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[SANET-MG] mitigation of volunteer transgenic canola weeds through shortness
Volunteer transgenic herbicide tolerant canola canola is a growing
problem because the canola seeds may persists for a decade in the soil
and compete as volunteers with rotation crops.Johnny Gressel and his
co-workers devised a clever solution by genetically dwarfing the canola.
The short plants did very well alone but were eliminated by tall
competitors when they volunteered.
Plant Biotechnology Journal
Volume 0 Issue 0 - August 2005
Mitigation of establishment of Brassica napus transgenes in volunteers
using a tandem construct containing a selectively unfit gene
Hani Al-Ahmad, Jennice Dwyer, Maurice Moloney and Jonathan Gressel
Transgenic oilseed rape (Brassica napus) plants may remain as
'volunteer' weeds in following crops, complicating cultivation and
contaminating crop yield. Volunteers can become feral as well as act as
a genetic bridge for the transfer of transgenes to weedy relatives.
Transgenic mitigation using genes that are positive or neutral to the
crop, but deleterious to weeds, should prevent volunteer establishment,
as previously intimated using a tobacco (Nicotiana tabacum) model. A
transgenically mitigated (TM), dwarf, herbicide-resistant construct
using a gibberellic acid-insensitive (Deltagai) gene in the B. napus
crop was effective in offsetting the risks of transgene establishment in
volunteer populations of B. napus. This may be useful in the absence of
herbicide, e.g. when wheat is rotated with oilseed rape. The TM dwarf B.
napus plants grown alone had a much higher yield than the
non-transgenics, but were exceedingly unfit in competition with
non-transgenic tall cohorts. The reproductive fitness of TM B. napus was
0% at 2.5-cm and 4% at 5-cm spacing between glasshouse-grown plants
relative to non-transgenic B. napus. Under screen-house conditions, the
reproductive fitness of TM B. napus relative to non-transgenic B. napus
was less than 12%, and the harvest index of the TM plants was less than
40% of that of the non-transgenic competitors. The data clearly indicate
that the Deltagai gene greatly enhances the yield in a weed-free
transgenic crop, but the dwarf plants can be eliminated when competing
with non-transgenic cohorts (and presumably other species) when the
selective herbicide is not used.
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