Principles of Plant Genetics and Breeding

Purpose and expected outcomes
The market value and utilization of a plant product is affected by a variety of factors. For example, for grain crops,
the factors that affect grain quality and form the basis of crop quality improvement programs, include market
quality, milling quality, cooking and processing qualities, and nutritional quality. The specific breeding goals with
respect to each of these factors differ among crop species and agricultural production regions. For example, for the
same crop, the quality aspect of importance in developed economies may be very different and even opposite to that
of developing economies. Some cultures prefer white, non-scented, or non-sticky rice, whereas other cultures prefer
colored, scented, or sticky rice. After completing this chapter, the student should be able to:
1 Discuss breeding for improved protein content.
2 Describe breeding for improved fatty acid content.
3 Discuss breeding for seedlessness in fruits.
4 Discuss breeding for delayed ripening.
5 Discuss breeding for novel traits in plant using biotechnology.
Concept of quality
Quality means different things to different people. The
terms used to describe quality vary from crop production
to food consumption, and include terms for appearance,
storage quality, processing quality, and nutritional
worth or quality. Of these, most attention has been
devoted to processing quality for the major crops, such
as milling quality and baking quality of wheat, canning
quality of beans, chipping or baking quality of potatoes,
malting quality of barley, and fermenting quality of
grapes. These crops and others are of such high economic
value that special labs operating at the private,
state, and national levels have been set up to research
and develop standards for these specialized processes for
the benefit of plant breeders and industry.
Plant breeders should be very familiar with the market
quality standards for their crops. These standards are
22
Breeding compositional
traits and added value
based on a complex interaction of social, economic, and
biological factors, and are highly crop-specific.
Nutritional quality of food crops
Plant parts used for food differ in nutritional quality.
Different species and cultivars of the same species may
differ significantly in total protein as well as in the
nutritional value of the protein. The amino acid profiles
of cereal grains and legumes differ according to certain
patterns. Cereals tend to be low in lysine while legumes
tend to be deficient in tryptophan (Table 22.1).
Three of the main crops that feed the world are cereals
(corn, wheat, rice). Other important species are roots or
tubers. Cereals and tubers are generally low in protein
content. Rice averages about 8% protein, corn 10%,
and potato 2%, versus 38–42% in soybean and 26%