Resistance-phenotype and Stability of Botrytis cinerea to Three Fungicides

With MIC and colony diameter methods, the resistance-phenotype and stability of 188 Botrytis cinerea isolates, collected from Jinzhong, Jinnan, Jindongnan and Jinbei regions of Shanxi province, to 3 fungicides were tested for evaluating the resistance situation and predicting the trend of resistancedevelopment. The results showed that resistance-phenotype to carbendazim (Ben) could be divided into sensitive (S), low or moderate (RM) and high resistant (R) groups, whereas to procymidone (Dic) and diethofencarb(NPC) could be classified into sensitive (S) and resistant (R) groups. Eight different resistance-phenotype to three fungicides, MBC, Dic and NPC, have been detected, they were RRR, RRS, RSR, RSS, RMRS, RMSR, RMSS and SSR. The frequency distribution of the resistance-phenotype in different regions is varied with the history and level of fungicide use, and was consistent with the result of resistance monitoring. The results of stability tests of 55 isolates with different resistance-phenotype indicated that after ten generations of subculture in the absence of fungicides, RRR and RSS phenotypes exhibited most stable, but other phenotypes have been mutated to different extent. All of RMSS and RMRS phenotypes mutated, and unstable isolates accounted for 52.7%. The variation trend of resistance to Ben was from sensitive or low-level of resistance to high-level of resistance, whereas the resistance to Dic inclined to vary from resistance to sensitivity, and the resistance to NPC was relatively stable.