Principles of Plant Genetics and Breeding

Purpose and expected outcomes
Plant breeders manipulate the genotype of plants to create heritable modifications in plant structure and function.
Sometimes plants are genetically modified to change their shape, height, or size, to facilitate a production operation
or system. For example, dwarf plants are more environmentally responsive and tend to resist lodging. Changes in
stature and size impact their metabolic activities. To undertake such modifications, it is important for breeders to
understand the fundamental plant structure and organization at the molecular, cellular, and whole-plant levels.
Manipulating plants by some biotechnological procedures occurs at the cellular level, hence the need to understand
DNA and cellular structure and function. Because the goal of plant breeding is to create modifications that are
permanent and heritable, it is important to also understand the genetic architecture of plants and how genes condition
plant traits. This chapter is designed to present an overview of concepts pertaining to the cellular organization
and genetic structure of plants. After studying this chapter, the student should be able to:
1 Briefly describe plant cell structure and organization.
2 Briefly discuss nuclear division processes.
3 Discuss Mendelian concepts.
4 Discuss DNA structure and function.
5 Distinguish between phenotype and genotype.
6 Discuss the role of genetic linkage in plant breeding.
7 More importantly, the student should be able to discuss the role of these plant structures and processes in plant
breeding.
Units of organization of living things
The cell is the fundamental unit of organization of living
things. Some organisms consist entirely of one cell
(called unicellular) whereas others consist of numerous
cells working together (called multicellular). Except
for a bacterium, which lacks cellular compartmentalization
into discrete functional units called organelles, and
is called a prokaryote, all other cells have a membrane-
3
Plant cellular
organization and genetic
structure: an overview
bound nucleus and several other membrane-enclosed
organelles and are called eukaryotes.
The cell can be a unit for selection in breeding if, for
example, molecular tools are used. The technology of
genetic engineering targets single cells for manipulation.
After successfully transferring foreign genes into
the cell, it is isolated and nurtured into a full plant. On
the other hand, when conventional tools are used, the
whole plant is the unit of selection. It should be pointed