The Measurement of Disease Severity in Cereal Smut

  • J. V. Groth
  • C. O. Person
  • T. Ebba
Part of the Basic Life Sciences book series (BLSC, volume 8)


For smut diseases of cereal crops in which the presence of disease is signaled by the occurrence of diseased culms, the tradition has been developed whereby disease severity is measured in percentages, either of plants or of culms, which show the disease. However, the data that have accrued have contributed relatively little to an understanding of either the disease or host resistance to it. In this study the percentages of infected tillers on diseased plants (within-plant disease severity) were both recorded and were found, on analysis, to be strongly correlated. Although the strong correlation suggested a general identity of genes responsible for among-and within-plant disease severity, other aspects of the analysis suggest that the fungus must pass through two distinct barriers, or thresholds, in order to produce teliospores. If the first threshold is surmounted, the fungus will be able to cause smutting in at least one tiller of the plant (as measured by among-plant disease severity); if the second threshold is also crossed, additional culms will also be smutted (as measured by within-plant disease severity). One can regard the individual culm as having two separate (but not independent) opportunities of remaining healthy following inoculation of the seed. Both are measured and defined in terms of probability.


Barley Cultivar Genotypic Combination Disease Reaction Host Fitness Loose Smut 
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Copyright information

© Plenum Press, New York 1977

Authors and Affiliations

  • J. V. Groth
    • 1
  • C. O. Person
    • 2
  • T. Ebba
    • 3
  1. 1.University of MinnesotaSt. PaulUSA
  2. 2.University of British ColumbiaVancouverCanada
  3. 3.Institute of Agricultural ResearchAddis AbabaEthiopia

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