Safeners for chlorsulfuron on maize (Zea mays L.)

Abstract

Introduction Chlorsulfuron inhibits acetolactate synthase (ALS), a key enzyme in plants needed in the biosynthesis of the branched amino acids isoleucine, leucine and valine. Maize is a susceptible crop to the action of this herbicide. Objectives This article examines the synthetic compound 1-(4-fluorophenylthiocarbamoyl)-4-methylpiperazine as a possible safener for chlorsulfuron in maize (Zea mays L. cv. Kneja 530). Methods Commercial herbicide safener, 1,8-naphthalic anhydride, was used as a standard. Maize seeds were impregnated with 1-(4-fluorophenylthiocarbamoyl)-4-methylpiperazine or naphthalic anhydride by soaking for 5 h in aqueous solutions, followed by a herbicide treatment for 5 h. Plants were grown as water cultures. Results Changes in growth and in specific activity of acetolactate synthase were determined 8 and 12 days after the treatment. Shoot length and fresh weight of maize plants treated with 105 M chlorsulfuron were inhibited 59% and 52%, respectively, compared with untreated plants, whereas pretreatment with 5 104 M 1-(4-fluorophenylthiocarbamoyl)-4-methylpiperazine and naphthalic anhydride reduced these inhibitions. Moreover, the decrease in the root growth caused by chlorsulfuron alone was almost completely reversed by 1-(4-fluorophenylthiocarbamoyl)-4-methylpiperazine. The specificity of naphthalic anhydride and 1-(4-fluorophenylthiocarbamoyl)-4-methylpiperazine’s action on acetolactate synthase was supported by the lack of effect on the enzyme activity in vitro. However, pretreatment of seeds with both safeners overcomes chlorsulfuroninduced inhibition of acetolactate synthase activity in leaves and roots, 8 and 12 days after treatment. Conclusion Our data showed that the synthetic compound 1-(4-fluorophenylthiocarbamoyl)-4-methylpiperazine was a more active herbicide safener in the roots whereas the naphthalic anhydride, in the leaves.