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2.2 Commercialisation of genetically modified products
The first approval of a genetically engineered plant for human
consumption was given in the United States. The Flavr Savr tomato
from Calgene received approval from USDA/APHIS and FDA in 1992
and 1994, respectively. Since then, 25 additional transgenic plants
have been approved by US authorities. Several of these products
have also been approved in other countries, and two further ones
in the European Community. These and others are summarised in
tables in the following sections.
The new traits introduced into currently approved genetically
engineered plants can be categorised as follows (see also
Field trials Table 2 [end of
- Improved product quality (durability, firmness, fruit ripening
delayed, processing value)
- Pest resistance (insects, nematodes, viruses)
- Agronomic benefits (herbicide tolerance, hybrid system)
The Flavr Savr tomato belongs to the first category. Constitutive
expression of the Flavr Savr gene (antisense-construct derived
from the polygalacturonase [PG] gene from tomato) results in a
dramatically decreased PG-activity in the transgenic tomatoes.
The enzyme PG degrades pectin, a major constituent of the cell
wall of the fruit. Thus the Flavr Savr tomatoes can ripen on the
vine longer and be harvested long after they turned red, without
the risk of excessive softening after harvest. In contrast, more
than 80 % of the conventional tomatoes sold in the US are picked
while green and exposed to external sources of ethylene in industrial
pants to develop red colour.
The majority of the approved genetically modified plants can be
categorised under groups II and III. Several of the pest-resistant
transgenic crops carry genes also conferring herbicide resistance
for selection purposes
( List of Tables: Tables 3-10).
The most frequently used selection marker is the nptII gene also
termed kanr or neor, coding for the enzyme aminoglycoside 3'-phosphotransferase
II (APH(3')II). Expression of this enzyme allows for selection
on media containing kanamycin (kan), and neomycin (neo, G418)
(see also section 4).