The Experts below are selected from a list of 2316 Experts worldwide ranked by ideXlab platform

Nian Wang - One of the best experts on this subject based on the ideXlab platform.

  • functional characterization of the Citrus Canker susceptibility gene cslob1
    Molecular Plant Pathology, 2018
    Co-Authors: Shuo Duan, Nian Wang, J B Jones, Zhiqian Pang, Doron Teper, Frank F White, Changyong Zhou
    Abstract:

    : Xanthomonas citri ssp. citri (Xcc) is an important plant-pathogenic bacterium that causes Citrus Canker disease worldwide. PthA, a transcriptional activator-like (TAL) effector, directs the expression of the Canker susceptibility gene CsLOB1. Here, we report our recent progress in the functional characterization of CsLOB1. Subcellular localization analysis of CsLOB1 protein in Citrus protoplast revealed that CsLOB1 is primarily localized in the nucleus. We showed that CsLOB1 expression driven by dexamethasone (DEX) in CsLOB1-GR transgenic plants is associated with pustule formation following treatment with DEX. Pustule formation was not observed in DEX-treated wild-type plants and in non-treated CsLOB1-GR transgenic plants. Water soaking is typically associated with symptoms of Citrus Canker. Weaker water soaking was observed with pustule formation in CsLOB1-GR transgenic plants following DEX treatment. When CsLOB1-GR-transgenic Duncan grapefruit leaves were inoculated with Xcc306ΔpthA4 and treated with DEX, typical Canker symptoms, including hypertrophy, hyperplasia and water soaking symptoms, were observed on DEX-treated transgenic plant leaves, but not on mock-treated plants. Twelve Citrus genes that are induced by PthA4 are also stimulated by the DEX-induced expression of CsLOB1. As CsLOB1 acts as a transcriptional factor, we identified putative targets of CsLOB1 via bioinformatic and electrophoretic mobility shift assays. Cs2g20600, which encodes a zinc finger C3HC4-type RING finger protein, has been identified to be a direct target of CsLOB1. This study advances our understanding of the function of CsLOB1 and the molecular mechanism of how Xcc causes Canker symptoms via CsLOB1.

  • induced systemic resistance against Citrus Canker disease by rhizobacteria
    Phytopathology, 2018
    Co-Authors: Nadia Riera, Jinyun Li, Han Wang, Yong Li, Kirsten S Pelzstelinski, Nian Wang
    Abstract:

    : Citrus Canker, caused by Xanthomonas citri subsp. citri, is an important Citrus disease that causes significant economic losses worldwide. All commercial Citrus varieties are susceptible to Citrus Canker. Currently, chemical control with copper based products is the main approach to control X. citri subsp. citri dispersal and plant colonization. However, extensive use of copper compounds can result in copper-resistant strains and cause adverse effects on the environment. Alternatives to chemical control involve the activation of Citrus immunity to control the disease. Here, we investigated the ability of multiple rhizobacteria to induce a systemic defense response in cultivar Duncan grapefruit. Burkholderia territorii strain A63, Burkholderia metallica strain A53, and Pseudomonas geniculata strain 95 were found to effectively activate plant defense and significantly reduce symptom development in leaves challenged with X. citri subsp. citri. In the priming phase, root application of P. geniculata induced the expression of salicylic acid (SA)-signaling pathway marker genes (PR1, PR2, PR5, and salicylic acid carboxyl methyltransferase [SAM-SACM]). Gene expression analyses after X. citri subsp. citri challenge showed that root inoculation with P. geniculata strain 95 increased the relative levels of phenylalanine ammonia lyase 1 and SAM-SACM, two genes involved in the phenylpropanoid pathway as well as the biosynthesis of SA and methyl salicylate (MeSA), respectively. However, hormone analyses by UPLC-MS/MS showed no significant difference between SA in P. geniculata-treated plants and control plants at 8 days post-beneficial bacteria root inoculation. Moreover, P. geniculata root-treated plants contained higher reactive oxygen species levels in aerial tissues than control plants 8 days post-treatment application. This study demonstrates that rhizobacteria can modulate Citrus immunity resulting in a systemic defense response against X. citri subsp. citri under greenhouse conditions.

  • positive selection is the main driving force for evolution of Citrus Canker causing xanthomonas
    The ISME Journal, 2015
    Co-Authors: Yunzeng Zhang, J B Jones, Neha Jalan, Xiaofeng Zhou, Erica M Goss, Joao C Setubal, Xiaoling Deng, Nian Wang
    Abstract:

    Understanding the evolutionary history and potential of bacterial pathogens is critical to prevent the emergence of new infectious bacterial diseases. Xanthomonas axonopodis subsp. citri (Xac) (synonym X. citri subsp. citri), which causes Citrus Canker, is one of the hardest-fought plant bacterial pathogens in US history. Here, we sequenced 21 Xac strains (14 XacA, 3 XacA* and 4 XacAw) with different host ranges from North America and Asia and conducted comparative genomic and evolutionary analyses. Our analyses suggest that acquisition of beneficial genes and loss of detrimental genes most likely allowed XacA to infect a broader range of hosts as compared with XacAw and XacA*. Recombination was found to have occurred frequently on the relative ancient branches, but rarely on the young branches of the clonal genealogy. The ratio of recombination/mutation ρ/θ was 0.0790±0.0005, implying that the Xac population was clonal in structure. Positive selection has affected 14% (395 out of 2822) of core genes of the Citrus Canker-causing Xanthomonas. The genes affected are enriched in ‘carbohydrate transport and metabolism’ and ‘DNA replication, recombination and repair’ genes (P<0.05). Many genes related to virulence, especially genes involved in the type III secretion system and effectors, are affected by positive selection, further highlighting the contribution of positive selection to the evolution of Citrus Canker-causing Xanthomonas. Our results suggest that both metabolism and virulence genes provide advantages to endow XacA with higher virulence and a wider host range. Our analysis advances our understanding of the genomic basis of specialization by positive selection in bacterial evolution.

  • Positive selection is the main driving force for evolution of Citrus Canker-causing Xanthomonas
    The ISME Journal, 2015
    Co-Authors: Yunzeng Zhang, Jeffrey B. Jones, Neha Jalan, Xiaofeng Zhou, Erica M Goss, Joao C Setubal, Xiaoling Deng, Nian Wang
    Abstract:

    Understanding the evolutionary history and potential of bacterial pathogens is critical to prevent the emergence of new infectious bacterial diseases. Xanthomonas axonopodis subsp. citri (Xac) (synonym X. citri subsp. citri), which causes Citrus Canker, is one of the hardest-fought plant bacterial pathogens in US history. Here, we sequenced 21 Xac strains (14 XacA, 3 XacA* and 4 XacAw) with different host ranges from North America and Asia and conducted comparative genomic and evolutionary analyses. Our analyses suggest that acquisition of beneficial genes and loss of detrimental genes most likely allowed XacA to infect a broader range of hosts as compared with XacAw and XacA*. Recombination was found to have occurred frequently on the relative ancient branches, but rarely on the young branches of the clonal genealogy. The ratio of recombination/mutation ρ/θ was 0.0790±0.0005, implying that the Xac population was clonal in structure. Positive selection has affected 14% (395 out of 2822) of core genes of the Citrus Canker-causing Xanthomonas. The genes affected are enriched in ‘carbohydrate transport and metabolism’ and ‘DNA replication, recombination and repair’ genes (P

  • Foliar Application of Biofilm Formation–Inhibiting Compounds Enhances Control of Citrus Canker Caused by Xanthomonas citri subsp. citri
    Phytopathology, 2014
    Co-Authors: Jinyun Li, Nian Wang
    Abstract:

    Citrus Canker caused by the bacterium Xanthomonas citri subsp. citri is an economically important disease of Citrus worldwide. Biofilm formation plays an important role in early infection of X. citri subsp. citri on host leaves. In this study, we assessed the hypothesis that small molecules inhibiting biofilm formation reduce X. citri subsp. citri infection and enhance the control of Citrus Canker disease. D-leucine and 3-indolylacetonitrile (IAN) were found to prevent biofilm formation by X. citri subsp. citri on different abiotic surfaces and host leaves at a concentration lower than the minimum inhibitory concentration (MIC). Quantitative reverse transcription-polymerase chain reaction (qRT-PCR) analysis indicated that IAN repressed expression of chemotaxis/motility-related genes in X. citri subsp. citri. In laboratory experiments, planktonic and biofilm cells of X. citri subsp. citri treated with D-leucine and IAN, either alone or in combination, were more susceptible to copper (CuSO4) than those untreated. In greenhouse assays, D-leucine and IAN applied alone or combined with copper reduced both the number of Canker lesions and bacterial populations of X. citri subsp. citri on Citrus host leaves. This study provides the basis for the use of foliar-applied biofilm inhibitors for the control of Citrus Canker alone or combined with copper-based bactericides.

T. R. Gottwald - One of the best experts on this subject based on the ideXlab platform.

  • Copper sprays and windbreaks for control of Citrus Canker on young orange trees in southern Brazil
    Crop Protection, 2020
    Co-Authors: F. Behlau, J H Graham, J Belasque, R P Leite, A. Bergamin Filho, T. R. Gottwald
    Abstract:

    The benefit of windbreaks and copper sprays for control of Citrus Canker caused by Xanthomonas axonopodis pv. citri was investigated in a commercial Citrus orchard located in a Citrus Canker endemic area in southern Brazil. Control of Canker was evaluated as incidence and severity of lesions on foliage and by the effect on premature leaf and fruit drop for three production seasons. Effect of the treatments on fruit production was evaluated as incidence of Citrus Canker on prematurely abscised fruits and harvested fruits. Copper application significantly reduced damage to foliage and fruit, while windbreaks made little contribution to disease control. Copper sprays increased fruit yield for 3 years. This could be attributed to lower incidence of fruit with lesions and fewer fruits abscised due to Canker infection. Incidence and severity on the leaves were inversely related to the number of fruits harvested per tree and directly related to the number of fruits abscised per tree. Published by Elsevier Ltd

  • annual and polyetic progression of Citrus Canker on trees protected with copper sprays
    Plant Pathology, 2010
    Co-Authors: Franklin Behlau, Lilian Amorim, J H Graham, J Belasque, Bergamin A Filho, R P Leite, T. R. Gottwald
    Abstract:

    The effects of copper sprays on annual and polyetic progress of Citrus Canker, caused by Xanthomonas citri subsp. citri, in the presence of the Asian Citrus leafminer (Phyllocnistis citrella), were evaluated in a study conducted in a commercial orchard in northwest Parana state, Brazil, where Citrus Canker is endemic. Nonlinear monomolecular, logistic and Gompertz models were fitted to monthly disease incidence data (proportion of leaves with symptoms) for each treatment for three seasons. The logistic model provided the best estimate of disease progress for all years and treatments evaluated and logistic parameter estimates were used to describe polyetic disease dynamics. Although Citrus Canker incidence increased during each of the seasons studied, it decreased over the whole study period, more so in copper-treated trees than in water-sprayed controls. Copper treatment reduced disease incidence compared with controls in every year, especially 2004–2005, when incidence was ca. 10-fold higher in controls than in treated plots (estimated asymptote values 0·82 and 0·07, respectively). Copper treatment also reduced estimated initial disease incidence and epidemic growth rates every year.

  • optimal strategies for the eradication of asiatic Citrus Canker in heterogeneous host landscapes
    Phytopathology, 2009
    Co-Authors: Stephen Parnell, T. R. Gottwald, F Van Den Bosch, Christopher A Gilligan
    Abstract:

    The eradication of nonnative plant pathogens is a key challenge in plant disease epidemiology. Asiatic Citrus Canker is an economically significant disease of Citrus caused by the bacterial plant pathogen Xanthomonas citri subsp. citri. The pathogen is a major exotic disease problem in many Citrus producing areas of the world including the United States, Brazil, and Australia. Various eradication attempts have been made on the disease but have been associated with significant social and economic costs due to the necessary removal of large numbers of host trees. In this paper, a spatially explicit stochastic simulation model of Asiatic Citrus Canker is introduced that describes an epidemic of the disease in a heterogeneous host landscape. We show that an optimum eradication strategy can be determined that minimizes the adverse costs associated with eradication. In particular, we show how the optimum strategy and its total cost depend on the topological arrangement of the host landscape. We discuss the implications of the results for invading plant disease epidemics in general and for historical and future eradication attempts on Asiatic Citrus Canker.

  • Optimal Strategies for the Eradication of Asiatic Citrus Canker in Heterogeneous Host Landscapes
    Phytopathology, 2009
    Co-Authors: Stephen Parnell, T. R. Gottwald, F Van Den Bosch, Christopher A Gilligan
    Abstract:

    ABSTRACT The eradication of nonnative plant pathogens is a key challenge in plant disease epidemiology. Asiatic Citrus Canker is an economically significant disease of Citrus caused by the bacterial plant pathogen Xanthomonas citri subsp. citri. The pathogen is a major exotic disease problem in many Citrus producing areas of the world including the United States, Brazil, and Australia. Various eradication attempts have been made on the disease but have been associated with significant social and economic costs due to the necessary removal of large numbers of host trees. In this paper, a spatially explicit stochastic simulation model of Asiatic Citrus Canker is introduced that describes an epidemic of the disease in a heterogeneous host landscape. We show that an optimum eradication strategy can be determined that minimizes the adverse costs associated with eradication. In particular, we show how the optimum strategy and its total cost depend on the topological arrangement of the host landscape. We discuss...

  • copper sprays and windbreaks for control of Citrus Canker on young orange trees in southern brazil
    Crop Protection, 2008
    Co-Authors: Franklin Behlau, J H Graham, J Belasque, Bergamin A Filho, R P Leite, T. R. Gottwald
    Abstract:

    The benefit of windbreaks and copper sprays for control of Citrus Canker caused by Xanthomonas axonopodis pv. citri was investigated in a commercial Citrus orchard located in a Citrus Canker endemic area in southern Brazil. Control of Canker was evaluated as incidence and severity of lesions on foliage and by the effect on premature leaf and fruit drop for three production seasons. Effect of the treatments on fruit production was evaluated as incidence of Citrus Canker on prematurely abscised fruits and harvested fruits. Copper application significantly reduced damage to foliage and fruit, while windbreaks made little contribution to disease control. Copper sprays increased fruit yield for 3 years. This could be attributed to lower incidence of fruit with lesions and fewer fruits abscised due to Canker infection. Incidence and severity on the leaves were inversely related to the number of fruits harvested per tree and directly related to the number of fruits abscised per tree.

J H Graham - One of the best experts on this subject based on the ideXlab platform.

  • Copper sprays and windbreaks for control of Citrus Canker on young orange trees in southern Brazil
    Crop Protection, 2020
    Co-Authors: F. Behlau, J H Graham, J Belasque, R P Leite, A. Bergamin Filho, T. R. Gottwald
    Abstract:

    The benefit of windbreaks and copper sprays for control of Citrus Canker caused by Xanthomonas axonopodis pv. citri was investigated in a commercial Citrus orchard located in a Citrus Canker endemic area in southern Brazil. Control of Canker was evaluated as incidence and severity of lesions on foliage and by the effect on premature leaf and fruit drop for three production seasons. Effect of the treatments on fruit production was evaluated as incidence of Citrus Canker on prematurely abscised fruits and harvested fruits. Copper application significantly reduced damage to foliage and fruit, while windbreaks made little contribution to disease control. Copper sprays increased fruit yield for 3 years. This could be attributed to lower incidence of fruit with lesions and fewer fruits abscised due to Canker infection. Incidence and severity on the leaves were inversely related to the number of fruits harvested per tree and directly related to the number of fruits abscised per tree. Published by Elsevier Ltd

  • novel plastid nuclear genome combinations enhance resistance to Citrus Canker in cybrid grapefruit
    Frontiers in Plant Science, 2019
    Co-Authors: Mayara M Murata, Jude W. Grosser, Ahmad A Omar, Christine D Chase, J H Graham
    Abstract:

    Host disease resistance is the most desirable strategy for control of Citrus Canker, a disease caused by a gram-negative bacterium Xanthomonas citri subsp. citri (Xcc). However, no resistant commercial Citrus cultivar has been identified. Cybridization, a somatic hybridization approach that combines the organelle and nuclear genomes from different species, was used to create cybrids between Citrus Canker resistant ‘Meiwa’ kumquat (Fortunella crassifolia Swingle snym. Citrus japonica Thunb.) and susceptible grapefruit (Citrus paradisi Macfad) cultivars. From these fusions, cybrids with grapefruit nucleus, kumquat mitochondria and kumquat chloroplasts and cybrids with grapefruit nucleus, kumquat mitochondria and grapefruit chloroplasts were generated. These cybrids showed a range of Citrus Canker response, but all cybrids with kumquat chloroplasts had a significantly lower number of lesions and lower Xcc populations than the grapefruit controls. Cybrids with grapefruit chloroplasts had a significantly higher number of lesions than those with kumquat chloroplasts. To understand the role of chloroplasts in the cybrid disease defense, quantitative PCR was performed on both cybrid types and their parents to examine changes in gene expression during Xcc infection. The results revealed chloroplast influences on nuclear gene expression, since isonuclear cybrids and ‘Marsh’ grapefruit had different gene expression profiles. In addition, only genotypes with kumquat chloroplasts showed an early up-regulation of reactive oxygen species genes upon Xcc infection. These cybrids have the potential to enhance Citrus Canker resistance in commercial grapefruit orchards. They also serve as models for understanding the contribution of chloroplasts to plant disease response and raise the question of whether other alien chloroplast genotypes would condition similar results.

  • potential of nano formulated zinc oxide for control of Citrus Canker on grapefruit trees
    Plant Disease, 2016
    Co-Authors: J H Graham, Evan G Johnson, Monty E Myers, Mikaeel Young, Parthiban Rajasekaran, Swadeshmukul Santra
    Abstract:

    Antimicrobial activity of experimental formulations of two structurally different nano-zinc oxide materials, plate-like Zinkicide SG4 and particulate Zinkicide SG6, was evaluated against Xanthomonas citri subsp. citri, the cause of Citrus Canker. In vitro assay demonstrated Zinkicide SG4 had a twofold lower minimum inhibitory concentration (MIC) against Escherichia coli and X. alfalfae subsp. citrumelonis (62.5 to 250 µg/ml) compared with copper sulfate (250 µg/ml), copper hydroxide (250 to 500 µg/ml), or cuprous oxide/zinc oxide (125 to 250 µg/ml). Zinkicide SG6 had a sevenfold to eightfold lower MIC against Escherichia coli and X. alfalfae subsp. citrumelonis (31 to 250 μg/ml). Leaves of sweet orange (Citrus sinensis) and fruit of ‘Ruby Red’ grapefruit (C. paradisi) were evaluated for Citrus Canker disease control. A greenhouse assay with foliage demonstrated that spray treatment with Zinkicide reduced Citrus Canker lesion development after injection-infiltration of X. citri subsp. citri into the leaf i...

  • annual and polyetic progression of Citrus Canker on trees protected with copper sprays
    Plant Pathology, 2010
    Co-Authors: Franklin Behlau, Lilian Amorim, J H Graham, J Belasque, Bergamin A Filho, R P Leite, T. R. Gottwald
    Abstract:

    The effects of copper sprays on annual and polyetic progress of Citrus Canker, caused by Xanthomonas citri subsp. citri, in the presence of the Asian Citrus leafminer (Phyllocnistis citrella), were evaluated in a study conducted in a commercial orchard in northwest Parana state, Brazil, where Citrus Canker is endemic. Nonlinear monomolecular, logistic and Gompertz models were fitted to monthly disease incidence data (proportion of leaves with symptoms) for each treatment for three seasons. The logistic model provided the best estimate of disease progress for all years and treatments evaluated and logistic parameter estimates were used to describe polyetic disease dynamics. Although Citrus Canker incidence increased during each of the seasons studied, it decreased over the whole study period, more so in copper-treated trees than in water-sprayed controls. Copper treatment reduced disease incidence compared with controls in every year, especially 2004–2005, when incidence was ca. 10-fold higher in controls than in treated plots (estimated asymptote values 0·82 and 0·07, respectively). Copper treatment also reduced estimated initial disease incidence and epidemic growth rates every year.

  • over expression of the arabidopsis npr1 gene in Citrus increases resistance to Citrus Canker
    European Journal of Plant Pathology, 2010
    Co-Authors: Xudong Zhang, Marta I Francis, William O Dawson, J H Graham, Vladimir Orbovic, Eric W Triplett
    Abstract:

    Citrus Canker, caused by the bacterial pathogen Xanthomonas citri subsp. citri (Xcc), is a serious leaf and fruit spotting disease affecting many important Citrus cultivars including grapefruit and certain sweet oranges. Currently, efficacious and economical disease control measures for highly susceptible Citrus cultivars are lacking. Development of commercial cultivars with greater field resistance to Citrus Canker is the optimum strategy for effective disease management. In this study, we generated transgenic ‘Duncan’ grapefruit (DG) and ‘Hamlin’ sweet orange (Ham) expressing the Arabidopsis NPR1 gene (AtNPR1), which is a key positive regulator of the long-lasting broad-spectrum resistance known as systemic acquired resistance (SAR). Our results indicate that over-expression of AtNPR1 in Citrus increases resistance to Citrus Canker and that the resistance is related with the expression levels of AtNPR1 in the transgenic plants. The line (DG 42-2) with the highest expression level of AtNPR1 was also the most resistant, which developed significant fewer lesions accompanied by a ten-fold reduction in Xcc population. The lesions developed on DG 42-2 were smaller and darker than those on the control and lacked callus formation. These lesion phenotypes resemble those on Canker resistant kumquats and Canker susceptible Citrus trees treated with SAR-inducing compounds. Therefore, over-expression of AtNPR1 in Citrus is a promising approach for development of more resistant cultivars to Citrus Canker.

Mark A Ritenour - One of the best experts on this subject based on the ideXlab platform.

  • Detecting Citrus Canker by Hyperspectral Reflectance Imaging and Spectral Information Divergence
    2008 Providence Rhode Island June 29 - July 2 2008, 2020
    Co-Authors: Thomas F Burks, Mark A Ritenour, Gordon W Bonn
    Abstract:

    Citrus Canker is one of the most devastating diseases that threaten marketability of Citrus crops. This research was aimed to develop a hyperspectral imaging approach for detecting Canker lesions on Citrus fruit. A hyperspectral imaging system was developed for acquiring reflectance images from Citrus samples in the spectral region from 450 nm to 930 nm. Ruby Red grapefruits with Cankerous, normal and other common peel diseases including greasy spot, insect damage, melanose, scab, and wind scar were tested. Spectral information divergence (SID) classification method, which was based on quantifying the spectral similarities by using a predetermined Canker reference spectrum, was performed to the hyperspectral images of the grapefruits for differentiating Canker from normal fruit peels and other Citrus diseases. The overall accuracy for Canker detection was achieved as 96.2% using an optimized SID threshold value of 0.008. This research demonstrated that hyperspectral imaging technique coupled with the SID based image classification method could be used for discriminating Citrus Canker from other confounding diseases.

  • development of a two band spectral imaging system for real time Citrus Canker detection
    Journal of Food Engineering, 2012
    Co-Authors: Thomas F Burks, Xuhui Zhao, Nikhil P Niphadkar, Mark A Ritenour
    Abstract:

    Abstract Inspection of Citrus Canker is crucial due to its fast spread, high damage potential, and massive impact on export and domestic trade. This research was aimed to develop a prototype for real-time Citrus Canker detection. An inspection module was developed on a one-line commercial fruit sorting machine. Twenty tungsten halogen spotlights coupled with an aluminum dome painted with white diffuse paint provided reflectance illumination to the fruits in the detection chamber. The camera unit was a two-band spectral imaging system, which mainly consisted of a beamsplitter, two bandpass filters with central wavelengths at 730 and 830 nm, and two identical monochrome cameras. Using an exposure time of 10 ms, the imaging system can capture narrowband images without blurring from samples moving at a speed of 5 fruits/s. Spatial resolution of the acquired images was 2.3 pixels/mm. Real-time image processing and classification algorithms were developed based on a two-band ratio approach (i.e., R830/R730). The system was tested using 360 grapefruits with normal surface, Canker lesions, and other peel diseases and defects. The overall classification accuracy was 95.3%, demonstrating that the methodology as well as the hardware and the software are effective and suitable for real-time Citrus Canker detection. Greasy spot, melanose, and sooty mold could generate false positive errors for the fruits without Canker. The current system setup was limited to a single perspective view of the fruits. Future work will be conducted with an emphasis on whole surface inspection of each fruit.

  • multispectral detection of Citrus Canker using hyperspectral band selection
    Transactions of the ASABE, 2011
    Co-Authors: T F Burks, Nikhil P Niphadkar, Xuhui Zhao, Mark A Ritenour
    Abstract:

    The Citrus industry has need for effective and efficient approaches to remove fruits with Canker before they are shipped to selective international markets. This research was aimed to develop a multispectral method to inspect Citrus Canker based on band selections of the hyperspectral image data. A total of 960 Ruby Red grapefruits with normal surface, Canker, and five common peel diseases including greasy spot, insect damage, melanose, scab, and wind scar were collected during a seven-month harvest period. Hyperspectral reflectance images were acquired in the spectral region of 450 to 930 nm. Correlation analysis (CA) and principal component analysis (PCA) were used for hyperspectral band selections. The Canker detection capabilities of the selected bands were evaluated and compared based on the classifications of the pixels in the selected regions of interest (ROIs) of all the peel conditions. A two-band ratio using wavelengths of 729 and 834 nm selected by CA (R834/R729) gave the best overall classification accuracy (95.1%) for the ROI pixel classification, while the highest accuracy using the PCA-selected bands (R907/R718) was 93.1%. CA band selection outperformed PCA in terms of classification performance owing to its supervised nature. The accuracies for three-band and four-band ratios formed by a sequential forward CA selection approach were lower than that of the two-band ratio. Based on the ratio of R834/R729, algorithms for multispectral image processing and classification were developed to differentiate Canker from other peel conditions. The overall classification accuracy on a sample basis was 95.7%. The two-band ratio images have great potential to be adopted by a multispectral imaging system for real-time Citrus Canker detection.

  • detection of Citrus Canker using hyperspectral reflectance imaging with spectral information divergence
    Journal of Food Engineering, 2009
    Co-Authors: Thomas F Burks, Mark A Ritenour, Gordon W Bonn
    Abstract:

    Abstract Citrus Canker is one of the most devastating diseases that threaten marketability of Citrus crops. This research was aimed to develop a hyperspectral imaging approach for detecting Canker lesions on Citrus fruit. A hyperspectral imaging system was developed for acquiring reflectance images from Citrus samples in the spectral region from 450 to 930 nm. Ruby Red grapefruits with Cankerous, normal and other common peel diseases including greasy spot, insect damage, melanose, scab, and wind scar were tested. Spectral information divergence (SID) classification method, which was based on quantifying the spectral similarities by using a predetermined Canker reference spectrum, was performed on the hyperspectral images of the grapefruits for differentiating Canker from normal fruit peels and other Citrus surface conditions. The overall classification accuracy was 96.2% using an optimized SID threshold value of 0.008, which was determined under the condition that the errors of false negative and false positive were weighted equally. Considering the high economic impact of missing a Cankerous fruit, zero false negative error was achieved by using a threshold value of 0.009, under which the classification accuracy was 95.2%. This research demonstrated that hyperspectral imaging technique coupled with the SID based image classification method could be used for discriminating Citrus Canker from other confounding diseases.

  • Detecting Citrus Canker by hyperspectral reflectance imaging and PCA-based image classification method
    Defense and Security 2008: Special Sessions on Food Safety Visual Analytics Resource Restricted Embedded and Sensor Networks and 3D Imaging and Displa, 2008
    Co-Authors: Thomas F Burks, Kuanglin Chao, Mark A Ritenour
    Abstract:

    Citrus Canker is one of the most devastating diseases that threaten Citrus crops. Technologies that can efficiently identify Citrus Canker would assure fruit quality and safety and enhance the competitiveness and profitability of the Citrus industry. This research was aimed to investigate the potential of using hyperspectral imaging technique for detecting Canker lesions on Citrus fruit. A portable hyperspectral imaging system consisting of an automatic sample handling unit, a light source, and a hyperspectral imaging unit was developed for Citrus Canker detection. The imaging system was used to acquire reflectance images from Citrus samples in the wavelength range between 400 nm and 900 nm. Ruby Red grapefruits with normal and various diseased skin conditions including Canker, copper burn, greasy spot, wind scar, cake melanose, and specular melanose were tested. Hyperspectral reflectance images were analyzed using principal component analysis (PCA) to compress the 3-D hyperspectral image data and extract useful image features that could be used to discriminate Cankerous samples from normal and other diseased samples. Image processing and classification algorithms were developed based upon the transformed images of PCA. The overall accuracy for Canker detection was 92.7%. This research demonstrated that hyperspectral imaging technique could be used for discriminating Citrus Canker from other confounding diseases.

L G Marcassa - One of the best experts on this subject based on the ideXlab platform.

  • optical fiber laser induced fluorescence spectroscopy as a Citrus Canker diagnostic
    Applied Optics, 2010
    Co-Authors: E C Lins, Jr J Belasque, L G Marcassa
    Abstract:

    Citrus Canker is a serious disease caused by Xanthomonas citri subsp. citri bacteria, which infects Citrus plants (Citrus spp.) leading to large economic losses in Citrus production worldwide. In this work, laser induced fluorescence spectroscopy (LIF) was investigated as a diagnostic technique for Citrus Canker disease in Citrus trees at an orchard using a portable optical fiber based spectrometer. For comparison we have applied LIF to leaves contaminated with Citrus Canker, Citrus scab, Citrus variegates chlorosis, and Huanglongbing (HLB, Greening). In order to reduce the noise in the data, we collected spectra from ten leaves with visual symptoms of diseases and from five healthy leaves per plant. This procedure is carried out in order to minimize the environmental effect on the spectrum (water and nutrient supply) of each plant. Our results show that this method presents a high sensitivity (~90%), however it does present a low specificity (~70%) for Citrus Canker diagnostic. We believe that such poor performance is due to the fact that the optical fiber collects light from only a small part of the leaf. Such results may be improved using the fluorescence imaging technique on the whole leaf.

  • detection of Citrus Canker in Citrus plants using laser induced fluorescence spectroscopy
    Precision Agriculture, 2009
    Co-Authors: E C Lins, Jr J Belasque, L G Marcassa
    Abstract:

    Citrus Canker is a serious disease caused by Xanthomonas citri subsp. citri bacteria, which infects Citrus plants (Citrus spp.) leading to a large economic loss in Citrus production worldwide. In Brazil Citrus Canker control is done by an official eradication campaign, therefore early detection of such disease is important to prevent greater economic losses. However, detection is difficult and so far it has been done by visual inspection of each tree. Suspicious leaves from Citrus plants in the field are sent to the laboratory to confirm the infection by laboratory analysis, which is a time consuming. Our goal was to develop a new optical technique to detect and diagnose Citrus Canker in Citrus plants with a portable field spectrometer unit. In this paper, we review two experiments on laser induced fluorescence spectroscopy (LIF) applied to detect Citrus Canker. We also present new data to show that the length of time a leaf has been detached is an important variable in our studies. Our results show that LIF has the potential to be applied to Citrus plants.

  • Fluorescence Spectroscopy for Detection of Citrus Canker in Orange Plantation
    Frontiers in Optics, 2006
    Co-Authors: E C Lins, Jose Belasque, Maria C. Gasparoto, Vanderlei Salvador Bagnato, L G Marcassa
    Abstract:

    In this work, we investigate the use of induced fluorescence for the detection of Citrus Canker in orange plantations in Brazil. The spectrum allows us to detect the disease in a very early stage.