Glyphosate-resistant cotton showed abnormal reproductive development when
sprayed with glyphosate.
Cotton (Gossypium hirsutum).
CP4 EPSPS gene cloned from Agrobacterium, which produces an
herbicide-resistant version of the enzyme targeted by the herbicide
Goal of This Study:
Although glyphosate is not lethal to glyphosate-resistant (GR) cotton
(as intended), there have been "[n]umerous reports of increased
boll abscission and pollination problems in response to glyphosate
applications...occasionally leading to yield loss and a modified
fruiting pattern" (p. 438). To investigate this phenomenon further,
the authors characterized the effects of glyphosate on floral anatomy,
pollen deposition, and pollen morphology.
Results of This Study:
In the flowers of GR cotton sprayed with glyphosate, there was 40% less
loose pollen per stigma compared with unsprayed GR cotton. (Reduced
pollen coverage can reduce the cotton yield from that boll.)
One reason for the reduced pollen coverage appeared to be a significant
increase in the distance between the pollen-producing anthers and the
stigma, which is the organ through which pollen reaches the ovary.
(Cotton is primarily self-pollinated, although if insect pollinators
were present, this increased distance might not be as deleterious.)
Spraying with glyphosate also reduced pollen viability by 50% in the first
four weeks of flowering. Microscopic examination of the pollen showed a
variety of cellular abnormalities at various stages of pollen
The two GR cotton varieties in this study clearly did not have complete
resistance to the herbicide.
Pline, W. A., R. Viator, J. W. Wilcut, K. L. Edmisten et al. (2002).
"Reproductive Abnormalities in Glyphosate-resistant Cotton Caused by Lower
CP4-EPSPS Levels in the Male Reproductive Tissue," Weed Science
vol. 50, pp. 438-47.
North Carolina State University.
GR cotton is grown worldwide, including since 1997 in the US.
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