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Detection of Alternaria alternata Causing Leaf Spot on Rumex obtusifolius in Southern Brazil
2018; American Phytopathological Society; Volume: 102; Issue: 8 Linguagem: Inglês
10.1094/pdis-12-17-2038-pdn
ISSN1943-7692
AutoresRenata Moccellin, Cristiano Bellé, Tiago Edu Kaspary, Martin Groth, Bruna Rohrig, Luan Cutti, Gabriele Casarotto,
Tópico(s)Powdery Mildew Fungal Diseases
ResumoHomePlant DiseaseVol. 102, No. 8Detection of Alternaria alternata Causing Leaf Spot on Rumex obtusifolius in Southern Brazil PreviousNext DISEASE NOTES OPENOpen Access licenseDetection of Alternaria alternata Causing Leaf Spot on Rumex obtusifolius in Southern BrazilR. Moccellin, C. Bellé, T. E. Kaspary, M. Z. Groth, B. Rohrig, L. Cutti, and G. CasarottoR. MoccellinSearch for more papers by this author, C. Bellé†Corresponding author: C. Bellé; E-mail: E-mail Address: [email protected]http://orcid.org/0000-0003-2247-3207Search for more papers by this author, T. E. KasparySearch for more papers by this author, M. Z. GrothSearch for more papers by this author, B. RohrigSearch for more papers by this author, L. CuttiSearch for more papers by this author, and G. CasarottoSearch for more papers by this authorAffiliationsAuthors and Affiliations R. Moccellin C. Bellé † , Universidade Federal de Pelotas, Departamento de Fitossanidade, 96010-900, Capão do Leão, RS, Brazil T. E. Kaspary , Universidade Federal do Rio Grande do Sul, Departamento de Fitotecnia, 91540-000, Porto Alegre, RS, Brazil M. Z. Groth B. Rohrig , Universidade Federal de Pelotas, Departamento de Fitossanidade, 96010-900, Capão do Leão, RS, Brazil L. Cutti G. Casarotto , Universidade Federal do Rio Grande do Sul, Departamento de Fitotecnia, 91540-000, Porto Alegre, RS, Brazil. Published Online:6 Jun 2018https://doi.org/10.1094/PDIS-12-17-2038-PDNAboutSectionsSupplemental ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InRedditEmailWechat Rumex obtusifolius L., commonly known as bitter or butter dock, is a perennial weed belonging to the family Polygonaceae, which is native to Brazil and Europe. This weed infests grassland and crop field areas where rice, sugarcane, soybean, wheat, apple, and citrus grows. It decreases crop yield and reduces the forage feeding value of grasslands (Marten et al. 1987; Zaller 2004). In September 2016, R. obtusifolius plants with severe spots on their leaves were observed in a field at Jaguarão in the Rio Grande do Sul state of Brazil. Initially, symptoms were small, circular, light brown spots that eventually turned into irregular, dark brown lesions, and a few remained circular with concentric rings. On severely diseased leaves, several spots coalesced to form large necrotic areas. Leaf spots varied from 1.5 to 30 mm in diameter. Leaf lesion samples were surface-sterilized (1% NaClO for 2 min) and placed on potato dextrose agar (PDA) medium. Morphologically, colonies were round, comprising a cottony mycelium of dark olivaceous hyphae. Conidiophores were septate, light-to-olive golden brown, with a conidial scar from which conidia were produced. Conidia (n = 100) were obclavate to obpyriform, golden brown, with a cylindrical or coniform beak at the tip, and measured 29.8 to 64.9 μm long × 12.3 to 17.5 μm wide with 2 to 6 transverse and 1 to 3 longitudinal septa. For molecular characterization, the internal transcribed spacer (ITS), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), the second largest subunit of RNA polymerase II (RPB2), and translation elongation factor (TEF-1α) gene regions were amplified using primers following the method by Woudenberg et al. (2013). Sequences were submitted to GenBank (ITS: MG650061; GAPDH: MG652467; RPB2: MG652468; TEF-1α: MG652466). BLAST searches showed 99 to 100% identity with the existing sequences (including ex-type CBS 916.96) of Alternaria alternata (Fr.) Keissl. (1912) (ITS: LC317410; GAPDH: AY278808; RPB2: KC584375; TEF-1α: KY099723). The pathogenicity test was performed under growth chamber conditions (25°C), sterile water was added in PDA cultures of A. alternata at 7 days old, and a 1 × 106 conidia/ml conidial suspension was sprayed on the leaf surface of four 1-month-old R. obtusifolius plants. The same number of noninoculated plants were used as a control. After inoculation, the plants were covered with plastic bags to maintain a high relative humidity. The plastic bags were removed 24 h postinoculation, and the plants were monitored on a daily basis for symptom development. The test was performed two times. Within 10 to 15 days postinoculation, all pathogen inoculated plants developed small, light brown, circular spots with concentric rings, similar to the typical symptoms as previously observed in the field. Control plants remained symptomless. Fungal cultures reisolated from the inoculated leaves showed the same morphological and molecular traits as those observed in fungal cultures isolated previously from the field plants. Our findings highlight the relevance of R. obtusifolius, which may serve as a reservoir for an important crop pathogen in addition to being a major crop competitor. To our knowledge, this is the first report on the presence of A. alternata affecting R. obtusifolius plants in Brazil.References:Marten, G. C., et al. 1987. Agron. J. 79:980. https://doi.org/10.2134/agronj1987.00021962007900060006x Crossref, ISI, Google ScholarWoudenberg, J. H. C., et al. 2013. Stud. Mycol. 75:171. https://doi.org/10.3114/sim0015 Crossref, ISI, Google ScholarZaller, J. G. 2004. J. Plant Dis. Prot. 19:345. Google ScholarR. Moccellin and C. Bellé contributed equally to this work.DetailsFiguresLiterature CitedRelated Vol. 102, No. 8 August 2018SubscribeISSN:0191-2917e-ISSN:1943-7692 Metrics Article History Issue Date: 18 Jul 2018Published: 6 Jun 2018First Look: 16 Feb 2018Accepted: 15 Feb 2018 Pages: 1656-1656 Information© 2018 The American Phytopathological SocietyCited byAlternaria alternata (alternaria leaf spot)CABI Compendium, Vol. CABI Compendium
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