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Corn Breeding: Introduction to Concepts in Quantitative Genetics:
Overview and Objectives
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The two ears in Figure 1 are from different corn plants. Would you be surprised to learn that the plant that produced the second and larger ear could be genetically inferior for grain yield than the first plant? How could this be true?
 | Figure 1
Two ears of corn harvested from two different plants that were grown in close proximity to each other.
(UNL, 2004) |
Plant breeders often work with traits, such as grain yield, whose values are controlled by many genes and/or are affected greatly by the environment. Such traits are known as quantitative traits, and the study of the inheritance of these traits is known as quantitative genetics. Because many traits that are of economic importance are quantitatively inherited, understanding quantitative genetics is important to plant breeders. In this lesson, some key concepts in quantitative genetics will be introduced, and these will give you some insight into the apparent paradox presented in the preceeding paragraph.
Objectives
At the completion of this lesson you will be able to:
- Explain the difference between phenotype and genotype
- Explain the difference between qualitative and quantitative traits
- Explain the difference between micro-environmental and macro-environmental effects
- Discuss why breeders are interested in genotype and what they must do to measure genotypic value accurately
- Distinguish between the statistical concepts of mean and variance
- Define heritability
- Explain why the heritability of a quantitative trait is important to a breeder wanting to modify that trait
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