Identification of Exserohilum rostratum causing leaf spot on Dendrobium amabile and Dendrobium clavatum
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Abstract
Fungal diseases are among the most persistent and underestimated threats to orchid cultivation, often causing severe decline if not detected early. In this study, leaf spot disease was recorded on two native orchid species, Dendrobium amabile and D. clavatum. To identify the causal agent, symptomatic leaves were collected and subjected to fungal isolation, pathogenicity testing, morphological characterization, and multi‑locus sequence analysis. Artificial inoculation reproduced typical leaf spot symptoms, confirming pathogenicity. Morphological traits of colonies and conidia indicated affiliation with the genus Exserohilum. Molecular analyses of the ITS, LSU, TEF1, and ACT gene regions further resolved the isolates as E. rostratum, with high sequence similarity among the representative strains. Minor morphological variation was noted, particularly in conidial dimensions, but overall consistency supported species‑level identification. This study establishes a new host association between E. rostratum and D. amabile and D. clavatum and demonstrates the effectiveness of combining morphological and molecular approaches for precise fungal identification. The generated multilocus dataset provides a useful reference for future studies on orchid pathogens and fungal taxonomy.
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© 2026 The authors. This is an open access article distributed under the terms of the Creative Commons Attribution-NonCommercial 4.0 International License.
References
Agrios, G. N. (2005). Plant Pathology. Elsevier.
Averyanov, L. V., Truong, V. B., Nguyen, C. V., Nguyen, K. S., Nuraliev, M. S., Averyanova, A. L., Maisak, T. V., & Nguyen, C. H. (2025). Orchids of Vietnam in Color and Graphics. Komarov Botanical Institute.
Boonkorn, Y., Tongsri, V., Piasai, O., & Songkumarn, P. (2024). Characterization, pathogenicity and fungicide response of Exserohilum rostratum causing leaf spot on rice in Thailand. European Journal of Plant Pathology, 170(3), 549–566. https://doi.org/10.1007/s10658-024-02918-w
Crous, P. W., Schoch, C. L., Hyde, K. D., Wood, A. R., Gueidan, C., de Hoog, G. S., & Groenewald, J. Z. (2009). Phylogenetic lineages in the Capnodiales. Studies in Mycology, 64(1), 17–47. https://doi.org/10.3114/sim.2009.64.02
Hernández-Restrepo, M., Madrid, H., Tan, Y. P., Cunha, K. C. D., Gené, J., Guarro, J., & Crous, P. W. (2018). Multi-locus phylogeny and taxonomy of Exserohilum. Persoonia - Molecular Phylogeny and Evolution of Fungi, 41(1), 71–108. https://doi.org/10.3767/persoonia.2018.41.05
Huynh, P. T. H., Thach, T. B., Nguyen, D. M., Dang, Q. T. B., Le, D. D., & Bui, T. C. (2025). Identification of Phyllosticta capitalensis on Dendrobium nobile Yamamoto using ITS, TEF1, LSU sequences and morphological characteristics. Proceedings of the National Biotechnology Conference, 2, 321–326.
Ministry of Science and Technology of Viet Nam. (2007). Vietnam Red Data Book (Part II – Plants), Part 1. Natural Science and Technology Publishing House.
Nakayashiki, H., Kiyotomi, K., Tosa, Y., & Mayama, S. (1999). Transposition of the Retrotransposon MAGGY in Heterologous Species of Filamentous Fungi. Genetics, 153(2), 693–703. https://doi.org/10.1093/genetics/153.2.693
Phillips, A. J. L., Alves, A., Abdollahzadeh, J., Slippers, B., Wingfield, M. J., Groenewald, J. Z., & Crous, P. W. (2013). The Botryosphaeriaceae: Genera and species known from culture. Studies in Mycology, 76(1), 51–167. https://doi.org/10.3114/sim0021
Sivanesan, A. (1987). Graminicolous species of Bipolaris, Curvularia, Drechslera, Exserohilum and their teleomorphs. C.A.B. International.
Vitt, P., Taylor, A., Rakosy, D., Kreft, H., Meyer, A., Weigelt, P., & Knight, T. M. (2023). Global conservation prioritization for the Orchidaceae. Scientific Reports, 13(1), 6718. https://doi.org/10.1038/s41598-023-30177-y
Wang, Z.-M., Wang, Z.-Q., Yuan, H.-X., Liu, M.-J., Chen, C., Kang, J.-G., Li, H.-L., & Wang, Y.-F. (2025). Genomic and functional analysis of carbohydrate esterases in the maize pathogen Exserohilum rostratum. Microorganisms, 13(11), 2588. https://doi.org/10.3390/microorganisms13112588
Yang, Y. L., Liu, Z. Y., Cai, L., Hyde, K. D., Yu, Z. N., & McKenzie, E. H. C. (2009). Colletotrichum anthracnose of Amaryllidaceae. Fungal Diversity, 39, 123–146.