scoring stripe rust

Scoring stripe rust

Detailed outlines for recording stripe 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.

Peterson R. F., Campbell A. B. and Hannah A. E. 1948. A diagrammatic scale for rust intensity on leaves and stems of cereals. Can. J. Res. 26, 496–500.