Abstract
White clover (Trifolium repens L.) belongs to the Fabaceae family legume and is cultivated in China for its medicinal properties and ornamental value. White clover is grown around the world for forage, turf , green manure and soil conservation purposes (Zhang el al. 2016). In October 2021, an investigation of a 1,000 m2 plant nursery in Lanzhou, China (36°06'N, 103°83'E) found that 80% of White clover plants were infected, and powdery mildew covered 95% of the leaf area. The disease had seriously destroyed the forage quality and reduced the ornamental value. Initially, thin, radial, irregular white colonies appeared on leaves and gradually spread to stems. The white colonies then expanded and thickened to cover upper surface of the leaf, and microscopic hyphae appeared on the bottom of the leaf. In severe cases, the infection resulted in dieback of the leaf. A small area of sporulating fungus was stripped off from the leaf surface with tape and mounted in sterile water for microscopic examination (Mukhtar et al. 2017). Conidiophores were cylindrical, consisting of a foot cell followed by three to four short cells, measuring 75 to 160 × 7 to 10 μm. Conidiophores had straight, cylindric foot cells ranging from 25 to 40 µm long. Singly produced conidia were hyaline and ranged in shape from oblong to cylindrical. Conidia lacked distinct fibrotic bodies and measured 30 to 45 × 15 to 25 μm in length. Long, unbranched germ tubes formed from the ends of the conidia and nipple-shaped appressoria developed on epiphytic mycelia. Based on these morphological characteristics, the pathogen was initially identified morphologically as Erysiphe polygoni (Braun and Cook 2012). To validate the identity, the internal transcribed spacer (ITS) region of the pathogen (SY77) rDNA was amplified by PCR and sequenced using the ITS1/ITS4 primers (White et al. 1990). The resulting sequences were registered to GenBank (GenBank Accession No.OM280998). The ITS sequence of the SY77 was 100% (640/640) identical to E. polygoni (LC009892) on Polygonum aviculare in the United Kingdom and 99% (638/640) identical to E. polygoni (MK685172) on Antigonon leptopus in Taiwan. MEGA 7.0 was used to conduct the neighbor-joining phylogenetic analysis using the ITS sequences from GenBank. The data indicated that the strain SY77 and E. polygoni clustered together on the same branch. Pathogenicity tests were conducted by gently pressing the infected leaves onto five healthy potted White clover plants, while five non-inoculated plants were used as controls (Michael et al. 2021). The plants were maintained in a growth chamber (25 ℃, 14 h light, and 10 h dark period, RH > 80%). After 10 days, the inoculated plants developed powdery mildew symptoms, whereas the control plants remained symptom-free. The fungus on the inoculated plants was re-isolated, re-identified, and confirmed as E. polygoni based on morphological observations and molecular identification. There is no previous report on E. polygoni causing powdery mildew on White clover in China. The powdery mildew caused by E. polygoni on Red clover has been reported in China and Bulgaria, respectively (Yuan el al.1991; Galina el al. 2017). To our knowledge, this is the first report of powdery mildew caused by E. polygoni on White clover in China. References: 1. Zheng, L., et al. 2018. Plant Dis. 102:628. 2. Mukhtar, G., et al. 2017. Plant Dis.101:1, 246. 3. Braun, U., and Cook, R. T. A. 2012. Taxonomic Manual of the Erysiphales (Powdery Mildews), CBS Biodiversity Series No.11. CBS, Utrecht. 4. Michael, R. F., et al. 2021.Plant Dis. First look.( doi.org/ 10.1094/PDIS-09-21-2060-PDN). 5. Yuan, Q. H., el al.1991. Pratacult Sci.05:59 (in Chinese). 6. Galina, N., et al, 2017. BIOTECHNOL Anim Husb.33.127.
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Claims 11
Claim · model-written summary
In the Lanzhou nursery, 80% of white clover plants were infected.
- Taxon
- White clover
Trifolium repense0 - Outcome
- plants were infectede0
- Value
- 80%e0
- Setting
- Lanzhou, Chinae0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“In October 2021, an investigation of a 1,000 m2 plant nursery in Lanzhou, China (36°06'N, 103°83'E) found that 80% of White clover plants were infected”
Claim · model-written summary
Powdery mildew covered 95% of white clover leaf area.
- Taxon
- Trifolium repensTrifolium repenst0
- Interactor
- powdery mildewe0pathogen
- Outcome
- leaf areae0
- Value
- 95%e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“powdery mildew covered 95% of the leaf area”
t0“Trifolium repens”
Claim · model-written summary
Powdery mildew reduced white clover forage quality and ornamental value.
- Taxon
- Trifolium repensTrifolium repenst0
- Outcome
- forage quality and reduced the ornamental valuee0
- Direction
- reducede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The disease had seriously destroyed the forage quality and reduced the ornamental value”
t0“Trifolium repens”
Claim · model-written summary
White clover powdery mildew spread from leaves to stems and caused leaf dieback in severe cases.
- Taxon
- Trifolium repensTrifolium repenst0
- Outcome
- dieback of the leafe0
- Qualifier
- In severe casese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Initially, thin, radial, irregular white colonies appeared on leaves and gradually spread to stems. The white colonies then expanded and thickened to cover upper surface of the leaf, and microscopic hyphae appeared on the bottom of the leaf. In severe cases, the infection resulted in dieback of the leaf”
t0“Trifolium repens”
Claim · model-written summary
The powdery mildew pathogen was identified as Erysiphe polygoni by morphology.
- Taxon
- Trifolium repensTrifolium repenst0
- Interactor
- Erysiphe polygoni
Erysiphe polygonie0pathogen - Outcome
- identified morphologically as Erysiphe polygonie0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Based on these morphological characteristics, the pathogen was initially identified morphologically as Erysiphe polygoni”
t0“Trifolium repens”
Claim · model-written summary
SY77 ITS sequence was 100% identical to a United Kingdom E. polygoni sequence.
- Taxon
- Trifolium repensTrifolium repenst0
- Interactor
- E. polygoniErysiphe polygonie0pathogen
- Outcome
- identical to E. polygonie0
- Value
- 100%e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The ITS sequence of the SY77 was 100% (640/640) identical to E. polygoni (LC009892) on Polygonum aviculare in the United Kingdom”
t0“Trifolium repens”
Claim · model-written summary
SY77 ITS sequence was 99% identical to a Taiwan E. polygoni sequence.
- Taxon
- Trifolium repensTrifolium repenst0
- Interactor
- E. polygoniErysiphe polygonie0pathogen
- Outcome
- identical to E. polygonie0
- Value
- 99%e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“99% (638/640) identical to E. polygoni (MK685172) on Antigonon leptopus in Taiwan”
t0“Trifolium repens”
Claim · model-written summary
SY77 and E. polygoni clustered on the same phylogenetic branch.
- Taxon
- Trifolium repensTrifolium repenst0
- Interactor
- E. polygoniErysiphe polygonie0pathogen
- Outcome
- clustered together on the same branche0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The data indicated that the strain SY77 and E. polygoni clustered together on the same branch”
t0“Trifolium repens”
Claim · model-written summary
Inoculated white clover developed powdery mildew symptoms after 10 days while controls remained symptom-free.
- Taxon
- Trifolium repensTrifolium repenst0
- Treatment
- inoculated plantse0
- Outcome
- powdery mildew symptomse0
- Direction
- developede0
- Qualifier
- After 10 dayse0
- Comparator
- control plantse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“After 10 days, the inoculated plants developed powdery mildew symptoms, whereas the control plants remained symptom-free”
t0“Trifolium repens”
Claim · model-written summary
The fungus was re-isolated from inoculated clover and confirmed as E. polygoni.
- Taxon
- Trifolium repensTrifolium repenst0
- Interactor
- E. polygoniErysiphe polygonie0pathogen
- Outcome
- confirmed as E. polygonie0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The fungus on the inoculated plants was re-isolated, re-identified, and confirmed as E. polygoni”
t0“Trifolium repens”
Claim · model-written summary
The authors report E. polygoni powdery mildew on white clover in China for the first time.
- Taxon
- White cloverTrifolium repense0
- Interactor
- E. polygoniErysiphe polygonie0pathogen
- Outcome
- first report of powdery mildewe0
- Setting
- Chinae0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“To our knowledge, this is the first report of powdery mildew caused by E. polygoni on White clover in China”
The same questions in other papers
inoculation · disease · Trifolium repens (white clover)Positive and negative results
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