These tomatoes, introduced in 1994 by Calgene, contained
a genetic sequence that made them soften more slowly than
conventional tomatoes. The FlavrSavr tomato often was
marketed as a transgenic variety that cost more because
of its improved flavor. Calgene has said that there were
quality control problems with the FlavrSavr. The company
did not have access to the best cultivars, so the genetic
sequence was inserted into a cultivar that lacked consistent
production qualities. The resulting tomatoes sometimes
fell below the marketing standards set for the FlavrSavr
label. FlavrSavr tomatoes were available sporadically
for several years, but eventually production was discontinued.
Two informative and highly readable web pages on the FlavrSavr
tomato are available at http://www.usis.usemb.se/biotech/tomatoes.html
Zeneca tomato paste was another product openly marketed
as transgenic. Zeneca tomatoes were slower to soften,
as were FlavrSavr tomatoes, but the method for achieving
this was somewhat different. In both tomatoes the activity
of polygalcturonase, the softening enzyme, was reduced.
But FlavrSavr tomatoes were engineered with an anti-sense
gene for this enzyme while Zeneca tomatoes were engineered
with a non-functional, shortened version of the gene.
Safeway and Sainsbury's supermarkets in Britain stocked
Zeneca tomato paste for about three years, but it was
withdrawn in 1999 because of negative public opinion
about transgenics in general. More information on Zeneca
tomato paste is available at http://www.ncbe.reading.ac.uk/NCBE/GMFOOD/tomato.html.
Monsanto's NatureMark "NewLeaf" potato, genetically
engineered with the Bt gene to provide resistance to
insect pests, was first marketed in 1996. Two additonal
products, NewLeaf Y, which had Bt and resistance to
potato virus Y, and NewLeaf Plus, which had Bt and resistance
to the potato leaf roll virus, were introduced later.
NewLeaf potatoes never commanded a large share of the
market, partly because several fast-food chains and
chip makers declined to accept them. Monsanto announced
in the spring of 2001 that NewLeaf potatoes would be
discontinued so that the company could focus on more
profitable products. More information about NewLeaf
potatoes is available at http://www.comm.cornell.edu/gmo/crops/potato.html.
A news story on Monsanto's announcement is available
Triffid flax, developed by the University of Saskatchewan
to be tolerant to the herbicide sulfonylurea, was discontinued
in the spring of 2001. Canadian flax growers were concerned
because their biggest customers, European buyers, declined
to buy GM flax. Worries about possible contamination of
conventional flax seed led to the withdrawal of Triffid
flax. A story on the discontinuation is available at http://www.cp.org/english/online/full/agriculture/010621/a062152A.html.
StarLink corn, like other kinds of Bt corn, was genetically
engineered to be resistant to the European corn borer.
In tests, the Bt Cry9C protein used in StarLink corn
showed several similarities to allergens. Among other
characteristics, it was slower to break down in simulated
disgestion tests than the Cry1A protein used in other
kinds of Bt corn. Concern about the possibility of allergic
responses led U.S. regulators to approve StarLink corn
for production with the restriction that it be used
only for animal food or non-food purposes. Before regulators
could determine whether the Cry9C protein was allergenic
or not, it was reported that StarLink corn products
were showing up on grocery store shelves. Aventis, the
maker of StarLink corn, discontinued seed sales in the
fall of 2000. More information on StarLink corn is available
on our StarLink
news page and on our Hot
Topics page dealing with StarLink corn.
Bt 176 corn
The transgenic corn known as Event 176 was used to produce
Bt seed corn sold under the labels KnockOut (Novartis)
and NatureGard (Mycogen). In contrast to other types
of Bt corn, sold as YieldGard by Novartis, Cargill,
DeKalb, and Pioneer, the pollen from Bt 176 corn was
toxic to Monarch caterpillars, which often live in corn
fields but do not eat corn. Studies showed that even
small amounts of this pollen caused Monarch caterpillars
to eat less of the milkweed leaf tissue that is their
exclusive diet, and amounts of pollen commonly encountered
in corn fields killed many of the caterpillars. Bt 176
corn was not a commercial success, probably because
it provided good protection against the European corn
borer early in the summer but not later in the season.
It was estimated that acreage planted to Bt 176 varieties
constituted 2 percent of the total in 2000, declining
to 1 percent in 2001. The registration was allowed to
lapse in the fall of 2001 and no more of this kind of
corn will be sold. More information is available on
Topics page dealing with Bt and Monarch butterflies.