An Emerging Potato Purple Top Disease Associated with a New 16SrIII Group Phytoplasma in Montana
Bibliographic record
Abstract
Potato purple top (PPT) is a devastating disease that occurs in the United States, Canada, Mexico, Russia, and elsewhere causing great economic loss to the potato industry through substantially reduced tuber yield and quality. Chips and fries processed from infected tubers often develop brown discoloration, greatly reducing their marketability. At least seven distinct phytoplasma strains belonging to five different phytoplasma groups (16SrI, 16SrII, 16SrVI, 16SrXII, and 16SrXVIII) have been reported to cause purple top and related symptoms in potato (3). During an unusual drought in 2007, a newly emerging potato disease with extensive yellowish or reddish purple discoloration of terminal shoots and leaves, similar to PPT symptoms, was observed in isolated potato fields in Montana where over 50% of plants exhibited symptoms. Shoot tissues were collected from three symptomatic plants and 17 tubers randomly collected from 17 other symptomatic plants. The tubers were cold treated to induce sprouting and then planted in the greenhouse. All tubers produced plants of which seven exhibited PPT symptoms including severe stunting. Total nucleic acid was extracted from leaf veinal tissue, stolons, or tubers of 10 symptomatic and 10 asymptomatic plants (both field-collected and greenhouse samples) as previously described (3). A nested-PCR assay, using universal primer pair P1/16S-SR followed by R16F2n/R16R2n, was performed as previously described (2,3) to detect phytoplasmas in these samples. Phytoplasma strains were detected in all symptomatic plants. Restriction fragment length polymorphism (RFLP) analyses of nested-PCR products (approximately 1.2 kb) with seven key restriction enzymes (AluI, MseI, HhaI, Tsp509I, HpaII, RsaI, and BfaI) indicated that all samples contained a very similar or identical phytoplasma most closely related to reference strain MW1 (belonging to subgroup 16SrIII-F) (1). Analysis of cloned 16S rDNA sequences confirmed the identity of this new phytoplasma and sequences of three representative PPT-MT strains were deposited in GenBank with Accession Nos. FJ226074-FJ226076. Computer-simulated RFLP analyses of 1.2-kb 16S rDNA sequences of this new phytoplasma and representative members in the peach X-disease phytoplasma group (16SrIII) available in GenBank indicated the strain is distinct and represents a new subgroup, 16SrIII-M (4). This study also indicated that the phytoplasma is tuber transmissible since approximately 35% of plants produced from infected tubers collected in this study developed symptoms. Transmission via infected tubers may pose a potential threat for disease spread by planting uncertified seed potatoes. To our knowledge, this is the first report of 16SrIII group phytoplasmas-associated diseases in potato. A phytoplasma closely related to the PPT-MT strains has recently been detected in potato seedlings exhibiting purple top, rosette, and stunting in Alaska (GenBank Accession No. FJ376628). References: (1) I.-M. Lee et al. Int. J. Syst. Bacteriol. 48:1153, 1998. (2) I.-M. Lee et al. Int. J. Syst. Evol. Microbiol. 54:337, 2004. (3) I.-M. Lee et al. Int. J. Syst. Evol. Microbiol. 56:1593, 2006. (4) W. Wei et al. Int. J. Syst. Evol. Microbiol. 58:2368, 2008.
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How this classification was reachedexpand
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 itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, 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".