet
2747 research outputs found
Sort by
Compatibility of Phytoseiulus persimilis and Neoseiulus californicus (Acari: Phytoseiidae) with imidacloprid to manage clementine nursery pests
No full textBiological control is not common in citrus nurseries where chemical control is prevalent. The systemic neonicotinoid imidacloprid applied as a drench is effective against three out of four key pests of young clementine plants in Spain aphids, whiteflies, and scales. However, mites, the fourth key pest, are not control by imidacloprid and could be regulated by introduction of the predatory Phytoseiid mites Phytoseiulus persimilis Athias-Henriot and Neoseiulus californicus (McGregor). The aim of this study was to evaluate the effects of imidacloprid applied as a drench on the demographic parameters of these two predatory mites and the compatibility of P. persimilis releases with imidacloprid to control key pest populations in young clementine plants under field conditions. The results showed that some demographic parameters of P. persimilis were affected by imidacloprid. However, their combined effect on its intrinsic rate of increase was neutral. In contrast, imidacloprid negatively affected the demographic parameters of N. californicus. Field results proved that young clementine plants could be satisfactorily protected against key pests with releases of P. persimilis combined with drench applications of imidacloprid. The combination of imidacloprid with P. persimilis releases was highly effective for management of the key pests of young clementine plants in the nursery. (C) 2012 Elsevier Ltd. All rights reserved
Citrus leaf blotch virus invades meristematic regions in Nicotiana benthamiana and citrus.
Get PDFTo invade systemically host plants, viruses need to replicate in the infected cells, spread to neighbouring cells through plasmodesmata and move to distal parts of the plant via sieve tubes to start new infection foci. To monitor the infection of Nicotiana benthamiana plants by Citrus leaf blotch virus (CLBV), leaves were agroinoculated with an infectious cDNA clone of the CLBV genomic RNA expressing green fluorescent protein (GFP) under the transcriptional control of a duplicate promoter of the coat protein subgenomic RNA. Fluorescent spots first appeared in agroinfiltrated leaves 11-12 days after infiltration, indicating CLBV replication. Then, after entering the phloem vascular system, CLBV was unloaded in the upper parts of the plant and invaded all tissues, including flower organs and meristems. GFP fluorescence was not visible in citrus plants infected with CLBV-GFP. Therefore, to detect CLBV in meristematic regions, Mexican lime (Citrus aurantifolia) plants were graft inoculated with CLBV, with Citrus tristeza virus (CTV), a virus readily eliminated by shoot-tip grafting invitro, or with both simultaneously. Although CLBV was detected by hybridization and real-time reverse transcription-polymerase chain reaction (RT-PCR) in 0.2-mm shoot tips in all CLBV-inoculated plants, CTV was not detected. These results explain the difficulty in eliminating CLBV by shoot-tip grafting invitro
In vitro shoot-tip grafting for safe Prunus budwood exchange
No full textThe exchange of fruit tree propagation material to different growing regions and countries is a primary source of new pests and pathogens, particularly graft-transmissible viruses and viroids affecting Prunus species worldwide. Traditional procedures often cannot effectively quarantine pathogens and pests with unknown etiology, prompting the study of alternative procedures including those based on tissue culture techniques. In vitro shoot-tip grafting (STG), also called micrografting, consists of aseptically grafting a small shoot-tip onto an in vitro rootstock seedling and is often used to produce virus-free plants. In this study, an improved STG procedure for obtaining and introducing virus-free peach and Japanese plum plants is presented as an alternative to standard quarantine methods. The shoot-tip source is critical for STG success. Two viruses (Apple chlorotic leaf spot virus, Prunus necrotic ringspot virus) and a viroid (Peach latent mosaic viroid) were successfully eliminated in nearly 100% of the micrografted plants using buds from contaminated plants, grafted onto rootstocks forced in vivo at 35 degrees C, as shoot-tip source. The subsequent development of healthy plants for tested peach and Japanese plum cultivars demonstrates the suitability of this method for safe transport of plant material
Mejora de la Tecnología de desverdización de cítricos y aptitud a la frigoconservación de nuevas variedades. Estudios sobre parámetros de calidad y composición nutricional
Get PDFCitrus fruits are attractive fruits sought after by consumers overall the world for their unique taste, flavor, eating quality and health benefits. After harvest, fresh citrus fruit need to be manipulated at different stages with postharvest treatments before reaching consumers. Degreening process, by exposing fruit to ethylene, is a postharvest treatment, commonly used to accelerate external color change of citrus fruit since in the Mediterranean area early-season citrus fruit are harvested when fruit reach acceptable internal maturity standards for marketing while their external peel color is still green. Nevertheless, the application of ethylene during degreening treatment, besides the desirable color change, can induce physiological disorders related to peel and calyx senescence (browning and dropping). One objective of the present Thesis was to study different postharvest treatments to improve quality of early-season citrus fruit submitted to degreening treatment. The application of degreening treatments combining periods without ethylene exposure with other with ethylene application significantly reduced the calyx alterations associated with this treatment without affecting the external color evolution. The postharvest application of HFCalibra®, a growth regulator, also decreased the calyx alteration incidence in all assayed varieties; the higher the doses applied, the lower percentage of fruit with calyx alterations symptom
Transmissibility of Broad bean wilt virus 1 by aphids: influence of virus accumulation in plants, virus genotype and aphid species
No full textBroad bean wilt virus 1 (BBWV-1) is transmitted by several aphid species in a non-persistent manner. Transmission efficiency by vectors is a key factor for understanding virus epidemiology and applying disease control measures based on limiting virus spread. We evaluated the transmission rates of two genetically divergent BBWV-1 isolates (PV-132 from USA and Ben from Spain) infecting broad bean (Vicia faba L.) by isofemale lines of nine aphid species from eight different genera collected in Spain. Our analyses showed that: (a) the virus concentration in the source plant was a key factor in BBWV-1 transmissibility; (b) The Spanish isolate Ben was transmitted more efficiently than the American isolate PV-132 by most aphid species, but this was only due to the higher accumulation of Ben in plants, as both isolates had similar transmissibility after adjusting virus concentration and (c) The transmission rate varied greatly between the different aphid species
Effects of Pesticides Used on Citrus Grown in Spain on the Mortality of Ceratitis capitata (Diptera: Tephritidae) Vienna-8 Strain Sterile Males
No full textVienna-8 sterile males are currently released in Spain to reduce wild populations of the medfly. Because pesticides are required to maintain populations of some citrus key pests below economic thresholds, there is a need to evaluate the effects of pesticides commonly used in citrus on Vienna-8 males. Males were exposed to differently aged residues of eight pesticides. Abamectin, etofenprox, etoxazole, petroleum spray oil, pymetrozine, and pyriproxyfen resulted harmless to Vienna-8 males. However, fresh residues of chlorpyrifos and spinosad caused high mortalities and had residual effects until 21 and 28 d after treatment, respectively. Following the same method, the lethal effects of chlorpyrifos and spinosad on Ceratitis capitata (Wiedemann) wild-type (wt) males were determined. Surprisingly, these pesticides resulted more toxic for wt than for Vienna-8 males. To determine whether these results could be attributed to intrinsic characteristics of the pesticides or to behavioral differences among Vienna-8 and wt males, a topical application trial was conducted. Vienna-8 males were twice as susceptible to chlorpyrifos as wt males, whereas their susceptibility to spinosad was slightly lower. These results in intrinsic toxicity did not directly explain the differences observed in the extended-laboratory tests with these pesticides. We hypothesize that the lower flight activity of Vienna-8 males relative to wt conspecifies can explain the lower risk observed for Vienna-8 males in the residual tests. Our results should be taken into account when planning area-wide Sterile Insect Technique programs against C. capitata especially in those areas where treatments with chlorpyrifos are approved
Selection of Optimal Wavelength Features for Decay Detection in Citrus Fruit Using the ROC Curve and Neural Networks
Get PDFEarly automatic detection of fungal infections in post-harvest citrus fruits is especially important for the citrus industry because only a few infected fruits can spread the infection to a whole batch during operations such as storage or exportation, thus causing great economic losses. Nowadays, this detection is carried out manually by trained workers illuminating the fruit with dangerous ultraviolet lighting. The use of hyperspectral imaging systems makes it possible to advance in the development of systems capable of carrying out this detection process automatically. However, these systems present the disadvantage of generating a huge amount of data, which must be selected in order to achieve a result that is useful to the sector. This work proposes a methodology to select features in multi-class classification problems using the receiver operating characteristic curve, in order to detect rottenness in citrus fruits by means of hyperspectral images. The classifier used is a multilayer perceptron, trained with a new learning algorithm called extreme learning machine. The results are obtained using images of mandarins with the pixels labelled in five different classes: two kinds of sound skin, two kinds of decay and scars. This method yields a reduced set of features and a classification success rate of around 89%
First Report of Penicillium expansum Causing Postharvest Blue Mold of Fresh Date Palm Fruit (Phoenix dactylifera) in Spain
No full textPostharvest Fruit rot of Persimmon (Diospyros kaki) in Spain Caused by Lasiodiplodia theobromae and Neofusicoccum spp.
No full textThree different fungi (isolates IVIA QCV‐1, IVIA QCV‐3 and IVIA QCV‐4) were isolated as potential causal agents of postharvest decay losses observed on sweet persimmons (Diospyros kaki L.) cv. ‘Rojo Brillante’ from commercial packinghouses in the Valencia area (Spain). Disease symptoms were irregular brownish and soft lesions mainly located under and surrounding the fruit calyx (stem‐end) that expanded rapidly at room temperature and turned to dark brown or black colour producing apparent and in some cases abundant white to grey mycelium. The identification of Lasiodiplodia theobromae, Neofusicoccum mediterraneum and Neofusicoccum luteum by macroscopic and microscopic morphological observations was confirmed with the amplification and subsequent sequencing of the ribosomal DNA ITS2 region. Representative nucleotide sequences were deposited in GenBank. Pathogenicity of all three isolates was demonstrated by fulfilling Koch's postulates
