Detailed outlines for recording stem rust intensities in cereals are based upon:
- Severity (percentage of rust infection on the plant) and
- Field response (type of disease reaction).
Severity is recorded as a percentage, according to the modifed Cobb scale. This recording process relies upon visual observations, and it is common to use the following intervals: Trace / 5 / 10 / 20 / 40 / 60 / 100 percent infection.
Field response is recorded using the following letters:
| O | No visible infection on plant. |
| R | Resistant: visible chlorosis or necrosis, no uredia are present. |
| MR | Moderately Resistant: small uredia are present and surrounded by either chlorotic or necrotic areas. |
| M | Intermediate: variable sized uredia are present; some with chlorosis, necrosis, or both. |
| MS | Moderately Susceptible: medium sized uredia are present and possible surrounded by chlorotic areas. |
| S | Susceptible: Large uredia are present, generally with little or no chlorosis and no necrosis. |
Severity and field response readings are usually combined.
For example:
tR = Trace severity with a resistant field response.
5MR = 5% severity with a moderately resistant field response.
60S = 60% severity with a susceptible field response.
Figure 1. Examples of scoring Stem rust severity
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Figure 2. Examples of scoring Stem rust field responses
| R | MR | MS | S |
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