Effects of Inorganic Salts, Carbonate-Bicarbonate Anions, Ammonia, and the Modifying Influence of pH on Sclerotial Germination ofSclerotium rolfsii

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Abstract
Eruptive and hyphal germination on 1% Noble water agar and on 1% Bacto water agar, respectively, of dried sclerotia of 2 isolates of S. rolfsii were totally inhibited in buffered systems above pH 7.0, but sclerotia remained viable even at pH values as high as 9.7. Maximum germination of sclerotia was observed on agar adjusted to pHs ranging from 2.0-5.0. Of 33 inorganic salts (primarily anions of Ca, ammonium, K, Na and Li) tested for ability to inhibit sclerotial germination at 10, 30, and 50 mM concentrations; 18 salts reduced germination at the 50 mM concentration to < 10% of that in plates not receiving salts. of the cations tested, Ca2+, K+ and Na+ were less inhibitory than Li+ and NH4+. The anions acetate, formate and phosphate reduced germination, whereas nitrate, sulfate, and chloride had no significant effect. Calcium propionate, ammonium acetate, ammonium molybdate, potassium sorbate, sodium formate, lithium chloride, tris ((hydroxymethyl)aminomethane), and the carbonate and bicarbonate salts of ammonium, K, Na and Li prevented germination, but only the carbonate and bicarbonate salts were fungicidal. The H+ concentration of the agar had a profound influence on toxicity of the salts to sclerotia; at high pH (about 8.6), but not at low pH (about 6.0), ammonium salts and carbonate and bicarbonate salts were fungicidal to sclerotia, apparently due to the prevalence of free NH3 and CO32--HCO3-, respectively, at high pH.