Abstract
During a field study in the Baili Azalea Forest Area in Guizhou Province, China (27°12′N, 105°48′E) between May and July 2023, symptoms of leaf spot were observed on Rhododendron latoucheae Franch. The incidence of leaf spot on R. latoucheae leaves was about 12% in a field of 1 hm2, significantly reducing their ornamental and economic value. The affected leaves bore irregular, grey-white lesions with distinct dark brown borders, accompanied by black conidiomata. To isolate the pathogen, 15 symptomatic leaves were collected from 10 plants. Conidiomata present on the lesions were transferred onto water agar and incubated at 25℃ for 24 hours. Germinated spores were then transferred onto potato dextrose agar (PDA) to generate single spore cultures for morphological analysis. This process yielded three single-spore isolates: GZULJ 3-6.1, GZULJ 3-6.2, and GZULJ 3-6.3, all displaying identical morphological characteristics. Representative isolate GZULJ 3-6.1 was used for further study. The colonies, cultivated on PDA at 25°C in the dark, appeared pale gray with white aerial mycelium. Alpha conidia were single celled, translucent and fusiform, measuring 6.2 to 8.1 × 2.6 to 3.0 μm (n=50). Beta conidia were filamentous and hook-shaped, measuring 17.0 to 23.0 × 0.9 to 1.5 μm (n=50). The morphological features were consistent with the established description of Diaporthe hongkongensis (Zhang et al. 2021). For molecular identification, total genomic DNA was extracted. The complete internal transcribed spacer region (ITS), partial sequence of beta-tubulin (TUB), translation elongation factor 1-alpha (TEF1), and calmodulin (CAL) gene were amplified and sequenced using primers ITS1/ITS4 (White et al. 1990), Bt2a/Bt2b (Glass and Donaldson. 1995), EF1-728F/EF1-986R and CAL-228F/CAL-737R (Carbone and Kohn. 1999), respectively. The ITS, TUB, TEF1, and CAL sequences (GenBank accession nos. OR807761, OR825453, OR825450, and OR825447, respectively) were obtained, and BLASTn analysis against sequences in GenBank showed 97.37 to 99.30% identity with Diaporthe hongkongensis CBS 115448. Phylogenetic analysis reaffirmed the isolate’s placement within a well-supported cluster alongside D. hongkongensis. The pathogenicity of GZULJ 3-6.1 was evaluated using three 2-year-old R. latoucheae plants inoculated with spore suspension (106 spores per ml). The inoculation targeted three leaves per plant, while an additional three plants, serving as controls, were sprayed with sterile water. The plants were maintained in the growth chamber at 25°C, with a 12-hour photoperiod and 75% relative humidity. The pathogenicity test was repeated three times. After 14 days, the inoculated leaves developed brown lesions similar to those observed in the field, whereas the control leaves remained symptom-free. The fungus was successfully reisolated from the infected leaves and identified through morphological characterization and molecular analyses, confirming its identity. D. eres, a closely related species to D. hongkongensis, has been reported to induce similar disease symptoms on R. latoucheae (Wu et al. 2024). However, to our knowledge, this is the first report of D. hongkongensis causing leaf spot disease on R. latoucheae in China. This finding will facilitate the development of effective management strategies to control the complex leaf spot disease affecting R. latoucheae and provide critical insights into its broader implications for the health of this species.
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Claims 14
Claim · model-written summary
Leaf spot occurred on Rhododendron latoucheae in the Baili Azalea Forest Area during May–July 2023.
- Taxon
- Rhododendron latoucheae Franch.
.jpg?width=60)
Rhododendron latoucheaee0 - Outcome
- symptoms of leaf spote0
- Qualifier
- between May and July 2023e0
- Setting
- Baili Azalea Forest Area in Guizhou Province, Chinae0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
.jpg?width=500)
Verbatim
e0“During a field study in the Baili Azalea Forest Area in Guizhou Province, China (27°12′N, 105°48′E) between May and July 2023, symptoms of leaf spot were observed on Rhododendron latoucheae Franch.”
Claim · model-written summary
Leaf spot incidence was about 12% in a 1 hm2 field and substantially reduced ornamental and economic value.
- Taxon
- R. latoucheaeRhododendron latoucheaee0
- Organ / stage
- leavese0
- Outcome
- incidence of leaf spote0
- Value
- 12%e0
- Qualifier
- aboute0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The incidence of leaf spot on R. latoucheae leaves was about 12% in a field of 1 hm2, significantly reducing their ornamental and economic value.”
Claim · model-written summary
Affected leaves had irregular grey-white lesions with dark brown borders and black conidiomata.
- Taxon
- Rhododendron latoucheaeRhododendron latoucheaet0
- Organ / stage
- leavese0
- Outcome
- irregular, grey-white lesions with distinct dark brown borders, accompanied by black conidiomatae0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The affected leaves bore irregular, grey-white lesions with distinct dark brown borders, accompanied by black conidiomata.”
t0“Rhododendron latoucheae”
Claim · model-written summary
Three single-spore isolates had identical morphological characteristics.
- Taxon
- Diaporthe hongkongensis
_Figure_4.jpg?width=60)
Diaporthe hongkongensist0 - Outcome
- identical morphological characteristicse0
- Value
- threee0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
_Figure_4.jpg?width=500)
Verbatim
e0“This process yielded three single-spore isolates: GZULJ 3-6.1, GZULJ 3-6.2, and GZULJ 3-6.3, all displaying identical morphological characteristics.”
t0“Diaporthe hongkongensis”
Claim · model-written summary
The pathogen colonies were pale gray with white aerial mycelium on PDA in darkness.
- Taxon
- Diaporthe hongkongensisDiaporthe hongkongensist0
- Outcome
- pale gray with white aerial myceliume0
- Qualifier
- cultivated on PDA at 25°C in the darke0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The colonies, cultivated on PDA at 25°C in the dark, appeared pale gray with white aerial mycelium.”
t0“Diaporthe hongkongensis”
Claim · model-written summary
Alpha conidia were single-celled, translucent and fusiform, measuring 6.2 to 8.1 × 2.6 to 3.0 μm.
- Taxon
- Diaporthe hongkongensisDiaporthe hongkongensist0
- Organ / stage
- Alpha conidiae0
- Outcome
- single celled, translucent and fusiforme0
- Value
- 6.2 to 8.1 × 2.6 to 3.0 μme0
- Qualifier
- n=50e0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Alpha conidia were single celled, translucent and fusiform, measuring 6.2 to 8.1 × 2.6 to 3.0 μm (n=50).”
t0“Diaporthe hongkongensis”
Claim · model-written summary
Beta conidia were filamentous and hook-shaped, measuring 17.0 to 23.0 × 0.9 to 1.5 μm.
- Taxon
- Diaporthe hongkongensisDiaporthe hongkongensist0
- Organ / stage
- Beta conidiae0
- Outcome
- filamentous and hook-shapede0
- Value
- 17.0 to 23.0 × 0.9 to 1.5 μme0
- Qualifier
- n=50e0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Beta conidia were filamentous and hook-shaped, measuring 17.0 to 23.0 × 0.9 to 1.5 μm (n=50).”
t0“Diaporthe hongkongensis”
Claim · model-written summary
Morphological features matched the established description of Diaporthe hongkongensis.
- Taxon
- Diaporthe hongkongensisDiaporthe hongkongensise0
- Outcome
- morphological features were consistent with the established descriptione0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The morphological features were consistent with the established description of Diaporthe hongkongensis (Zhang et al. 2021).”
Claim · model-written summary
ITS, TUB, TEF1 and CAL sequences were obtained and showed 97.37 to 99.30% identity to Diaporthe hongkongensis CBS 115448.
- Taxon
- Diaporthe hongkongensisDiaporthe hongkongensise0
- Outcome
- identitye0
- Value
- 97.37 to 99.30%e0
- Comparator
- Diaporthe hongkongensis CBS 115448e0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The ITS, TUB, TEF1, and CAL sequences (GenBank accession nos. OR807761, OR825453, OR825450, and OR825447, respectively) were obtained, and BLASTn analysis against sequences in GenBank showed 97.37 to 99.30% identity with Diaporthe hongkongensis CBS 115448.”
Claim · model-written summary
Phylogenetic analysis placed the isolate in a well-supported cluster with D. hongkongensis.
- Taxon
- D. hongkongensisDiaporthe hongkongensise0
- Outcome
- placement within a well-supported clustere0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Phylogenetic analysis reaffirmed the isolate’s placement within a well-supported cluster alongside D. hongkongensis.”
Claim · model-written summary
Inoculated Rhododendron leaves developed field-like brown lesions after 14 days whereas controls remained symptom-free.
- Taxon
- Rhododendron latoucheaeRhododendron latoucheaet0
- Treatment
- inoculatede0
- Interactor
- Diaporthe hongkongensisDiaporthe hongkongensist0pathogen
- Outcome
- developed brown lesionse0
- Qualifier
- After 14 dayse0
- Comparator
- control leavese0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“After 14 days, the inoculated leaves developed brown lesions similar to those observed in the field, whereas the control leaves remained symptom-free.”
t0“Diaporthe hongkongensis Causing Leaf Spot on Rhododendron latoucheae”
Claim · model-written summary
The fungus was reisolated from infected leaves and its identity confirmed morphologically and molecularly.
- Taxon
- Diaporthe hongkongensisDiaporthe hongkongensist0
- Interactor
- Rhododendron latoucheaeRhododendron latoucheaet0host
- Outcome
- successfully reisolated from the infected leavese0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The fungus was successfully reisolated from the infected leaves and identified through morphological characterization and molecular analyses, confirming its identity.”
t0“Diaporthe hongkongensis Causing Leaf Spot on Rhododendron latoucheae”
Claim · model-written summary
The authors report the first D. hongkongensis leaf spot occurrence on R. latoucheae in China.
- Taxon
- R. latoucheaeRhododendron latoucheaee0
- Interactor
- D. hongkongensisDiaporthe hongkongensise0pathogen
- Outcome
- first reporte0
- Qualifier
- to our knowledgee0
- Setting
- Chinae0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“However, to our knowledge, this is the first report of D. hongkongensis causing leaf spot disease on R. latoucheae in China.”
Claim · model-written summary
The authors interpret the finding as supporting management strategy development and understanding implications for Rhododendron health.
- Taxon
- R. latoucheaeRhododendron latoucheaee0
- Outcome
- development of effective management strategiese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“This finding will facilitate the development of effective management strategies to control the complex leaf spot disease affecting R. latoucheae and provide critical insights into its broader implications for the health of this species.”