First Report of <i>Perenniporia fraxinea</i> Causing Heart Rot Disease of <i>Styphnolobium japonicum</i> in China
Bibliographic record
Abstract
Styphnolobium japonicum (L.) Schott, is an ornamental species of Leguminosae, widely planted as a roadside tree in north regions of China (Kite et al. 2007). In mid-June of 2022, 45 ca. 30-year-old plants of S. japonicum growing along roadsides in Dalian, China were found to be infected by a polypore fungus that appeared to be killing many of these plants. The infected trees show leaf wilt early in the growing season, and in mid-summer, pale yellow fruiting bodies appeared at the base of the tree trunks. The fruiting bodies were effused-reflexed, with a pale yellow to yellow-brown pileus when dry, and gradually formed whitish pores on their undersurface. Over two years, approximately 15% of S. japonicum trees became infected in a ca. 10-ha area. Thirteen morphologically identical strains were generated from 20 samples by collecting 8 mm3 tissue pieces from 20 fruiting body stroma and growing these out on potato dextrose agar (PDA). The basidiospores from field collected fruiting bodies were abundantly produced in pores which were circular and 4-6 per mm, hemispherical and dropletshaped, hyaline, thick-walled and smooth, (5.8-6.9)×(4.8-5.7) μm. On PDA, the mycelia were initially white and sparse, later becoming fluffy in the center, white at the margins, and pale yellow on the underside. These morphological characteristics were consistent with Perenniporia spp., as described recently in Cui et al. (2019). To further confirm species identification, representative isolate DL was selected for molecular identification. The small subunit (SSU), internal transcribed spacer (ITS), and large subunit (LSU) of the ribosomal DNA (rDNA) were amplified with primers NS1/NS4, ITS1/ITS4 (White et al 1990), and LROR/LR7 (Aveskamp et al. 2010), respectively. The sequences were uploaded to GenBank as accession OQ592891 for ITS; OQ629793 for SSU; and OQ629858 for LSU. Sequence comparisons against the GenBank database showed 99% to 100% identity (GenBank accessions KX081110.1, MG847270.1, JF706344.1) with a strain of Perenniporia fraxinea (Bull.) Ryvarden [syn.: Vanderbylia fraxinea (Bull.) D.A. Reid]. Phylogenetic analysis also placed these isolates in a highly supported clade with the other isolates of Perenniporia fraxinea. To test pathogenicity, fresh hyphal plugs were inoculated onto sterile wounds artificially punctured on the stem surface of five healthy one-year-old S. japonicum seedlings, and plants were incubated at 28℃ with a 12-hour photoperiod in a humid chamber for 7 days. PDA plugs were used as controls and the pathogenicity test was repeated three times. After 7 days, lesions were observed on all inoculated stems, while the mock-inoculated stems were asymptomatic, and no fungal pathogen was isolated. The same fungus was re-isolated from the inoculated wounds to complete Koch's Postulates. The original pathogenic and the re-isolated inoculated fungus was identified as P. fraxinea. This fungus has also been found on Robinia pseudoacacia in Japan (Matsumoto et al. 2023) and in Germany (Kehr et al. 2020). However, to our knowledge, this is the first report of P. fraxinea causing heart rot of S. japonicum in China. The wide occurrence of this pathogenic fungus on stem bases of S. japonicum, and its lethal effect on host plants should be given more attention by landscape maintenance workers and extension agents.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.000 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".