A standard area diagram set to aid estimation of the severity of Asiatic citrus canker on ripe sweet orange fruit

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.

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Development of PCR Assays for the Identification of Species and Pathotypes of Elsinoë Causing Scab on Citrus

Plant Disease ◽

10.1094/pdis-91-7-0865 ◽

2007 ◽

Vol 91 (7) ◽

pp. 865-870 ◽

Cited By ~ 16

Author(s):

J. W. Hyun ◽

N. A. Peres ◽

S.-Y. Yi ◽

L. W. Timmer ◽

K. S. Kim ◽

...

Keyword(s):

Internal Transcribed Spacer ◽

Sweet Orange ◽

Random Amplified Polymorphic Dna ◽

Its Region ◽

The United States ◽

Specific Primer ◽

Identification Of Species ◽

Orange Fruit ◽

Pcr Assays ◽

Primer Sets

Two scab pathogens of citrus, Elsinoë fawcettii and E. australis, cause citrus scab and sweet orange scab, respectively, and pathotypes of each species have been described. The two species cannot be readily distinguished by morphological or cultural characteristics and can be distinguished only by host range and the sequence of the internal transcribed spacer (ITS) region. In this study, random amplified polymorphic DNA (RAPD) assays clearly distinguished E. fawcettii and E. australis, and the sweet orange and natsudaidai pathotypes within E. australis also could be differentiated. We developed specific primer sets, Efaw-1 for E. fawcettii; Eaut-1, Eaut-2, Eaut-3, and Eaut-4 for E. australis; and EaNat-1 and EaNat-2 for the natsudaidai pathotype within E. australis using RAPD products unique to each species or pathotype. Other primer sets, Efaw-2 and Eaut-5, which were specific for E. fawcettii and E. australis, respectively, were designed from previously determined ITS sequences. The Efaw-1 and Efaw-2 primer sets successfully identified E. fawcettii isolates from Korea, Australia, and the United States (Florida) and the Eaut-1 to Eaut-5 primer sets identified both the sweet orange pathotype isolates of E. australis from Argentina and the natsudaidai pathotype isolates from Korea. The EaNat-1 and EaNat-2 primer sets were specific for isolates of the natsudaidai pathotype. The Efaw-1 and Efaw-2 primer sets successfully detected E. fawcettii from lesions on diseased leaves and fruit from Korea and primer pairs Eaut-1, Eaut-2, Eaut-3, Eaut-4, and Eaut-5 detected E. australis from lesions on sweet orange fruit from Brazil.

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

Crop Protection ◽

10.1016/j.cropro.2009.12.010 ◽

2010 ◽

Vol 29 (3) ◽

pp. 300-305 ◽

Cited By ~ 57

Author(s):

F. Behlau ◽

J. Belasque ◽

J.H. Graham ◽

R.P. Leite

Keyword(s):

Sweet Orange ◽

Citrus Canker ◽

Orange Trees

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

Plant Disease ◽

10.1094/pdis-10-20-2153-re ◽

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.

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

Acta Horticulturae ◽

10.17660/actahortic.2015.1065.62 ◽

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

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

Molecular Plant-Microbe Interactions ◽

10.1094/mpmi-04-13-0122-r ◽

2013 ◽

Vol 26 (10) ◽

pp. 1190-1199 ◽

Cited By ~ 15

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.

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

Plant Disease ◽

10.1094/pdis-01-13-0128-pdn ◽

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.

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Volatile Profile Comparison of USDA Sweet Orange-like Hybrids versus ‘Hamlin’ and ‘Ambersweet’

HortScience ◽

10.21273/hortsci.49.10.1262 ◽

2014 ◽

Vol 49 (10) ◽

pp. 1262-1267 ◽

Cited By ~ 12

Author(s):

Jinhe Bai ◽

Elizabeth Baldwin ◽

Jack Hearn ◽

Randy Driggers ◽

Ed Stover

Keyword(s):

Sweet Orange ◽

Fruit Size ◽

Poncirus Trifoliata ◽

Harvest Time ◽

Volatile Analysis ◽

Volatile Profiles ◽

Orange Fruit ◽

Hybrid Lines ◽

Very High

Six ‘Ambersweet’-derived hybrids, similar to sweet orange fruit size, color, and taste and potential as new sweet orange cultivars, were selected to determine their fruit categorization by comparison of their volatile profiles with the parent and ‘Hamlin’, a typical sweet orange. All hybrids are at least ½ sweet orange and varying amounts of mandarin, grapefruit, Poncirus trifoliata, and sour orange in each pedigree. In total, 135 volatiles were detected in the eight hybrid lines/commercial cultivars over two harvests, and 20 compounds were detected in all samples, including terpenes (limonene, β-myrcene, α-pinene, α-terpinene, α-terpineol, and linalool), esters (ethyl butanote, ethyl pentanoate, and ethyl acetate), aldehydes (acetaldehyde, hexanal, and nonanal), and alcohols (ethanol and hexanol). Total abundance of volatiles in January-harvested fruits averaged 30% higher than for fruits of the same trees harvested in November. ‘Ambersweet’ contained the highest total amount of volatiles (mainly as a result of very high levels of monoterpenes), and of them, nootkatone and six other compounds were not detected in any of the hybrids, and some of them were also not detected in ‘Hamlin’. On the other hand, 12 compounds, including pentanal, ethyl 2-butenoate, and ethyl nonanoate, were not detected in ‘Ambersweet’ but were found in ‘Hamlin’ and some of the hybrids. Cluster analysis separated the cultivar/hybrid and harvest time combinations into three clusters. FF-1-76-50, FF-1-76-52 and January FF-1-75-55, all with the same parents (‘Ambersweet’ × FF-1-30-52), were close to FF-1-65-55, but they were separated from ‘Hamlin’ and further separated from ‘Ambersweet’. The cluster containing ‘Hamlin’ has three subclusters: January ‘Hamlin’ and November FF-1-74-14, a hybrid with one-eighth P. trifoliata, which includes a slight off-flavor frequently found in P. trifoliata hybrids, independent of each other, and both were separated from a group of November ‘Hamlin’, FF-1-64-97, and FF-1-75-55. The cluster containing ‘Ambersweet’ included January FF-1-64-97. A principle component analysis (PCA) separated ‘Ambersweet’ from all hybrids and ‘Hamlin’ along the PC1 axis and separated November harvests from January harvests along PC2. This volatile analysis supports the classification of the hybrids as sweet orange.

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Hydrothermal treatment favors peeling of 'Pera' sweet orange fruit and does not alter quality

Scientia Agricola ◽

10.1590/s0103-90162008000200007 ◽

2008 ◽

Vol 65 (2) ◽

pp. 151-156 ◽

Cited By ~ 9

Author(s):

Maria Cecília de Arruda ◽

Angelo Pedro Jacomino ◽

Ana Luíza Pinheiro ◽

Rafael Vasconcelos Ribeiro ◽

Michelle Antonio Lochoski ◽

...

Keyword(s):

Hydrothermal Treatment ◽

Respiratory Activity ◽

Sweet Orange ◽

Ascorbic Acid Content ◽

Titratable Acidity ◽

Soluble Solids ◽

Orange Fruit ◽

New Processing ◽

Processing Techniques ◽

Fruit Flavor

Consumer demand for ready-to-eat-products has stimulated the development of new processing techniques to prepare fresh-cut fruit and vegetables. The aim of this study was to propose a peeling method for 'Pera' oranges (Citrus sinensis [L.] Osb.) by using a hydrothermal treatment and to determine its influence on the respiratory activity, physicochemical and sensorial characteristics, as well as on the peeling time. Cooled oranges (6ºC) were immersed in heated water (50ºC) for eight minutes and then, peeled and stored at 6ºC. The internal fruit temperatures taken at 1 and 3 cm depths (from fruit surface) were 15ºC and 10ºC, respectively, at the end of the hydrothermal treatment. Non-hydrothermally-treated peeled oranges were used as control. The peeling time for treated oranges was 3.2 times as short as the time used for the control. The yield of marketable oranges was 95% for hydrothermally-treated oranges versus 60% for control. The respiratory activity of hydrothermally-treated oranges was greater than that of control oranges only during the first hour after peeling. The hydrothermal treatment influenced neither the physicochemical quality (given by soluble solids, titratable acidity and ascorbic acid content) nor fruit flavor. Oranges peeled with the aid of the hydrothermal treatment had better appearance. The hydrothermal treatment makes the peeling of oranges easier and does not affect their respiratory activity or their physicochemical and sensorial qualities.

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

HortScience ◽

10.21273/hortsci.41.4.972d ◽

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.

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