Examination of 2,4-D tolerance in perennial Glycine species

Abstract

High levels of tolerance to 2,4-D [(2,4-dichlorophenoxy)acetic acid] were expressed at the cell and whole plant level by several accessions of wild perennial Glycine species. To determine the mechanism(s) responsible for tolerance, heterotrophic cell suspension cultures of soybean [ Glycine max (L.) Merr.] and four perennial Glycine accessions were used to investigate[ 14C]2,4-D uptake and metabolism. Uptake of 2,4-D was similar between soybean and the perennials. However, soybean metabolized only 7% of the absorbed 2,4-D at 2 and 10 μ M concentrations. The four perennial accessions metabolized 2,4-D at least 79% at 10 μ M and 64% at 50 μ M 2,4-D. The primary metabolite produced by the tolerant perennial lines was the glycoside conjugate of 4-OH-2,5-D, as determined by high-performance liquid chromatography cochromatography and a gas chromatography-mass spectrometer. 2,4-D-sensitive soybean and the least tolerant perennial accession produced high quantities of amino acid conjugates of 2,4-D. Varying levels of 2,4-D tolerance among the perennial Glycine accessions may also be influenced by differential sensitivity of each accession to 2,4-D and/or metabolites.