First report of late leaf rust on raspberry caused by <i>Aculeastrum americanum</i> in New Zealand
Why this work is in the frame
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Bibliographic record
Abstract
In April 2023 and 2024, rust symptoms were detected on a small number of red raspberry (Rubus idaeus) plants growing on two residential properties in Auckland, New Zealand (Fig. 1). Nearly all leaves of the affected host plants were infected, displaying symptoms of rust disease ranging from mild to severe. Further examination showed yellow to orange rust pustules (uredinia) scattered on the lower leaf surface (Fig. 2). Microscopic examination revealed obovoid to ellipsoid echinulate urediniospores (n = 30), measuring 19.5 × 13.3 µm (14.8–23.6 × 9.8–17.7 µm), with yellow to orange pigmented contents, and cell walls measuring 1–1.5 µm (Fig. 3). In addition, knob-like aculeate ostiolar cells were found, measuring up to 30 µm in diameter, with spikes up to 5 µm long (Fig. 4). These morphological characters differed from the rust fungi known to infect Rubus in New Zealand and aligned with those of Aculeastrum americanum (syn. Thekopsora americana, Pucciniastrum americanum) (Laundon & Rainbow, 1969). No telia or teliospores were found. For molecular identification, DNA was extracted from the uredinia and the internal transcribed spacer region 2 (ITS2) and partial ribosomal RNA large subunit (LSU) were amplified and sequenced using primers Rust2inv / LR6 (Aime 2006; Vilgalys & Hester 1990). BLAST analysis confirmed the initial morphological identification with 99.8–100.0% identity to sequences of other A. americanum isolates (e.g. MG907237). Specimens were deposited in the New Zealand Fungarium as vouchers PDD 121369 and PDD 124516. The sequences from this study were deposited in GenBank (Accession Nos. PP795360 (PDD 121369); PP795362 (PDD 124516)). Aculeastrum americanum uredinial stage causes late yellow rust or late leaf rust mainly on red and purple raspberry (R. idaeus and R. × neglectus, respectively). Other Rubus species reported to be susceptible are R. leucodermis, R. occidentalis and R. ursinus. Infection can occur on all aerial plant parts and leads to premature leaf drop and defoliation. The disease can have a significant impact as symptomatic fruit is deemed unmarketable (Martin et al., 2017). The management of the disease is reported to be difficult (Delisle-Houde et al., 2020). If host alternation occurs, the aecial stage of A. americanum forms on white spruce (Picea spp.), causing needle rust (Martin et al., 2017). The pathogen has been reported from Argentina, Brazil, Canada, Japan, Mexico and the USA (USDA, 2024). The infected plants detected in Auckland in 2023 were removed as an urgent biosecurity measure to attempt to stop the spread of the pathogen (Bleach, 2023). The subsequent detection of A. americanum in a different area of Auckland in 2024 suggests that the fungus is distributed in the region. It is also possible that the pathogen has been present for some time but overlooked due to its macroscopic similarity to other Rubus rusts in New Zealand. Aculeastrum americanum was regarded as a regulated and unwanted organism in New Zealand during the time of these detections. Its unwanted organism status was revoked in September 2024 as the rust fungus is considered to be present in the country. Chris Inglis (SPS Biota, New Zealand) collected samples and took the field photograph. Alexander Bisson and Graham Surrey (Incursion Investigation Plant Health, Ministry for Primary Industries, New Zealand) led the incursion investigation.
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Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 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) | 0.000 | 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 it