Imazamox detoxification and recovery of plants after application of imazamox to an imidazolinone resistant sunflower hybrid

Abstract

Imidazolinone herbicides combined with imidazolinone resistant (IMI-R) crops provide a tool for solving the important problem of the occurrence of weeds during the early growth stages of sunflower. These herbicides inhibit the synthesis of branched chain amino acids by interrupting the key enzyme acetohydroxyacid synthase (AHAS). We studied the imazamox detoxification in an IMI-R sunflower hybrid together with plant growth and photosynthetic performance. Inhibition of photosynthesis and growth were observed as initial effects of imazamox application. A slight decrease in AHAS activity was also noticed. These effects disappeared within two weeks after application. A fast and well-functioning detoxification mechanism for the herbicide, of which the content decreased for about 90 % at 14 d after application, seems to be responsible for this. The activity of the xenobiotic detoxifying enzyme glutathione S-transferases (GSTs) significantly increased after imazamox application. Our results suggest that the metabolite glutathione serves as an auxiliary tool for imazamox detoxification through conjugation reactions realized by the GSTs, thereby taking part in the non-target mechanisms of resistance in IMI-R sunflower hybrids.