Results are presented of tests conducted at the University of Alberta, Edmonton, during the years 1931–34, to determine the relative resistance of barley varieties to the covered smut disease caused by Ustilago hordei.Extensive field trials, including 138 varieties, carried out in 1931, with hulled seed gave inconclusive results owing to low infection percentages. Junior and Eureka, two naturally hulless varieties, evidenced high susceptibility with 66 and 42% infection respectively. Field tests of a number of standard varieties in 1932 in which the seed was dehulled with sulphuric acid, resulted in an increase in the percentage of smutted plants. Unfortunately, the acid treatment of the kernels caused a general impairment in germination which lessened somewhat the significance of the results obtained. In 1934, the comparative infections and stands of varieties grown from hulled, hand-dehulled, scarified and acid-dehulled seed were determined. The data were treated statistically by the analysis of variance method. Significant variations due to varieties, treatments and interaction of varieties and treatments were obtained with regard to both percentage infection and percentage stand. All three of the dehulling measures increased smut infection significantly. Highest infection percentages resulted from hand-dehulled seed, followed by acid-dehulled and scarified seed in the order mentioned.The least reduction in stand resulted from hulled seed and the greatest from acid-dehulled seed. Scarified and hand-dehulled seed gave stands intermediate in numbers. Distinct varietal differences existed in thickness of hull or in the resistance of the hull to acid treatment. The average percentage stands of the different varieties tended to be directly proportional, and the average percentage smut infection inversely proportional to the amount of hull remaining on the kernels following acid treatment. Varieties grown from acid-dehulled and scarified seed were found to be delayed in heading [Formula: see text] and [Formula: see text] days respectively as compared with varieties grown from hulled or hand-dehulled seed, There was a tendency for the later varieties to be more susceptible to covered smut than the earlier ones.The varieties used in these investigations differed greatly in their reaction to covered smut. A fair degree of correlation was found to exist between the varietal infection percentages induced in 1932 by acid-dehulled seed and those induced by either hand-dehulled or acid-dehulled seed in 1934.Two distinct physiologic forms of U. hordei were found in collections gathered from six points in central Alberta. These are readily distinguished by their reaction on the varieties Eureka and Canadian Thorpe or Hannchen.From the experimental data it was concluded that the following varieties showed resistance to covered smut:Six-rowed, hulled types—O.A.C. No. 21, Atlas, Sacramento Glabron, Velvet, Leiorrhynchum, Wisconsin Barbless No. 38, Shaw, Sol and Success.Two-rowed, hulled types—Spartan, Golden Pheasant and Horn.Hulless types—Himalayan, New Era, Russian, Mongolian and Burbank.The following varieties showed susceptibility to one or more of the smut collections used:Six-rowed, hulled types—Bearer, Lapland, Star, Manchurian, Peatland, Trebi, Silver King, Vaughn, Comfort, Regal, Newal and Colsess.Two-rowed, hulled types—Binder, Canadian Thorpe, Duckbill, Gold, Hannchen, Swanneck and Charlottetown.Hulless types—Junior, Eureka, Improved White Hulless and Trifurcatum.
Field trials and tribulations-making sense of the regulations for experimental field trials of transgenic crops in Europe
