VIABILITY OF TILLETIA INDICA FUNGUS OF WHEAT AFTER LETHAL AND SUBLETHAL TEMPERATURE TREATMENTS

Abstract

Karnal bunt is an invasive disease of wheat caused by the soil borne smut fungus Tilletia indica Mitra. Due to international trade restrictions on Karnal bunt infected wheat, soil solarization has been investigated as a technique to prevent its establishment. Temperatures reached during solarization are 35°C - 60°C, depending on soil depth. These temperatures are lethal to many plant pathogens. Interestingly, studies indicate that sublethal doses of heat may be harmful to pathogens as well. Though heat is the major killing agent, soil moisture is thought to be a critical variable in soil solarization. In this study, teliospores of T. indica were exposed to heat treatments that included lethal and sublethal temperatures for 7 to 35 days. All heat treatments included 2 soil moisture regimes (10 or 25%). Teliospore germination was reduced to 0 over time for all treatments except one. Specifically, teliospores subjected to 22°C - 42°C had reduced germination of 4 and 17% after 35 days for 10 and 25% soil moistures, respectively. Results show that soil solarization is an effective method to help control the spread of T. indica.