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First Report of Desarmillaria tabescens Found on Ulmus pumila in South Korea

Lee, D. H., Seo, S. T., Park, H. C., Lee, S. K.
Plant disease 2018 v.102 no.8 pp. 1660
Acer tataricum, Araucaria araucana, Armillaria mellea, Armillaria root rot, Carpinus, DNA primers, Eucalyptus, Pinus densiflora, Prunus dulcis, Prunus salicina, Quercus, Ulmus pumila, bark, basidiomata, basidiospores, forests, fungi, monitoring, mycelium, pathogens, polymerase chain reaction, ribosomal DNA, roots, saprophytes, stumps, surveys, trees, wood, Central Asia, China, India, Japan, Mexico, Mongolia, Siberia, South Korea
In November 2013, basidiomes of Desarmillaria sp. were observed at the base of a single Ulmus pumila L. (Siberian elm) tree planted along the street nearby the main gate of the National Institute of Forest Science, Seoul, South Korea (37°35′29.46″N, 127°02′32.74″E, elevation 28 m). Bark and basidiome samples were collected from this tree, which was suspected of having been associated with Armillaria root disease. Symptoms and signs, respectively, included crown thinning and a mycelial fan between the bark and wood of the trunk of the tree, roots of the tree, and basidiomes at the tree base. No rhizomorphs were formed. Since the first detection where basidiomes of Desarmillaria sp. were observed on U. pumila in November 2013, the tree was subjected to be monitored, and was felled for safety in June 2017. U. pumila, native to Central Asia, eastern Siberia, Mongolia, Xizang (Tibet), northern China, India (northern Kashmir), and Korea (Fu and Whittemore 2002), is a commonly planted street and shade tree in South Korea and is widely distributed across the country. Fungal isolations (CFPR-UP14AT:1 and 2) were directly made from the mycelial fan and basidiomes produced on the tree, and were deposited at the culture collection (CFPR) of the Forest Pathology Research Laboratory, National Institute of Forest Science, Seoul, South Korea. Genomic DNA was extracted using the isolate CFPR-UP14AT:1. The intergenic spacer-1 (IGS-1) region of rDNA was amplified with the primers LR12R (5′-CTGAACGCCTCTAAGTCAGAA-3′) and O-1 (5′-AGTCCTATGGCCGTGGAT-3′), and sequenced. The resulting sequence was deposited in GenBank (accession no. KT004513). A BLAST search in GenBank revealed that the xsequence from U. pumila was 99% identical (100% query cover) to Desarmillaria tabescens (Scop.) R.A. Koch & Aime sequences reported from Japan (AB510824.1, AB510839, and AB510823). Somatic pairing tests of the isolate with other Korean armillarioid species, including Armillaria mellea (CFPR-AME5), A. ostoyae (CFPR-AOS6), D. tabescens (CFPR-ATA3), and A. gallica (CFPR-AGA5), also confirmed that the species is D. tabescens (syn. A. tabescens). In addition, basidiomes produced on the trunk base in 2014 matched morphological features of D. tabescens, e.g., exannulate, cespitose growth in clusters, brown-gray stipes turning blackish toward the base, longitudinally fibrillose, basidiospores (6-) 7 to 9 × 4 to 5 (-5.5) μm. On the basis of these features, particularly the absence of rhizomorphs, the identity of the fungus isolated from U. pumila was ensured as being D. tabescens (Burdsall and Volk 1993; Koch et al. 2017). D. tabescens–Ulmus associations were only recorded in North America (Farr and Rossman 2018). In this regard, this is the first confirmed report of D. tabescens found on U. pumila in South Korea. In addition to the present report of D. tabescens on U. pumila, the fungus was previously reported as a causal agent of Armillaria root rot of Acer tataricum, Carpinus tschonoskii, Pinus densiflora, Prunus salicina, and Quercus sp. in South Korea (Lee and Seo 2016) as well as Eucalyptus spp. and Prunus dulcis in Europe and Araucaria araucana in Mexico (Farr and Rossman 2018), although, in most cases, the fungus is considered a saprophyte colonizing the stumps of trees. Given the fact that D. tabescens is occurring on U. pumila, more surveys and monitoring are needed to determine the occurrence of the fungus as a pathogen on U. pumila trees.