Glyphosate negatively affects pollen viability but not pollination and seed set in glyphosate-resistant corn

Experiments were conducted in the North Carolina State University Phytotron greenhouse and field locations in Clayton, Rocky Mount, and Lewiston-Woodville, NC, in 2002 to determine the effect of glyphosate on pollen viability and seed set in glyphosate-resistant (GR) corn. Varieties representing bot...

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Bibliographic Details
Published in:Weed science 2004-09, Vol.52 (5), p.725-734
Main Authors: Thomas, Walter E., Pline-Srnić, Wendy A., Thomas, Judith F., Edmisten, Keith L., Wells, Randy, Wilcut, John W.
Format: Article
Language:English
Subjects:
Alexander stain
Anthers
application rate
Corn
Cotton
CP4-EPSPS
cultivars
developmental stages
ELISA
Flowering
fluorochromatic reaction
GA21
genetic variation
glyphosate
Grains
herbicide resistance
mEPSPS
NK603
PHYSIOLOGY, CHEMISTRY, AND BIOCHEMISTRY
phytotoxicity
Phytotrons
plant damage
Plants
Pollen
pollen viability
pollination
seed set
Tassels
ultrastructure
Viability
Zea mays
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Summary:Experiments were conducted in the North Carolina State University Phytotron greenhouse and field locations in Clayton, Rocky Mount, and Lewiston-Woodville, NC, in 2002 to determine the effect of glyphosate on pollen viability and seed set in glyphosate-resistant (GR) corn. Varieties representing both currently commercial GR corn events, GA21 and NK603, were used in phytotron and field studies. All glyphosate treatments were applied at 1.12 kg ai ha−1 at various growth stages. Regardless of hybrid, pollen viability was reduced in phytotron and field studies with glyphosate treatments applied at the V6 stage or later. Scanning electron microscopy of pollen from affected treatments showed distinct morphological alterations correlating with reduced pollen viability as determined by Alexander stain. Transmission electron microscopy showed pollen anatomy alterations including large vacuoles and lower starch accumulation with these same glyphosate treatments. Although pollen viability and pollen production were reduced in glyphosate treatments after V6, no effect on kernel set or yield was found among any of the reciprocal crosses in the phytotron or field studies. There were also no yield differences among any of the hand self-pollinated (nontreated male × nontreated female, etc.) crosses. Using enzyme-linked immunosorbent assay to examine CP4-5-enolpyruvlshikimate-3-phosphate synthase expression in DKC 64-10RR (NK603) at anthesis, we found the highest expression in pollen with progressively less in brace roots, ear leaf, anthers, roots, ovaries, silks, stem, flag leaf, and husk. Nomenclature: Glyphosate; corn, Zea mays L.; ‘DK 662RR’; ‘DK 687RR’; ‘DKC 64-10RR/SIL’.
ISSN:0043-1745
1550-2759
DOI:10.1614/WS-03-134R