The Cardinal Temperatures and pH Response of Thielaviopsis Basicola

SUMMARY

On oatmeal agar, isolates of Thielaviopsis basicola from 5 widely separated areas had similar temperature-response growth curves. No isolate grew at 8° C, or at 36° C. Maximum growth for all isolates occurred between 22 and 28° C, contrary to previous reports of an optimum of 28–30° C. In buffered potato-dextrose-broth no growth occurred below 3.3 or above 7.2. Optimum growth occurred between pH 3.9 and 6.2. In the presence of excess calcium in potato-dextrose-broth the fungus grew sparsely at pH 3.0, and the mycelial mat weights were increased over cultures grown in medium lacking excess calcium and grown at comparable pH levels. In a buffered synthetic medium little or no growth occurred below pH 3.0 or above 8.0. The addition of excess calcium to this medium did not change these values but did increase the yield of mycelium.