白术黑斑病菌对甲基硫菌灵和腐霉利的抗性检测及对咪鲜胺敏感性基线的建立

黑斑病是影响白术种植的主要病害之一，2015—2017年从浙江省磐安、天台、新昌和嵊州4地采集、分离得到137株白术黑斑病菌Alternaria alternata，采用菌丝生长速率法检测其对甲基硫菌灵和腐霉利的抗性。结果表明:供试的黑斑病菌群体 (n = 137) 对甲基硫菌灵的高水平抗性频率为77.4%，中等水平抗性频率为22.6%，未检测到敏感菌株；对腐霉利的抗性频率为20.4%，含21株低水平抗性菌株和7株中等水平抗性菌株。7种杀菌剂的室内毒力测定结果表明:咪鲜胺对白术黑斑病菌的活性最高，EC₅₀值为0.15 mg/L。供试的137株白术黑斑病菌对咪鲜胺的EC₅₀值分布在0.05~0.87 mg/L之间，平均EC₅₀值为 (0.29 ± 0.11) mg/L，可作为敏感性基线。

Resistance of Alternaria alternata to thiophanate-methyl, procymidone and its baseline sensitivity to prochloraz

Black spot, caused by Alternaria alternate, is one of the main diseases of Atractylodes macrocephala in China. In this study, resistance of 137 A. alternate isolates to thiophanate-methyl and procymidone was evaluated using mycelial growth rate method. The isolates were collected from Pan''an, Tiantai, Xinchang and Shengzhou in Zhejiang Province from 2015 to 2017. Results showed that the frequency of A. alternata population (n=137) with high-level and medium-level resistance to thiophanate-methyl was 77.4% and 22.6%, respectively, and no sensitive isolates were observed. The resistance frequency to procymidone was 20.4%, wherein 21 isolates have low-level resistance and 7 isolates have medium resistance. Prochloraz showed the strongest activity against the mycelial growth of A. alternata among the 7 tested fungicides with the EC₅₀ value of 0.15 mg/L. Next, the baseline sensitivity of A. alternata to prochloraz was established. The EC₅₀ values for the tested population (n=137) to prochloraz varied from 0.05 to 0.87 mg/L, mean value is (0.29 ±0.11) mg/L, and their mean EC₅₀ value could be used as the sensitive baseline.