Glossary Plant Breeding

F
F 1 . The first generation of a cross between genetically unrelated parents. It is also called
first filial generation.
F 2 . The second filial generation obtained by self-fertilization or crossings inter se of F 1
individuals.
F 3 . The third filial generation progeny obtained by self-fertilizing F 2 individuals.
Factor. A genetic determinant of a character. It is synonymously used for gene by
classical geneticists; same as gene.
Factorial. Multiplication of the number by all integers down to 1. It is designated by the
symbol ‘!’. For example, 5! = 5.4.3.2.1 = 120. It should be noted that 0! (zero
factorial) equals 1, and any number raised to the zero power also equals 1 [e.g., (½) 0 =
1].
Factorial Experiment. An experiment in which the treatments consist of all possible
combinations of given levels of two or more factors. The term complete factorial
experiment is sometimes used when the treatments include all possible combinations
of the selected levels of the variable factors. In contrast, the term incomplete factorial
experiment is used when only a fraction of all the combinations is tested. Note that
the term factorial describes a specific way in which the treatments are formed and
does not, in any way, refer to the experimental design used. For instance, if a factorial
experiment is performed in a randomized complete block design, then the correct
description would be ‘a factorial experiment in a randomized complete block design’.
A factorial experiment provides valuable information on interaction, and is more
informative than a single factor experiment. However, practical considerations like
large size, complexity and cost limit the use of factorial experiments.
Familial Trait. A trait shared by members of a family for whatever reasons (not
necessarily the genetic ones). It should be carefully differentiated from a heritable trait
for which similarity arises from shared genotypes.
Family. A group of individuals directly related by descent from a common ancestor.
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