Leaf spot disease on seedlings of Quercus acutissima caused by Tubakia dryina in Korea

Australasian Plant Disease Notes, May 2018

Severe attack by a leaf spot disease was found on seedlings of Quercus acutissima in Jeungpyeong, Korea in 2017. Based on the morphological characteristics of the fungus, it was identified as a member of Tubakia. Sequence comparisons based on the ITS and 28S rDNA regions confirmed the identity of the fungus as Tubakia dryina. This is the first report of Tubakia leaf spot caused by T. dryina on Q. acutissima.

A PDF file should load here. If you do not see its contents the file may be temporarily unavailable at the journal website or you do not have a PDF plug-in installed and enabled in your browser.

Alternatively, you can download the file locally and open with any standalone PDF reader:

https://link.springer.com/content/pdf/10.1007%2Fs13314-018-0299-0.pdf

Leaf spot disease on seedlings of Quercus acutissima caused by Tubakia dryina in Korea

Australasian Plant Disease Notes Leaf spot disease on seedlings of Quercus acutissima caused by Tubakia dryina in Korea Dong-Hyeon Lee 0 Sang-Tae Seo 0 Seung Kyu Lee 0 Sun Keun Lee 0 0 Division of Forest Diseases & Insect Pests, National Institute of Forest Science , Seoul 02455 , South Korea 1 Sun Keun Lee Severe attack by a leaf spot disease was found on seedlings of Quercus acutissima in Jeungpyeong, Korea in 2017. Based on the morphological characteristics of the fungus, it was identified as a member of Tubakia. Sequence comparisons based on the ITS and 28S rDNA regions confirmed the identity of the fungus as Tubakia dryina. This is the first report of Tubakia leaf spot caused by T. dryina on Q. acutissima. Fagaceae; Melanconidaceae; Oak - Tubakia species have been reported as endophytes or causing leaf spots on Castanea spp., Quercus spp., and some other members of Fagaceae in Asia, Europe and North America (Yun and Rossman 2011; Harrington et al. 2012; Boroń and Grad 2017) . Tubakia dryina is a known leaf spotting fungus which has been reported in many countries. Although a wide range of host species have been recorded for T. dryina, the fungus is most frequently found on oaks (Proffer 1990; Kowalski 2006) , including at least 40 species according to Farr and Rossman (2017). During a recent survey of plant diseases carried out to identify the fungal pathogens infecting oaks in 2017, a damaging leaf spot disease was consistently observed on seedlings of Quercus acutissima (sawtooth oak) (Fagaceae), in Jeungpyeong, Korea. Quercus acutissima is a deciduous broad-leaved tree, native to eastern Asia with a wide distribution and is one of the important forest components in hillsides of South Korea. Leaf spots were brown necrotic, circular to irregular, 49–74 mm diam, occasionally coalescing to form large blotches (Fig. 1a–b). Fresh specimen were mounted in water and examined under the following microscopes: Olympus BX51 and Zeiss AX10 (equipped with a Carl Zeiss AxioCam MRc5 camera). At least 30 measurements were made for each structure examined. Fungal morphology was as follows: Conidiomata (pycnothyria) scutelloid, convex, 40–75 μm in diam, membranaceous, consisting of brown to blackish, thick-walled cells radiating from a central point, blackish; conidiogenous cells, 5 to 7 × 9 to 13 μm, cylindrical to clavate, narrowing toward the neck, brown to dark brown, radiating from the center below the developing scutellum; conidia solitary, acrogenous, ellipsoidal, 5–7 × 15–18 μm, with a basal frill, pale to light brown, walls smooth; microconidia absent (Fig. 1d–f). Pure cultures were obtained by single conidia transfer onto 2% malt extract-agar (MEA; 20 g Bacto malt extract and 20 g Bacto Agar) plates (Fig. 1c). All isolates obtained in this study were deposited in the culture collection (CFPR) of the Forest Pathology Research Laboratory, National Institute of Forest Science, Seoul, South Korea (Accession Nos. CFPR-QA1TD and CFPR-QA2TD) as well as in the Korean Agricultural Culture Collection (KACC) of the National Academy of Agricultural Science in South Korea (Accession Nos. KACC48481 for CFPR-QA1TD and KACC48482 for CFPR-QA2TD). In addition to the morphological identifications, DNA barcode sequences were compared with sequences deposited in GenBank to assure the correct identity of the fungus. DNA sequence analyses were carried out following the techniques described by Lee et al. (2015) for internal transcribed spacer (ITS) regions including the 5.8S rDNA gene region and large-subunit (LSU) 28S rDNA. A BLASTn search with the isolates obtained in this study further revealed >99% similarity with those of T. dryina isolates from Poland (KR362909 for ITS) and from Italy (JF704187 for LSU). All sequence data obtained in this study were deposited in the NCBI database (accession n u m b e r s ; M F 5 7 9 7 5 5 a n d M F 5 7 9 7 5 6 f o r I T S ; MG798658 and MG793660 for LSU). To construct a phylogenetic tree, sequences obtained were aligned with ten published sequences of Tubakia species retrieved from GenBank using the online version of MAFFT ver.7.215 (http://mafft.cbrc.jp/alignment/ server/) (Katoh et al. 2002) . A Maximum likelihood (ML) analysis was performed using RAxML HPC BlackBox ver.8.1.11 (Stamatakis 2006; Stamatakis et al. 2008) , by using the default option with the GTR substitution model implemented in the CIPRES cluster server ( h t t p s : / / w w w . p h y l o . o r g / ) a t t h e S a n D i e g o Supercomputing Center. The ML analysis based on the ITS region resulted in a marginally supported placement of isolates obtained in this study (CFPR-QA1TD, CFPRQA2TD) with authenticated isolates of T. dryina retrieved from GenBank (Fig. 2). Pathogenicity of CFPR-QA1TD and CFPR-QA2TD to Q. acutissima, was tested through inoculations of healthy detached leaves of Q. acutissima. Three weeks-old culture formed on 2% MEA plates at 25 °C were flooded with sterile distilled water and the su (...truncated)


This is a preview of a remote PDF: https://link.springer.com/content/pdf/10.1007%2Fs13314-018-0299-0.pdf

Dong-Hyeon Lee, Sang-Tae Seo, Seung Kyu Lee, Sun Keun Lee. Leaf spot disease on seedlings of Quercus acutissima caused by Tubakia dryina in Korea, Australasian Plant Disease Notes, 2018, pp. 14, Volume 13, Issue 1, DOI: 10.1007/s13314-018-0299-0