First Report of Oidium anamorph of Erysiphe hypophylla Causing Powdery Mildew on Leafy Lespedeza (Lespedeza cyrtobotrya) in Korea.

Abstract

Leafy lespedeza (Lespedeza cyrtobotrya Miq.) is a deciduous shrub in the pea family (Fabaceae) that occurs in areas of East Asia including Korea, China, and Japan. It has been commonly used as a fence plant and for sand control in Korea. In late October 2011, a powdery mildew disease was observed on leafy lespedeza in several areas near Gwangju River, Gwangju, Korea. Symptoms appeared late in October when temperature fluctuation was high. Major symptoms included scattered white powdery to cottony colonies on both surfaces of the leaves which spread to stems, causing a minor chlorosis and distortion. Conidia were formed singly on conidiophores with 2 to 4 (commonly 3) septa including basal septum, primary conidia ellipsoid, apex rounded to subtruncate, base truncate; and secondary conidia subcylindrical to oblong when mature, and ends truncate. The size was 26.4 to 43.2 (av. 35.1) × 11.2 to 13.2 (av. 11.3) μm. Conidiophores were erect, cylindrical, wider at apex than foot cell, and straight or slightly flexuous in foot cells. The size was 60.1 to 81.3 (av. 78.1) × 6.2 to 12.1 (av. 8.3) μm. Chasmothecia were not observed. Morphologically, the conidia and conidiophores of our strain (EML-LCPW1) were very similar to those of Erysiphe hypophylla (syn. Microsphaera hypophylla) (4). From extracted genomic DNA, the internal transcribed spacer (ITS) region inclusive of 5.8S and 28S rDNA were amplified with ITS1 (5'-TCCGTAGGTGAACCTGCGG-3'), LR5F (5'-GCTATCCTGAGGGAAAC-3'), LROR (5'-ACCCGCTGAACTTAAGC-3'), and LR5F primer sets, respectively. Based on the morphology and ITS rDNA sequence analysis, the fungus was identified as E. hypophylla. rDNA ITS and 28S homologies of the fungus (EML-LCPW1, GenBank Accession Nos. JX512557 and JX512558) represented 100% (771/771) and 100% (775/775) identity values with E. hypophylla (AB292712 and AB292716, respectively) via NCBI BLASTn search of each isolate. The rDNA ITS (JX512557) and 28S (JX512558) sequence analysis revealed that the causal fungus matched E. hypophylla, forming a HypophyllaAlphitoides clade as Takamatsu et al. suggested that E. hypophylla is conspecific to E. alphitoides (3). So far, it has been known that E. communis, E. glycines var. lespedezae, and E. lespedezae cause powdery mildews on Lespedeza plants in the world (1). In Korea, only one Erysiphe species, E. lespedezae (= E. pisi), has been reported to cause powdery mildew on Lespedeza plants including L. bicolor and L. cyrtobotrya (2). In addition, 10 records with respect to Oidium sp. have been found on Lespedeza spp., including L. cyrtobotrya from Japan and L. chinensis from China (1). However, powdery mildew on Lespedeza plants, including leafy lespedeza caused by E. hypophylla, has not been reported in Korea or elsewhere in the world. This fungus has been reported in association with numerous oak (Quercus) species in nearby countries such as China and Russia (Far East), showing that it may be a potential source of inoculum in Korea as well. To our knowledge, this is the first report of Oidium anamorph of E. hypophylla on leafy lespedeza (L. cyrtobotrya) in Korea.