First Report of Twig and Branch Dieback, Caused by Eutypa lata, on Loquat in the Western Cape Province of South Africa

Abstract

HomePlant DiseaseVol. 104, No. 3First Report of Twig and Branch Dieback, Caused by Eutypa lata, on Loquat in the Western Cape Province of South Africa PreviousNext DISEASE NOTES OPENOpen Access licenseFirst Report of Twig and Branch Dieback, Caused by Eutypa lata, on Loquat in the Western Cape Province of South AfricaP. Moyo, L. Mostert, R. Dedekind, W. J. van Jaarsveld, R. Pierron, and F. HalleenP. MoyoDepartment of Plant Pathology, University of Stellenbosch, Matieland, 7602, South AfricaSearch for more papers by this author, L. Mosterthttp://orcid.org/0000-0001-9063-2447Department of Plant Pathology, University of Stellenbosch, Matieland, 7602, South AfricaSearch for more papers by this author, R. DedekindDepartment of Plant Pathology, University of Stellenbosch, Matieland, 7602, South AfricaSearch for more papers by this author, W. J. van JaarsveldDepartment of Plant Pathology, University of Stellenbosch, Matieland, 7602, South AfricaSearch for more papers by this author, R. PierronDepartment of Plant Pathology, University of Stellenbosch, Matieland, 7602, South AfricaSearch for more papers by this author, and F. Halleen†Corresponding author: F. Halleen; E-mail Address: HalleenF@arc.agric.zahttp://orcid.org/0000-0002-2348-1201Plant Protection Division, ARC Infruitec-Nietvoorbij, Stellenbosch, 7599, South AfricaSearch for more papers by this author AffiliationsAuthors and Affiliations P. Moyo1 L. Mostert1 R. Dedekind1 W. J. van Jaarsveld1 R. Pierron1 F. Halleen2 † 1Department of Plant Pathology, University of Stellenbosch, Matieland, 7602, South Africa 2Plant Protection Division, ARC Infruitec-Nietvoorbij, Stellenbosch, 7599, South Africa Published Online:5 Jan 2020https://doi.org/10.1094/PDIS-06-19-1284-PDNAboutSections ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InRedditEmailWechat Loquat (Eriobotrya japonica Lindl., Rosaceae) is a subtropical tree grown for its edible fruit (Tziros 2013). In South Africa, loquat is grown as an ornamental tree. Twig and branch dieback symptoms as well as cankers extending from pruning wounds or natural openings were observed on trees during surveys conducted in the Western Cape Province, South Africa, between July 2013 and November 2014 (Moyo et al. 2019). Internal symptoms included black discoloration below wounds or along cankers, which appeared wedge-shaped in cross section. Wood pieces removed from the margin between healthy and diseased tissues were surface sterilized (70% ethanol for 30 s, 2.5% sodium hypochlorite for 2 min, and 70% ethanol for 30 s), plated onto potato dextrose agar plates containing chloromycetin (250 mg/liter), and incubated at 24°C and 12-h photoperiod. Two representative isolates (STEU 8519 and STEU 8520) were purified and characterized. The fungus had cottony-white mycelium that was cream in reverse. No sexual morph was observed in culture, but the cottony-white mycelium turned gray with age. Filiform conidia, measuring (17 to) 21 to 39 (to 42) × 1 to 2 μm (n = 60), were formed in pycnidia and exuded in cream-orange droplets. Conidiophores were branched. These characteristics fit those of Eutypa lata (Pers:Fr) Tul & C. Tul. (Munkvold 2001). The identity of the isolates was confirmed by DNA sequencing of the internal transcribed spacer (ITS) rDNA region (GenBank accession nos. MG978312 and MG978313) and partial β-tubulin gene (MG978308 and MG978309). Nucleotide BLAST analysis of ITS sequences showed 99% identity with E. lata strain CA38 (AY462541) and strain LATA1 (KR909218) for STEU 8519 and STEU 8520, respectively. Partial β-tubulin sequences were 100% similar to E. lata strain STEU 8522 (MG978307) and strain STEU 8239 (MF359689) for STEU 8519 and STEU 8520, respectively. Pathogenicity was tested on 2-year-old healthy loquat shoots on 5-year-old trees (n = 12). Three shoots per plant were surface sterilized at the point of inoculation by spraying with 70% ethanol and wounded using a 4-mm-diameter cork borer. Mycelial plugs harvested from the periphery of 14-day-old colonies were placed into two of these wounds. Noncolonized PDA plugs (control) were placed into the third wound. All inoculated wounds were wrapped with Parafilm. After 8 weeks, inoculated shoots were removed, sterilized as described above, and cut open longitudinally through the inoculation point. The mean length of discoloration, which extended in both directions from the inoculation point, measured 43.6 and 51.7 mm for STEU 8519 and STEU 8520, respectively. The inoculated fungus was reisolated from all inoculated shoots. Control shoots remained asymptomatic, and no fungus was isolated. E. lata has been reported on loquat in Australia (Rappaz 1987). This is the first report of E. lata causing twig and branch dieback of loquat in South Africa. This is a significant finding because loquat, which is often found in close proximity to vineyards and pome and stone fruit orchards, could potentially serve as an inoculum source of E. lata to these important crops.The author(s) declare no conflict of interest.