The influence of sodium salts of the macronutrients nitrate, phosphate, sulfate, and chloride; and the micronutrients iron, calcium, copper, cobalt, nickel, and manganese on growth of Phytophthora infestans and synthesis of glycoalkaloids by the fungus was investigated. Maximum growth levels were demonstrated when 0.04% phosphate, 0.04% chloride, or 2–5 mg of iron/liter were employed in the culture medium. Results indicate that upon substitution of the individual sodium salts of the macronutrients for the potassium and magnesium salts or addition of sodium chloride to the basal medium, the concentration of glycoalkaloids synthesized by the fungus decreased significantly. Regression analysis showed that the concentration of phosphate in the medium had the most influence on the amount of glycoalkaloids produced by P. infestans. Increasing the phosphate concentration in the medium resulted in increasing amounts of glycoalkaloids being produced by the fungus. As the mass of mycelium increased in media containing different amounts of phosphate, the quantity of glycoalkaloids synthesized by the fungus decreased.

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Author notes

1University of Wisconsin.

2Department of Biology, Utah State University.

3Department of Nutrition and Food Science, Utah State University.