Sensitivity Detection of Phytophthora infestans to Azoxystrobin and Fluopicolide

[Aims]The aims were to investigate the development of fungicide resistance of Phytophthora infestans to azoxystrobin and fluopicolide in Yunnan province.[Methods]The sensitivities of 97 P.infestans isolated from Yema district in Yunnan province during 2012 and 2014 to azoxystrobin and fluopicolide were determined in vitro by using mycelium growth rate method;and the sensitivities to azoxystrobin plus 10 mg/L of salicylhydroxamic acid(SHAM)were also determined.[Results]The mycelium growth of all isolates were completely inhibited by 1 mg/L of azoxystrobin,which indicated that all isolates were sensitive to azoxystrobin;the EC_(50) values for population from 2012,2013 and 2014 were ranged from 0.279-0.884,0.252-0.582 and 0.171-0.710 mg/L,respectively,and there was no significant difference.In addition,the mean EC_(50) value was 0.427 mg/L for all 97 isolates.[Conclusions]The resistance of P.infestans to azoxystrobin and fluopicohde has not been occurred in Yema district,Yunnan province;the mean EC_(50) value for all 97 isolates can be a sensitivity baseline for P.infestans to fluopicolide,which can be a reference in resistance monitor in the future.