Preliminary assessment of the usefulness of magnesium hydroxide and selected yeast strains for protecting potatoes against potato blight in organic farming systems

Abstract: The pathogen Phytophthora infestans is a very important pathogen that causes
significant losses in potato yields, especially in organic farming. Many alternative methods and products are being tested to limit losses and extend the growing plant to allow tuber production. In vitro tests P. infestans was evaluated for its sensitivity to magnesium hydroxide. The concentration of 125 µg Mg(OH)₂ in ml PDA did not inhibit mycelial growth, while concentrations of 250 and 500 µg/ml were effective. At the concentration of 250 µg/ml, the coefficient of inhibition of linear growth of P. infestans was over 16 %, and at the concentration of 250 µg/ml almost 30 %. Yeast species selected in other tests and potentially useful in limiting growth of mycelium pathogen, in the presence of magnesium hydroxide developed less intensively than on the control plate. The concentration of 125 µg Mg(OH)₂/ml of PDA was neutral for colonies of all yeast species, while the concentration of 250 and 500 µg/ ml caused that yeasts Saccharomyces cerevisiae were completely inhibited, and Cryptococcus albidosimilis 117/10 isolate and Torulaspora delbrueckii grew less intensively.