Cereals processing technology

54 Cereals processing technology
Molecular markers can be used to improve the efficiency of cereal breeding
programs aiming to improve the value of cereal crops. Molecular analysis may
also be applied in fingerprinting or identification of cereal genotypes with more
immediate potential for improvement of cereals. For example, molecular
analysis of genotypes can be used to monitor seed purity and identity prior to
planting and to characterise grain lots in trading and processing (Henry et al.
1997). The composition of cereal-based foods or products can be monitored to
ensure authenticity of labelling. These applications of biotechnology can have
an almost immediate impact on the quality and value of cereal production.
Genetic engineering offers the possibility of going beyond these short-term
outcomes of biotechnology applications to the generation of more novel cereals
with increased value in the longer term (Henry 1995). In the sections that follow,
the main benefits of genetic engineering are summarised under the following
headings:
• productivity
• product quality
• safety.
4.2 Herbicide resistance
The control of weeds in cereal crops may have a major influence on grain yields
but usually has a much lesser impact on grain quality (Kettlewell 1996). This is
because the major effect is in early crop growth impacting more on grain
number than size. Late weeds are an exception. Generally, contamination of
seed crops with weed seeds is likely to be the major quality defect.
4.2.1 Classes of herbicides and available resistance genes
Resistance genes are available for many different classes of herbicide. The
major groups of herbicides and the genes available for conferring resistance to
these herbicides are listed in Table 4.1.
The most attractive herbicide resistance genes for introduction into cereals
are those that confer resistance to herbicides that are considered safe in the
environment. Herbicides with low mammalian toxicity and little or no other
environmental problem may be attractive alternatives to the more specific
herbicides currently in use. The development of transgenic cereals with
resistance to appropriate herbicides may facilitate the reduction in use of less
desirable herbicides in agriculture and food production.
4.2.2 Problems of escape of herbicide genes to weeds
A major risk associated with the production of transgenic cereals with herbicide
resistance is the possibility that new weeds may result either from escape of the