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The inheritance of resistance to an Ottawa isolate of H. sativum was studied in two varieties of barley, Anoidium and Br. 3962-4, resistant to the root rot and seedling blight phase of the disease. Anoidium and Br. 3962-4 each possess two dominant genes for resistance. The genes in Anoidium are allelic or closely linked with those of Br. 3962-4. No linkage was detected between the gene for awn character in linkage group 7 and the genes for resistance.

A satisfactory inoculation technique for testing the reaction of barley varieties and selections to root rot and seedling blight incited by Helminthosporium sativum was developed. Surface-sterilized seeds were grown in a planting mixture of 90 per cent sterilized white silica sand and 10 per cent sand-cornmeal inoculum of the Ottawa isolate of the fungus. Disease ratings of the seedlings were recorded after 21 days in a glass-enclosed chamber kept at a temperature of 20–22 °C. and a high humidity. A total of 600 varieties and selections were tested in this study. Fifty-one were classified as resistant and, of these, Anoidium, Br.3962-4, Lenta and Opal B were rated the highest. One hundred and forty-two entries were classified as susceptible. The remaining entries were intermediate in reaction.