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[SANET-MG] segregation distortion in roundup ready soy
The glyphosate resistance trait has been introduced into a number of
soybean lines. The paper below shows that glyphosate treatment of crops
causes elimination of pollen that does not bear the resistance gene
(around half). That effect is called segregation distortion leading to
unpredictable growth characteristics in the progeny of the treated crop.
This is but one of a number of problems associated with GM soy.
Crop Sci 46:30-35 (2006)
Gametic Selection by Glyphosate in Soybean Plants Hemizygous for the CP4
David R. Walkera, Alan K. Walkerb, E. Dale Wooda, Magda E. Bonet
Taleverac, Francisco E. Fernandezc, Gina B. Rowana, Craig K. Mootsd,
Richard A. Leitze, Phillip A. Owenf, W. Earl Baxtera, Joseph L. Heada
and H. Roger Boermaa,*
a Dep. of Crop and Soil Sciences, Center for Applied Genetic
Technologies, 111 Riverbend Road, Univ. of Georgia, Athens, GA 30602-6810
b Monsanto Co., 3302 S.E. Convenience Blvd., Ankeny, IA 50021
c Monsanto Co., 2229 Avenida Militar, Isabela, PR 00662
d Monsanto Co., P.O. Box 410, State Route 48– Bldg. 2, Stonington, IL 62567
e Monsanto Co., 703 E. Benton Street, Oxford, IN 47971
f Monsanto Co., 9631 Hedden Road, Evansville, IN 47725
Glyphosate application to glyphosate-tolerant soybean [Glycine max (L.)
Merr.] cultivars expressing a CP4 EPSPS transgene has become the most
common method of soybean weed control in the USA. The objectives of this
research were (i) to determine whether atypical segregation ratios for
glyphosate tolerance and glyphosate sensitivity in the progeny of
hemizygous plants resulted from gametic selection caused by glyphosate
applications, (ii) to investigate the effects of different glyphosate
application rates and timing of application on segregation ratios, and
(iii) to determine whether male gametes, female gametes, or both were
sensitive to the levels of glyphosate used. Segregation for glyphosate
tolerance in a no-glyphosate control treatment fit the expected 3:1
segregation ratio, indicating segregation of a single transgene.
Glyphosate applications at three stages of plant development (V3, V3 + 2
to 3 wk, V3 + 3 to 4 wk) eliminated the glyphosate-sensitive phenotypic
class irrespective of plant maturation stage in a field experiment.
Variations observed in the relative proportions of lines with either
all-tolerant or segregating phenotypic classes depended on glyphosate
dosage and stage of plant development at the time of application.
Overall, the data suggest that glyphosate application to hemizygous
plants shortly before the onset of flowering was lethal to male gametes
that do not carry the glyphosate tolerance transgene.
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