PRELIMINARY STUDIES OF THE PHYSIOLOGY OF SCLEROTINIA BOREALIS, A HIGHLY PSYCHROPHILIC FUNGUS

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Abstract
A study was made of the influence of temperature on growth and oxygen uptake by Sclerotinia borealis Bub. and Vleug. Growth was measured as the increase in diameter of colonies on agar media and oxygen uptake, by conventional manometric procedures with cells removed from shake cultures incubated at 0 °C.The results indicated that the fungus is highly psychrophilic with an optimum temperature for growth at 0 °C, a maximum at approximately 15 °C, and a minimum below −5 °C. Cultures grown at 0 °C ceased to grow when transferred to temperatures above 15 °C but, within limits, resumed growth again after a lag when returned to 0 °C. The length of the lag period was proportional to both the degree and the duration of the temperature elevation.The optimum temperature for oxygen uptake was 25 °C, the rate remaining linear at this temperature during a 6-hour incubation period. The rate at 25 °C declined slowly over a period of 4 days but the rate at 1 °C declined to a similar degree. The Q10for oxygen uptake was very low, the rate at 25 °C being only double that at 1 °C.