TEMPERATURE AND CULTURAL STUDIES ON UROCYSTIS TRITICI KOERN.
A study of the effect of temperature on the infection of wheat by Urocystis tritici was made using Petri dishes in incubators held at various temperatures from 9° to 26 °C. The seedlings were transferred to pots as soon as the plumules broke through the coleoptiles. The percentages of infection obtained at various temperatures were as follows:—10.8% at 9° to 14 °C., 13.8 at 16°, 21.1 at 18°, 26.1 at 20°, 15.7 at 22°, 6.9 at 24°, and 3.0% at 26 °C. Growth studies of three geographical isolates of U. tritici were made on 12 different artificial media. Cultures were obtained by plating bits of disinfected unbroken, fresh, smutted plant tissue. The smut organism was found to be culturable on various media, though its growth rate was rather slow. The three isolates grew well on potato dextrose agar, Thaxter's hard agar, 4% sucrose potato agar, wheat seedling agar, and Czapek's synthetic medium, and were found to differ characteristically on five different media.