Principles of Plant Genetics and Breeding

94 CHAPTER 6
Table 3 Varieties registered from 1973 to 1990 that
proved to have been developed with material from the
genebank Gatersleben (Hammer 1991).
transgenic plants have been incorporated as parents of hybrids
in US breeding programs for crops such as maize and oilseed
rape. Molecular markers are being used to tag specific chromosome
segments bearing the desired gene(s) to be transferred (or
incorporated) into the breeding lines (or populations).
Crop Number of varieties
Spring barley
Winter barley
Spring wheat
Winter wheat
Dry soup pea
Fodder pea
30
3
1
12
2
3
Examples of successful uses of plant genetic resources
Over the last few decades, awareness of the rich diversity of
exotic or wild germplasm has increased. This has lead to a more
intensive use of this germplasm in breeding (Kearsey 1997) and
thereby yields of many crops have increased dramatically. The
introgression of genes that reduce plant height and increase disease
and viral resistance in wheat provided the foundation for
Lettuce 1
the Green Revolution and demonstrated the tremendous impact
Vegetable pea 4
that genetic resources can have on production (Hoisington et al.
Total 56
1999).
In Germany, PGR material stored in the Gatersleben gene
bank has been successfully used for the development of
improved varieties (Table 3).
Developing improved varieties using gene bank materials takes a long time. For instance, when developing disease-resistant
material, the resistance must be located with great expenditure of time and effort, from extensive collections. The experience in
Gatersleben indicates that it take roughly 20 years between the first discovery of the material and the launching of a new variety,
even if modern breeding methods are employed (Hammer 2004). A positive correlation has been observed between the number
of evaluated accessions in gene banks and the number of released varieties on the basis of evaluated material (Hammer et al. 1994).
The use of Turkish wheat to develop genetic resistance to diseases in Western wheat crops was valued in 1995 at US$50
million per year. Ethiopian barley has been used to protect Californian barley from dwarf yellow virus, saving damage estimated
at $160 million per year. Mexican beans have been used to improve resistance to the Mexican bean weevil, which destroys as
much as 25% of stored beans in Africa and 15% in South America (Perrings 1998).
Conclusion
PGRs are useful for present and future agriculture and horticulture production. They are particularly needed for the genetic
improvement of crop plants. Because of their usefulness and their ongoing erosion in the agroecosystems, it was necessary to
establish large collections of PGRs. The material in these collections has to be characterized and evaluated in order to introduce
it into breeding programs. Prebreeding and germplasm enhancement are necessary as first steps for the introduction of primitive
material into modern varieties.
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