PHYSIOLOGY OF GLYPHOSATE-RESISTANT PALMER AMARANTH (AMARANTHUS PALMERI)

摘要

Glyphosate resistance has been confirmed in a population of Palmer amaranth (Amaranthus palmeri) in central Georgia. The resistance/susceptible ratio are approximately 27 for this population. Uptake of foliar applied 14 C-glyphosate was examined in glyphosate-susceptible and –resistant biotypes. No differences in foliar uptake were observed. Leaf samples of from glyphosate-susceptible and –resistant biotypes were analyzed via atomic absorption spectrometry for differences in calcium concentration that could affect glyphosate activity. No differences were observed between the biotypes. A laboratory bioassay was conducted to determine the inhibition of EPSP via shikimate accumulation in glyphosate-resistant and – susceptible Palmer amaranth. In theglyphosate-susceptible biotype, shikimate accumulated at glyphosate concentrations above 40 μg glyphosate ml -1 at the lowest glyphosate concentration exposed (8.4 mg ae L -1 ). In the glyphosate-resistant biotype, shikimate accumulation was not observed except at the highest glyphosate concentration of 84 mg L -1 . Translocation experiments were conducted to determine if glyphosate translocation out of the treated leaf was limited. Significant differences in glyphosate translocation out of the treated leaf were not observed between the glyphosate-susceptible and -resistant biotype. These data indicate that glyphosate-resistance for this Palmer amaranth biotype is based on a difference in the site of action rather than limited translocation.