&CHAPTER 3

Plant Breeding

NICHOLAS A. TINKER

Agriculture and Agri-Food Canada, Ottawa, Ontario, Canada

3.0. CHAPTER SUMMARY AND OBJECTIVES

3.0.1 Summary

Breeding modifies plant genetics in thousands of genes at a time by hybridizing plant types

then selecting on traits (and genes) of interest. An iterative process, the plant breeder makes

crosses to accumulate genes and desirable traits into genetic backgrounds of choice.

Breeding relies on the principles of Mendelian genetics and the use of statistical

methods. In practice, biotechnology is nearly always combined with plant breeding for

crop improvement.

3.0.2 Discussion Questions

1. Describe how plant breeding is both an art and a science.


2. Is seed color a qualitative or quantitative trait?


3. List six factors that can affect the distribution of quantitative trait phenotypes that will
   appear in a given population.


4. What proportion of plants in an F 6 generation are heterozygous at a given locus?


5. What is the probability that five segregating loci will all be homozygous in the F 6
   generation?


6. What is the difference between a landrace and a pure-line plant variety?


7. The pedigree and the SSD methods are two strategies for developing pure-line var-
   ieties. List some factors that might influence your choice of onevs.the other.


8. Using the terms homozygous,heterozygous,homogeneous, and heterogeneous,
   describe each of the following: (a) a modern maize hybrid, (b) a synthetic alfalfa
   variety, (c) a mass-selected population of maize, (d) a landrace of wheat, and (e) a
   modern variety of wheat.

This chapter is the work of the Department of Agriculture and Agri-Food (Canada) (AAAF).

Plant Biotechnology and Genetics: Principles, Techniques, and Applications, Edited by C. Neal Stewart, Jr.

Copyright#2008 John Wiley & Sons, Inc.

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