Principles of Plant Genetics and Breeding

Purpose and expected outcomes
The cell is the fundamental unit of structure and function of a plant. Conventional plant breeding entails manipulating
plants at the whole-plant level. However, modern technologies enable scientists to manipulate plants at the
tissue and cellular levels. Tissues and even single cells can be nurtured into full plants. The technique of tissue culture
may be used to assist plant breeders who conduct wide crosses to be able to nurture young embryos into full plants.
In biotechnology, it is critical to be able to nurture a single cell into a full plant in order to apply some of the sophisticated
techniques such as gene transfer or transformation. Plant germplasm of vegetatively propagated species may
be maintained in germplasm banks or tissue culture systems. Breeding vegetatively or clonally propagated species
often includes the use of tissue culture systems. After completing this chapter, the student should be able to:
1 Describe the general properties of a tissue culture medium.
2 Discuss how cells and tissues can be regenerated into full plants.
3 Discuss micropropagation and its applications.
4 Discuss the importance of cell and tissue culture in plant breeding.
5 Discuss the method of in vitro selection for generating variability.
6 Discuss the method of somatic hybridization
7 Discuss the methods of asexual propagation.
8 Describe the characteristics of asexual propagation that have breeding implications.
9 Discuss the breeding of apomictic species.
10 Compare the advantages and limitations of asexual propagation.
Concept of totipotency
Plants reproduce sexually or asexually. Pieces of plant
parts (leaf, stem, roots) can be used to grow full plants
in the soil. In vitro (growing plants under sterile
conditions) plant culture was first proposed in the
early 1900s. By the 1930s, cell culture had been
accomplished. Each cell in a multicelluar organism is
totipotent (i.e., endowed with the full complement
of genes to direct the development of the cell into a
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Tissue culture and the
breeding of clonally
propagated plants
full organism). In theory, a cell can be taken from a
root, leaf, or stem, and cultured in vitro into a complete
plant. However, some cells are unable to differentiate
into all the kinds of cells in an adult organism
and are said to be multipotent or pluripotent. In vitro
culture of cells, tissues, organs, and protoplasts is used
as the technique by plant breeders for propagation
and also for manipulating the genetics of plants to
produce new materials for breeding and for genetic
studies.