Screening for Antagonistic Yeasts to Manage Alternaria spp. in Organic Farming

Abstract

Early blight of potatoes when not controlled can lead to major yield loss. In organic farming, disease control methods using beneficial microorganisms are needed. This study aimed to use commercially available yeast strains to prevent early blight in organically grown potatoes. Six commercially yeast strains used in the food industry, mainly in baking, brewing and winemaking, were evaluated against Alternaria alternata and A. solani. An in vitro test was conducted to assess yeast antagonistic properties. Production of lytic exoenzymes by yeast strains was determined. In the greenhouse experiments, the abilities of yeast strains to colonize potato leaf surface and to minimize Alternaria symptoms on plants were assessed. Saccharomyces cerevisiae Coobra strain inhibited in vitro Alternaria mycelium growth and most effectively reduced Alternaria symptoms on inoculated plants (from approximately 60% to 9% for A. solani and 14% for A. alternata) after seven days. This strain produced the most enzymes, i.e., amylase, pectinase and protease. After eighteen days, only the S. cerevisiae Coobra population was isolated from the leaves. In conclusion, the Coobra strain shows antagonistic properties against Alternaria spp. and is promising for further field tests.