Magnesium hydroxide and selected yeast strains as alternative substances applied towards limitation of potato light blight symptoms

Abstract: Phytophthora infestans, a significant pathogen in organic farming, particularly
affects potato crops. Researchers are exploring alternative control methods, including the use
of magnesium hydroxide (MH), a basic substance approved for organic farming. Laboratory (in vitro) and greenhouse (in planta) tests were conducted to assess the effectiveness of MH (125-500 µg/ml) in inhibiting the pathogen’s growth. While 125 µg/ml had no effect, higher
concentrations (250 and 500 µg/ml) significantly reduced mycelial growth by over 16 % and
30 %, respectively. MH also inhibited yeast growth which were tested against this pathogen,
particularly Saccharomyces cerevisiae, while Naganishia albidosimilis and Torulaspora
delbrueckii showed reduced but continued growth. MH (at 125 g/100 l water) shows potential
for managing late blight in combination with these yeasts. Greenhouse trials, including low
copper doses, have been completed, and field trials with varied strategies and potato varieties
are planned.