AMINOMETHYLPHOSPHONIC ACID, A METABOLITE OF GLYPHOSATE, CAUSES INJURY IN GLYPHOSATE-TREATED, GLYPHOSATE-RESISTANT SOYBEAN

Authors: Reddy, Krishna; RIMANDO, A - USDA, ARS, NPURU; DUKE, S - USDA, ARS, NPURU

Submitted to: Weed Science Society of America Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 6/20/2004
Publication Date: 6/20/2004
Citation: Reddy, K.N., Rimando, A.M., Duke, S.O. 2004. Aminomethylphosphonic acid, a metabolite of glyphosate, causes 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 results in significant injury under certain conditions. We hypothesized that if GR soybean is completely resistant to glyphosate, injury could be caused by a metabolite of glyphosate, 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 and conventional soybean in the greenhouse. In GR soybean, single applications of glyphosate-isopropylammonium (1.12 to 13.44 kg/ha) reduced chlorophyll content of the 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 (0.12 to 8.0 kg/ha) reduced chlorophyll content of the second trifoliolate leaf by 16 to 69% at 4 DAT and shoot fresh weight by 4 to 49% at 14 DAT in both GR and conventional soybeans. AMPA at 0.12 kg/ha produced chlorotic effects in both GR and conventional soybean similar to those caused by glyphosate-isopropylammonium at 13.44 kg/ha in GR soybean. AMPA levels found in AMPA-treated soybeans of both types and in glyphosate-treated GR soybeans correlated similarly with phytotoxicity. These results suggest that soybean injury to GR soybean from glyphosate is due to AMPA formed from glyphosate degradation.