crop, based on the performance data from the trials. Only if the committee agrees is the candidate variety allowed to be registered as a new commercial variety. If the variety does not perform within prescribed parameters for all characteristics, it is not commercially released (CFIA, 2003).

Unintended Effects of Conventional Plant Breeding

Naturally Occurring Toxins

All foods, whether or not they are genetically engineered, carry potentially hazardous substances or pathogenic microbes and must be properly and prudently assessed to ensure a reasonable degree of safety. Furthermore, all crop strains, including organic strains, potentially express traits generated by various forms of induced mutagenesis. (Under organic regulations, radiation breeding and induced mutagenesis are acceptable, but irradiation of the final food itself is not. For more information on organic regulations, see USDA-AMS, 2001.)

History provides examples of traditional breeding that resulted in potentially hazardous foods (see Box 3-1). Solanaceous (tobacco family) crops, such as potato and tomato, naturally produce various steroidal glycoalkaloids. These substances are toxic not only to humans, but also to insects and pathogenic fungi. During the course of ordinary plant breeding assessments, breeding lines with increased levels of glycoalkaloids may be identified by the breeder as showing superior insect or disease resistance and retained for possible commercial release. The elevation of glycoalkaloid levels responsible for the pest tolerance may not be noted until people become ill from consuming the foods.

Tomatine, a glycoalkaloid naturally present in tomatoes, can be produced in hazardous quantities in certain conventionally bred varieties. Ordinarily, alpha tomatine is present in immature tomato fruit, but is degraded as the fruit matures, so that by the time the fruit ripens to the preferred stage for human consumption, tomatine content is reduced to safe levels. Nevertheless, levels of naturally occurring tomatine in ordinary tomatoes bred using conventional methods can vary considerably, primarily based on maturity, type, and environmental growing conditions (Gilbert and Mohankumaran, 1969; Leonardi et al., 2000). In this respect, environment is more responsible for food hazards than genetic makeup or breeding method.

Another example of a possible effect is the unintended elevation of glycoalkaloid content in potatoes. All potatoes produce the toxic glycoalkaloid solanine, but mature potatoes from most cultivars have amounts so small as to be nonhazardous. However, some varieties produce more than others, and certain environmental stimuli, such as growing or storage conditions, can cause potentially hazardous increases in solanine content, even within a usually safe cultivar (Concon, 1988). For example, potatoes exposed to sunlight turn green, making them particularly prone to high solanine content. Dark-skinned varieties are less



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