Sensitivity determination and resistance mechanism of Sclerotium rolfsii to difenoconazole

Abstract

BACKGROUNDPeanut stem rot, caused by Sclerotium rolfsii, has become increasingly prevalent in China, leading to significant yield losses in peanut production. To effectively manage peanut stem rot, we assessed the potential application of difenoconazole against peanut stem rot.RESULTSDifenoconazole has a good inhibitory effect on the mycelial growth of S. rolfsii, with half maximal effective concentration (EC50) values ranging from 0.10 to 1.58 μg/mL and an average of 0.33 ± 0.02 μg/mL. Nonetheless, a small percentage of wild‐type isolates exhibiting low resistance to difenoconazole were identified in the field. The primary reason for S. rolfsii resistance to difenoconazole was found to be attributed to the overexpression of CYP51. In addition, a small number of resistant isolates also exhibited multidrug resistance through the overexpression of efflux pump genes atrB and atrD. Pot experiments revealed that difenoconazole demonstrated superior protective efficacy against peanut stem rot, with mist spray treatment exhibiting better control efficacy compared to root drench treatment. Specifically, at a concentration of 100 μg/mL, the protective efficacy of difenoconazole mist spray against peanut stem rot reached 65.24%, which was statistically similar to that of tebuconazole. Furthermore, no significant correlation was observed between sensitivity to difenoconazole and mefentrifluconazole, benzovindiflupyr, boscalid, thifluzamide, carboxin, or picoxystrobin.CONCLUSIONTo delay the emergence of resistant populations, we recommend early‐stage application of difenoconazole via spraying for peanut stem rot management, alongside the judicious use of fungicides with no cross‐resistance like thifluzamide and boscalid for optimal control. © 2024 Society of Chemical Industry.