Cereals processing technology

Table 4.1 Herbicide resistance genes (Henry 1997)
Herbicide Mode of action
Glyphosate Inhibits 5-enolpyruvyl shikimate-3-phosphate
(EPSP) 1
Sulphonylureas Inhibits acetolactate synthesis (ALS) 2
Imidazolinones Inhibits acetolactate synthesis
Triazalopyrimidines Inhibits acetolactate synthesis
2-dichlorophenoxyacetic acid Auxin action
Phosphinothricin Inhibits glutamine synthesis
Atrazine Inhibits electron transport in photosystem II
1 Prevents the synthesis of aromatic amino acids.
2 Prevents the synthesis of leucine, isoleucine and valine.
gene into other plants or by the transgenic cereals themselves becoming weeds.
The production of transgenic plants with resistance to herbicides that have
unique modes of action is highly desirable. Multiple herbicide resistance may
arise if genes target biochemical pathways that are associated with the action of
several classes of herbicide. The problem of escape of herbicide resistance genes
from cereals is likely to be a more serious issue for species that are out-crossing
rather than for those that are predominantly or exclusively self-pollinating. In
some species such as rice, weedy varieties have developed as a result of current
agricultural practices. The introduction of herbicide-resistant rices could lead to
the development of a further class of weedy rices based upon their herbicide
resistance if appropriate agricultural practices are not adopted in association
with the new varieties. This could require production to be limited to specific
regions and to include the rotation of herbicides or varieties. Despite these
limitations, herbicide-resistant cereals should provide enormous advantages in
the enhancement of cereal productivity.
4.3 Disease resistance
Biotechnology, cereal and cereal products quality 55
4.3.1 Disease resistance
Diseases may seriously reduce grain quality. Fungal diseases may have a large
impact on grain quality (especially grain size) because they may be active on the
leaves during grain filling or directly infect the head. Insect pests may reduce
yield and grain quality. Post-harvest damage from insects can be a major
problem (Mills 1996). Mycotoxins resulting from fungal growth on the grain are
a serious safety issue for grain from some environments.
Development of pest- and disease-resistant cereals provides a major
opportunity for enhancing cereal productivity. In many environments single
diseases may be associated with very serious losses in grain yield. Breeding
resistant varieties has been a major strategy used in increasing cereal yields.
Transgenic cereals with high levels of disease resistance may extend the options
available from conventional plant improvement. Resistance to a wide range of