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Disease Resistance Lookup.
Disease Resistance Cultivar Lookup
If you have a recurring disease, the cheapest fix is usually a resistant cultivar. Decode the resistance codes and find specific varieties.
Tomato resistance codes (the big one)
| Code | Disease | Notes |
|---|---|---|
| V | Verticillium wilt | Soil-borne fungus; common in cool-summer regions |
| F / F1 | Fusarium wilt race 1 | Soil-borne; widespread |
| F2 / F3 | Fusarium wilt race 2 / race 3 | Newer races emerging; F3 increasingly important |
| FOR | Fusarium oxysporum f.sp. radicis (crown/root rot) | Different from regular Fusarium wilt |
| N | Root-knot nematode | Soil-borne; warm-soil regions |
| T / TMV | Tobacco Mosaic Virus | Sap-transmitted virus |
| ToMV | Tomato Mosaic Virus | Distinct from TMV |
| TYLCV | Tomato Yellow Leaf Curl Virus | Whitefly-transmitted; major issue in warm regions |
| TSWV | Tomato Spotted Wilt Virus | Thrips-transmitted |
| EB / Aal | Early blight (Alternaria) | Foliar fungus; resistance is partial |
| LB / Pi | Late blight (Phytophthora) | Famine-causing fungus; tolerance not full immunity |
| St / Stemphylium | Gray leaf spot | Foliar fungus |
| PM / On / Lt | Powdery mildew (Leveillula taurica / Oidium) | Greenhouse and field |
A label like "Big Beef VFFNT" means: resistant to Verticillium, Fusarium race 1+2, Nematode, and Tobacco mosaic virus.
Resistance vs tolerance
| Term | Meaning |
|---|---|
| Immune | Pathogen does not infect at all (rare; usually species-level) |
| Resistant (HR / High) | Plant restricts pathogen growth; minimal disease symptoms; minimal yield loss |
| Intermediate (IR) | Plant slows pathogen; some symptoms but reduced damage |
| Tolerant | Plant gets disease but yields anyway. Can still spread pathogen to neighbors. |
| Susceptible | Plant gets disease and yield is reduced or destroyed |
Beyond resistance: integrated approach
Resistant cultivars are step #1, not the whole answer:
- Resistance can be overcome by new pathogen races. Always rotate cultivars and watch for new strains.
- Resistance is partial. Cultural practices still matter — sanitation, rotation, spacing, watering practices.
- Genetic monoculture is risky. If one resistant cultivar represents 80% of plantings and the resistance breaks, the whole region collapses (Irish potato famine, 1840s).
- Stack resistance with cultural practices. Resistant cultivar + drip irrigation + 3-yr rotation + sanitation = effective control.
- Some pathogens have no resistant cultivars yet. Hop downy mildew, cannabis hop latent viroid, fusarium race 4 in banana — wait for breeding programs or use other tools.
Free under CC BY 4.0. Cite as "OAT Disease Resistance Lookup (openagriculturetechnology.com)". Cultivar resistance data current as of 2025; verify with seed company catalogs as resistance breeding evolves.