Ascochyta blight of chickpea: infection and host resistance mechanisms
Bibliographic record
Abstract
Ascochyta rabiei (teleomorph Didymella rabiei) is a directly penetrating, necrotrophic fungus that infects all aboveground parts of chickpea (Cicer arietinum). During spore germination and infection, germ tubes secrete a mucilaginous substance to facilitate attachment to the host surface, and the invading fungus produces cell-wall-lytic enzymes to penetrate the host. The pathogen produces several phytotoxins (solanapyrones A, B, and C, cytochalasin D, and a proteinaceous toxin) that seem to be responsible for necrosis and cell death. The pathogen can degrade antimicrobial compounds and suppress their production in chickpea. On the basis of aggressiveness, the population of A. rabiei can be classified into two broad pathotypes: pathotype I (less aggressive) and pathotype II (aggressive). Complete resistance to A. rabiei has not been found in chickpea; the resistance present in superior cultivars used in chickpea production is partial or incomplete. There is a high degree of variation in resistance among chickpea cultivars, and the resistance declines as the plant matures. The symptoms of infection and disease severity follow a quantitative continuum based on aggressiveness of the pathogen, genetic resistance present in the cultivar, and age of the plant. The well-established defense responses in chickpea are cross-linking of cell walls mediated by hydrogen peroxide, production of pathogenesis-related (PR) proteins (chitinase, β-1,3-glucanase, and thaumatin-like proteins), and accumulation of phytoalexins. However, expression of these induced defense responses does not correlate with pathotype-specific resistance, indicating that other constitutive or unknown components may be involved in providing resistance to aggressive pathotypes. Lack of information about the attribute that makes the pathogen aggressive, as well as inadequate knowledge of pathotype-specific defense mechanisms and the causes for decline in resistance, are major constraints in developing cultivars with durable resistance.
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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 | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.001 | 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".