First Report of Alternaria alternata Causing Leaf Spot Disease on Daylily in China
Daylilies (Hemerocallis spp.; Xanthorrhoeaceae) originated from Eastern Asia and are widely cultivated as perennial ornamentals from the tropics to their native high latitudes. In June 2021, daylily cultivar 'Tao Hua Zhai' with leaf spot symptoms were found at the Shanghai Institute of Tec...
| Veröffentlicht in: | Plant disease. - 1997. - (2022) vom: 12. Apr. |
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| Weitere Verfasser: | , , , , |
| Format: | Online-Aufsatz |
| Sprache: | English |
| Veröffentlicht: |
2022
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| Zugriff auf das übergeordnete Werk: | Plant disease |
| Schlagworte: | Journal Article Causal Agent Crop Type Disease management Fungi Ornamentals Pathogen detection Subject Areas herbaceous/flowering plants |
| Zusammenfassung: | Daylilies (Hemerocallis spp.; Xanthorrhoeaceae) originated from Eastern Asia and are widely cultivated as perennial ornamentals from the tropics to their native high latitudes. In June 2021, daylily cultivar 'Tao Hua Zhai' with leaf spot symptoms were found at the Shanghai Institute of Technology, Shanghai, China. The disease prevalence was about 14.5 % in a 33,000 m2 planting area indicated by survey statistics. Symptoms of the disease initially appeared as small, circular, brown spots on the leaves. As disease progressed, spots increased gradually until they were distributed uniformly over the lamina, the leaf tip became withered and the rest of the leaf became chlorotic. Symptomatic leaf tissue pieces (5 × 5 mm) from lesion margins were sterilized with 75 % ethanol for 1 min, rinsed three times with sterile distilled water, then incubated on potato dextrose agar (PDA) plates at 28 °C in the dark. A pure culture (ATHF-1) was obtained. Its upper surface on PDA was olive green with loose aerial hyphae, and its lower surface was brown.Conidiophores were brown, single or branched, producing numerous short chains conidia. Conidia were obclavate to obpyriform or ellipsoid, pale brown to dark brown, with a short cylindrical beak at the tip, contained 2-6 transverse septa and 0-4 longitudinal septa. The size of conidia were 15.9-47.3 µm × 7.6-16.6 µm (n=50), and length/width ratios were 1.51 to 4.92. Based on the morphological characteristics, the fungus was identified as Alternaria spp. (Simmons, 2007). For molecular characterization, three genes (the internal transcribed spacers [ITS], plasma membrane ATPase [ATPase] and major allergen Alt a 1) of ATHF-1 were amplified with primer pairs ITS1/ITS4 (White et al. 1990), ATPDF1/ATPDR1 (Lawrence et al. 2013) and Alt-for/Alt-rev (Hong et al. 2005), respectively. The sequences were deposited in GenBank (ITS, MZ983611; ATPase, MZ962978; Alt a 1, OK021654). Blastn searches showed the nucleotide sequences of ATHF-1 were highly similar to the reference sequences of Alternaria tenuissima (ITS, 99 % to KU982591; ATPase, 98 % to MT833928; Alt a 1, 100 % to MT109294). A phylogenetic tree based on the ITS, ATPase and Alt a 1 sequences was constructed by MEGA7.0, which showed that ATHF-1 was closely related to A. tenuissima and A. alternata. But according to Woudenberg et al. (2015), they were synonymized under the species name A. alternata. So, based on morphological and molecular characteristics, the fungus was identified as A. alternata. For pathogenicity tests, ten healthy two-month-old potted seedlings from tissue culture daylilies were sprayed with 20 ml of suspension (approximately 2×105 spores/ml), ten daylilies were used as controls and sprayed with sterile water. After covering with transparent plastic bags for 48 h to maintain humidity, the plants were placed in the greenhouse at 25 ℃ with 12 h photoperiod. The pathogenicity tests were repeated twice. Seven days after inoculation, lesions appeared on the plants inoculated with the pathogen, which were consistent with the symptoms observed in the field, while the controls remained symptomless. The morphological characteristics and gene sequences of the re-isolated strain from the diseased leaves were consistent with those of the inoculated strain. To our knowledge, this is the first report of A. alternata affecting leaf spot disease on daylily in China. Identification of the causal agent of the disease is important for developing effective disease management strategies. References: Hong, S.G., et al. 2005. Fungal Genet Biol. 42(2):119-129. https://doi.org/10.1016/j.fgb.2004.10.009 Lawrence, D.P., et al. 2013. Mycologia. 105(3):530-546. https://doi.org/10.3852/12-249 Simmons, E.G. 2007. Alternaria: An Identification Manual. CBS Fungal Biodiversity Centre, Utrecht, the Netherlands. White, T. J., et al. 1990. Amplification and Direct Sequencing of Fungal Ribosomal RNA Genes for Phylogenetics. PCR protocols: a guide to methods and applications, 18(1), 315-322. Woudenberg J.H.C., et al. 2015. Studies in Mycology. 82(82):1-21. https://doi.org/10.1016/j.simyco.2015.07.001 |
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| Beschreibung: | Date Revised 20.02.2024 published: Print-Electronic Citation Status Publisher |
| ISSN: | 0191-2917 |
| DOI: | 10.1094/PDIS-12-21-2691-PDN |