Breeding Objectives - An Introduction to Plant Breeding - page 20

banned the use of soil fumigants such as methyl bro-
mide. One possible alternative to using synthetic fumi-
gation is Brassicaceae cover crops (plow-down crops)
or high glucosinolate containing seed meal soil amend-
ments. Glucosinolates, per se , are not toxic, but when
mixed with water in the presence of myrosinase, they
degrade into a number of toxic compounds including:
isothiocyanates and ionic thiocyanate. Past research has
shown that different Brassicaceae species produce dif-
ferent quantities and types of glucosinolate which have
greater or lesser pesticidal activity to different pests.
Insightful plant breeders have recognized the poten-
tial of biopesticides and have found that interspecific
hybridization between different Brassicaceae species
offers an opportunity to develop ' designer glucosinolate '
plants with specific pesticidal effects.
Political government agencies (i.e. the Food and
Drug Administration in the United States) can greatly
influence consumer acceptance and choice. One recent
example of this relates to trans fats in cooking oils.
Research has proven that hydrogenated vegetable oils
which contain trans fats have adverse effects on human
health when included in diets. Indeed, the Food and
Drug Administration now requires trans fat content to
be listed on all food products. Traditional vegetable oils
like oilseed rape (canola) and soy, although relatively
low in saturated fats, are usually hydrogenated to avoid
off-flavours in high temperature frying and to increase
shelf life of the oil products. Rancidity and off-flavours
in vegetable oil are caused by high concentrations of
polyunsaturated fats. This has greatly raised the con-
sumer awareness of trans fats and as a result, there is
now high demand for vegetable oils which have a low
polyunsaturated fat content. Perceptive canola and soy
breeders had anticipated trans fat labelling and had low
polyunsaturated (high oleic acid) cultivars of canola and
soy available to meet market needs. These low polyun-
saturated fat cultivars produce oils that show higher
thermal stability, lower levels of oxidation products, and
increased shelf life with minimal hydrogenation.
Political pressure can also have an influence on
the types of crop that are grown. Within several
countries in the world, and also groups of countries
(e.g. the European Union) the farming community are
offered subsidies to grow certain crops. As a result,
over-production can occur, which can affect the world
price of the crop, and hence influence the economics
of farming outside the subsidized regions. Similarly,
if crop subsidies are reduced or stopped, this also can

Figure 3.1 Volkswagen Beetle ('Bio-Bug') powered by
biodiesel produced from mustard oil.

have a similarly large but opposite affect on the eco-
nomics and hence directly affect acreage of the crop
in these other regions. Crop price is always driven
by demand, greater demand resulting in higher price.
This can give rise to increased acreage, leading to over
production, which leads to reduced crop prices.
The United States, like many other western
countries, has become increasingly dependent upon
imported oil to satisfy energy demand. It is possible
to substitute oils from fossil fuels with renewable agri-
cultural products (Figure 3.1). Therefore, bio-ethanol
and biodiesel fuel, lubricating oil, hydraulic oil and
transmission oil, can all be derived from plants. At
present the agricultural substitutes are still higher in
cost than traditional fossil derived equivalents. How-
ever, in the future this may change either as a result of a
change in fossil oil costs or in further breakthroughs in
either increasing crop productivity or the process needed
to obtain these substitutes from agriculture. Govern-
ments in several countries have mandated that liquid
fuel should contain a certain proportion of biodiesel or
bio-ethanol, and public transport vehicles in inner cities
are being encouraged to use biofuels as these have fewer
emission problems. Similarly, in many countries (par-
ticularly Northern Europe) governments are legislating
that certain operations (e.g. chain saw lubricants) use
only biodegradable oils. Also taxation decisions made by
relevant countries can affect the relative cost and hence
use of fossil and plant derived fuels and oils.
Economic criteria are important because the breeder
must ensure that the characteristics of cultivars that are