The Effect of Some Physical Factors on the Chlamydospores and Mycelium of Loose Smut of Wheat - Ustilago iritici (Pers.) Rostr.

Abstract

Summary Trials were undertaken to study the direct effect of different temperatures and time of exposure under anaerobic conditions on the chlamydospores and mycelium of loose smut of wheat — Ustilago tritici (Pers.) Rostr. — with different moisture contents. Several different laboratory techniques were employed to test the effect of anaerobic conditions on loose smut of wheat. The chlamydospores of loose smut of wheat, used in the trials, were of various origin. Chlamydospores from the ears of different wheat varieties were tested. They were 1–5 months old, and kept at the temperatures ranging from 8 to 20 °C during storage. No chlamydospore germinability and no wheat loose smut mycelium growth were observed during exposure to anaerobic conditions. When the exposure to anaerobic conditions was stopped and the chlamydospores and mycelium were subjected to aerobic conditions (grown in Petri dishes on sweet wort agar), the chlamydospore germination and mycelium growth were found to be inhibited, or the parasite was killed. It was found that there were some correlations between the mentioned factors affecting loose smut. Anaerobic conditions were more effective when the temperatures and the moisture levels in the spores and mycelium were higher and the time of exposure longer. The study has yielded new findings supporting our theory ( Ujevic 1958) according to which the mycelium of loose smut in grains is killed as a result of a direct complex and selective effect of the mentioned factors on the parasite. Our theoretical conclusions differ from the to-date theory asserting that the parasite mycelium is killed by the toxic substances produced in grains during seed disinfection by some physical methods.