Preliminary Studies of the Physiology of Sclerotinia Borealis, a Highly Psychrophilic Fungus

Abstract

X study was made of the influence of temperature on growth and oxygen uptake by Sclerotinin 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 a t 0 OC.The results indicated that the fungus is highly psychrophilic with an o p t i n~u~n temperature for growth a t 0 OC, a maximum a t approximately 15 "C, and a lninimurn below -5 "C. C u l t~~r e s grown a t 0 "C ceased to grow when transferred to temperatures above 15 OC but, within limits, resumed growth again after a lag when returned to 0 OC. The length of the lag period was proportional to both the degree and the duration of the temperature elevation.The opti~nirtn temperature for oxygen uptake was 25 "C, the rate remaining linear a t this temperature during a 6-hour incubation period. The rate a t 25 "C declined slowly over a period of 4 days but the rate a t 1 OC declined to a similar degree. The QIO for oxygen uptake was very low, the rate a t 25 "C being only double that a t 1 OC.

Cold adaptation in the phytopathogenic fungi causing snow molds

“…Oxygen uptake by T. ishikariensis was optimal at 20°C (maximum growth temperature), about 15°C higher than its optimal growth temperature (5°-10°C) (Dejardin and Ward 1971). Similar results were obtained from S. borealis (Ward 1966a(Ward , 1968a and C. psychromorbidus (Ward 1966b).…”

“…Two-dimensional native-gel electrophoresis at different temperatures revealed that some intracellular proteins of T. ishikariensis group III isolates were modifi ed (probably denatured) at the lethal temperature of 15°C (Hoshino et al 1997a). Oxygen uptake of snow molds at maximum growth to sublethal temperatures is higher than at its optimum growth temperatures (Ward 1966a(Ward ,b, 1968aDejardin and Ward 1971). Excess respiration probably induces denaturing of intracellular proteins by oxidation.…”

Non-gramineous hosts of Myriosclerotinia borealis

“…The slowest growth of colonies was observed at 0~ for all isolates, but this temperature was not totally inhibitory because the isolates grew throughout the experiment. The isolates differed slightly in their response to temperature from 5 to 15~ but all appeared to have an optimum temperature of 5~ Thus, all isolates from four non-gramineous plants as well as isolate of M. borealis on D. glomerata were apparently psychrophilic, though the optimum temperature for growth was higher than that reported by Ward (1966).…”

“…However, re-isolation from sclerotia in old cultures often avoids abnormalities in the subculture. In addition, when inoculum was taken from the inside of a colony, mycelial growth was often abnormal or retarded, as pointed out by Ward (1966).…”

“…This psychrophilic fungus has a lower optimum temperature than other snow mold fungi (Ward, 1966) and can develop on slightly frozen ground under snow. In Japan, the fungus is found in the less snowy areas in eastern and north-eastern Hokkaido, where snow comes later in winter and the depth of ground freezing is larger than the other areas of Hokkaido (Tomiyama, 1955).…”