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First Report of Powdery Mildew Caused by Erysiphe arcuata on Lanceleaf Coreopsis (Coreopsis lanceolata) in Korea

Lanceleaf coreopsis (Coreopsis lanceolata L.) is a plant species of the genus Coreopsis in Asteraceae native to the USA. This plant is a bushy perennial species with finely cut foliage and showy round flowers and is increasing as plants used in landscaping in the world. The invasive plant is also planted very commonly along roadsides in Korea. In late October 2011 and August 2012, signs and symptoms of a powdery mildew disease were observed on lanceleaf coreopsis in several land areas near Gwangju-river, Gwangju, Korea. Symptoms included typical white superficial mycelia. The conidia of the powdery mildew fungus occurred on adaxial and abaxial surfaces. Chasmothecia were not observed. Single conidia formed terminally on conidiophores. Conidial morphology was subcylindrical to oblong. Dimension of conidia was 23.6 to 41.4 (avg. 35.1) μm long × 11.3 to 18.2 (avg. 14.8) μm wide. Conidiophores were composed of five to six (up to seven) cells, ranged from 45.7 to 131.2 (avg. 98.1) μm long × 8.2 to 11.1 (avg. 8.3) μm wide with foot-cells straight to slightly flexuous. Oidium anamorph of this fungus matched that of E. arcuata U. Braun, Heluta and S. Takam. described by Pastircakova et al. (3). From extracted genomic DNA, the rDNA ITS was amplified with ITS1F (5′-CTTGGTCATTTAGAGGAAGT-3′) and LR5F (5′-GCTATCCTGAGGGAAAC-3′) primer set. The rDNA ITS homology of the fungus (EML-CDPW1, GenBank Accession No. JX485650) showed 100% (590/590) identity value with E. arcuata (GenBank Accession No. AB252459). The identification of the fungus as E. arcuata was based on morphological data combined with the results of sequence analysis. Until recently, E. arcuata has been known to widespread on Carpinus species of the family Betulaceae including European hornbeam (C. betulus L.) and Chonowski's hornbeam (C. tschonoskii Maxim.) in Asia and Europe since Braun et al. first reported it as a new species in 2006 (1). In Korea, Podosphaera fusca (= Sphaerotheca fusca) and P. fuliginea (= S. fuliginea) were reported to cause powdery mildews on Coreopsis lanceolata. E. cichoracearum (= Golovinomyces cichoracearum), Leveillula taurica, P. fusca (= S. fusca), and Oidium spp. have been reported on Coreopsis spp. in the world (3). To our knowledge, this is the first report of powdery mildew caused by Oidium anamorph of E. arcuata on lanceleaf coreopsis (C. lanceolata) in Korea or elsewhere in the world.

References: (1) U. Braun et al. Mycol. Prog. 5:139, 2006. (2) D. F. Farr and A. Y. Rossman. Fungal Databases, Systematic Mycology and Microbiology Laboratory, ARS, USDA. http://nt.ars-grin.gov/fungaldatabases/, 2012. (3) K. Pastircakova et al. J. Phytopathol. 156:597, 2008.