Does the application of herbicides with distinct mechanisms of action change enzymatic activity and grain yield of Clearfield® canola?

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Herbicides have a high potential for phytotoxicity and generate oxidative stress, even on tolerant crops. The canola hybrid Hyola 571 CL obtained through Clearfield® technology shows tolerance to imidazolinones. Given the importance of this hybrid, this work assessed the effect of using herbicides with different mechanisms of action on the activity of antioxidant enzymes, ALA-D, gas exchange, and grain yield of canola hybrid tolerant to imidazolinones. Treatments applied to Hyola 571 CL canola hybrid were: control without herbicides, diclosulam, imazaquim, sulfentrazone, sulfentrazone + diuron pendimenthalin, flumioxazin, imazethapyr + imazapic, imazapic + imazapyr, imazethapyr, imazamox, nicosulfuron, chlorimuron, netsulfuron-methyl, iodosulfuron, and pyroxsulam. Seven, 14, 21, and 28 days after application we assessed herbicide phytotoxicity to canola. Antioxidant enzyme systems, variables related to plant physiology, and grain yield of Hyola 571 CL were also determined. It was observed that the hybrid, even tolerant, showed sensitivity to herbicides. Pendimethalin, flumioxazin, chlorimuron-ethyl, metsulfuron-methyl, and iodosulfuron were the most harmful to Hyola 571 CL. Commercial mixtures by [imazethapyr + imazapic] and [imazapic + imazapyr], as well as imazamox, were the most selective ones. Catalase was inhibited by most treatments. Sulfentrazone promoted the greatest negative interference along with its mixture with diuron and nicosulfuron, chlorimuron, and metsulfuron-methyl. The hybrid showed sensitivity to herbicides and the differences in gas exchange rates and other analyzes for the types of treatment do not result in productivity.