Published online by Cambridge University Press: 12 June 2017
Chlorsulfuron {2-chloro-N-[[(4-methoxy-6-methyl-1,3,5-triazin-2-yl)amino] carbonyl]-benzenesulfonamide} applied preemergence or postemergence as a soil drench retards the growth of four corn (Zea mays L.) genotypes in soil with 50% inhibition in each case at a rate of approximately 5 g ai/ha. R-25788 (N,N-diallyl-2,2-dichloroacetamide), applied at 1.0 kg ai/ha to the soil preemergence with chlorsulfuron or postemergence 2 days prior to chlorsulfuron treatment, reverses shoot growth inhibition induced by the herbicide in varying degree in ‘XL25A’ and ‘XL72B’ corn hybrids and ‘FRM017’ and ‘FR619’ inbreds, but not in soybean [Glycine max (L.) Merr., var. ‘Amsoy-71’]. Under similar conditions, flurazole [2-chloro-4-(trifluoromethyl)-5-thiazolecarboxylic acid (phenylmethyl ester)] and CGA-92194 [α-(1,3-dioxolan-2-yl-methoxy)-imino-benzeneacetonitrile] are less effective than R-25788 in protecting corn genotypes from chlorsulfuron injury. R-25788 also partially reverses chlorsulfuron-induced root growth inhibition in XL25A and FR619 corn but not in pea (Pisum sativum L. var. ‘Dwarf Gray Sugar’). Acetohydroxyacid synthase (AHAS) is higher in both activity and the proportion that is very sensitive to in vitro chlorsulfuron inhibition when prepared from XL25A shoots than from the roots. R-25788 does not reverse the in vitro inhibition of corn acetohydroxyacid synthase (AHAS) by chlorsulfuron. Pretreatment of 5-day-old XL25A corn with R-25788 at 24 or 48 μM significantly increases AHAS activity by approximately 25% in both shoots and roots but does not change its in vitro sensitivity to chlorsulfuron. This antidote also increases the glutathione (GSH) content in roots and etiolated shoots. The R-25788-induced elevation of AHAS activity may contribute to its antidotal effect in corn.