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First Report of Pythium aphanidermatum Causing Root Rot and Decline of Poinsettia in Maryland

2017; American Phytopathological Society; Volume: 101; Issue: 8 Linguagem: Inglês

10.1094/pdis-11-16-1671-pdn

1943-7692

Johanna Del Castillo Múnera, Cassandra L. Swett,

Plant Disease Resistance and Genetics

HomePlant DiseaseVol. 101, No. 8First Report of Pythium aphanidermatum Causing Root Rot and Decline of Poinsettia in Maryland PreviousNext DISEASE NOTES OPENOpen Access licenseFirst Report of Pythium aphanidermatum Causing Root Rot and Decline of Poinsettia in MarylandJ. Del Castillo Múnera and C. L. SwettJ. Del Castillo MúneraSearch for more papers by this author and C. L. SwettSearch for more papers by this authorAffiliationsAuthors and Affiliations J. Del Castillo Múnera , Department of Plant Sciences and Landscape Architecture, University of Maryland, College Park, 20742 C. L. Swett , Department of Plant Pathology, University of California, Davis, 95616. Published Online:12 May 2017https://doi.org/10.1094/PDIS-11-16-1671-PDNAboutSections ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InRedditEmailWechat Wilted and stunted poinsettia (Euphorbia pulcherrima, cvs. Viking red, Enduring red, Prestige red, Premium red, and Christmas eve red) were collected at a greenhouse facility in Carroll County, Maryland, in October and November of 2015 (n = 53 plants). Lateral roots exhibiting necrosis and reduced fine root production were washed under running tap water, air dried, and four root pieces (1 cm length) per plant were placed on V8 medium amended with pimaricin (0.4 ml/liter), ampicillin (0.25 g/liter), rifampicin (0.01 g/liter), and pentachloronitrobenzene (0.05 g/liter) (PARP). Based on culture morphology, Pythium spp. were recovered from 41% of plants from each cultivar. Microscopic characterization revealed smooth and globose oogonia (avg. 22 µm diameter), globose oospores (avg. 24 µm diameter), and barrel shaped antheridia (avg. 13.1 µm length) (van der Plaats-Niterink 1981). DNA was extracted from 17 isolates grown on V8 medium, using the Prep Man Ultra kit (Life Technologies, Carlsbad, CA). Molecular identification was based on the ITS region primers ITS 1 and ITS 4 and the cytochrome oxidase (cox II) gene primers FM66 and FM 58 (Martin 2000). Resulting sequences were assembled using CLC work bench (Qiagen Inc., Germantown, MD) and compared with a local database of ITS and COX sequences obtained from the research collection of Andre Levesque at BOLD data portal (Ratnasingham and Hebert 2007). All 17 ITS and cox II sequences had 100% and 99% similarity with Pythium aphanidermatum (AY151180) and (AB468890.1), respectively. Sequences of two isolates (SL1167 and SL1172, tested for pathogenicity) were submitted to NCBI under the accession numbers KY646467 and KY646468. To confirm pathogenicity, 6-month-old poinsettia ‘Enduring red’ in 14 cm pots were inoculated with two P. aphanidermatum isolates (SL1167 and SL1172) by placing 3 g of infested millet seeds into 100 g of soilless peat-based medium adjacent to each plant root crown (Del Castillo Múnera and Hausbeck 2016). Five replicate plants per isolate and five noninoculated controls were maintained at 20.6 to 28.7°C, 12:12 h light/dark for 40 days, and the experiment was repeated once. Symptoms of leaf cupping and wilting were evident starting 10 to 14 days post inoculation (dpi), and 90% ± 0.1 of the inoculated plants exhibited root rot symptoms at 40 dpi in both isolate treatments. P. aphanidermatum was successfully reisolated on PARP from a subset of plants (n = 3 plants/isolate), obtaining identical sequences to the ones inoculated. Disease did not develop in noninoculated plants. P. aphanidermatum is a known root pathogen of poinsettia in the northeast (Del Castillo Múnera and Hausbeck 2016; Lookabaugh et al. 2015) but to the authors’ knowledge, this is the first report of the pathogen on poinsettia in Maryland. This new information enables regional diagnosticians and advisors to provide more accurate information to producers and facilitates downstream research efforts to improve disease management, allowing Maryland producers to better control root diseases.References:Del Castillo Múnera, J., and Hausbeck, M. K. 2016. Plant Dis. 100:569. https://doi.org/10.1094/PDIS-03-15-0296-RE Link, ISI, Google ScholarLookabaugh, E., et al. 2015. Plant Dis. 99:1550. https://doi.org/10.1094/PDIS-02-15-0232-RE Link, ISI, Google ScholarMartin, F. N. 2000. Mycologia 92:711. https://doi.org/10.2307/3761428 Crossref, ISI, Google ScholarRatnasingham, S., and Hebert, P. D. 2007. Mol. Ecol. Notes 7:355. https://doi.org/10.1111/j.1471-8286.2007.01678.x Crossref, Google Scholarvan der Plaats-Niterink, A. J. 1981. Stud. Mycol. 21:1. Google ScholarDetailsFiguresLiterature CitedRelated Vol. 101, No. 8 August 2017SubscribeISSN:0191-2917e-ISSN:1943-7692 Metrics Article History Issue Date: 12 Jul 2017Published: 12 May 2017First Look: 17 Apr 2017Accepted: 8 Apr 2017 Pages: 1556-1556 Information© 2017 The American Phytopathological SocietyCited byChanges in Fungal and Oomycete Community Composition Following Irrigation Reductions Aimed at Increasing Water Use Efficiency in a Containerized Nursery CropJohanna Del Castillo Múnera, Amisha T. Poret-Peterson, and Cassandra L. 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