Agriculture Reference
In-Depth Information
Chapter 13
Wheat Breeding: Procedures
and Strategies
P. Stephen Baenziger and Ronald M. DePauw
SUMMARY
improvement (hybridization) is covered
by numerous international treaties and
agreements.
(6) Some of the decisions all wheat breeders
must make are which generations to select
and when to end within-line selection. The
earlier the generation at which within-line
selection ends, the more heterogeneous the
resultant line will be. The level of within-
line heterogeneity will determine whether
or not the line can be released as a cultivar,
due to governmental regulations. Wheat
breeders also must decide how to effi ciently
use their resources to select and evaluate
lines in the diverse environments where
wheat is grown.
(7) Molecular markers and genomics are chang-
ing breeding methodology by supplement-
ing phenotypic selection with genotypic
selection. Marker-assisted selection is very
useful for selecting traits that have low heri-
tability or that are expressed in the adult
plant. Phenotypic selection on an adult plant
requires considerably more time, resources,
and space than selecting on seedling plants.
The use of molecular markers will increase
as they become less expensive and more
readily available to wheat breeders.
(8) Molecular markers and the quantitative
trait loci that they tag will be incorporated
into growth and development models to
help breeders select for new ideotypes with
superior performance.
(9) Wheat breeding remains a public-sector
and
(1) Plant breeding, in general, and wheat breed-
ing, in particular, have been practiced for
centuries since wheat was domesticated.
The predominant outcome of wheat breed-
ing is a pureline cultivar that takes advan-
tage of wheat being a self-pollinated plant.
(2) Principles underlying wheat improvement
include biology of sexual recombination,
Mendelian laws of inheritance, and selec-
tion. Effi cient improvement in a trait
requires knowledge of its heritability, the
level of genetic variation, the mode of
inheritance, and the number of genes con-
trolling the trait.
(3) The commonly used breeding methods
are pedigree, bulk, single-seed descent,
doubled haploid, and backcross. Each
method has its advantages and disadvan-
tages. Wheat breeding is remarkably fl exi-
ble, and these methods are often combined
in practice to take advantage of their
strengths and the selection environments
that occur during cultivar development.
(4)
Heritable genetic variation may be increased
in a population by hybridization, muta-
tion, tissue culture, or transformation (i.e.,
transgenic wheat). Though there is cur-
rently no commercial transgenic wheat,
transformation and transgenic wheat culti-
vars will be necessary to ensure wheat as a
crop remains competitive.
(5)
Wheat breeding is a global enterprise and
the exchange of germplasm for wheat
private-sector
activity,
often
