First Report of Fusarium euwallaceae Causing Necrotic Lesions on Persea americana in South Africa
2019; American Phytopathological Society; Volume: 103; Issue: 7 Linguagem: Inglês
10.1094/pdis-10-18-1818-pdn
ISSN1943-7692
AutoresNoëlani van den Berg, Madeleine Du Toit, Seamus Morgan, Gerda Fourie, Z. Wilhelm de Beer,
Tópico(s)Plant Pathogenic Bacteria Studies
ResumoHomePlant DiseaseVol. 103, No. 7First Report of Fusarium euwallaceae Causing Necrotic Lesions on Persea americana in South Africa PreviousNext DISEASE NOTESFirst Report of Fusarium euwallaceae Causing Necrotic Lesions on Persea americana in South AfricaN. van den Berg, M. du Toit, S. W. Morgan, G. Fourie, and Z. W. de BeerN. van den Berg†Corresponding author: N. van den Berg; E-mail Address: [email protected]http://orcid.org/0000-0001-9574-7331Department of Biochemistry, Genetics and Microbiology, Forestry and Agricultural Biotechnology Institute (FABI), University of Pretoria, Pretoria, South Africa, M. du ToitDepartment of Biochemistry, Genetics and Microbiology, Forestry and Agricultural Biotechnology Institute (FABI), University of Pretoria, Pretoria, South Africa, S. W. MorganDepartment of Biochemistry, Genetics and Microbiology, Forestry and Agricultural Biotechnology Institute (FABI), University of Pretoria, Pretoria, South Africa, G. FourieDepartment of Biochemistry, Genetics and Microbiology, Forestry and Agricultural Biotechnology Institute (FABI), University of Pretoria, Pretoria, South Africa, and Z. W. de BeerDepartment of Biochemistry, Genetics and Microbiology, Forestry and Agricultural Biotechnology Institute (FABI), University of Pretoria, Pretoria, South AfricaAffiliationsAuthors and Affiliations N. van den Berg † M. du Toit S. W. Morgan G. Fourie Z. W. de Beer Department of Biochemistry, Genetics and Microbiology, Forestry and Agricultural Biotechnology Institute (FABI), University of Pretoria, Pretoria, South Africa Published Online:7 May 2019https://doi.org/10.1094/PDIS-10-18-1818-PDNAboutSectionsSupplemental ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InRedditEmailWechat Avocado is an important fruit commodity in South Africa for both the local and export market. A total of 17,500 ha of avocado is grown, and production is expanding annually by approximately 1,000 ha. Avocados in Israel (Mendel et al. 2012) and California (Eskalen et al. 2013) are threatened by the invasive polyphagous shot hole borer (PSHB, Euwallacea nr. fornicatus) and its pathogenic symbiont, known now as Fusarium euwallaceae (Freeman et al. 2013). In 2017, the PSHB and the pathogen were identified on London plane trees (Platanus × acerifolia) in Pietermaritzburg, KwaZulu Natal, South Africa (Paap et al. 2018). During a tree health survey in Sandton, Gauteng, in January 2018 a diseased avocado tree was observed in the backyard of a home owner. Affected branches showed symptoms of a white powdery exudate (sugar volcano) in association with a single small beetle exit hole (0.8 to 1 mm). Some exit holes were surrounded by a wet discolored lesion. Examination of the underlying tissue revealed brown, necrotic lesions and galleries penetrating the sap wood. Symptomatic tissue from the beetle galleries was plated onto Fusarium selective media and malt extract agar. After 5 to 7 days incubation at 25°C, fungal colonies with aerial mycelia and reddish-brown margins were produced. Single-spore isolations were used to establish pure cultures of the fungus on potato dextrose agar. DNA was extracted from fresh mycelia scraped from actively growing cultures using Prepman Ultra Sample Preparation Reagent (Applied Biosystems) according to the manufacturer's instructions. The translation elongation factor 1α (TEF1, MH823818), β-tubulin (MH823816), and RNA polymerase II second largest subunit (RBP2, MH823817) gene regions were amplified, sequenced, and assembled into contigs. TEF1 sequence data were analyzed together with data generated by Eskalen et al. (2013), O'Donnell et al. (2015), Paap et al. (2018), and Na et al. (2018), using MEGA 7.0.26 (Kumar et al. 2016). A culture was deposited in the CMW collection (Culture collection Mike Wingfield; CMW 51808, FABI, University of Pretoria), and the sequences were submitted to GenBank. A PSHB specimen could not be retrieved from avocado, but a confirmed PSHB specimen (COX1, MH823819) was retrieved from a diseased Chinese maple (Acer buergerianum) tree approximately 2 km away harboring F. euwallaceae that was genetically identical to the isolate from avocado. The fungus produced characteristic clavate macroconidia when grown in culture (Freeman et al. 2013). Stems and shoots of seven healthy 1-year-old avocado trees were wounded (1 to 2 mm deep) with a cork borer, and 5-mm mycelial plugs from a 7-day-old culture were placed mycelial side down into the wound and wrapped with Parafilm. Three control plants were inoculated with sterile agar plugs. After the trees were maintained in a greenhouse (25°C) for 6 weeks, watering twice a week, external and internal lesions were measured. Brown, wet lesions were observed on all pathogen-inoculated stems and shoots. Internal reddish-brown lesions extended into the tissue. Mean lesion length was 5.56 cm and was significantly longer (one-way ANOVA with a multiple comparison test) than lesions on control plants (1.37 cm). Control plants had brown lesions around the point of inoculation, but the pathogen was not reisolated. F. euwallaceae was reisolated from all symptomatic material to fulfill Koch's postulates. Similar results were obtained in a repeat experiment. To our knowledge, this is the first report of F. euwallaceae isolated from and causing Fusarium dieback symptoms on avocado in South Africa. This discovery is of major concern to the avocado industry, but the PSHB and its symbiont also threaten other fruit trees, exotic trees, and indigenous trees in urban areas and natural forests.The author(s) declare no conflict of interest.References:Eskalen, A., et al. 2013. Plant Dis. 97:938. https://doi.org/10.1094/PDIS-11-12-1026-RE Link, ISI, Google ScholarFreeman, S., et al. 2013. Mycologia 105:1595. https://doi.org/10.3852/13-066 Crossref, ISI, Google ScholarKumar, S., et al. 2016. Mol. Biol. Evol. 33:1870. https://doi.org/10.1093/molbev/msw054 Crossref, ISI, Google ScholarMendel, Z., et al. 2012. Phytoparasitica 40:235. https://doi.org/10.1007/s12600-012-0223-7 Crossref, ISI, Google ScholarNa, F., et al. 2018. Plant Dis. 102:1154. https://doi.org/10.1094/PDIS-07-17-1042-RE Link, ISI, Google ScholarO'Donnell, K., et al. 2015. Fungal Genet. Biol. 82:277. https://doi.org/10.1016/j.fgb.2014.10.014 Crossref, ISI, Google ScholarPaap, T., et al. 2018. Australas. Plant Pathol. 47:231. https://doi.org/10.1007/s13313-018-0545-0 Crossref, ISI, Google ScholarThe author(s) declare no conflict of interest.Funding: Funding was provided by the Hans Merensky Foundation and Tree Protection Cooperative Programme (TPCP).DetailsFiguresLiterature CitedRelated Vol. 103, No. 7 July 2019SubscribeISSN:0191-2917e-ISSN:1943-7692 DownloadCaptionApple cultivar Joya Cripps Red lesions caused by Colletotrichum fructicola (Nodet et al.). Photo credit: P. Nodet. Symptoms of Lotus powdery mildew caused by Erysiphe takamatsui (Zhou et al.). Photo credit: C. Liang. Symptoms of tar spot (Phyllachora maydis) on maize leaves (Dalla Lana et al.). Photo credit: F. Dalla Lana. Metrics Article History Issue Date: 20 Jun 2019Published: 7 May 2019First Look: 4 Mar 2019Accepted: 26 Feb 2019 Page: 1774 Information© 2019 The American Phytopathological SocietyFundingHans Merensky FoundationTree Protection Cooperative Programme (TPCP)KeywordsFusarium diebackambrosia beetlepathogenavocadoThe author(s) declare no conflict of interest.Cited byCost effectiveness of spread mitigation strategies for polyphagous shot hole borer Euwallacea fornicatus (Coleoptera: Curculionidae: Scolytinae)18 December 2023 | Frontiers in Insect Science, Vol. 3Economic impact of polyphagous shot hole borer Euwallacea fornicatus (Coleoptera: Curculionidae: Scolytinae) in Western Australia11 March 2023 | Agricultural and Forest Entomology, Vol. 25, No. 3Efficacy of Commercially Available Entomopathogenic Agents against the Polyphagous Shot Hole Borer in South Africa5 April 2023 | Insects, Vol. 14, No. 4Fusarium Species Associated with Diseases of Major Tropical Fruit Crops1 March 2023 | Horticulturae, Vol. 9, No. 3Barks from avocado trees of different geographic locations have consistent microbial communities23 June 2021 | Archives of Microbiology, Vol. 203, No. 7Screening for Susceptibility of Macadamia to Euwallacea fornicatus and its Fungal Symbiont Fusarium euwallaceaeD. 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