First Report of Leaf Spot Caused by Colletotrichum aenigma on Acer rubrum in China

Abstract

HomePlant DiseaseAhead of PrintFirst Report of Leaf Spot Caused by Colletotrichum aenigma on Acer rubrum in China PreviousNext DISEASE NOTE OPENOpen Access licenseFirst Report of Leaf Spot Caused by Colletotrichum aenigma on Acer rubrum in ChinaYuhang Qiao, Xiangrong Zheng, Huan Li, and Fengmao ChenYuhang QiaoCo-Innovation Center for Sustainable Forestry in Southern China, College of Forestry, Nanjing Forestry University, Nanjing 210037, ChinaSearch for more papers by this author, Xiangrong Zhenghttps://orcid.org/0000-0002-9574-9449Co-Innovation Center for Sustainable Forestry in Southern China, College of Forestry, Nanjing Forestry University, Nanjing 210037, ChinaSearch for more papers by this author, Huan LiCo-Innovation Center for Sustainable Forestry in Southern China, College of Forestry, Nanjing Forestry University, Nanjing 210037, ChinaSearch for more papers by this author, and Fengmao Chen†Corresponding author: F. Chen; E-mail Address: [email protected]https://orcid.org/0000-0003-2412-7607Co-Innovation Center for Sustainable Forestry in Southern China, College of Forestry, Nanjing Forestry University, Nanjing 210037, ChinaSearch for more papers by this authorAffiliationsAuthors and Affiliations Yuhang Qiao Xiangrong Zheng Huan Li Fengmao Chen † Co-Innovation Center for Sustainable Forestry in Southern China, College of Forestry, Nanjing Forestry University, Nanjing 210037, China Published Online:10 Apr 2023https://doi.org/10.1094/PDIS-08-22-1845-PDNAboutSectionsView articlePDFSupplemental ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InRedditEmailWechat View articleAcer rubrum belongs to the family Aceraceae. It was introduced from North America by Chinese researchers in 2000 to promote the economic growth and value of forests (Lu et al. 2020). Since 2019, a serious leaf spot disease was observed on the petioles of A. rubrum in the Xuzhou Red Maple Park (34.28°N, 118.03°E) of Jiangsu Province. Lesions initially appeared black, surrounding more than half of the petioles of A. rubrum, and gradually expanded toward the branches and along the veins of leaves. Diseased leaves were sterilized in 10% sodium hypochlorite for 120 s, then rinsed in ddH2O twice for 30 s each time, and dried with sterile distilled paper. Afterward, the tissues were cultured on 2% potato dextrose agar (PDA), which was amended with 100 mg/liter ampicillin sodium and incubated in the dark at 25°C for 3 days. Twenty-four single-spore isolates were obtained as described by Cai et al. (2009). The colony morphology of 24 isolates was almost identical, so three isolates (XZC05, XZC15, and XZC27) were selected randomly for further study. Both sides of the colonies of the three isolates were white. Conidia were single-celled, hyaline, straight, cylindrical with circular ends, measuring 14.5 to 16.9 × 5.5 to 6.7 μm (n = 50). Appressoria were single-celled, subcircular or irregular, light brown to dark brown, thick-walled, measuring 6.1 to 11.8 × 5.5 to 11.6 μm (n = 50). Asci were clavate, eight-spored, thin-walled, measuring 74.5 to 52.4 × 14.7 to 9.2 μm (n = 50). Ascospores were one-celled, slightly curved, measuring 14.1 to 18.6 × 5.1 to 7.5 μm (n = 100). The morphology of the three isolates was basically the same. The morphological features were consistent with the description of Colletotrichum sp. (Weir et al. 2012). Six nuclear gene regions were amplified and sequenced, including ITS, CAL, GAPDH, TUB2, ACT, and CHS (Weir et al. 2012). The sequences were deposited in GenBank (accession nos. OM663716, OM681224, OM681272, OM681248, OM681200, and OM681296 for XZC05; OM663726, OM681234, OM681282, OM681258, OM681210, and OM681306 for XZC15; OM663736, OM681244, OM681292, OM681268, OM681220, and OM681316 for XZC27). IQtree v. 1.6.8 and Mr. Bayes v. 3.2.6 were used for phylogenetic reconstruction. The concatenated sequences placed XZC05, XZC15, and XZC27 in the clade of Colletotrichum aenigma with a high confidence level (ML/BI = 100/1). Pathogenicity assay was selected XZC15 and tested on 3-year-old A. rubrum seedlings. A. rubrum leaves were wounded by a sterilized needle (0.5-mm diameter) and inoculated with spore suspension (106 conidia/ml), and A. rubrum leaves inoculated with sterile water were used as the control group. Each treatment had five leaves and was incubated at 25°C under high moisture conditions. The experiments were conducted three times. After 7 days, all of the inoculated petioles showed lesions similar to the previous symptoms observed in the nursery, while the controls remained healthy. The fungus was reisolated from the lesions and morphologically identified, confirming Koch’s postulates. The leaf diseases caused by C. aenigma were widely distributed in China, with a variety of host plants, such as Cyclocarya paliurus (Zheng et al. 2021) and Aquilaria sinensis (Lour.) Spreng (Li et al. 2021). This is the first report of C. aenigma associated with leaf blight on Acer rubrum. The finding provides clear pathogen information for further evaluation of disease control strategies.The author(s) declare no conflict of interest.