Sensitivity to glyphosate and dynamics of shikimate accumulation in three weed species following glyphosate application

The GR50 value and shikimate accumulation in three problematic weed species were determined by whole plant bioassay and spectrophotometric assay,respectively,after treated by glyphosate.After treated by glyphosate at 410 g(a.i.)/ha,shikimate accumulation in Echinochloa crusgalli was first increased,then declined,increased slightly finally.However,it kept increasing in Chenopodium album and Digitaria sanguinalis.Based on the accumulation of shikimate by glyphosate treated within this dosage,the order of sensitivity to glyphosate from high to low was E.crusgalli, C.album and D.sanguinalis ,which was similar to the result of whole plant bioassay.Shikimate accumulation was increased rapidly in all three weeds after treated 2 days by glyphosate within the dose range of 820 to 3 280 g(a.i.)/ha,and the accumulation rate showed positive relationship to the treatment dosage.The highest shikimate accumulation in E.crusgalli , D.sanguinalis and C.album were 1 137.9 μ g/g,4 989.7 μ g/g and 2 084.2 μ g/g,which were 16.7-,23.7- and 82.9-fold compared to that of the untreated control,respectively.The knowledge obtained in this study will provide basis for developing method to detect the sensitivity of weeds to glyphosate.