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Trait Stem rust
Synonyms Black rust
Trait ID CO_321:0000118
Description The trait is scored for the response to the stem rust disease caused by Puccinia graminis f.sp. tritici.
Trait class Biotic stress
Type of measure Categorical
Scoring guide Detailed outlines for recording stripe, stem and leaf rust intensities in cereals based upon severity (percentage of rust infection on the plants) and field response (type of disease reaction) have been developed by Loegering.
Severity is recorded as a percentage, according to the modified 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 plants.
  • 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 possibly 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.

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