First Report of Exserohilum rostratum Causing Leaf Blight on Calathea orbifolia in China
Peacock plant (Calathea orbifolia (Linden) H.A.Kenn.) is cultivated as a valuable houseplant in China. In September 2024, leaf blight was found on this plant in a field located in Shenzhen (22°35'55"N, 113°59'21"E), Guangdong Province, China. The area investigated was ~900 m2. Th...
| Veröffentlicht in: | Plant disease. - 1997. - (2024) vom: 26. Dez. |
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| Weitere Verfasser: | , , , , |
| Format: | Online-Aufsatz |
| Sprache: | English |
| Veröffentlicht: |
2024
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| Zugriff auf das übergeordnete Werk: | Plant disease |
| Schlagworte: | Journal Article Exserohilum rostratum fungal pathogen ornamental plant pathogen identification plant disease |
| Zusammenfassung: | Peacock plant (Calathea orbifolia (Linden) H.A.Kenn.) is cultivated as a valuable houseplant in China. In September 2024, leaf blight was found on this plant in a field located in Shenzhen (22°35'55"N, 113°59'21"E), Guangdong Province, China. The area investigated was ~900 m2. The disease incidence was ~70% of 100 plants. Initial symptoms of brown spots appeared on leaves, gradually becoming enlarged, elongated, 0.5 to 10 × 0.2 to 4.5 cm, irregular, dark brown, with a yellow halo, and leaves blighted and desiccated. Ten symptomatic leaves were collected for pathogen isolation. Leaf pieces (5×5 mm2) of lesion margins were surface disinfected with 1% NaClO for 1 min, 70% ethanol for 30 s, rinsed in sterile distilled water, placed on PDA, and incubated at 25°C. After 3 days, fungal colonies were purified by a single hyphal tip method on PDA. Three isolates (MBSZU 24-001 to MBSZU 24-003) with similar morphology were obtained. Colonies on PDA were 48 to 54 mm in diameter after 1 week at 25°C, then gray, flat with entire edges, aerial mycelia dense, and dark in the center and gray at the margin on the reverse side after 2 weeks. Conidiophores were olivaceous-brown, cylindrical, septate, unbranched, up to 230 × 3.4 to 5 µm. Conidiogenous cells were integrated, straight to curved, proliferating sympodial, 25 to 60 × 4.5 to 7 µm. Conidia were straight to slightly curved, ellipsoid, pale olivaceous brown to dark olivaceous brown, 2-6-distoseptate, with a distinct basal hilum, 26.9 to 70 × 11.4 to 21.6 µm (n = 50). Morphological characteristics of all isolates resembled the Exserohilum (Hernández-Restrepo et al. 2018). The internal transcribed spacer (ITS) region, glyceraldehyde-3-phosphate dehydrogenase (GAPDH), and translation elongation factor 1-alpha (tef1-α) genes were amplified using primer pairs ITS5/ITS4 (White et al. 1990), GPD1/GPD2 (Berbee et al. 1999), and EF1-983F/EF1-2218R (Rehner and Buckley 2005), respectively. Sequences were deposited in GenBank (ITS: PQ498876 to PQ498878; GAPDH: PQ509760 to PQ509762; tef1-α: PQ509763 to PQ509765). In the BLAST analysis, the ITS, GAPDH, and tef1-α sequences showed 99.50% (599 bp out of 602 bp), 98.89% (536 bp out of 542 bp), and 99.78% (926 bp out of 928 bp), respectively, to E. rostratum (CBS 325.87). Maximum likelihood and Bayesian inference phylogenetic analyses of the concatenated three genes identified all isolates as E. rostratum. To test pathogenicity, both wounded and unwounded healthy leaves were used in this experiment. All leaves were wiped with 0.1% NaClO and then rinsed three times with sterile water. Conidia suspensions (15 µl of 1 × 106 conidia/ml) of each isolate grown on PDA at 25°C for 3 weeks were placed on all samples using the attached leaf assay. Control leaves were mock-inoculated with sterile distilled water. Ten replications were conducted for each treatment and repeated twice. Plants were incubated at 25°C with 80 to 85% relative humidity. After 10 days, all inoculated leaves had brown lesions with yellow halos, while control leaves remained asymptomatic. E. rostratum was consistently reisolated from the lesions on PDA to complete Koch's postulates. Prior to this study, E. rostratum was identified as a causal agent of leaf blight on Calathea picturata in China (Taiwan, Chern et al. 2011). This is the first report of leaf blight caused by E. rostratum on C. orbifolia in China and worldwide. These findings will provide insights for epidemiological investigations and future approaches to managing this disease |
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| Beschreibung: | Date Revised 26.12.2024 published: Print-Electronic Citation Status Publisher |
| ISSN: | 0191-2917 |
| DOI: | 10.1094/PDIS-11-24-2415-PDN |