VARIETAL TESTING FOR THE REACTION OF OATS TO DISEASES, ESPECIALLY COVERED SMUT

Abstract

Artificial inoculation of oat varieties was carried on for a period of five years. Sixty-one varieties of oats were tested in replicated plots for two years and thirteen for three years with a composite collection of inoculum of the covered smut organism, Ustilago levis (Kell. and Swingle) Mag. All gradations in reaction from high susceptibility to apparent immunity were found to exist.Dehulling the kernels previous to inoculation increased the incidence of smut approximately six times. Susceptible varieties gave relatively greater increases in smut when dehulled than did resistant varieties. The increase in smut obtained by dehulling was independent of the year in which the test was conducted.There were no significant differences in the total amount of smut obtained between any two of the seasons in which the tests were conducted but the season influenced the relative varietal reaction.Natural epidemics of halo-blight (Pseudomonas corona-faciens (Ch. Elliott) Stev.) and blast (cause unknown) provided opportunities for obtaining data on the reaction of a large number of oat varieties. Immunity from neither of these diseases was observed but marked varietal differences were noted.