Effects of imazethapyr on the physiological characteristics and yield components of foxtail millet

To explore the effects of imazethapyr on the physiological characteristics and yield components of imazethapyr-resistant and conventional foxtail millet varieties and the resistance mechanism, an imazethapyr-resistant variety Jigu35 and 7 conventional varieties Jigu38, Jigu41, Jingu21, Jingu59, Changnong44, Longgu39, and Zhonggu9 were used to compare the physiological characteristics and yield components in response to imazethapyr by pot and filed experiments. The results of the pot experiment showed that for conventional varieties, the aboveground fresh weight, the contents of chlorophyll a, chlorophyll b, carotenoid, and total chlorophyll in leaves were significantly decreased after active ingredient 93.5 g (a.i.)/hm² imazethapyr treatment by 21.60%-72.83%, 45.20%-92.12%, 18.10%-93.36%, 42.58%-84.21%, and 45.73%-92.38%, respectively. The apparent photosynthetic electron transfer rate and maximum photochemical yield of chlorophyll fluorescence parameters decreased by 20.4%-37.0% and 6.9%-24.8%, respectively. The non-photochemical quenching coefficient and the quantum yield of regulatory energy dissipation significantly increased by 101.0%-322.1% and 113.7%-319.7%, respectively, while the imazethapyr-resistant variety Jigu35 were not changed significantly. The catalase (CAT) activity of Jigu35 was significantly increased by 52.48%, while it was decreased by 19.70%-56.58% for conventional foxtail millet varieties. The contents of malondialdehyde (MDA) of conventional varieties were significantly increased by 16.70%-68.80%, but had no significant effect on resistant variety Jigu35. The acetolactate synthase (ALS) activity of the resistant variety Jigu35 was slightly changed after the treatment of imazethapyr. The ALS activity of the conventional variety Jigu38, it was significantly decreased from the 13th day of treatment compared with the control. The field experiment showed that spraying imazethapyr at the seedling stage significantly reduced the ear length, ear diameter, ear weight, ear grain weight, and theoretical yield of conventional varieties. Different from conventional varieties, the ear weight, ear grain weight, and theoretical yield of resistant variety Jigu35 were significantly increased by 7.8%-8.6%. This indicated that the Jigu35 has a strong resistance to imazethapyr by maintaining the stability of ALS activity, increasing CAT activity, enhancing the removal of H₂O₂, and reducing the membrane lipid peroxidation.