Evaluation of Late Blight Resistant Tomato Varieties, 2013
2013 · Organic research field, Long Island, New York · conducted by Cornell Long Island Horticultural Research and Extension Center
To repeat the 2012 evaluation with no fungicides at all, so that the resistance genes were tested unprotected rather than supported by a spray programme.
Protocol
- Crop
- Tomato
- Season
- full season
- Design
- not stated by the report
- Replications
- -
- Plants per plot
- -
- In-row spacing
- -
- Row spacing
- -
- Population basis
- -
- Seeded
- -
- Transplanted
- -
- Harvest
- -
- Harvests
- -
Production system. Certified organic field, natural infection, no fungicides applied.
Analysis. Disease was assessed nine times between July and October, recording the percentage of leaves showing symptoms and the severity on affected leaves. Severity figures below are the reading on 12 September; AUDPC integrates all nine dates and is relative to the other entries in this trial only.
Season conditions
Unprotected natural infection. Mountain Magic and Matt's Wild Cherry gave 93% and 98% control respectively over the whole assessment period when compared against the susceptible check Mountain Fresh Plus.
Results
11 of the 13 entries grown here are varieties AMSeed holds records for. Letters are the report's own mean-separation groups: values sharing a letter were not significantly different from one another.
| Variety | As published | Late Blight severity | Late Blight: disease progress (AUDPC) |
|---|---|---|---|
| New Yorker | New Yorker OP | 86 % | 1,285 index |
| Mountain Fresh Plus | Mountain Fresh Plus | 71.8 % | 1,058.1 index |
| Legend | Legend OP | 42.5 % | 728.3 index |
| Plum Regal | Plum Regal | 31.3 % | 894.5 index |
| Mr. Stripey | Mr Stripey | 11.9 % | 203.6 index |
| Jasper | Jasper | 8.6 % | 99.3 index |
| Mountain Merit | Mountain Merit | 3.1 % | 220.9 index |
| Defiant PhR | Defiant PhR | 2.3 % | 137.2 index |
| Iron Lady | Iron Lady | 1.6 % | 125.2 index |
| Mountain Magic | Mountain Magic | 1.3 % | 78.3 index |
| Matt's Wild Cherry | Matt's Wild Cherry | 0 % | 26.4 index |
- Best AUDPC of the resistant entries: 93% control against the susceptible check.
- 98% control against the susceptible check.
- Homozygous for both Ph2 and Ph3.
- Ph3 only. An order of magnitude more disease than the Ph2+Ph3 entries in the same field.
- Ph2 only.
- Ph1 only.
- Susceptible check, carrying no resistance gene.
How these numbers were produced
Visual severity rating under natural infection. Plants are exposed to whatever inoculum arrives on its own rather than being deliberately inoculated, and the proportion of leaf tissue showing symptoms is assessed by eye on repeated dates. Natural infection is the realistic test but not a controlled one: disease pressure varies across a field and between seasons, so a low severity means the variety resisted what actually arrived that year, not that it would resist a heavier or different challenge.
Area under the disease progress curve. Repeated severity ratings across a season are integrated into a single index, so a variety that resists early and collapses late is not scored the same as one that stays clean throughout. It is a relative measure with no natural units: the number is only interpretable against the other entries rated on the same dates in the same trial, and cannot be compared across trials.
Entries not published here
This trial grew 13 entries. AMSeed publishes results for 11 of them. The rest are listed by name below with the reason their numbers are withheld, so the trial is represented as what it actually was rather than as the slice we happen to cover.
| Entry | Why no result is shown |
|---|---|
| Lemon Drop | Not yet a record in AMSeed. A tomato of this name; not the Capsicum baccatum of the same name held here. |
| West Virginia | Not yet a record in AMSeed. |
What this trial does not establish
No fungicides were applied, so this is the harder and more informative of the two seasons, but it is still one site in one year under natural infection. AUDPC values are relative to the other entries rated on the same dates and cannot be compared with any other trial. A low severity here means the variety resisted the genotype that arrived, not late blight in general.
Growing conditions in New York · all trials · how AMSeed handles evidence
Sources & References
Evidence: 1 source, all independent references.
- Evaluation of Late Blight Resistant Tomato Varieties, 2013 · Cornell Long Island Horticultural Research and Extension Center (2013), University or Government