scholarly journals Development and Validation of Standard Area Diagrams as Assessment Aids for Estimating the Severity of Citrus Canker on Unripe Oranges

Plant Disease ◽  
2014 ◽  
Vol 98 (11) ◽  
pp. 1543-1550 ◽  
Author(s):  
Ricardo Braido ◽  
Aline M. O. Gonçalves-Zuliani ◽  
Vanderly Janeiro ◽  
Sérgio A. Carvalho ◽  
José Belasque Junior ◽  
...  
Keyword(s):  
Sweet Orange ◽  
Severe Disease ◽  
Citrus Canker ◽  
Visual Estimation ◽  
Concordance Correlation ◽  
Unripe Fruit ◽  
Diseased Fruit ◽  
Causal Pathogen ◽  
Development And Validation ◽  
Important Disease

Asiatic citrus canker (ACC) is an important disease of citrus in Brazil and elsewhere in the world. Infection with the causal pathogen, Xanthomonas citri subsp. citri, can cause severe disease on the fruit. Visual estimation of severity is the usual method used to quantify ACC on diseased fruit. The objective of this research was to construct and validate standard area diagram (SAD) sets as assessment aids for raters to improve the accuracy and reliability of visual estimates of ACC on unripe (green) fruit of sweet orange. Two SAD sets were constructed. A five-diagram SAD set had five severities depicted (0.5, 2.0, 8.0, 27.0, and 40.0%) and a six-diagram SAD set had six severities depicted (0.5, 1.0, 3.0, 9.0, 20.0, and 40.0%). Fifteen raters evaluated 40 images of cankered, unripe fruit. Both the five- and six-diagram SAD sets significantly improved the accuracy and reliability of estimates. Agreement, measured by Lin's concordance correlation coefficient, was 0.220 to 0.913 when not using SADs, 0.814 to 0.955 when using five-diagram SAD sets, and 0.863 to 0.925 when using six-diagram SAD sets. The five-diagram SAD set was significantly more accurate and reliable compared with the six-diagram set. Possible reasons for this are discussed. Based on the results, the five-diagram SAD set is preferable to use. Although the SAD set was developed for sweet orange, it doubtless has applicability to other citrus, including grapefruit. These SAD sets should be useful for research endeavors where accurate and reliable estimates of the severity of ACC are required.

Spray Volume and Rate Based on the Tree Row Volume for a Sustainable Use of Copper in the Control of Citrus Canker

Plant Disease ◽  
2021 ◽  
Vol 105 (1) ◽  
pp. 183-192
Author(s):  
Franklin Behlau ◽  
Fabrício E. Lanza ◽  
Marcelo da Silva Scapin ◽  
Luis Henrique Mariano Scandelai ◽  
Geraldo José Silva Junior
Keyword(s):  
Sweet Orange ◽  
Metallic Copper ◽  
Sustainable Use ◽  
Citrus Canker ◽  
Tree Canopy ◽  
Minimum Threshold ◽  
Diseased Fruit ◽  
Citrus Orchards ◽  
Spray Volume

Copper is the most efficient pesticide for the control of citrus canker (Xanthomonas citri subsp. citri). To mitigate the environmental impacts and costs, the copper sprays in citrus orchards are being optimized based on the tree row volume (TRV). A previous investigation allowed for significant reductions of the spray volume and copper rates. Nevertheless, the results also indicated the need for additional studies. The aim of this work was to assess whether both the spray volume and the metallic copper rate based on the TRV may be further reduced. A field trial was carried out during two seasons in a 3-year-old commercial orchard of Pera sweet orange located in the municipality of Paranavaí, Paraná, Brazil. The volumes of 20 and 40 ml of spray mixture per m3 of the tree canopy were assessed in combination with the metallic copper rates of 10.5, 21.0, 36.8, or 52.5 mg/m3. Disease was measured as the temporal progress of canker incidence on leaves, cumulative dropped fruit with canker, and incidence of diseased fruit at harvest. The quality of sprays was assessed by measuring the copper deposition and leaf coverage. The treatment with the highest citrus canker control for the lowest use of water and copper was the combination of 40 ml and 36.8 mg/m3. Regression analyses indicated that the minimum threshold deposition of copper was ∼1.5 µg Cu2+/cm2 leaf area. In addition, the lowest spray volume and copper rate necessary to achieve this deposition are 35 ml/m3 and 30 mg/m3. The use of 20 ml/m3 did not efficiently control the disease due to the deficient coverage of treated surfaces. This study demonstrated that it is possible to use even lower amounts of copper and water without interfering with the efficiency of control of citrus canker.

Effect of frequency of copper applications on control of citrus canker and the yield of young bearing sweet orange trees

2010 ◽  
Vol 29 (3) ◽  
pp. 300-305 ◽  
Author(s):  
F. Behlau ◽  
J. Belasque ◽  
J.H. Graham ◽  
R.P. Leite
Keyword(s):  
Sweet Orange ◽  
Citrus Canker ◽  
Orange Trees

scholarly journals Characteristics of Citrus Canker Lesions Associated with Premature Drop of Sweet Orange Fruit

2019 ◽  
Vol 109 (1) ◽  
pp. 44-51 ◽  
Author(s):  
Fabrício E. Lanza ◽  
Weber Marti ◽  
Geraldo J. Silva ◽  
Franklin Behlau
Keyword(s):  
Sweet Orange ◽  
Linear Regression Analysis ◽  
Negative Relationship ◽  
Citrus Fruit ◽  
Citrus Canker ◽  
Multiple Linear Regression Analysis ◽  
Detachment Force ◽  
Fruit Drop ◽  
Orange Fruit ◽  
The Relationship

During the development of a citrus fruit, many cycles of infection by Xanthomonas citri subsp. citri may occur leading to the development of a range of characteristics of citrus canker lesions scattered across the fruit surface. This study aimed to determine whether the size of the lesions, their distance from the peduncle, and the number and time of appearance of the lesions on fruit of sweet orange were associated with premature fruit drop. A multiple linear regression analysis revealed a negative relationship between the fruit detachment force and the lesion diameter, the proximity of the nearest lesion to the peduncle and the number of lesions. A survival analysis demonstrated that these characteristics significantly influenced the probability and the time that a cankered fruit remained attached to the tree. More than 90% of dropped fruit had large lesions (>5 mm) but not all fruit with large lesions dropped before harvest. Approximately 50% of the harvested fruit had lesions >5 mm. On the harvested fruit remaining on the tree, although large, the lesions had a smaller diameter, were located farther from the peduncle, and were less numerous than those observed on dropped fruit. Small canker lesions neither reduced the detachment force nor the survival of fruit in the tree. The earlier a fruit expressed canker symptoms, the higher the probability the fruit developed large lesions near the peduncle and/or developed lesions in greater numbers. This study provides a better understanding on the relationship between the time of appearance of lesions of citrus canker on fruit and premature fruit drop. This information defines the critical period for fruit protection and may be used to improve disease management.

scholarly journals Transmission of Xylella fastidiosa, Causal Agent of Citrus Variegated Chlorosis, by the Glassy-Winged Sharpshooter, Homalodisca coagulata

Plant Disease ◽  
2006 ◽  
Vol 90 (5) ◽  
pp. 567-570 ◽  
Author(s):  
V. D. Damsteegt ◽  
R. H. Brlansky ◽  
P. A. Phillips ◽  
Avijit Roy
Keyword(s):  
Xylella Fastidiosa ◽  
The United States ◽  
Citrus Variegated Chlorosis ◽  
Homalodisca Coagulata ◽  
Causal Pathogen ◽  
Polymerase Chain ◽  
Species Specific ◽  
Transmission Studies ◽  
Test Plants ◽  
Important Disease

Citrus variegated chlorosis (CVC) is an economically important disease of citrus in Brazil and Argentina. The causal pathogen is a strain of Xylella fastidiosa transmitted by several sharpshooter species. The glassy-winged sharpshooter (GWSS), Homalodisca coagulata, has become an important new pest of citrus and grapevines in California, where it transmits X. fastidiosa strains to several crops including grapes, oleander, and almonds. Transmission studies over a 3-year period at the USDA BSL3-P containment facility at Fort Detrick, MD, utilizing California field-collected GWSS, a Brazilian strain of CVC, and Madam Vinous sweet orange seedlings, have shown a consistent although low level of transmission of CVC. Test plants were observed for CVC symptoms, analyzed by polymerase chain reaction using species-specific primers for X. fastidiosa, membrane entrapment immunofluorescence, and scanning electron microscopy. X. fastidiosa was not detected in field-collected GWSS but was detected in GWSS following feeding on CVC-infected source plants. Transmission of the CVC strain of X. fastidiosa by GWSS increases the risk of establishment of CVC in the United States if it were introduced.

Relative contribution of windbreak, copper sprays and leafminer control for citrus canker management and prevention of crop loss in sweet orange trees

Plant Disease ◽  
2020 ◽  
Author(s):  
Franklin Behlau ◽  
José Belasque Junior ◽  
RUI LEITE ◽  
Armando Bergamin-Filho ◽  
Tim Gottwald ◽  
...  
Keyword(s):  
Sweet Orange ◽  
Disease Incidence ◽  
Citrus Canker ◽  
Control Measures ◽  
Disease Suppression ◽  
Additional Contribution ◽  
Crop Losses ◽  
Rangpur Lime ◽  
Relative Contribution ◽  
Orange Trees

The management of citrus canker, caused by Xanthomonas citri subsp. citri, has been widely studied in endemic areas due to the importance of the disease in several citrus producing countries. A set of control measures is well-established, but no study has investigated the efficiency of each measure individually and their combination for disease suppression. This study comprised a 3-year field study to assess the relative contribution of three measures for the control of citrus canker and reduction of crop losses. Windbreak (Wb), copper sprays (Cu), and leafminer control (Lc) were assessed in eight different combinations in a split-split plot design. The orchard was composed of ‘Valencia’ sweet orange trees grafted onto ‘Rangpur’ lime. Casuarina cunninghamiana trees were used as Wb. Cu and Lc sprays were performed every 21 days throughout the year. Individually, Cu showed the highest contribution for canker control, followed by Wb. Lc had no effect on reducing citrus canker. Wb+Cu showed the highest efficiency for control of the disease. This combination reduced the incidence of diseased trees by ~60%, and the incidence of diseased leaves and fruit by ≥ 90% and increased the yield in 2.0 to 2.6-fold in comparison with the unmanaged plots. Cu sprays were important for reducing disease incidence and crop losses, whereas Wb had an additional contribution in minimizing the incidence of cankered, non-marketable fruit. The results indicated that the adoption of these measures of control may depend on the characteristics of the orchard and destination of the production.

EVALUATION OF SUSCEPTIBILITY OF 'PERA' SWEET ORANGE GENOTYPES TO CITRUS CANKER UNDER FIELD AND GREENHOUSE CONDITIONS

2015 ◽  
pp. 511-516
Author(s):  
Aline M.O. Gonçalves-Zuliani ◽  
William M.C. Nunes ◽  
Carlos A. Zanutto ◽  
José Croce Filho ◽  
Paula T.R. Nocchi
Keyword(s):  
Sweet Orange ◽  
Citrus Canker

scholarly journals Increased Resistance Against Citrus Canker Mediated by a Citrus Mitogen-Activated Protein Kinase

2013 ◽  
Vol 26 (10) ◽  
pp. 1190-1199 ◽  
Author(s):  
Maria Luiza Peixoto de Oliveira ◽  
Caio Cesar de Lima Silva ◽  
Valéria Yukari Abe ◽  
Marcio Gilberto Cardoso Costa ◽  
Raúl Andrés Cernadas ◽  
...  
Keyword(s):  
Hydrogen Peroxide ◽  
Sweet Orange ◽  
Plant Immunity ◽  
Gene Promoter ◽  
Citrus Canker ◽  
Hypersensitive Reaction ◽  
Mitogen Activated Protein Kinase ◽  
Defense Gene Expression ◽  
Defense Gene ◽  
Mitogen Activated Protein

Mitogen-activated protein kinases (MAPK) play crucial roles in plant immunity. We previously identified a citrus MAPK (CsMAPK1) as a differentially expressed protein in response to infection by Xanthomonas aurantifolii, a bacterium that causes citrus canker in Mexican lime but a hypersensitive reaction in sweet oranges. Here, we confirm that, in sweet orange, CsMAPK1 is rapidly and preferentially induced by X. aurantifolii relative to Xanthomonas citri. To investigate the role of CsMAPK1 in citrus canker resistance, we expressed CsMAPK1 in citrus plants under the control of the PR5 gene promoter, which is induced by Xanthomonas infection and wounding. Increased expression of CsMAPK1 correlated with a reduction in canker symptoms and a decrease in bacterial growth. Canker lesions in plants with higher CsMAPK1 levels were smaller and showed fewer signs of epidermal rupture. Transgenic plants also revealed higher transcript levels of defense-related genes and a significant accumulation of hydrogen peroxide in response to wounding or X. citri infection. Accordingly, nontransgenic sweet orange leaves accumulate both CsMAPK1 and hydrogen peroxide in response to X. aurantifolii but not X. citri infection. These data, thus, indicate that CsMAPK1 functions in the citrus canker defense response by inducing defense gene expression and reactive oxygen species accumulation during infection.

scholarly journals First Report of Xanthomonas citri pv. citri-A Causing Asiatic Citrus Canker in Mayotte

Plant Disease ◽  
2013 ◽  
Vol 97 (7) ◽  
pp. 989-989
Author(s):  
J. Hoarau ◽  
C. Boyer ◽  
K. Vital ◽  
T. Chesneau ◽  
C. Vernière ◽  
...  
Keyword(s):  
Indian Ocean ◽  
Sweet Orange ◽  
Citrus Canker ◽  
Negative Control ◽  
Sterile Water ◽  
Citrus Species ◽  
Indian Ocean Region ◽  
Southwest Indian Ocean ◽  
Mexican Lime ◽  
Ocean Region

Asiatic citrus canker, caused by Xanthomonas citri pv. citri, is a bacterial disease of major economic importance in tropical and subtropical citrus-producing areas. X. citri pv. citri pathotype A can cause severe infection in a wide range of citrus species and induces erumpent, callus-like lesions with water-soaked margins evolving to corky cankers and leading to premature fruit and leaf drop and twig dieback on susceptible/very susceptible cultivars. A chlorotic halo is typically visible around canker lesions on leaves and young fruit, but not on mature fruit and twigs. This quarantine organism can strongly impact both national and international citrus markets. Long distance dispersal is mainly through infected propagative material. Asiatic citrus canker occurs on most islands in the Southwest Indian Ocean region (Comoros, Mauritius, Reunion, Rodrigues, and Seychelles islands), but was not yet reported in Mayotte (EPPO-PQR available at http://www.eppo.int ). In May 2012, typical canker-like symptoms were observed on sweet orange (Citrus sinensis) groves on Mtsamboro islet and soon after on the main island of Mayotte, mostly on sweet oranges, but also on Tahiti limes (C. latifolia) and mandarins (C. reticulata). Eighty-one Xanthomonas-like strains were isolated using KC semi-selective medium (4) from disease samples collected from both commercial groves and nurseries on different Citrus species located all over the island. Sixteen Xanthomonas-like isolates were tentatively identified as X. citri pv. citri based on a specific PCR assay with 4/7 primers (3). All strains but the negative control, sterile water, produced an amplicon of the expected size similar to X. citri pv. citri strain IAPAR 306 used as positive control. Multilocus sequence analysis targeting six housekeeping genes (atpD, dnaK, efp, gltA, gyrB, and lepA) (1,2) fully identified three strains from Mayotte (LJ225-3, LJ228-1, and LJ229-11) as X. citri pv. citri (and not other xanthomonad pathovars pathogenic to citrus or host range-restricted pathotypes of pathovar citri), and more specifically as sequence type ST2 composed of pathotype A strains of X. citri pv. citri (2) (including all strains from the Southwest Indian Ocean region). Eight strains were inoculated by a detached leaf assay (2) to Mexican lime SRA 140 (C. aurantifolia), Tahiti lime SRA 58, sweet orange cv. Washington Navel, alemow SRA 779 (C. macrophylla), and tangor cv. Ortanique (C. reticulata × C. sinensis) and developed typical erumpent, callus-like tissue at wound sites for all Citrus species, fulfilling Koch's postulates. Xanthomonas-like yellow colonies were reisolated from symptoms produced by the eight strains inoculated on Mexican lime. Boiled bacterial suspensions were assayed by PCR with 4/7 primers (3) and produced the expected 468-bp amplicon in contrast with the negative control (sterile water). No lesions developed on the negative control consisting of inoculations by 10 mM tris buffer (pH 7.2). Citrus canker-free nurseries and grove sanitation should be implemented for decreasing the prevalence of Asiatic canker in this island territory. References: (1) N. F. Almeida et al. Phytopathology 100:208, 2010. (2) L. Bui Thi Ngoc et al. Int. J. Syst. Evol. Microbiol. 60:515, 2010. (3) J. S. Hartung et al. Phytopathology 86:95, 1996. (4) O. Pruvost et al. J. Appl. Microbiol. 99:803, 2005.

scholarly journals Comparison between Protoplast Transformation and Co-transformation in `Hamlin' Sweet Orange [Citrus sinensis (L.) Osbeck]

HortScience ◽  
2006 ◽  
Vol 41 (4) ◽  
pp. 972D-973
Author(s):  
Ahmad A. Omar ◽  
Wen-Yuan Song ◽  
James H. Graham ◽  
Jude W. Grosser
Keyword(s):  
Transgenic Plants ◽  
Citrus Sinensis ◽  
Fluorescent Protein ◽  
Sweet Orange ◽  
Citrus Canker ◽  
Yield Potential ◽  
High Yield ◽  
Pcr Analysis ◽  
Dna Encoding ◽  
Early Maturity

Citrus canker disease caused by the bacterial pathogen Xanthomonas axonopodis pv. citri is becoming a worldwide problem. Xa21 gene is a member of the Xa21 gene family of rice, which provides broad spectrum Xanthomonas resistance in rice. `Hamlin' sweet orange [Citrus sinensis (L.) Osbeck) is one of the leading commercial cultivars in Florida because of its high yield potential and early maturity. `Hamlin' also has a high regeneration capacity from protoplasts and is often used in transformation experiments. Since the citrus canker pathogen is in the same genus, this gene may have potential to function against canker in citrus. The wild-type Xa21 gene contains an intron, and there are some questions whether dicot plants can process genes containing monocot introns (the cDNA is intron-free). Plasmids DNA, encoding the non-destructive selectable marker EGFP (Enhanced Green Fluorescent Protein) gene and the cDNA of the Xa21 gene were transformed or co-transformed into `Hamlin' orange protoplasts using polyethylene glycol. More than 200 transgenic embryoids were recovered. More than 400 transgenic plants were developed from 75 independent transgenic events. PCR analysis revealed the presence of the cDNA of the Xa21 and the GFP genes in the transgenic plants. Some of the plants have the GFP only. Southern analysis is showing integration of the cDNA into different sites ranges from one to five sites. Western analysis is showing the expression of the cDNA of the Xa21 gene in the transgenic citrus plants. This is the first time that a gene from rice has been stably integrated and expressed in citrus plants. Canker challenge assay is in progress.

scholarly journals First Report of Gray Mold Caused by Botrytis cinerea on Greenhouse-Grown Zucchini in Korea

Plant Disease ◽  
2013 ◽  
Vol 97 (8) ◽  
pp. 1116-1116 ◽  
Author(s):  
W. Cheon ◽  
Y. H. Jeon
Keyword(s):  
New York ◽  
Botrytis Cinerea ◽  
Severe Disease ◽  
Morphological Characteristics ◽  
Its Region ◽  
Gray Mold ◽  
Greenhouse Production ◽  
First Report ◽  
Plastic Bags ◽  
Diseased Fruit

In the winter of 2011, greenhouse-grown zucchini (Cucurbita pepo) in Andong City, Korea, showed severe disease symptoms on fruits and dying leaves of zucchini plants that resembled gray mold disease with about 20% yield loss. Symptoms included extensive growth of mycelia and gray conidia on stem and fruit lesions. Lesions expanded rapidly under cool, humid conditions. As the disease progressed, leaves, stems, and fruits became necrotic and were covered by an abundant, soft, gray, sporulating mycelium. Diseased fruit tissue was excised and surface sterilized by immersion in 2% NaOCl for 1 min, placed on PDA (potato dextrose agar), and incubated at 22°C. Fungal colonies were initially white and became gray to brown after 72 h. Analysis of light micrographs showed the presence of elliptical conidia on PDA that was 7.5 to 16.0 μm long and 5 to 10.5 μm wide. In culture, a few, black, small and large irregular sclerotia were produced. Microsclerotia were round, spherical or irregular in shape, and ranged from 1.0 to 3.3 and 1.2 to 3.4 mm (width and length). Conidiophores were slender and branched with enlarged apical cells bearing smooth, ash-colored conidia. These morphological characteristics identified the fungus as Botrytis cinerea (1). The internal transcribed spacer (ITS) region of rDNA was amplified using the ITS1 (forward) and ITS4 (reverse) primer set (ITS1: 5′-TCCGTAGGTGAACCTGCGG-3′, ITS4: 5′-TCCTCCGCTTATTGATATGC-3′) and sequenced (2). BLAST analysis of the PCR product showed that the sequence had 100% identity with the nucleotide sequences for B. cinerea. Pathogenicity tests were performed by placing mycelium fragments (1 cm2) of PDA cultures on zucchini fruits. Controls were treated with PDA alone. Five replicates for the inoculated and control plants were used. All fruits were covered with plastic bags and incubated in a growth chamber to maintain 90 to 100% relative humidity at 22°C. Typical symptoms appeared 2 to 6 days after inoculation. The inoculated plants developed typical gray mold symptoms with gray sporulating lesions, while controls remained healthy with no lesions. B. cinerea reisolated from the inoculated tissues was morphologically identical to the original isolates. In a cold outside (below 0°C), wet greenhouse, plants are likely to be exposed to resident Botrytis populations and if the gray mold disease occurs, it can spread on zucchini plants very fast, in 2 days to a week inside a 100 m2 greenhouse. Therefore, gray mold disease could have a significant impact on greenhouse production of zucchini. To our knowledge, this is the first report of B. cinerea causing gray mold of greenhouse-grown zucchini in Korea. References: (1) H. L. Barnett and B. B. Hunter. Illustrated Genera of Imperfect Fungi. Burgess Publishing Company, Minneapolis, MN, 1972. (2) T. J. White et al. PCR Protocols. Academic Press, Inc., New York, 1990.

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