Quantification of Multiple Herbicide Resistance in Phalaris minor Populations of the North-Western Indo-Gangetic Plains of India

Multiple resistance to different herbicides used for management of Phalaris minor Retz. in Northern India was quantified for its two populations—one susceptible and the other resistant to acetyl-CoA carboxylase (ACCase) inhibitor herbicide clodinafop-propargyl. Clodinafop-propargyl and pinoxaden at their recommended dose recorded complete control of clodinafop-propargyl susceptible P. minor population, whereas sulfosulfuron and mesosulfuron plus iodosulfuron at their recommended dose exhibited 48.5 and 51.5% control of this population. In clodinafop-propargyl-resistant P. minor population, sulfosulfuron and mesosulfuron plus iodosulfuron even at 4X dose did not cause any mortality; however, pinoxaden at 4X dose caused complete mortality at 30 DAS. Metribuzin plus clodinafop-propargyl applied at all the doses (0.25X, 0.5X, X, 2X and 4X) recorded complete mortality of both the populations. Application of different herbicides caused reduction in chlorophyll fluorescence and chlorophyll content index in leaves of both the populations in a dose-dependent manner. But the magnitude of reduction was higher in susceptible population as compared to the resistant population.