Food Safety - The Oxford Topic of Food, Politics, and Society - page 589

opportunity costs in terms of failure to regulate other food hazards that do real harm
and cause real economic loss around the globe.
The Objective of All Breeding Is to
Induce Mutations in DNA
The concept is so simple it seems almost unnecessary to state that breeding of new vari-
eties of any organism requires that permanent changes (e.g., mutations) be introduced
into the chromosomal DNA (genome). Historically, a variety of methods have been used
to introduce DNA changes into crop plants (Chrispeels and Sadava, 2003). Presumably,
the original farmers selected the seeds of edible wild plants and planted them in man-
aged fields in the first attempts at agriculture (Hancock, 2012). The word edible is used
with great caution here since many crop- plant ancestors are poisonous, as are a few of
today's crops such as bitter cassava ( Manihot esculenta ). Most crops retain a battery of
natural pesticides that are used by the plants for protection against pests and predators.
The earliest plant breeders were ancient farmers who simply waited for natural variation
of a crop that was originally a wild plant to create a spectrum of new phenotypes from
which they selected the most desirable traits. Fortunately they did not have to wait long,
since many crop plants display a high level of genomic fluidity, which is to say they have
a high rate of spontaneous DNA mutation (Parrott, 2005; Weber et al., 2012). Farmers
were able to select for plants that did not shatter (spread their seeds), which made har-
vesting easier, produced higher yields, displayed resistance to diseases, produced thin-
ner husks and more rows of seeds, and a host of other important traits.
The process of plant domestication usually depended on a number important muta-
tions that made the plant variety more attractive to ancient farmers and often less able
to survive without human intervention (seed saving, planting, cultivation, fertilization,
etc). This has been called the domestication syndrome. The resulting varieties do not
exist in nature and very often do not recognizably resemble their original wild ances-
tors. By any reasonable criteria, almost all crop plants are not natural, do not occur in
nature, and are highly genetically modified with respect to their natural wild ancestors
(see McHughen, this volume).
Historically, different crop plants were developed in many different regions of the
world. This occurred largely because the wild ancestors of various modern crops can
only be found in one or a few restricted geographical areas. Tomatoes, potatoes, and
maize originated in the Americas, rice from Asia, and wheat from the Middle East.
Over the millennia, these crop plants were widely disseminated, but only in the past
few centuries were most plant crops spread around the world. As a consequence of the
era of European exploration, and more recently with the advent of modern shipping,
the world's diet has been globalized. What the world eats has changed dramatically as a
result (Chassy, 2010).