In vitro evaluation of carbendazim resistant Colletotrichum gloeosporioides isolates of grapes for sensitivity to QoI and DMI fungicides.

Abstract

Carbendazim is the only systemic fungicide recommended for anthracnose disease management in India, but its frequent use leads to increase in resistant strains compromising disease management. The present study was undertaken to find out carbendazim resistance in natural field population of Colletotrichum gloeosporioides, the causal agent of grape anthracnose. Three hundred and seventy nine isolates of C. gloeosporioides from the culture collection of ICAR-National Research Centre for Grapes, Pune, India, were screened for determining minimum inhibitory concentration (MIC) of carbendazim. Most of the isolates were found to be moderately resistant MIC, >10 - <100 μg/ml to highly resistant MIC, >1000 μg/ml; while only five isolates were sensitive to carbendazim with MIC value less than <1 μg/ml. Fifty three isolates with broad range of MIC for carbendazim were selected to study their sensitivity to fungicides of different chemical groups, quinone outside Inhibitors (QoI), demethylation Inhibitors (DMI), copper oxychloride and propineb apart from carbendazim. The effective concentration at 50% mycelium inhibition (EC50) values ranged from 0.09 to 75.39 μg/ml for carbendazim, 243.79 to 399.46 μg/ml for copper oxychloride, and 220.31 to 6664.50 μg/ml for propineb. These isolates were also found sensitive to azoxystrobin with EC50 values 0.22 to 6.63 μg/ml and for flusilazole 0.04 to 2.14 μg/ml, which are recommended for control of downy and powdery mildews, respectively.