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 


Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.


  1. Batts, C. C. V. and Jeater, A. (1958). The development of loose smut (Ustilago tritici) in susceptible varieties of wheat, and some observations on field infection. Brit. Mycol. Soc. Trans. 41:115125.CrossRefGoogle Scholar
  2. Briggs, F. N. (1926). Inheritance of resistance to bunt, Tilletia tritici, in wheat. J. Agri. Res. 32: 973–990.Google Scholar
  3. Churchward, J. C. (1937–1938). Studies on physiologic specialization of the organisms causing bunt in wheat and the genetics of resistance to this and certain other wheat diseases. Roy. Soc. N S W 71:362–384; 547–590.Google Scholar
  4. Clark, J. A., Quisenberry, K. S., and Powers, L. (1933). Inheritance of bunt reaction and other characters in Hope wheat crosses. J. Agric. Res 46: 413–425.Google Scholar
  5. Gaines, E. F. (1923). Genetics of bunt resistance in wheat. J. Agri. Res. 23: 445–480.Google Scholar
  6. Groth, J. V. and Person, C, O. (1975). Estimating the efficiency of partial-vacuum inoculation of barley with Ustilago hordei. Phytopathology 66: 65–69.Google Scholar
  7. Milan, A. (1939). Sensibilità per la Ustilago tritici (Pers.) Jens. di alcuni ibridi normali di frumento. Riv. Pathol. Veg. 29: 71–84.Google Scholar
  8. Oort, A. J. P. (1947). Specialization of loose smut of wheat. A problem for the breeder. Tijdschr. Plantenziekt. A. 53: 25–43.CrossRefGoogle Scholar
  9. Reed, G. M. and Stanton, T. R. (1938). Inheritance of resistance to loose and covered smuts in Markton hybrids. J. Agri. Rea 56:159175.Google Scholar
  10. Ruttle, M. L. (1934). Studies on barley smuts and on loose smut of wheat. NY Agric. Exp. Sta. Tech. Bull. 221: 48 pp.Google Scholar
  11. Steel, R. G. D. and Torrie, J. H. (1960). Principles and Procedures of Statistics, 481 pp. McGraw-Hill, New York.Google Scholar
  12. Tapke, V. F. (1929). Influence of varietal resistance, sap acidity, and certain environmental factors on the occurrence of loose smut in wheat. J. Agri. Res. 39: 313–339.Google Scholar
  13. Tapke, V. F. (1931), Intluence of humidity on floral infection of wheat and barley by loose smut. J. Agri. Res. 43: 503–516.Google Scholar
  14. Tapke, V. F. (1945). New physiologic races of Ustilago hordei. Phytopathology 35: 970–976.Google Scholar
  15. Thomas, P. L. and Person, C. (1965). Genetic control of low virulence in Ustilago. Can. J. Genet. CytoL 7: 583–588.Google Scholar
  16. Welsh, J. N. (1932). The effect of smut on rust development and plant vigor in oats. Sci. Agr. 13: 154–164.Google Scholar
  17. Woodward, R. W. and Tingey, D. C. (1941). Inoculation experiments with covered smut of barley. J. Amer. Soc. Agron. 33: 632–642.CrossRefGoogle Scholar

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

Personalised recommendations