Submitted to: Weed Science Society of America Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 2/9/2004
Publication Date: 2/9/2004
Citation: Reddy, K.N., Rimando, A.M., Duke, S.O. 2004. Is aminomethlyphosphonic acid a metabolite of glyphosate causing injury in glyphosate treated glyphosate-resistant soybean. Weed Science Society of America Meeting Abstracts. Interpretive Summary:
Technical Abstract: Application of glyphosate to glyphosate-resistant (GR) soybean has resulted in significant injury under certain conditions. If GR soybean is completely resistant to glyphosate, injury could be caused by a metabolite of glyphosate. We hypothesized that GR soybean injury possibly results from the plant metabolism of glyphosate into aminomethylphosphonic acid (AMPA), a known phytotoxin. We examined glyphosate and AMPA effects on one- to two-trifoliolate leaf stage (16- to 18-d old) GR (AG 4702RR) and conventional (HBK 4891) soybean in the greenhouse. In AG 4702RR, a single application of glyphosate-isopropylammonium at 1.12 to 13.44 kg/ha with 0.5 % Tween 20 reduced chlorophyll content of second trifoliolate leaf by 4 to 14% at 7 d after treatment (DAT) and shoot dry weight by 7 to 16% at 14 DAT. A single application of AMPA at 0.12 to 8.0 kg/ha with 0.5 % Tween 20 reduced chlorophyll content of second trifoliolate leaf by 28 to 66% and 16 to 69% at 4 DAT in AG 4702RR and HBK 4891, respectively, and shoot fresh weight by 4 to 39% and 7 to 49% at 14 DAT in AG 4702RR and HBK 4891, respectively. Evidently, AMPA at as low as 0.12 kg/ha can produce chlorotic effects in both GR and conventional soybean similar to those of glyphosate-isopropylammonium at 13.44 kg/ha observed in GR soybean. These results suggest that under field conditions, the extent of soybean injury from glyphosate depends on soybean ability (e.g., genotype and environmental conditions) to degrade glyphosate to AMPA.