For centuries, people have tried to improve the varieties of fruits and vegetables offered to farmers and consumers by making them better tasting, higher yielding, different looking, longer storing, or resistant to diseases, nematodes, and insects. We hear a lot about traditional plant breeding versus Genetic Engineering (GE)/Genetically Modified Organisms (GMO). Let me explain.
Traditional plant breeding: One of my jobs in the late 1960s was to take a small piece of 200 grit sandpaper folded into a small pointed trough and collect the pollen (male flower part) from certain alfalfa plants. I then transferred this pollen to the pistil (female flower part) of another alfalfa plant. The resulting seed produced was then evaluated to see if it had nematode resistance, first in the greenhouse, then in field plots. The traditional breeding process can take 10 years or more to cross plants and select a good variety. In other plants, crosses are made using paintbrushes and tweezers to physically transfer pollen from one parent to another parent to try to combine desirable characteristics of each parent into the progeny (babies). Luther Burbank (1849-1926), the famous plant breeder/botanist, developed over 800 different varieties of fruits and vegetables using classical plant breeding methods.
Genetic Engineering (GE) and GMO: In the 1980’s, scientists in a laboratory were able to introduce a reverse-orientation copy of an “antisense” gene in a tomato (sort of taking out a gene in the chromosome and putting it back in backwards). This slowed the ripening of the tomato which increased the shelf life dramatically. In 1994, the FLAVR SAVR tomato was released to the public. Calgene, the company marketing this tomato and tomato paste products, met with resistance from consumers and retailers in the United States and the United Kingdom and soon after the tomato was deemed ‘not profitable’ and the project stopped.
Today, several products have been commercialized using GE techniques including insect-resistant varieties of cotton and corn, herbicide-tolerant soybean, corn, canola, and alfalfa, and virus-resistant papaya and squash. Over 93 percent of the soybeans grown in the United States have been engineered to be herbicide tolerant (the herbicide being Glyphosate, also known as Roundup). Introducing new genes into plants can involve using the same kind of plant, a different plant, or a different organism, such as a microorganism. In classical breeding, thousands of genes are being rearranged, whereas GE involves the specific handling of single genes (using “chemical scissors”). The genes used in GE can come from any organism, and the genes in classical breeding must be very closely related. The current controversy is whether GMO foods should be labeled so that the consumer knows what they are buying (Proposition 37 in California).
What about Bt in sweet corn? Bt (Bacillus thuringiensis) is a protein produced by common soil bacteria that has some insecticidal properties. It has been used as a pesticide spray for decades, including in organic farming. In the past 15 years or so, the gene for Bt has been engineered into corn and cotton seeds such that the plants produce the protein themselves.
What about virus resistant squash and papaya? In the case of virus resistant plants like squash and papaya, they were actually modified by using a part of the virus genetic information itself engineered in such a way as to shut off the replication of the virus. Squash and papaya are the only small acreage crops that are GE and are available on the commercial market.
It is estimated that 93 percent of the soybean acreage (2010), 10 percent of the squash acreage (2004), and 53 percent of the papaya acreage (2006) is genetically engineered.