First Report of Neofusicoccum australe Causing Dieback of Honeybush in the Western Cape, South Africa

HomePlant DiseaseVol. 107, No. 3First Report of Neofusicoccum australe Causing Dieback of Honeybush in the Western Cape, South Africa PreviousNext DISEASE NOTE OPENOpen Access licenseFirst Report of Neofusicoccum australe Causing Dieback of Honeybush in the Western Cape, South AfricaF. Halleen, M. Havenga, A. McLeod, and L. MostertF. Halleen†Corresponding author: F. Halleen; E-mail Address: [email protected]https://orcid.org/0000-0002-2348-1201ARC Infruitec-Nietvoorbij, Stellenbosch 7599, South AfricaDepartment of Plant Pathology, University of Stellenbosch, Matieland 7602, South AfricaSearch for more papers by this author, M. Havengahttps://orcid.org/0000-0001-5870-3778ARC Infruitec-Nietvoorbij, Stellenbosch 7599, South AfricaSearch for more papers by this author, A. McLeodhttps://orcid.org/0000-0002-1807-9154Department of Plant Pathology, University of Stellenbosch, Matieland 7602, South AfricaSearch for more papers by this author, and L. Mosterthttps://orcid.org/0000-0001-9063-2447Department of Plant Pathology, University of Stellenbosch, Matieland 7602, South AfricaSearch for more papers by this authorAffiliationsAuthors and Affiliations F. Halleen1 2 † M. Havenga1 A. McLeod2 L. Mostert2 1ARC Infruitec-Nietvoorbij, Stellenbosch 7599, South Africa 2Department of Plant Pathology, University of Stellenbosch, Matieland 7602, South Africa Published Online:1 Mar 2023https://doi.org/10.1094/PDIS-06-22-1429-PDNAboutSectionsView articlePDFSupplemental ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InRedditEmailWechat View articleHoneybush (Cyclopia spp.) is an indigenous, leguminous member of the Cape fynbos biome growing in the coastal winter rainfall districts of the Western and Eastern Cape Provinces of South Africa (Joubert et al. 2011). Honeybush is used for the production of herbal teas and is harvested from wild-growing and cultivated plantations (du Toit et al. 1998). Very little is known regarding diseases caused by pathogens on this indigenous plant. There is only one report of twig dieback on honeybush caused by several Diaporthe Nitschke species in South Africa (Smit et al. 2021). Several honeybush producers reported poor growth and dieback in their C. subternata plantations in the Western Cape Province. Symptoms included twig dieback, branch dieback, death of branches, and death of entire plants. In April 2008, branches from 8-year-old cultivated plants with dieback symptoms were collected in Stellenbosch. Fungal isolations carried out from affected material as described by Van Niekerk et al. (2004) consistently revealed the presence of a Botryosphaeriaceae species. Two isolates were grown on water agar with sterile pine needles and incubated at 25°C using a 12-h day/night cycle and near-ultraviolet light. Pycnidia formed after 2 weeks. Morphological characteristics similar to Neofusicoccum australe (Slippers, Crous & Wingfield) Crous, Slippers & Phillips were observed (Phillips et al. 2013). Conidia were hyaline, aseptate, fusiform with subtruncate bases, and (16.8–) 18.8 to 22.1 (–24.6) × (4.8–) 5.3 to 6.1 (–6.4) μm (n = 50). Conidiogenous cells were holoblastic, hyaline, and subcylindrical to flask-shaped tapering to the apex (11 to 15 × 2 μm) (n = 10). Colonies on potato dextrose agar (PDA) were light primrose turning olivaceous gray after 7 days with a light-yellow pigment diffusing into the medium. Mycelia were moderately dense with an appressed center mat. The identity of the isolates was further confirmed by sequencing the ribosomal RNA internal transcribed spacer (ITS) and the elongation factor 1-alpha (EF-1α) gene regions using primer pairs ITS4–ITS5 (White et al. 1990) and EF1-728F-EF1-986R (Alves et al. 2008), respectively. Sequences had 100% similarity to N. australe ex-type CMW6837 isolate (accessions AY339262 and AY339270) (Slippers et al. 2004). Two isolates (STEU6554 and STEU6557) were deposited in the culture collection at the Department of Plant Pathology at Stellenbosch University and the sequences were submitted to GenBank (accession nos.: ON745603, ON745604, ON746573, and ON746574). Pathogenicity tests using the two N. australe isolates were conducted by inoculating two shoots each of three field-grown C. subternata plants with a 4-mm colonized PDA mycelium plug of each isolate on wounds made by a 4-mm cork borer (van Niekerk et al. 2004). A third shoot was inoculated with a uncolonized PDA plug as the negative control. After 12 weeks, brown-black lesions that were significantly longer (average 55.2 mm) than the uncolonized agar plug control (16.1 mm) were observed. Lesions were observed in all three plants. Neofusicoccum australe was reisolated (van Niekerk et al. 2004) from all inoculated shoots, confirming Koch’s postulates. The economic impact and damages caused by N. australe and its incidence and severity on honeybush in South Africa are unknown. However, the pathogen caused dieback of entire branches and death of plants, indicating that it could be an important pathogen of honeybush. Additionally, N. australe is one of the most important disease-causing Botryosphaeriaceae pathogens on a wide range of valuable fruit and vine crops globally (Mojeremane et al. 2020). This is the first report of N. australe causing decline and dieback of C. subternata in South Africa.The author(s) declare no conflict of interest.References:Alves, A., et al. 2008. Fungal Divers. 28:1. ISI, Google Scholardu Toit, J., et al. 1998. J. Sustain. Agric. 12:67. https://doi.org/10.1300/j064v12n02_06 Crossref, Google ScholarJoubert, E., et al. 2011. S. Afr. J. 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Crossref, Google ScholarFunding: This work benefitted from the financial support of the Agricultural Research Council, Infruitec-Nietvoorbij, South Africa.The author(s) declare no conflict of interest.DetailsFiguresLiterature CitedRelated Vol. 107, No. 3 March 2023SubscribeISSN:0191-2917e-ISSN:1943-7692 Download Metrics Article History Issue Date: 3 Apr 2023Published: 1 Mar 2023First Look: 15 Aug 2022Accepted: 15 Aug 2022 Page: 961 Information© 2023 The American Phytopathological SocietyFundingAgricultural Research CouncilKeywordsBotryosphaeriaceaecankerCyclopia subternatadiebacketiologyfungiornamentalspathogenicitypathogen detectionwoody ornamentalsThe author(s) declare no conflict of interest.PDF download