Examples of genetically engineered plants used commercially

The use of recombinant DNA technology has much to offer in the way of improving basic life if it is applied responsibly.  The initial expectations of these new technologies were at first  unrealistic because of the poor knowledge base of our understanding of genes.  As we learn more about the function and regulation of genes so do the applications of these genes in agriculture become apparent.  One cannot learn to walk before you can crawl and so the learning curve in genetic manipulation is ongoing.  The following must be taken into consideration with genetically engineered plants:
 

• the purpose or the intended effect of the genetic modification,
• the source, function and stable incorporation (after successive generations) of introduced genetic material,
• analytical studies to determine whether the genetic modification has any effects on the composition of the food (levels of nutrients and naturally occurring toxicants),
• the safety of new or modified substances in the food,
• the effect of the altered genotype on naturally occurring populations of the plant.

One of the first examples of a commercially genetic engineered plant was the FLAVRSAVR tomato developed by Calgene Inc., of Davis California.  It was claimed that the FLAVRSAVR tomato remains on the vine longer to ripen to full flavour before harvest.  In order to reach markets without being crushed, other tomato varieties are harvested while they are green and ripening induced after shipment with ethylene gas, the natural ripening agent in tomatoes.  The FLAVRSAVR tomato stays firm after harvest because, through gene manipulation, the production of the enzyme polygalacturonase (PG), is suppressed.  PG breaks down the pectin found in the cell walls causing ripe tomatoes to soften.  PG is suppressed by introducing a reverse copy of the PG gene called an antisense gene into the plant.  Thus, FLAVRSAVR tomatoes have lower levels of PG allowing them to soften more slowly when ripe.

Another approach to crop improvement is to improve the application of chemicals in crop management.  Chemical herbicides are used to eliminate weedy competitors to optimize crop yield.  Currently soybean farmers apply persistent slow degrading herbicides.  Soybeans are naturally tolerant to certain herbicides.  Unfortunately herbicides produce damage to non-target plants as well.  Through genetic manipulation, a variety of soybean which is tolerant to the herbicide Roundup has been developed.  Roundup is non-persistent, cannot move freely in the soil and degrades to harmless compounds quickly.  Thus the damage to the environment is reduced.