Evidence That Xylella fastidiosa Is Associated with Pecan Fungal Leaf Scorch

Several different leaf scorch symptomatologies occur on the foliage of pecan (Carya illinoinensis). The causes of these different scorch symptoms have been associated with environmental stresses, nutritional imbalances, mites, and pathogens. One type of leaf scorch is characterized by necrosis beginning at the tips or margins of the leaflets and progressing toward the midrib and base of the leaflets. The most distinguishing feature of this type of leaf scorch is a dark brown, black, or purplish band of tissue at the interface of the necrotic and green leaflet tissue. This band does not occur on all affected leaflets, but is a consistent feature with this symptomatology. Leaflets with this leaf scorch usually abscise before the entire leaflet becomes necrotic. Affected leaflets will abscise from a compound leaf, while leaflets without symptoms remain on the rachis. When this scorch is severe, the entire leaf including the rachis may abscise. The symptoms are often confined to one area of the tree. Symptoms of this disease appear as early as June but often begin in July. Incidence and severity increase through the remainder of summer and into fall. Over the past 25 years, several different genera of fungi have been reported as being associated with this leaf scorch (2). The phenomenon was named fungal leaf scorch (FLS) because of the association with fungi and the observation that some fungicides reduced the severity of leaf scorch. Genera of fungi implicated in the development of FLS were Pestalotia, Epicoccum, Curvularia, and Fusarium. Recent work has indicated that the disease could be caused by a Phomopsis sp. or Glomerella cingulata or both (1). The symptoms and epidemiology of the FLS are similar to other leaf scorch diseases of hardwood caused by the fastidious xylem-limited bacterium Xylella fastidiosa. A commercial enzyme-linked immunosorbent assay (Agdia, Elkhart, IN) was used to screen for this organism in association with FLS. Assays were conducted by extracting from a composite sample of 9 to 12 sections (approximately 3 cm long) taken from 3 to 4 rachises of each tree tested. Positive reaction for the presence of X. fastidiosa in rachises was recorded from 10 of 10 trees with symptoms of FLS on the Cape Fear cultivar. One of two trees was positive from Cape Fear leaves without symptoms. Symptomless foliage from two less susceptible cultivars, Stuart (two trees) and Sumner (one tree), assayed negative for the bacterium. The association of X. fastidiosa with symptoms of FLS provides evidence that this organism is involved in the etiology of pecan leaf scorch; however, further work is needed to determine the exact etiology. References: (1). A. J. Latham et al. Plant Dis. 79:182, 1995. (2) R. H. Littrell and R. E. Worley. Phytopathology 62:805, 1972.

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Reduction of Xylella fastidiosa Transmission Through Pecan Scion Wood by Hot-Water Treatment

Plant Disease ◽

10.1094/pdis-92-7-1124 ◽

2008 ◽

Vol 92 (7) ◽

pp. 1124-1126 ◽

Cited By ~ 11

Author(s):

R. S. Sanderlin ◽

R. A. Melanson

Keyword(s):

Water Treatment ◽

Xylella Fastidiosa ◽

Carya Illinoinensis ◽

Hot Water ◽

Hot Water Treatment ◽

Leaf Scorch ◽

Cape Fear ◽

Graft Success ◽

Water Treatments ◽

Bacterial Leaf Scorch

Pecan (Carya illinoinensis) bacterial leaf scorch disease, caused by the bacterium Xylella fastidiosa, causes leaf loss and reduction in yield of pecans. One of the ways that the pathogen infects newly developing trees is by graft-transmission through infected scion wood. Submersion of pecan scion wood in 46°C water for 30 min greatly reduced transmission of X. fastidiosa following grafting. During a 2-year study with potted rootstock grafted to either hot-water-treated or nontreated scion wood collected from limbs of ‘Cape Fear’ pecan infected with X. fastidiosa, the pathogen was detected in 21% of the trees that developed from the nontreated scion wood and 0.7% of the trees from the hot-water-treated scions. The hot-water treatment of 46°C for 30 min did not affect graft success. Likewise, scion diameter had no effect on success of grafting or on the efficacy of hot-water treatment. Similar hot-water treatments have been efficacious in elimination of X. fastidiosa and some other pathogens from grapevine cuttings. The use of the hot-water treatment demonstrated in this report could be helpful to individual pecan growers and nurseries that use scion wood that may be infected with X. fastidiosa to reduce the occurrence of pecan bacterial leaf scorch disease in new trees.

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First Report of Xylella fastidiosa Associated with Leaf Scorch in Black Oak in Washington, D.C.

Plant Disease ◽

10.1094/pdis.2004.88.2.224c ◽

2004 ◽

Vol 88 (2) ◽

pp. 224-224 ◽

Cited By ~ 2

Author(s):

Q. Huang

Keyword(s):

Xylella Fastidiosa ◽

The United States ◽

Enzyme Linked Immunosorbent Assay ◽

Bacterial Suspension ◽

White Oak ◽

First Report ◽

Leaf Petiole ◽

Leaf Scorch ◽

Pcr Product ◽

Black Oak

Bacterial leaf scorch caused by Xylella fastidiosa has been reported in 17 species of oak including bur, pin, red, scarlet, shingle, and white oaks (3). In September 2002, a leaf scorch symptom characterized by marginal necrosis of leaves bordered by a darker brown band was observed in a mature black oak (Quercus velutina Lam.) at the U.S. National Arboretum in Washington, D.C. The leaf petiole of the black oak was processed in general extraction buffer (Agdia, Inc., Elkhart, IN) contained in a FastDNA lysing matrix tube using the FastPrep FP120 instrument (Qbiogene, Inc., Carlsbad, CA) (1). The leaf petiole extract reacted with an antiserum specific for X. fastidiosa (Agadia, Inc.) in an enzyme-linked immunosorbent assay (ELISA). A slow-growing bacterium was cultured from leaf petioles of the affected black oak tree by soaking the surface-sterilized, finely cut leaf petioles in sterile water for 30 min, followed by spreading the bacterial suspension on periwinkle wilt plates (1). When the cultured bacterium was subjected to polymerase chain reaction (PCR) with primers specific for X. fastidiosa (2), a 472-bp PCR product was detected. The PCR product was confirmed to be the predicted X. fastidiosa product by sequencing and sequence comparison with the reported genomic sequence of X. fastidiosa. ELISA and bacterial isolation from leaf petioles of a nearby symptomless white oak (Q. alba L.) tree were negative. To our knowledge, this is the first report of X. fastidiosa associated with leaf scorch in black oak in the United States, expanding the host range of the bacterium in economically important landscape tree species. References: (1) Q. Huang and J. L. Sherald. Curr. Microbiol. 48:73, 2004. (2) M. R. Pooler and J. S. Hartung. Curr. Microbiol. 31:377, 1995. (3) J. L. Sherald. Xylella fastidiosa, A bacterial pathogen of landscape trees. Page 191 in: Shade Tree Wilt Diseases, C. L. Ash, ed. The American Phytopathological Society, 2001.

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Pecan Bacterial Leaf Scorch, Caused by Xylella fastidiosa, Is Endemic in Georgia Pecan Orchards

Plant Health Progress ◽

10.1094/php-08-18-0045-s ◽

2018 ◽

Vol 19 (4) ◽

pp. 284-287 ◽

Cited By ~ 1

Author(s):

Clive H. Bock ◽

Jonathan E. Oliver ◽

Chunxian Chen ◽

Michael H. Hotchkiss ◽

Katherine L. Stevenson ◽

...

Keyword(s):

Yield Loss ◽

Xylella Fastidiosa ◽

Severe Disease ◽

The United States ◽

Susceptible Cultivar ◽

Leaf Scorch ◽

Central Production ◽

Cape Fear ◽

Production Areas ◽

Bacterial Leaf Scorch

Pecan bacterial leaf scorch (PBLS), caused by Xylella fastidiosa, can cause severe disease in some pecan cultivars, resulting in yield loss. Only recently has some information been obtained regarding the distribution and extent of the disease in pecan in any state in the United States. With emphasis on a susceptible cultivar, Cape Fear, we sampled a total of 91 trees in eight orchards from the southwestern and central production areas in Georgia (GA) and found 60.4% of trees sampled infected, most showing symptoms of PBLS. Further multilocus sequence typing from 16 of these trees confirmed presence X. fastidiosa. The results confirm that X. fastidiosa is widespread geographically in GA, and different cultivars may be infected. This is the first definitive report confirming X. fastidiosa causing PBLS in different pecan producing areas and cultivars in GA.

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Distribution of Xylella fastidiosa in Oaks in Florida and Its Association with Growth Decline in Quercus laevis

Plant Disease ◽

10.1094/pdis.1998.82.5.569 ◽

1998 ◽

Vol 82 (5) ◽

pp. 569-572 ◽

Cited By ~ 19

Author(s):

E. L. Barnard ◽

E. C. Ash ◽

D. L. Hopkins ◽

R. J. McGovern

Keyword(s):

Immunosorbent Assay ◽

Xylella Fastidiosa ◽

Shoot Length ◽

Enzyme Linked Immunosorbent Assay ◽

Oak Decline ◽

Widespread Occurrence ◽

Leaf Scorch ◽

Growth Decline ◽

Quercus Laevis

A survey of more than 200 trees has documented the widespread occurrence of Xylella fastidiosa in Florida oak populations. The pathogen was detected readily via enzyme-linked immunosorbent assay in oaks exhibiting decline or leaf scorch symptoms and was infrequently detected in asymptomatic trees. It was also associated with reduced growth in Quercus laevis as measured by current-year shoot length. The occurrence of X. fastidiosa in Q. laevis and the evidence for its occurrence in Q. incana represent first reports for these oak hosts. The role of X. fastidiosa in oak decline scenarios deserves further attention.

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Evidence that Xylella fastidiosa Can Cause Leaf Scorch Disease of Pecan

Plant Disease ◽

10.1094/pdis.2000.84.12.1282 ◽

2000 ◽

Vol 84 (12) ◽

pp. 1282-1286 ◽

Cited By ~ 24

Author(s):

R. S. Sanderlin ◽

K. I. Heyderich-Alger

Keyword(s):

Xylella Fastidiosa ◽

Carya Illinoinensis ◽

Symptom Development ◽

Koch’S Postulates ◽

Leaf Scorch ◽

Symptomatic Tissue ◽

Koch's Postulates ◽

Bacterial Leaf Scorch

The disease known as pecan fungal leaf scorch has been reported to be either caused by or associated with several fungi since it was first recognized in 1972. Data are presented that indicate the disease is initiated by the fastidious xylem-limited bacterium Xylella fastidiosa. X. fastidiosa was found consistently associated with fungal leaf scorch disease of pecan (Carya illinoinensis) in commercial orchards in Louisiana. It was generally not detected in symptomless trees. The disease was reproduced by inoculation of greenhouse seedlings and grafted trees with cultures of the bacterium obtained from leaves with fungal leaf scorch. The bacterium was reisolated from symptomatic tissue of inoculated pecan seedlings, but not from symptomless plants inoculated with water to complete Koch's postulates. It is proposed that the name of the disease be changed to pecan bacterial leaf scorch because fungi do not appear to be necessary for symptom development.

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First Report of Pecan Bacterial Leaf Scorch Caused by Xylella fastidiosa in Pecan (Carya illinoinensis) in Arizona, New Mexico, California, and Texas

Plant Disease ◽

10.1094/pdis-02-17-0298-pdn ◽

2017 ◽

Vol 101 (11) ◽

pp. 1949-1949 ◽

Cited By ~ 2

Author(s):

A. E. Hilton ◽

Y-.K. Jo ◽

K. Cervantes ◽

R. A. Stamler ◽

J. J. Randall ◽

...

Keyword(s):

New Mexico ◽

Xylella Fastidiosa ◽

Carya Illinoinensis ◽

First Report ◽

Leaf Scorch ◽

Bacterial Leaf Scorch

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Discovery and Characterization of Xylella fastidiosa Strains in Southern California Causing Mulberry Leaf Scorch

Plant Disease ◽

10.1094/pd-90-1143 ◽

2006 ◽

Vol 90 (9) ◽

pp. 1143-1149 ◽

Cited By ~ 19

Author(s):

R. Hernandez-Martinez ◽

T. R. Pinckard ◽

H. S. Costa ◽

D. A. Cooksey ◽

F. P. Wong

Keyword(s):

Southern California ◽

Xylella Fastidiosa ◽

Random Amplified Polymorphic Dna ◽

Intergenic Spacer ◽

Genomic Analysis ◽

The United States ◽

Enzyme Linked Immunosorbent Assay ◽

Leaf Scorch ◽

Mulberry Leaf ◽

White Mulberry

Mulberry leaf scorch (MLS), caused by Xylella fastidiosa, is a disease of mulberry trees in the United States that has largely been documented from locations in the eastern and central areas of the country. MLS was recently detected for the first time in white mulberry (Morus alba) trees in southern California. Four MLS-strains were isolated from two locations and confirmed as X. fastidiosa by enzyme-linked immunosorbent assay (ELISA), direct isolation of the pathogen, and use of the X. fastidiosa-specific PCR primers RST31-33. Isolated strains were characterized by the sequencing of their 16S-23S rDNA intergenic spacer regions (ISR) and random amplified polymorphic DNA (RAPD) analysis and subsequent comparison with a previously characterized MLS-strain (Mulberry-VA) and representatives of X. fastidiosa subsp. fastidiosa, X. fastidiosa subsp. multiplex, and X. fastidiosa subsp. sandyi. MLS-strains isolated from California were distinct from strains causing almond leaf scorch, oleander leaf scorch, and Pierce's disease and similar to the Mulberry-VA-strain. The ISR sequences of two MLS-strains, MLS063 and MLS059, were 100% identical to that of the Mulberry-VA sequence, whereas MLS012 and MLS024 were 99.8 and 99.6% identical to the Mulberry-VA-strain and 99.4% identical among themselves. Genomic analysis using RAPD revealed no differences among the four strains. The pathogenicity of one strain, MLS063, was confirmed by inoculation of glasshouse-grown white mulberry plants. Three months after inoculation, the pathogen was recovered from 21 of 25 inoculated plants, and 5 of 25 plants were dead within a year of inoculation. Inoculation of grapevines and oleanders with MLS063 did not result in any disease or recovery of the pathogen up to 1 year later, showing that this strain was not cross-infective to these hosts.

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Coffee Leaf Scorch Bacterium: Axenic Culture, Pathogenicity, and Comparison with Xylella fastidiosa of Citrus

Plant Disease ◽

10.1094/pdis.1998.82.1.94 ◽

1998 ◽

Vol 82 (1) ◽

pp. 94-97 ◽

Cited By ~ 66

Author(s):

J. E. O. de Lima ◽

V. S. Miranda ◽

J. S. Hartung ◽

R. H. Brlansky ◽

A. Coutinho ◽

...

Keyword(s):

Shoot Growth ◽

Xylella Fastidiosa ◽

Polymerase Chain Reaction Amplification ◽

Axenic Culture ◽

Enzyme Linked Immunosorbent Assay ◽

Leaf Scorch ◽

Mature Leaves ◽

Reaction Amplification ◽

Polymerase Chain ◽

Cultured Bacteria

Symptoms of coffee leaf scorch (CLS) appear on young flushes of field plants as large marginal and apical scorched areas on recently mature leaves. Affected leaves drop, shoot growth is stunted, and apical leaves are small and chlorotic. Symptoms may progress to shoot dieback. Only scorched leaves which could not be related to other known agents consistently contained bacteria and bacterial agglomerates when observed with light microscopy. Only plants with these symptoms were positive in enzyme-linked immunosorbent assay (ELISA) tests using antiserum to Xylella fastidiosa Wells et al. The bacterium Xylella fastidiosa Wells et al. was isolated in November 1995 from coffee (Coffea arabica) leaves with scorch symptoms on supplemented periwinkle wilt medium. Colonies were circular, dome-shaped, white, and 0.5 to 1.5 mm in diameter. Two of 10 young coffee seedlings stem-inoculated with a suspension of the isolated X. fastidiosa in January 1996 showed leaf scorch symptoms 3 to 5 months later, contained bacteria in xylem extracts, and reacted positively in ELISA using antiserum to the citrus variegated chlorosis (CVC) strain of X. fastidiosa. ELISA-positive bacteria were reisolated from this plant. None of the symptomless plants, including controls, revealed bacteria on microscopic examinations, ELISA, or isolation attempts. Antisera developed against cultured bacteria from both CLS and CVC plants reacted positively against plant extracts of both diseases in dot immunobinding assays (DIBA). The level of detection was about 5 × 105 bacteria ml-1 for both homologous and heterologous reactions. The polymerase chain reaction amplification products produced by CLS and CVC strains of X. fastidiosa were indistinguishable. Geographical distribution of these strains is not the same. CLS is widespread and usually occurs if coffee is adjacent to CVC-affected citrus. However, CVC does not always occur when citrus is grown adjacent to CLS-affected coffee. The bacteria are closely related, if not identical.

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Leaf Scorch of Purple-Leafed Plum and Sweetgum Dieback: Two New Diseases in Southern California Caused by Xylella fastidiosa Strains with Different Host Ranges

Plant Disease ◽

10.1094/pdis-93-11-1131 ◽

2009 ◽

Vol 93 (11) ◽

pp. 1131-1138 ◽

Cited By ~ 7

Author(s):

R. Hernandez-Martinez ◽

D. A. Cooksey ◽

F. P. Wong

Keyword(s):

Southern California ◽

Xylella Fastidiosa ◽

Liquidambar Styraciflua ◽

Pierce's Disease ◽

Enzyme Linked Immunosorbent Assay ◽

Leaf Scorch ◽

Pierce’S Disease ◽

Prunus Cerasifera ◽

Almond Leaf Scorch

Sweetgum dieback and leaf scorch of purple-leafed plum are two new diseases of southern California landscape ornamentals. Samplings were conducted in 2003 and 2004 and 28 of 105 sweetgum (Liquidambar styraciflua) and 38 of 62 purple-leafed plum (Prunus cerasifera) plants tested positive for Xylella fastidiosa by enzyme linked immunosorbent assay. In all, 3 strains of X. fastidiosa were isolated from sweetgum and 13 from purple-leafed plum. All sweetgum strains and some purple-leafed plum strains grew on PW but not PD3 media. Strain PC045 from purple-leafed plum and strain LS022 from sweetgum were inoculated into their original hosts in addition to almond, oleander, and grapevine plants. Sweetgum plants also were inoculated with strains causing Pierce's disease, almond leaf scorch, and oleander leaf scorch. Strain PC045 caused symptoms in purple-leafed plum and almond plants within 6 months, and the pathogen was recovered from 93 and 100% of inoculated plants, respectively. Inoculation of grapevine and oleander plants with PC045 did not result in disease or recovery of the pathogen. In all, 5 of 25 sweetgum plants inoculated with LS022 showed symptoms after 9 months, and the pathogen was recovered from 3 of these plants. Inoculation of grapevine, oleander, and almond with LS022 resulted in no disease or recovery of the pathogen from the plants. A strain of Pierce's disease, a strain of oleander leaf scorch, and two strains from almond did not cause disease in sweetgum. These results confirm the role of X. fastidiosa strains as pathogens of purple-leafed plum and sweetgum, and that strains from sweetgum are unique in their host range.

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Bacterial Leaf Scorch, a New Blueberry Disease Caused by Xylella fastidiosa

HortScience ◽

10.21273/hortsci.44.2.413 ◽

2009 ◽

Vol 44 (2) ◽

pp. 413-417 ◽

Cited By ~ 34

Author(s):

Chung-Jan Chang ◽

Ruth Donaldson ◽

Phil Brannen ◽

Gerard Krewer ◽

Robert Boland

Keyword(s):

Tissue Sample ◽

Xylella Fastidiosa ◽

Root Tissue ◽

Enzyme Linked Immunosorbent Assay ◽

Initial Symptom ◽

Tissue Samples ◽

Leaf Scorch ◽

Elisa Testing ◽

Southern Belle ◽

Bacterial Leaf Scorch

Since 2004, growers and scientists have observed a disorder described as “yellow twig” or “yellow stem” affecting a major selection of southern highbush blueberry, FL 86-19, in the south Georgia blueberry production region. The initial symptom observed was leaf marginal chlorosis and subsequent necrosis, which eventually progressed throughout the whole leaf resulting in early leaf fall. Thin, yellow twigs or yellow stems became evident on some cultivars. The described symptoms on blueberry were similar to those exhibited on grapes with Pierce's disease and on plum with leaf scald disease. This prompted the enzyme-linked immunosorbent assay (ELISA) tests and isolations of Xylella fastidiosa, which is the causal agent of the previously mentioned grape and plum diseases. Two leaf and two root tissue samples were collected from a diseased FL 86-19 plant for isolation and ELISA testing on 2 Mar. 2006. ELISA results indicated all four tissues tested positive for the bacterial pathogen, X. fastidiosa, whereas only the two root tissues provided positive isolations. One leaf and one root tissue sample were later collected from each of five additional diseased plants for isolation and ELISA testing. Both isolation and ELISA testing methods obtained positive results. Cultures were multiplied to inoculate seedlings of three cultivars: ‘Southern Belle’ (eight plants), ‘Premier’ (six), and ‘Powderblue’ (six) on 23 May 2006 and one selection, FL 86-19 (eight), on 31 May 2006. Two FL 86-19 plants started to show symptoms of marginal necrosis 54 days postinoculation, whereas one plant each of ‘Southern Belle’ and ‘Powderblue’ started to show symptoms of marginal necrosis 63 days postinoculation and ‘Premier’ stayed symptomless. All eight culture-inoculated FL 86-19 plants (100%) showed symptoms 72 days postinoculation, but no symptoms were observed on the control plants. One hundred twenty-six days postinoculation, two ‘Powderblue’ and four ‘Southern Belle’ plants showed mild symptoms, whereas all ‘Premier’ plants were asymptomatic. Positive reisolations of the bacteria from the inoculated symptomatic plants, not from asymptomatic plants, fulfilled Koch's postulates, which confirmed X. fastidiosa was the causal bacterium of the new blueberry disorder, the bacterial leaf scorch of blueberry.

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