specific parents, and the selection (or elimination) of progeny. This seemingly simple itera-
tive process is elaborated by many factors: knowledge of what traits are important, knowl-
edge of genetic control, knowledge of how environment affects traits, and knowledge of
strategies to reduce the sheer numbers of progeny that must be examined. On top of this,
a breeder must be a communicator, a team builder, an extension worker, an expert in com-
mercialization, and a specialist in legal, ethical, and social issues. Plant breeding is often
described as being an art as well as a science. While there are deterministic principles to
discover and apply, there is often more than one acceptable result, and more than one
way to achieve the same result. Plant breeders sometimes claim to recognize another bree-
der’s “handiwork” by the way a variety looks in the field, and often, they find that the most
efficient use of time and resources is to walk through a field and identify plants that “just
look right.”
While studying the topic of plant breeding, you might think of numerous analogies that
help you conceptualize the process. For example, you might draw a parallel between a good
plant variety and a favorite song; they are both dependent on many subtle characteristics,
and although their quality may be widely acknowledged, appreciation of this quality is
varied. In some ways, breeding is also similar to the iterative trial-and-error process that
investors use to build strong and diverse investment portfolios, and principles of genetic
selection have even been applied with great success to areas such as this. But the processes
of genetic recombination and gene expression are unique to DNA-based organisms, and no
analogy can completely replace the concepts that must be learned to become a successful
plant breeder.
This chapter introduces some fundamental concepts of plant breeding, and describes
some generic strategies that are typically used to breed plant species that have a variety
of mating systems. In the “real world,” every plant species presents unique challenges
and opportunities, and it is beyond the scope of this chapter to discuss strategies used
for specific crops. The emphasis in this chapter has been placed on describing the under-
lying concepts of plant breeding, which will help you understand and appreciate literature
that is more detailed or specific. You are encouraged to look at some of the references listed
at the end of this chapter to see how breeding is typically applied in plant species that
interest you.
3.2 Central Concepts in Plant Breeding
Prior to reading this chapter, you should have studied the previous chapter, and you should
have a good working knowledge of plant genetics and reproduction. The concepts
introduced in this section will build on that knowledge. The following paragraphs
introduce key concepts that collectively determine most of the decisions and strategies of
a breeding program.
3.2.1 Simple versus Complex Inheritance
The previous chapter introduced Mendelian genetics—undeniably, the most important
concept that a breeder must understand. The discovery of Mendelian principles was
made in a plant species (pea) using traits that might be important in a pea breeding
program (color, height, and starch content). These traits are considered qualitative
(having discrete values such as green or yellow, tall or short) andmonogenic(controlled
3.2. CENTRAL CONCEPTS IN PLANT BREEDING 49