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| Establishment of Sensitive Baselines and Resistance Monitoring of Corynespora cassiicola to Diethofencarb and Procymidone |
| WEN Zhihao，ZHU Guangxue，SUN Bingxue，ZHOU Rongjia，XIE Xuewen，CHAI Ali，LI Lei，FAN Tengfei，LI Baoju*，SHI Yanxia* |
| State Key Laboratory of Vegetable Biobreeding，Institute of Vegetables and Flowers，Chinese Academy of Agricultural Sciences，Beijing 100081，China |
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Abstract In order to determine the resistance level of Corynespora cassiicola from different regions（Shandong and Liaoning）to diethofencarb and procymidone，in this experiment，the mycelial growth rate method was used to determine the sensitivity of C.cassiicola to diethofencarb and procymidone and the sensitive baselines of C.cassiicola to diethofencarb and procymidone were established．The resistance of C.cassiicola to diethofencarb and procymidone were detected with discriminating dose method．The results showed that the mean EC50 value of C.cassiicola to diethofencarb was（0.22 ± 0.06）μg·mL-1 and the mean EC50 value of C.cassiicola to procymidone was（2.75 ± 0.91）μg·mL-1．The sensitivity frequencies of both showed a continuous unimodal curve，overall following a normal distribution，which can serve as a sensitive baseline for the sensitivity of C.cassiicola to diethofencarb and procymidone．By monitoring the resistance level of 828 C.cassiicola isolates，it was found that the resistance level of C.cassiicola to diethofencarb and procymidone is continuously increasing．The level of resistance of strains in Shandong to diethofencarb and procymidone increased from 58.06% and 43.55% in 2017 to 91.30% and 78.99% in 2021．The level of resistance of strains in Liaoning to diethofencarb and procymidone increased from 67.44% and 53.49% in 2017 to 82.14% and 83.33% in 2021．It indicates that C.cassiicola has a high resistance risk to diethofencarb and procymidone．It is recommended to alternate or mix the application of diethofencarb and procymidon with other types of fungicides in cucumber production to delay the development of resistance．
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Received: 12 April 2023
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