1 October 2001 Response of Glyphosate-Resistant Soybean (Glycine max) to Trimethylsulfonium and Isopropylamine Salts of Glyphosate
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Field studies were conducted from 1998 to 2000 to evaluate the effects of the trimethylsulfonium (Tms) salt of glyphosate on glyphosate-resistant soybean at Belleville, IL. Glyphosate-Tms and glyphosate-isopropylamine (Ipa) at 1,120, 1,680, 2,240, 3,360, and 4,480 g ai/ha were applied at the V4 and R1 growth stages of glyphosate-resistant soybean. Glyphosate-Tms and glyphosate-Ipa caused greater chlorosis when applied at the R1 growth stage when compared with the V4 growth stage, and chlorosis increased with rate. Chlorosis ranged from 0 to 20% depending on the year. In 1998, glyphosate-Ipa at 2,240 and 3,360 g/ha applied at the R1 growth stage caused 4 to 5% more chlorosis than glyphosate-Tms at the same rates. In addition to chlorosis, glyphosate-Tms caused bleaching (white speckling) of soybean leaves, with bleaching increasing as glyphosate-Tms rate increased. Glyphosate-Ipa caused no bleaching, regardless of rate. Glyphosate-Tms and -Ipa caused no visible height reduction at 14 and 28 d after treatment in any year. In 1998 and 1999, glyphosate-Tms and -Ipa, at the highest rate applied at the R1 growth stage, increased days to maturity of soybean. Despite the injury and delay in maturity caused by glyphosate-Tms and -Ipa, there was no difference in grain yield across years because of glyphosate salt, rate, or application timing.

Nomenclature: Glyphosate; soybean, Glycine max (L.) Merr. ‘Pioneer 94B01 RR’.

Additional index words: Herbicide injury, postemergence, transgenic soybean.

Abbreviations: DAT, days after treatment; EPSPS, 5-enolpyruvylshikimate-3-phosphate synthase; Ipa, isopropylamine; Tms, trimethylsulfonium.

RONALD F. KRAUSZ and BRYAN G. YOUNG "Response of Glyphosate-Resistant Soybean (Glycine max) to Trimethylsulfonium and Isopropylamine Salts of Glyphosate," Weed Technology 15(4), 745-749, (1 October 2001). https://doi.org/10.1614/0890-037X(2001)015[0745:ROGRSG]2.0.CO;2
Published: 1 October 2001
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