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[SANET-MG] defense against stray transgenic pollen
4 July 2005
Prof. Joe Cummins
A conventional genetic defense against transgene pollution in maize
The major problem with genetically modified (GM) crops has been the
pollution of conventional crops by the spread of pollen and seeds which
pollute the conventional crop with undesirable transgenes. A little
effort has been made to provide isolation boundaries which are intended
to limit spread of the GM pollen but these boundaries have not proved
effective. A recent patent by Thomas Hoegemeyer from Hooper ,Nebraska,
Method for producing field corn seed and plants (United States Patent
6,875,905 April 5,2005) provides a conventional genetic to transgene
pollution in maize.
The invention provides for a method of producing hybrid corn seed and
grain which are either free of contamination or pollination from outside
sources or have a dramatically reduced pollination from outside sources.
The genetic restriction was selected from pop corn which requires
extensive sorting if contaminated with pollen from. field or sweet
corn. Pop corn lines were established that would not set seed if
pollinated by field or sweet corn but in a reciprocal cross the popcorn
would pollinate field or sweet corn. The process is called
non-reciprocal cross incompatibility. The genetic basis for is a linked
multiple allelic at the ga locus on chromosome 4 of maize. The
dominant allele Ga.sup.s/Ga.sup.s will not set seed with ga (field
corn) pollen but will set seed with Ga.supp.s pollen. Plants which
are ga/ga will set seed with ga or Ga.sup.s pollen. When ga and
Ga.supp.s pollen are competing in ga/Ga.supp.s styles, only the
Ga.supp.s pollen tubes effect fertilization.
The invention acknowledged that Ga.supp.s is ,in nature, linked to poor
roots and stalks and it has proved difficult to move the gene into field
corn without a performance drag along with the difficulty in making
crosses. However the invention does provide stray pollen protection for
a crop . Both endosperm and embryo are protected from stray pollen. It
seems likely that the poor performance drag may be overcome by fuller
conventional genetic selections. The patent includes one peculiar
application, it was suggested that maize modified with pharmaceutical
genes would be protected from stray field corn pollen. The field corn
really should be protected from the pharmaceutical maize but it is very
unwise to release pharmaceutical maize that can fertilize field corn
but cannot be fertilized by field corn.
A patent neither requires nor demands proof of performance in the
field. It will be indeed wonderful if the pollen incompatibility system
provides complete protection from stray pollen. However, realistically,
some degree of stray pollen leakage may occur in a range of
environmental conditions. Nevertheless, the approach is promising and
may provide a useful way to protect conventional maize from GM crops.
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