Abstract
Taraxacum mongolicum, which is valued for its both feeding and medicinal values (Lin et al. 2022; Wang et al. 2022), is one of the main associated species in the alpine meadow of China. In August 2023, a new leaf spot disease of T. mongolicum with an incidence rate of about 90% was observed on natural grassland in Hongyuan County, Aba (Ngawa) Tibetan and Qiang Autonomous Prefecture, China (32°48' N, 102°33' E, alt. 3500 m). The symptoms appeared as grayish white spots in the center with dark brown or purple black margins. For isolation, 18 tissue pieces (5mm × 5mm) from 2 symptomatic plants were surface sterilized with 70% ethanol for 30 s and rinsed three times with sterilized distilled water. Then, these tissues were placed on potato dextrose agar (PDA) at 25°C and incubated in the dark for 2 to 7 days. Finally, six pure strains with consistent colony characteristics were obtained from hyphal tips. Colonies on PDA were dark brown or green black with abundant aerial mycelia on the upper side, and black on the reverse side. Hyphae were hyaline to brown, septate, 3 to 6 μm wide. Conidia were hyaline, cylindrical, 10.7 to 15.4 × 3.0 to 4.9 μm (average 12.8 × 3.8 μm; n = 50), guttulate. For further identification, the internal transcribed spacer region (ITS), 28S nrRNA gene (LSU), partial beta-tubulin (tub2) and RNA polymerase II subunit 2 (rpb2) genes of the six strains were amplified with primers described by Valenzuela-Lopez et al. (2018). Sequences were deposited in GenBank (PP345804, PV840064-PV840068 for ITS; PQ002493, PV840076-PV840080 for LSU; PQ015093, PV854533-PV854537 for rpb2; and PQ015094, PV854538-PV854542 for tub2). A maximum likelihood (ML) phylogenetic tree based on the combined ITS, LSU, rpb2, and tub2 alignments showed the six strains, and UTHSC: DI16-352 and ex-type CBS 142456 of N. cylindrispora (Valenzuela-Lopez et al. 2018) formed a subclade with 97% bootstrap support. Based on the above morphological and molecular features, the six strains were finally confirmed as Neoascochyta cylindrispora. For pathogenicity tests, 7-week-old healthy plants were obtained by growing T. mongolicum seeds in pots (two plants per pot). Above six pure cultures were subsequently used to inoculate healthy plants as follows: for each strain, four pots were spray inoculated with a conidial suspension (about 1 × 106 conidia/ml); in addition, four pots considered as non-inoculated controls were sprayed with sterilized distilled water. All pots were individually covered with transparent polyethylene bags for 5 days to maintain high relative humidity and placed in a greenhouse with a temperature of 23 to 29°C, humidity of 60 to 70%, 12 hours of light and 12 hours of darkness. After incubation for 10 days, plants developed symptoms similar to those observed in the field. No symptoms were observed on the non-inoculated control plants. Pathogenicity tests were conducted thrice using the same method. The same fungus was re-isolated from the lesions and confirmed by the morphological and molecular methods described in this note, thus fulfilling Koch’s postulates. N. desmazieri, closely phylogenetically related to N. cylindrispora, has been recorded on Lolium perenne (Poaceae) in Germany (Chen et al. 2015; Valenzuela-Lopez et al. 2018). To our knowledge, this is the first report of N. cylindrispora as pathogen on T. mongolicum worldwide. This information would be benefit for the diagnosis, detection and pathogen identification of leaf spot disease on T. mongolicum in natural grassland.
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Claims 7
Claim · model-written summary
Leaf spot incidence in natural grassland was about 90%.
- Taxon
- T. mongolicum
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Taraxacum mongolicume0 - Outcome
- leaf spot diseasee0
- Value
- about 90%e0
- Setting
- Hongyuan County, Aba (Ngawa) Tibetan and Qiang Autonomous Prefecture, Chinae0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
.jpg?width=500)
Verbatim
e0“a new leaf spot disease of T. mongolicum with an incidence rate of about 90% was observed on natural grassland in Hongyuan County, Aba (Ngawa) Tibetan and Qiang Autonomous Prefecture, China”
Claim · model-written summary
Symptoms had grayish white centers and dark brown or purple black margins.
- Taxon
- Taraxacum mongolicumTaraxacum mongolicumt0
- Outcome
- grayish white spots in the center with dark brown or purple black marginse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The symptoms appeared as grayish white spots in the center with dark brown or purple black margins”
t0“Taraxacum mongolicum”
Claim · model-written summary
Morphological and molecular evidence identified the six isolates as Neoascochyta cylindrispora.
- Taxon
- Taraxacum mongolicumTaraxacum mongolicumt0
- Interactor
- Neoascochyta cylindrisporaNeoascochyta cylindrisporae0pathogen
- Outcome
- confirmed as Neoascochyta cylindrisporae0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the six strains were finally confirmed as Neoascochyta cylindrispora”
t0“Taraxacum mongolicum”
Claim · model-written summary
The six isolates formed a phylogenetic subclade with reference N. cylindrispora strains at 97% bootstrap support.
- Taxon
- Taraxacum mongolicumTaraxacum mongolicumt0
- Interactor
- N. cylindrisporaNeoascochyta cylindrisporae0pathogen
- Outcome
- formed a subcladee0
- Value
- 97%e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the six strains, and UTHSC: DI16-352 and ex-type CBS 142456 of N. cylindrispora (Valenzuela-Lopez et al. 2018) formed a subclade with 97% bootstrap support”
t0“Taraxacum mongolicum”
Claim · model-written summary
Inoculated plants developed leaf spot symptoms after ten days.
- Taxon
- Taraxacum mongolicumTaraxacum mongolicumt0
- Treatment
- spray inoculated with a conidial suspensione1
- Interactor
- Neoascochyta cylindrisporaNeoascochyta cylindrisporae2pathogent0
- Outcome
- symptoms similar to those observed in the fielde0
- Comparator
- non-inoculated control plantse0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“After incubation for 10 days, plants developed symptoms similar to those observed in the field. No symptoms were observed on the non-inoculated control plants”
t0“Taraxacum mongolicum”
e1“for each strain, four pots were spray inoculated with a conidial suspension (about 1 × 106 conidia/ml)”
e2“the six strains were finally confirmed as Neoascochyta cylindrispora”
Claim · model-written summary
The same fungus was reisolated from lesions, fulfilling Koch’s postulates.
- Taxon
- Taraxacum mongolicumTaraxacum mongolicumt0
- Interactor
- Neoascochyta cylindrisporaNeoascochyta cylindrisporae1pathogent0
- Outcome
- re-isolated from the lesionse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The same fungus was re-isolated from the lesions and confirmed by the morphological and molecular methods described in this note, thus fulfilling Koch’s postulates”
t0“Taraxacum mongolicum”
e1“the six strains were finally confirmed as Neoascochyta cylindrispora”
Claim · model-written summary
The authors report the first worldwide finding of N. cylindrispora as a pathogen on T. mongolicum.
- Taxon
- T. mongolicumTaraxacum mongolicume0
- Interactor
- N. cylindrisporaNeoascochyta cylindrisporae0pathogen
- Outcome
- first reporte0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“this is the first report of N. cylindrispora as pathogen on T. mongolicum worldwide”