First Report of Curvularia asianensis Causing Leaf Blotch of Epipremnum pinnatum in Guangxi Autonomous Region of China

Abstract

Epipremnum pinnatum Engl. is a flowering plant in the family Araceae. In southern China, it is often cultivated for medicinal and ornamental purposes. A distinct leaf blotch was observed on E. pinnatum in October 2017. Symptoms included gray or tan irregular blotches, with reddish to yellow margins. Portions of the symptomatic leaves were surface sterilized in 70% ethanol for 30 s and then in 2% NaClO for 1 min, rinsed three times in sterile distilled water, and plated onto potato dextrose agar (PDA). Seven strains (GUCC 8601 to GUCC 8607) from four diseased E. pinnatum plants were obtained by single spore selection. Fungal colonies on PDA reached 70 to 75 mm in diameter after 7 days, were velvety to slightly powdery, and were gray olivaceous to olivaceous black both top and reverse. Conidiophores were single or in groups, septate, straight or flexuous, and geniculate. Conidiogenous cells were smooth walled to finely verruculose, terminal or intercalary, proliferating sympodially, pale brown to brown, subcylindrical to swollen, and 6 to 14 × 3 to 5 μm (n = 30). Conidia were curved, pale brown to brown, 3 to 4 distoseptate, 23 × 9 μm (n = 50) with a protuberant hilum; morphology was consistent with Curvularia asianensis Manamgoda, L. Cai & K. D. Hyde, isolated from a dried Panicum sp. leaf in northern Thailand (Manamgoda et al. 2012). The internal transcribed spacer (ITS) region and partial sequences of two protein-coding genes, namely, glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and translation elongation factor 1-α (TEF1), were amplified using primers ITS1 and ITS4 (White et al. 1990), gpd1 and gpd2 (Berbee et al. 1999), and EF983F and 2218R (Schoch et al. 2009). The ITS, GAPDH, and TEF1 sequences were compared with entries in GenBank database, through nucleotide BLAST search, and our isolates showed higher than 99% identity to the ex-type strain (MFLUCC 10-0711) of C. asianensis (ITS, JX256424; GAPDH, JX276436; and TEF1, JX266593) for these three gene regions. The three gene regions were combined into a multigene phylogenetic tree. On the basis of morphological characteristics and nucleotide homology, our isolates were confirmed as C. asianensis. For pathogenicity tests, mycelial disks (5 mm in diameter) cut from 1-week-old PDA cultures of two strains (GUCC 8601 and GUCC 8602) were placed on four healthy leaves (two inoculated points on every leaf) of an E. pinnatum plant under natural conditions on 20 November 2017 and removed after 48 h. Leaves inoculated with sterile PDA disks served as controls. Within 24 h after discs were removed, tan lesions began to appear on the leaves. Seven days after inoculation, all inoculated leaves developed blotch symptoms consistent with what was observed in nature. C. asianensis strains were reisolated from infected tissues and confirmed by the methods mentioned above. Controls remained healthy. To our knowledge, this is the first report of C. asianensis causing leaf blotch disease on E. pinnatum in China.