The letters after a tomato name are disease-resistance codes. V is Verticillium wilt, F is Fusarium wilt, N is nematodes, and LB is late blight. If a disease keeps hitting your tomatoes, pick it below to see the code to look for and example resistant varieties.
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What Your Result Means: the code is the letter to look for on a seed packet or plant tag, and the varieties are well-known examples carrying it. Resistance lowers the risk but is not a guarantee, so pair it with good growing habits.
How Do You Find a Disease-Resistant Tomato?
Pick the disease that keeps troubling your tomatoes. The tool gives the resistance code to look for on the label, what it means, and example varieties that carry it, so you can choose a tougher plant next season.
- Pick the Disease, matching the symptoms you have seen, or choose Not Sure for broad resistance.
- Read the Code, the letter printed after a tomato’s name that signals resistance.
- Choose a Variety, from the examples or any local one that lists the code.
What Each Result Means
| Result | What It Tells You |
|---|---|
| Code | The letter to look for on the label |
| Code means | The disease it resists |
| Look for | How it appears on packets and tags |
| Example varieties | Well-known resistant cultivars |
Tomato Resistance Codes
The letters you will see after a tomato variety name and what each one resists.
| Code | Resists |
|---|---|
| V | Verticillium wilt |
| F, FF, FFF | Fusarium wilt (races 1, 2, 3) |
| N | Root-knot nematodes |
| T or ToMV | Tobacco / tomato mosaic virus |
| TSWV | Tomato spotted wilt virus |
| LB | Late blight |
| EB or AB | Early blight (usually tolerance) |
| A (ASC) | Alternaria stem canker (not the same as early blight) |
| St | Gray leaf spot (Stemphylium) |
How Does the Matcher Work?
The tool maps each common tomato disease to its standard resistance code and to varieties known to carry that resistance. Choosing Not Sure returns the broad combination codes worth looking for.
Code -> how it appears on the label
Code -> example varieties that carry it
Not sure -> look for VFN or longer combination codes
Codes are an industry standard, so a tomato labeled VFN resists Verticillium, Fusarium, and nematodes. Longer strings like VFFNTA cover more diseases; the A there is Alternaria stem canker, not early blight.
Worked Example
Say Fusarium wilt keeps collapsing your plants. The tool returns the code F (or FF, FFF for races 1, 2, and 3), tells you to look for that letter after the variety name, and lists resistant examples like Celebrity, Better Boy, and Big Beef. Combined with a 3 to 4 year rotation, a resistant variety greatly cuts the risk.
Factors That Change Your Choice
- Local disease pressure: pick resistance for the diseases common in your area, which your extension office can name.
- Resistance versus tolerance: resistance strongly limits a disease; tolerance only reduces its impact.
- Races and strains: Fusarium has races, so FF or FFF covers more than a plain F.
- Heirloom preference: most heirlooms lack coded resistance, so lean on rotation and sanitation with them.
- Availability: not every resistant variety is sold everywhere; check local seed sources.
Understanding Your Outputs
| Output | Meaning | Best Used For |
|---|---|---|
| Code | Letter to seek | Reading labels |
| Code means | Disease resisted | Matching your problem |
| Look for | Label format | Shopping seeds and plants |
| Examples | Named varieties | A starting shortlist |
When to Use It
Use it when a disease returns year after year, when planning next season’s varieties, or when shopping seeds and puzzled by the letters on the packet. It pairs with the problem diagnosis and crop rotation tools for a full defense.
Common Mistakes to Avoid
- Expecting immunity: resistance lowers risk but a plant can still get sick under heavy pressure.
- Ignoring rotation: even resistant plants do better with a 3 to 4 year rotation and clean soil.
- Wrong disease: match the code to your actual problem; get a diagnosis if unsure.
- Overhead watering: resistance does not replace watering at the base and good airflow.
- Assuming all heirlooms cope: most lack coded resistance and need extra care.
Accuracy and Limitations
This maps diseases to standard codes and example varieties, not a guarantee for your garden.
What It Does Well: explains the resistance letters and points to proven resistant cultivars.
What It Does Not Account For: your local disease races, which varieties are sold near you, or growing conditions. Confirm the diagnosis and check local availability before buying.
Methodology
Method: maps each common tomato disease to its standard resistance code and to example resistant varieties. Input Used: the disease you select. Codes: V Verticillium, F/FF/FFF Fusarium races, N nematodes, T or ToMV mosaic virus, TSWV spotted wilt, LB late blight, EB or AB early blight tolerance, A Alternaria stem canker, St gray leaf spot. Examples: widely grown resistant cultivars such as Celebrity, Better Boy, Big Beef, Mountain Magic, Iron Lady, Defiant PhR, Jasper, Amelia, and Mountain Merit; many others carry the same codes. Note: resistance is not immunity; combine with rotation, sanitation, and base watering. Edge cases: Not Sure returns broad combination codes.
Sources: Iowa State University Extension – Growing Tomatoes, Royal Horticultural Society – Tomatoes, The Old Farmer’s Almanac – Tomatoes. Last reviewed: September 24, 2026 · Reviewed by Aiza Anwar.
Frequently Asked Questions
What do the letters VFN mean on a tomato?
They are resistance codes: V for Verticillium wilt, F for Fusarium wilt, and N for root-knot nematodes. A VFN tomato resists all three.
Are disease-resistant tomatoes genetically modified?
No. Nearly all resistant garden tomatoes are conventionally bred hybrids, not GMOs. The resistance comes from traditional cross-breeding.
Do heirloom tomatoes have disease resistance?
Most heirlooms lack coded resistance and are more disease-prone. A few have some tolerance, but with heirlooms lean on rotation, spacing, and sanitation.
What is the difference between resistance and tolerance?
Resistance strongly limits a disease taking hold. Tolerance means the plant still gets the disease but suffers less. Labels sometimes list tolerance for early blight.
What is the best late-blight-resistant tomato?
Bred-for-blight varieties like Mountain Magic, Iron Lady, Defiant PhR, and the cherry Jasper hold up far better than most, though none is fully immune.
How do I prevent Fusarium and Verticillium wilt?
Grow VF or VFF resistant varieties, rotate beds 3 to 4 years, and remove infected plants. These soil diseases have no cure once a plant is infected.
Can a resistant tomato still get sick?
Yes. Resistance lowers the risk but is not immunity. Under heavy disease pressure or poor conditions, even resistant plants can be affected.
What is TSWV in tomatoes?
Tomato spotted wilt virus, spread by tiny thrips, causing ringspots and bronzing. Some varieties, such as Amelia and Mountain Merit, carry the Sw-5 resistance gene, listed as TSWV.
Where can I find resistant tomato varieties?
Check seed catalogs and plant tags for the codes, and ask your local extension office or a trusted nursery which resistant varieties do well in your area.
Related Tomato Tools
Plan a Rotation to Back It Up
This matcher explains standard resistance codes and gives example varieties, not a guarantee for your conditions or a substitute for a diagnosis. Confirm the disease and check local availability. Spotted an error? Tell us here.