ABSTRACT : To investigate the changes of the resistance to prochloraz of species causing bakanae disease,
isolates were collected from various regions in Korea, and pathogenicity tests were performed using rice seeds. Minimum
inhibitory concentration (MIC) and effective concentration of 50% (EC50) values of isolates were determined using the agar dilution
method. High frequency distribution of MIC values of prochloraz against isolates collected in 2006~2007 and 2013~2014 years
were 3.125~6.25 μg/mL and 6.25~12.5 μg/mL, respectively. The mean EC50 value of isolates increased from 0.3142 μg/mL in
2006~2007 to 0.8124 μg/mL in 2013~2014. Based on the EC50 value of isolates collected in 2006~2007, the resistant baseline
of prochloraz was determined as 0.6 μg/mL. Compared with the ratio of resistant isolates in 2006~2007, the ratio of resistant
isolates in 2013~2014 increased from 6.5% to 41.6%.