First Report of Laurel Wilt Caused by Raffaelea on...
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Share Share University of Florida Welcome Guest user Sign in | Register | Mobile Journals Home APS Home IS-MPMI Home My Profile Subscribe Search Advanced Search Help About the cover for August 2014 ISSN: 0191-2917 SEARCH Enter Keywords MPMI Phytobiomes Phytopathology Plant Disease Advanced Search Resources Subscribe About Plant Disease First Look Most Downloaded Articles Submit a Manuscript Customer Care About My Password Rights and Permissions Plagiarism and Ethics Advertise Open Access ORCID Registry Editor-in-Chief: Alison E. Robertson Published by The American Phytopathological Society Home > Plant Disease > Table of Contents > Abstract Previous Article | Next Article August 2014, Volume 98, Number 8 Page 1159 http://dx.doi.org.lp.hscl.ufl.edu/10.1094/PDIS-02-14-0194-PDN Disease Notes First Report of Laurel Wilt Caused by Raffaelea lauricola on Bay Laurel (Laurus nobilis) in the United States M. A. Hughes, A. Black, and J. A. Smith, School of Forest Resources and Conservation, University of Florida, Gainesville 32611 Open Access. Bay laurel (Laurus nobilis L.) is an economically important evergreen tree of the family Lauraceae. It is native to Asia Minor and the Balkans and was introduced into the United States for its ornamental and culinary uses (4). In September 2013, a 6-m-tall bay laurel in Gainesville, FL, attracted our attention because it had wilted leaves, discolored sapwood, and ambrosia beetle entrance holes, all symptoms of laurel wilt. In addition, the tree was growing close to an avocado that succumbed to the disease months earlier. In an effort to determine whether the laurel wilt pathogen (Raffaelea lauricola T.C. Harr., Fraedrich & Agaveya) was, indeed, involved in the decline of the tree of current interest, discolored sapwood was sectioned into 5-mm 2 pieces, surface disinfested for 30 s in a 4% sodium hypochlorite solution, and plated onto CSMA media (1,2). Within 7 to 14 days, cream-colored, adpressed fungal growth typical of R. lauricola grew from the sapwood pieces (2). DNA was extracted from an isolate of a single conidium (PL1634) and a portion of the 18S rRNA gene was PCR- amplified with primers NS1/NS4, resulting in a 1,021-bp amplicon (GenBank Accession No. KF913344.1), with a BLASTn search revealing 100% homology to several R. lauricola isolates (3). To confirm pathogenicity, six bay laurel seedlings (0.5 m) and a silk bay (0.65 m) (Persea humilis, susceptible control) were wounded twice with a 0.5-mm-diameter drill bit. Then, 30 μl of a spore suspension of PL1634 (1.38 × 10 5 condia/plant) were introduced into the xylem by pipette and the wounds were wrapped in Parafilm (1). Negative controls consisted of a mock-inoculated (water) and non-inoculated bay laurel plus a mock-inoculated silk bay. Plants were placed in a growth chamber set to a 16/8 h (25/22°C) diurnal light/temperature cycle. After 60 days, all fungal-inoculated plants were completely wilted with dead leaves and subsequent necrosis of stems, while mock- and non-inoculated controls remained asymptomatic. Sapwood dissection revealed xylem discoloration similar to the original infected tree, and fungi morphologically similar to PL1634 were recovered from all Quick Links Add to favorites E-mail to a colleague Alert me when new articles cite this article Download to citation manager Related articles found in APS Journals This Journal is brought to you via a subscription from the University of Florida Books Home
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Journals Home APS Home IS-MPMI Home My Profile Subscribe Search Advanced Search Help
About the cover forAugust 2014
ISSN: 0191-2917
SEARCH
Enter KeywordsMPMI
Phytobiomes
Phytopathology
Plant Disease
Advanced Search
Resources Subscribe
About Plant Disease
First Look
Most DownloadedArticles
Submit a Manuscript
Customer Care
About My Password
Rights andPermissions
Plagiarism and Ethics
Advertise
Open Access
ORCID Registry
Editor-in-Chief: Alison E. Robertson Published by The American Phytopathological Society
Home > Plant Disease > Table of Contents > AbstractPrevious Article | Next Article
August 2014, Volume 98, Number 8Page 1159http://dx.doi.org.lp.hscl.ufl.edu/10.1094/PDIS-02-14-0194-PDN
Disease Notes
First Report of Laurel Wilt Caused by Raffaelealauricola on Bay Laurel (Laurus nobilis) in theUnited StatesM. A. Hughes, A. Black, and J. A. Smith, School of Forest Resources and Conservation,University of Florida, Gainesville 32611
Open Access.
Bay laurel (Laurus nobilis L.) is an economically important evergreen tree of the familyLauraceae. It is native to Asia Minor and the Balkans and was introduced into the UnitedStates for its ornamental and culinary uses (4). In September 2013, a 6-m-tall bay laurel inGainesville, FL, attracted our attention because it had wilted leaves, discolored sapwood, andambrosia beetle entrance holes, all symptoms of laurel wilt. In addition, the tree was growingclose to an avocado that succumbed to the disease months earlier. In an effort to determinewhether the laurel wilt pathogen (Raffaelea lauricola T.C. Harr., Fraedrich & Agaveya) was,
indeed, involved in the decline of the tree of current interest, discolored sapwood was
sectioned into 5-mm2 pieces, surface disinfested for 30 s in a 4% sodium hypochlorite
solution, and plated onto CSMA media (1,2). Within 7 to 14 days, cream-colored, adpressedfungal growth typical of R. lauricola grew from the sapwood pieces (2). DNA was extractedfrom an isolate of a single conidium (PL1634) and a portion of the 18S rRNA gene was PCR-amplified with primers NS1/NS4, resulting in a 1,021-bp amplicon (GenBank Accession No.KF913344.1), with a BLASTn search revealing 100% homology to several R. lauricola isolates(3). To confirm pathogenicity, six bay laurel seedlings (0.5 m) and a silk bay (0.65 m)(Persea humilis, susceptible control) were wounded twice with a 0.5-mm-diameter drill bit.
Then, 30 µl of a spore suspension of PL1634 (1.38 × 105 condia/plant) were introduced into
the xylem by pipette and the wounds were wrapped in Parafilm (1). Negative controlsconsisted of a mock-inoculated (water) and non-inoculated bay laurel plus a mock-inoculatedsilk bay. Plants were placed in a growth chamber set to a 16/8 h (25/22°C) diurnallight/temperature cycle. After 60 days, all fungal-inoculated plants were completely wiltedwith dead leaves and subsequent necrosis of stems, while mock- and non-inoculated controlsremained asymptomatic. Sapwood dissection revealed xylem discoloration similar to theoriginal infected tree, and fungi morphologically similar to PL1634 were recovered from all
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Alert me when new articlescite this article
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inoculated plants upon isolation on CSMA media. Mock- and non-inoculated controls lackedvascular discoloration and fungal growth on media. In order to determine if the redbayambrosia beetle, Xyleborus glabratus Eichoff (laurel wilt vector) could successfully reproducein this host, symptomatic branches (7 cm in diameter) of L. nobilis with external evidence ofambrosia beetle attack (frass “toothpicks”) were placed in a plastic rearing box within agrowth chamber (25°C). Within 4 weeks of incubation, dozens of immature and mature X.glabratus beetles emerged. This is the first record of Koch's postulates being completed forR. lauricola on L. nobilis and the ability of X. glabratus to infest and breed in its stems. Thisinformation may be of importance in the event of an introduction of X. glabratus and itsfungal associate to Mediterranean areas where bay laurel is either growing wild or beingcultivated as valuable commercial crop.
References: (1) S. W. Fraedrich et al. Plant Dis. 92:215, 2008. (2) T. C. Harrington et al.Mycotaxon 104:399, 2008. (3) M. A. Innis et al., eds. PCR Protocols: A Guide to Methods andApplications. Academic Press. San Diego, CA, 1990. (4) A. O. Sari et al. New Forest 31:403,2006.
Cited by
Genetic Variation in Native Populations of the Laurel Wilt Pathogen, Raffaelealauricola, in Taiwan and Japan and the Introduced Population in the United StatesCaroline E. Wuest, Thomas C. Harrington, Stephen W. Fraedrich, Hye-Young Yun, and Sheng-Shan LuPlant Disease, Volume 0, Number 0Abstract | Full Text HTML | PDF Print | PDF with Links
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