new techniques derived from new discoveries in biological sciences and major advances in the fields of genetics (e.g., the discovery of the structure of DNA and the understand­ing, at the molecular level, of genes as physical entities that could give rise to Mendelian-style inheritance). Post WWII, the study of genetics led to the development of new tech­niques to introduce inheritable traits into organisms, a sub­set of the broad set of methods known as biotechnologies designed to adapt living things for the production of useful products. These new techniques include genetic engineer­ing (where a genetic "cassette" manipulated in vitro and containing a recombinant DNA gene for a desired trait is inserted into the organism) and marker assisted breeding (where the use of known "marker" sequences associated with a desired trait are used to determine if the desired trait is inherited in offspring from conventional breeding).
     The new techniques of genetic engineering and marker assisted selection have yet to result in improved cultivars with higher yields and other quantitative traits controlled by many genes simultaneously. The current seed varieties avail­able in NAE for most crops, including those for increased yield, have been developed largely through conventional breeding where plants with desired traits are cross-bred and the resultant offspring contain the desired trait. Commercial hybrids are produced by the conventional breeding of two carefully chosen different high-quality true-breeding paren­tal lines to yield progeny that themselves do not breed true, but that in combination give good yield (show vigor) and exhibit superior qualities, above those of traditional (open pollinated) varieties.
     Hybrid varieties generally have increased vigor over their open-pollinated counterparts. With the growth of mechani­zation of agriculture, hybrids could provide uniform charac­teristics amenable to mechanical harvesting such as uniform maturity, concentrated fruit set, etc., thereby increasing their attractiveness to and profitability for farmers. At the end of World War II, the emphasis was almost solely on yield, rather than nutritional quality because of food shortages in Europe. Later this trend continued because of the rise of processed food where uniform standards were required. This emphasis has remained until very recently with the advent of foods with additional or extra vitamins or minerals.
     Between 1940 and 1960, new maize hybrids were de­veloped by private companies such as the forerunners to Pioneer Hi-Bred (Troyer, 1999) that were suited to the ap­plication of nitrogen fertilizers. Between 1950 and 1980, the amount of nitrogen fertilizer applied to corn in the USA in­creased by a factor of 17 (Kloppenburg, 2004). Changes in plant architecture brought about by hybridization allowed these plants to be grown more densely with higher rates of fertilizer application and they were typically managed with the use of insecticides, fungicides and herbicides. Indeed, de­velopments in crop protection have tended to parallel those in fertilizers.
     Breeding with conventional techniques and biotech­nologies has made considerable contributions to the devel­opment of non-cereal crops. The main targets for breeding have been agronomic properties such as crop pest and dis­ease resistance and tolerances to biotic stresses (e.g., cold, heat, salt). Extending crop flavor, quality, nutritional char­acteristics, shelf life and seasonality are increasingly of im-

portance in breeding programs for high value crops. Some breeding programs are even targeted at improving harvest­ing and transport. For vegetable cropping, quality has been the main driver of different breeding. There is currently re­newed interest in breeding for resistance against pest and diseases in order to decrease pesticide inputs.

Mutagenesis
Radiation (usually gamma or x-ray) and certain chemicals have been used to induce mutations in plants as part of plant breeding for the past 50-60 years. Induced mutations are used to provide a general increase in genetic variation for use in plant breeding, or for the direct production of a vari­ety with a certain characteristic. The techniques have been applied to almost all crops. Seed producing crops form the majority of new varieties produced through mutagenesis, but varieties of crops that can be reproduced vegetatively (e.g., the banana, trees, ornamental flowers) have also been developed (Ahloowalia et al., 2004). Mutagenesis has un­predictable effects and after exposure, plants must be grown to see if any useful mutants result that can be multiplied and developed as distinct varieties or used in plant breeding.
     Mutagenesis is reported to have resulted in the produc­tion of 2,252 varieties according to the FAO/IAEA mutation varieties database up to the end of 2000 (Maluszynski et al., 2000). It has been increasingly applied to ornamental plants and flowers. One factor favoring the use of induced mutants has been the lack of intellectual property restrictions on ac­cess for use in cross breeding programs. One of the highest profile uses of mutagensis in plant breeding in recent years has been in the production of non-GE herbicide tolerant crops, e.g., for imidazolinone tolerance.

Marker assisted selection
DNA knowledge-based techniques, such as marker-assisted selection (MAS) and genetic engineering, rely on genomic characteristics and mapping and have shown great promise over the past few years (Asíns, 2002). This is especially true for complex characteristics such as drought resistance that tend to be controlled by multiple genes and hence are not amenable to straightforward genetic engineering strategies. Furthermore, plants produced using MAS are considered conventionally bred in the US and Europe and are not sub­ject to the same consumer and safety concerns raised with respect to GE crops, although in Canada they are regulated in the same manner. Marker assisted selection can be per­formed by private companies or public institutes as varieties would be protected by plant breeders rights.

Genetic Engineering
In NAE, only North America has embraced genetically engineered crops since 1996 (Figure 2-10). Predominantly herbicide tolerant (HT) and/or insect resistant (IR) GE va­rieties of soybean, maize, cotton and canola are grown. For the most part, European acreage is limited to field trials of GE crops (ISAAA, 2005). GE crops producing novel com­pounds not intended for food use (industrial and pharma­ceutical crops) are currently grown only in the US in small quantities and under strict management systems.
     According to surveys conducted in 2001-2003, the ma­jority of US farmers adopting GE corn, cotton and soybeans