Principles of Plant Genetics and Breeding

Short short
short plants
Short short
plants
the population are subjected. Continuous variation is
caused by environmental variation and genetic variation
due to the simultaneous segregation of many genes
affecting the trait. These effects convert the intrinsically
discrete variation to a continuous one. Quantitative
genetics is used to distinguish between the two factors
that cause continuous variability to occur (see Chapter
8).
VARIATION 85
Short plants Tall plants
Tall short
short plants
Tall short
plants
Short tall
plants
Tall tall
plants
Figure 5.8 Quantitative traits are influenced to a larger degree by the environment than are qualitative traits. The mean of
the F 1 is generally intermediate between the parental means. The F 2 is usually spread within the entire range of the
parental values.
Acquaah, G. 2004. Horticulture: Principles and practices, 3rd
edn. Prentice Hall, Upper Saddle River, NJ.
Falconer, D.S. 1981. Introduction to quantitative genetics,
2nd edn. Longman, London.
Part A
Please answer the following questions true or false:
References and suggested reading
Outcomes assessment
1 The bionomial nomenclature was discovered by Gregor Mendel.
2 Angiosperms have naked seed.
3 Environmental variation is heritable.
4 Qualitative traits exhibit continuous variation.
Breeding quantitative traits
Breeding quantitative traits is more challenging than
breeding qualitative traits. A discussion of quantitative
genetics will give the reader an appreciation for the
nature of quantitative traits and a better understanding
of their breeding. Quantitative genetics is discussed in
Chapter 8.
Klug, W.S., and M.R. Cummings. 1997. Concepts of genetics,
5th edn. Prentice Hall, Upper Saddle, NJ.