Sensitivity differences of different maize inbred lines to tembotrione

Tembotrione, a 4-hydroxyphenylpyruvate dioxygenase (HPPD) inhibiting herbicide applied in maize fields, was first registered in China in 2021. To clarify the safety of tembotrione on different maize inbred lines, the effects of tembotrione on the growth as well as physiological and biochemical indicators of maize inbred lines HB05 (‘Mo17’), HB09 (‘PH6WC’), HB39 (‘J525’), and HB82 (‘KH8’) were studied. The results indicated that under tembotrione stress of 120 g a.i./hm², sensitive maize lines HB82 and HB39 exhibited wilting, chlorosis of leaves, and even death, significantly impairing maize growth. Conversely, the leaves of tolerant maize inbred lines HB05和HB09 showed no signs of injury, and the application of tembotrione had little impact on their growth. The Sensitive varieties HB82 and HB39 exhibited plant height inhibition rates of 64.63% and 63.79% and fresh weight inhibition rates of 70.06% and 66.02% under 240 g a.i./hm² tembotrione treatment for 14 days. In contrast, tolerant varieties HB05 and HB09 showed lower plant height inhibition rates of 48.61% and 38.05% after 720 g a.i./hm² treatment for the same duration, with fresh weight inhibition rates of 21.93% and 43.63%, respectively. The half maximal inhibitory concentration (IC₅₀) values of tembotrione for the root length were 223.50 and 37.42 mg/L for the tolerant HB05 and HB09, whereas the sensitive varieties HB82 and HB39 displayed lower IC₅₀ values, measuring 13.48 mg/L and 16.13 mg/L. Chlorophyll content measurements revealed a declining trend in chlorophyll a, chlorophyll b, and total chlorophyll for both sensitive and resistant maize. Following 7 days of treatment with 120 g a.i./hm² tembotrione, the total chlorophyll content in sensitive maize HB82 and HB39 experienced substantial decreases of 87.76% and 70.55% while the resistant maize HB05 and HB09 showed lower decreases, with reductions of 49.86% and 33.65%, respectively; The carotenoid content determination revealed an 83.72% and 74.02% decrease in sensitive maize varieties HB82 and HB39, respectively, after 7 days of tembotrione application. In contrast, resistant maize varieties HB05 and HB09 exhibited lower reductions, with decreases of 40.83% and 33.33%, respectively. The results of superoxide dismutase (SOD) and peroxidase (POD) enzyme activities indicated that tembotrione stress led to an elevation in enzyme activities in various maize inbred lines, with a pattern of initially increasing and subsequently decreasing. The extent of this change was more pronounced in sensitive maize compared to resistant maize. In summary, notable variations in the sensitivity to tembotrione exist among different maize inbred lines. The clarification of the resistance levels of various maize varieties to tembotrione is vital for mitigating unnecessary losses in maize production affected by this herbicide.