Resistance of Some Botrytis cinerea Isolates to Fungicides Benomyl, Iprodione and Fenhexamid in West Azarbaijan Province

Gray mold, caused by Botrytis cinerea, is one of the most important diseases of grape worldwide. Although, it has recently become a major problem in West Azarbaijan province causing significant yield losses, no fungicide has been registered to control the disease. In currentstudy, susceptibility of 103B. cinerea isolates collected from vineyards in different regions of the province was assessed to three fungicides including benomyl, iprodione and fenhexamid using discriminatory doses of fungicides in in vitro conditions. Results indicated that isolates resistant to benomyl and iprodione were widely distributed across the surveyed regions at different frequencies, whereas the isolates resistant to benomyl were not detected in the samples collected from Salmas. Isolates resistant to fenhexamid were detected at low frequency in six sampling locations. The results also showed that the isolates with multiple resistances to two fungicides were widely distributed in the studied regions. It is likely that application of benomyl and iprodione or fungicides with similar mode of action to control fungal diseases in grape other than gray mold, have resulted in selection of B. cinereastrains resistant to these fungicidesas non-target pathogen leading to increase in their frequencies. The results revealed that the use of benomyl and iprodione or fungicides with similar mode of action would be ineffective to control the disease, while fenhexamid seems to be an alternative and effective fungicide to be registered and used to control the disease.