Influence of Environal Factors on the Infection of Sorghums and Oats by Smuts Ii. Experiments With Covered Smut of Oats and General Considerations

Abstract

In a previous publication the writers (38) have described their experiments to determine the influence of environal factors on the infection of sorghums by covered and loose kernel smuts. The present paper takes up a similar series of experiments on the infection of oats by Ustilago levis (K. & S.) Magn. The methods employed were essentially the same as described for the previous studies.In 1922 a preliminary test was made to determine the influence of moisture on the infection of Avena nuda L. var. inermis (S. N. 30) by both Ustilago avenae (Pers.) lens. and U. levis (K. & S.) Magn. The experiment was planned primarily to determine whether sand would be a suitable substratum for carrying out an extended series of experiments on the influence of temperature, moisture, and other factors on infection. The sand used passed through a zo-mesh sieve but not through a 4o-mesh sieve, and had a reaction of pH 7.2. The seeds were germinated in the laboratory at a temperature of 19°-22°C. Four soil moistures were used-20, 40, 60, and 80 percent. The results are given in table I. TABLE I. Influence of Moisture on Infection of Avena nuda L. var. inermis (S. N.30) by Ustilago avenae and U. levis, I922; Laboratory Temperature, Sand, pH 7.2

Physiologic Races of Oat Smuts

“…A few varieties of A. sativa were infected by both collections, others remaining free. These results were confirmed by Sampson in 1925. Reed (1927 reported the occurrence of two distinct specialized races of the loose smut on the red oats, one on strains of Fulghum and the other on Red Rustproof.…”

“…Race 10 is based on a collection from Canada and, in the early experiments, was grouped with Race 1 (Reed, 1929), from which it can be separated, since Avena strigosa subsp. pilosa var, alba is resistant to it and susceptible to Race 1.…”

“…Reed (1927 reported the occurrence of two distinct specialized races of the loose smut on the red oats, one on strains of Fulghum and the other on Red Rustproof. Reed (1929) described 11 races of loose smut and 5 of covered on the basis of their behavior on various oat species and varieties, the smut collections having been obtained from widely separated regions. Reed and Stanton (1932) published additional data on the smuts of the red-oat group, describing a specialized race of the covered smut on Fulghum.…”

“…Reed and Stanton (1932) published additional data on the smuts of the red-oat group, describing a specialized race of the covered smut on Fulghum. Reed (1932) found that Black Mesdag, hitherto a recognized resistant variety of oats, was susceptible to the Fulghum covered smut. Reed and Stanton (1936) published data indicating that there was more than one race of covered smut on the Fulghum varieties.…”

“…In an earlier publication (Reed, 1929), numbers were given to 11 specialized races of Ustilago auen.ae and 5 of U. levis. In order to avoid possible confusion, the original race numbers have been retained, although it might be more convenient to renumber the races on the basis of their apparent relationship.…”