Temperature Effect on Rhizoctonia solani Analyzed by Microcalorimetry

Temperature is one of the factors playing an important role in fungi growth and spread. The aim of this study was to determine the effect of temperature on the growth of ten Rhizoctonia solani isolates. Colony Growth Rate (GR) was measured in potato-agar-dextrose cultures and Metabolic Efficiency (ME) by isothermal microcalorimetry in R. solani isolates growing in a temperature range of 10 to 40°C at 5°C intervals. The apparent activation Energy (Ea) was determined in the range of 15 to 30°C. Different values of Ea were found for each of the strains analyzed. GR increased as temperature increased up to 30°C, showing the highest values between 25°C. ME decreased as temperature increased in nine out of ten isolates, reaching an optimum for the different isolates between 15 and 25°C. Both GR and ME analyses showed different behaviors for each isolate. R. solani AG4 isolates showed a variable response to the same temperature of exposure and it appears that microcalorimetry is more sensitive in detecting early effects of heat stress.