ReDivia - Repositorio Digital de l'Instit Valencià d'Investigacions Agràries
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Plant defense responses triggered by phytoseiid predatory mites (Mesostigmata: Phytoseiidae) are species-specific, depend on plant genotype and may not be related to direct plant feeding
Get PDFZoophytophagous arthropods can elicit plant defense responses affecting potential prey beyond predation. Phytophagy prevails as the main trigger for these responses, as in the case of Euseius stipulatus (Athias-Henriot) (Mesostigmata: Phytoseiidae), a predator occurring in citrus. Because other triggers cannot be excluded, our aim was to examine whether other phytoseiids co-occurring with E. stipulatus but not engaged in plant feeding [Neoseiulus californicus (McGregor) and Phytoseiulus persimilis Athias-Henriot] could induce similar responses (in terms of herbivore induced plant volatiles, HIPVs, and main defensive pathways), and how these affected the behavior of conspecifics and the shared prey, Tetranychus urticae Koch (Prostigmata: Tetranychidae). N. californicus triggered plant genotype-specific defense responses, including the production of different HIPVs compared to clean plants. However, we could not observe these effects for P. persimilis. T. urticae avoided better protected plants, because of stronger direct or indirect defense. As plants with weaker direct defense levels should offer higher prey densities, and those harboring conspecific predators represent higher risk of cannibalism, predators were expected to behave similarly. However, they did not. Our results demonstrate that plant defense triggered by phytoseiids is species-specific, depend on plant genotype and can be triggered by non-feeding activities. As N. californicus is a highly efficient predator used worldwide, further studies with this species are needed. Likewise, cineol, one of the volatiles identified in the blends triggered by this phytoseiid, could be used to manipulate the prey. These studies could pave the way for a more efficient use of phytoseiids in agroecosystems
Sensitivity of soil electromagnetic induction measurements to salinity, water content, clay, organic matter and bulk density
Get PDFObserved variations in the ground electrical conductivity (σb*) measurements obtained with EMI instruments depend on several soil proxies that infuence crop growth and development such as salinity (σe), contents of water (θw), clay (wc) and organic matter (wom) and bulk density (ρb). However, the relative contributions of all these to σb* are unknown. This knowledge is needed to improve the planning and interpretation of σb* data for precision agriculture applications. Recently, a semi-empirical model has been developed to relate σb* measurements taken with an EM38 device to σe, θw, wc, wom and ρb and also soil temperature (t). In this work this model was subjected to a global sensitivity analysis (GSA) based on the soil data obtained during two surveys carried out, one in summer and
the other in autumn, in an ample irrigated area in SE Spain. On the basis of the multiple linear regression meta-models developed for the σb* measurements, these were found to linearly respond to the soil properties (R2 between 0.92 and 0.96) and thus, the GSA could be based on their standardised regression coefcients. According to these, the soil characteristics explain the following percentages of variance in σb* (PV): 30–34 (σe), 8–20 (θw),
32–47 (wc), 0.6–2.6 (wom), 5.7–7.5 (ρb) and 0.3–0.4 (t) with changes from the summer to the autumn season of − 4, − 12 and+15 in the PV explained by the most infuential properties, respectively, σe, θw and wc. The results of the GSA will help the planning and interpretation of σb* measurements for improving crop management
Sensors I: Color Imaging and Basics of Image Processing
No full textThis chapter provides an overview of the basic concepts of color imaging and image processing techniques applied to sensing, monitoring and robotic operations in agriculture. To obtain good results with a vision system, it is very important to acquire high-quality images, particularly when captured with moving platform in a natural environment, by selecting a proper camera, acquisition settings, and lighting conditions. Image acquisition using CMOS and CCD sensors are explained along with proper adjustment of various imaging parameters such as aperture and shutter speed. Various color models that are relevant to image processing are described including RGB, HSV, HLS, CIELAB, and CIELUV as well as conversions between different color models. Following the introduction of color models, some basic image preprocessing techniques including image enhancement using histograms, morphological operations, and lowpass filtering are described. Also, various segmentation methods are discussed such as pixelwise or region–based techniques and classifiers. In addition, the chapter describes different object detection methods (with examples) that utilize various features such as colors, shapes, and textures. Hough transform and pattern matching are also commonly used techniques to detect various objects, and example applications based on these techniques are discussed. Finally, some of the crucial challenges for outdoor imaging such as varying illumination, occlusion, clustering, and movement of either the object or the camera when it is installed on a ground robotic system are discussed and a brief thought on future direction around these topics is presented
First report of Passiflora edulis symptomless virus in pomegranate in Spain
No full textPassiflora edulis symptomless virus (PeSV), family Potyviridae, genus Roymovirus, was first identified in Israel infecting Passiflora edulis plants (Jover-Gil et al. 2018). PeSV has also been reported in Turkey, China and India infecting pomegranate (Caglayan et al. 2020). Although it has not been formally associated with symptoms in pomegranate, there are indications that PeSV may induce symptoms in this crop. In June 2020 leaves from a pomegranate growing in Alicante (Spain) and showing chlorotic spots along the veins were analyzed by RNAseq high throughput sequencing (HTS, TrueSeq Illumina technology, 150 bp paired-end). Data was analyzed using CLC Genomics Workbench 10.1.1. After quality control and host genome subtraction, de novo assembly of 1,887,133 reads generated 10,946 contigs (> 200 nt), from which 128 were related to PeSV according to BLAST analysis (e-value < 10–4). These contigs showed a high molecular variability indicating a mixed infection by several PeSV isolates. Contig extension performed by Geneious Prime 2020 allowed to recover a 9926 nt near full-length PeSV genomic sequence, (MZ361583, average coverage 528x). This sequence showed 78.1–80.8% nucleotide identity when compared to PeSV genomic sequences (MT680930-MT680935). No other virus was detected in the HTS analysis. RT-PCR from the original pomegranate plant using the newly designed primers SPeSV-6F (5’-GGCTAGAAACGGTGGGATGA-3’) and SPeSV-6R (5’-ACCACCTGGCTCATGGCGA-3’) generated the expected 165 nt amplicon, as confirmed by Sanger sequencing (100% nt identity with the HTS sequence). In further assays, the 165 nt fragment was also amplified from 17 symptomatic out of 65 tested trees from the same orchard. Although PeSV was not detected in asymptomatic plants, symptomatic trees that tested negative for PeSV were also found. These results could be explained by a limited inclusiveness of the primers used in this study and question the pathogenicity of PeSV in pomegranate. To our knowledge this is the first report of PeSV in Spain
Insights into the origin of the invasive populations of Trioza erytreae in Europe using microsatellite markers and mtDNA barcoding approaches
Get PDFThe African citrus psyllid Trioza erytreae is one of the major threats to citrus industry as the vector
of the incurable disease known as huanglongbing (HLB) or citrus greening. The psyllid invaded
the northwest of the Iberian Peninsula 6 years ago. The invasion alarmed citrus growers in the
Mediterranean basin, the largest citrus producing area in Europe, which is still free of HLB. Before
our study, no research had been carried out on the genetic diversity of T. erytreae populations
that have invaded the Iberian Peninsula and the archipelagos of the Macaronesia (Madeira and the
Canary Islands). In this study, combining microsatellites markers and mtDNA barcoding analysis,
we characterize the genetic diversity, structure and maternal relationship of these new invasive
populations of T. erytreae and those from Africa. Our results suggest that the outbreaks of T. erytreae
in the Iberian Peninsula may have derived from the Canary Islands. The populations of T. erytreae that
invaded Macaronesia and the Iberian Peninsula are likely to have originated from southern Africa.
We anticipate our results to be a starting point for tracking the spread of this invasive pest outside of
Africa and to be important for optimizing contingency and eradication plans in newly invaded and free
areas
Reversion of fruit-dependent inhibition of flowering in Citrusrequires sprouting of buds with epigenetically silenced CcMADS19
Get PDFIn Citrus, the response to environmental floral inductive signals is inhibited by the presence of developing fruits. The mechanism involves epigenetic activation of the CcMADS19 locus (FLC orthologue), encoding a floral repressor. To understand how this epigenetic regulation is reverted to allow flowering in the following season, we have forced precocious sprouting of axillary buds in fruit-bearing shoots, and examined the competence to floral inductive signals of old and new leaves derived from them. We have found that CcMADS19 is enriched in repressive H3K27me3 marks in young, but not old leaves, revealing that axillary buds retain a silenced version of the floral repressor that is mitotically transmitted to the newly emerging leaves, which are able to induce flowering. Therefore, we propose that flowering in Citrus is necessarily preceded by vegetative sprouting, so that the competence to respond to floral inductive signals is reset in the new leaves
Effect of Low Pressure and Low Oxygen Treatments on Fruit Quality and the In Vivo Growth of Penicillium digitatum and Penicillium italicum in Oranges
Get PDFPenicillium digitatum and P. italicum are the major postharvest pathogens in citrus. To reduce postharvest decay, the use of low-oxygen (0.9 kPa O2) (LO) or low-pressure (6.6 kPa) (LP) treatments were evaluated during the storage of navel oranges for four or eight days. The results showed that exposure to both LO and LP treatments reduced in vivo pathogen growth compared to the untreated (UTC) oranges, with LO being the most effective. The effects of LO and LP on fruit metabolism and quality were further assessed, and it was found that there was no effect on fruit ethylene production, respiration rate, TSS (total soluble solids), TA (titratable acidity) or fruit firmness. However, both LO and LP treatments did have an effect on juice ethanol concentration and fruit weight-loss. The effect of adding exogenous ethylene at either LP (1 µL/L) or atmospheric pressure (AP) (at either 0.1, 1 µL/L) was also evaluated, and results showed that the addition of ethylene at these concentrations had no effect on mould diameter at LP or AP. Therefore, both LO of 0.9 kPa O2 and LP of 6.6 kPa at 20 °C are potential non-chemical postharvest treatments to reduce mould development during storage with minimal effects on fruit quality
Secagem natural de frutos inteiros como estratégia de valorização dos descartes da produção de caqui
Get PDFO incremento exponencial na produção de caqui na Espanha vem sendo acompanhado de um importante aumento no volume de perdas. Neste sentido, a secagem natural surge como uma estratégia para atribuir valor às perdas geradas durante o manejo pós-colheita, bem como uma alternativa à sazonalidade do caqui como fruta fresca. Portanto, este estudo tem como objetivo fornecer informações sobre as mudanças fisicoquímicas e microestructurais que ocorrem durante o processo de secagem do caqui ‘Rojo Brillante’, visando sua utilização como um subproduto de alto valor agregado. Os resultados mostraram que após 21 dias de secagem os frutos apresentaram uma umidade média de 50%, valor a partir do qual o fruto se considera semi-seco. O processo de secagem deu origem à formação de uma epiderme secundária paralela à gelificação interna da polpa, que foi relacionada à perda de umidade e mudanças na atividade de água. O estudo microestrutural mostrou a degradação do parênquima do fruto durante a secagem. Além disso, esse processo levou à redução dos taninos solúveis até a perda completa da adstringência após 14 dias. As mudanças na coloração da polpa não comprometeram a qualidade externa do fruto
Influencia del material vegetal y la concentración bacteriana en la detección de Xylella fastidiosa mediante protocolos de PCR en tiempo real
Get PDFLa prevención de la introducción de una enfermedad en una zona libre de ella depende, en primer lugar, de la disponibilidad de técnicas de detección que sean sensibles y específicas. En el caso de las enfermedades causadas por la bacteria Xylella fastidiosa, el protocolo actual de la EPPO para la detección de esta bacteria fitopatógena, se basa en la detección molecular, y en él se describen varios protocolos de PCR en tiempo real dirigidos a diferentes secuencias diana del genoma de esta bacteria