Evaluation of differential herbicide sensitivity in Chinese winter wheat varieties under mesosulfuron-methyl stress

Mesosulfuron-methyl, also known by its product name ‘Sigma’, is a sulfonylurea herbicide commonly used for weed control in China. However, it appears that mesosulfuron-methyl can have harmful effects on some winter wheat cultivars. Subordinate function analysis was applied to seven wheat varieties for their tolerance to Sigma herbicide and different sensitivity levels were observed. Varietal sensitivities ranked as follows (ranging from lowest to highest): Shannong129 > Yanmai19 > CA0547 > 040542 > Changzhi9578 > Fengyu3 > Shunmai1718. Two winter wheat varieties, Shannong129 and Shumai1718, with contrasting seedling herbicide sensitivities (lowest and highest sensitivity, respectively) were selected. These varieties were further evaluated for their responses to Sigma herbicide. Wheat seedlings of both varieties were subjected to twice the recommended dose (80ml/m2) of Sigma and the following parameters were measured: seedling height, root length, root number, seedling fresh weight, seedling dry weight, active oxygen and malonaldehyde (MDA) levels as well as superoxide dismutase (SOD) and peroxidase (POD) activities. Shunmai1718 had a much greater decline in seedling height, root length, seedling fresh and dry weights compared to its untreated control than Shannong129. Similarly, Sigma treatment had little effect on root number for Shannong129 compared to its untreated control; whereas, Shunmai1718 exhibited significantly lower root number compared to its untreated control. Sigma treatment resulted in higher levels of active oxygen and MDA and increased activity of SOD and POD, the largest increase was observed for the active oxygen levels of Shunmai1718 and its accumulated activity of protective enzymes compared to its untreated control.