873.4.2 New Germplasm Development in Pre-breeding
Allard ( 1988 ) considered the events taking place in wheat breeding in the twentieth
century as a two-way process, involving on the one hand the erosion of the plant
germplasm due to the spread of modern cultivars consisting of homogeneous popu-
lations and the disappearance of landraces with heterogeneous populations, and on
the other hand the constant accumulation of alleles providing broad adaptability and
increased productivity in modern plant cultivars as the result of breeding cycles.
One consequence of commercial breeding is that differences between alleles are
diminishing in modern elite cultivars, so the development of new germplasm in pre-
breeding programmes has become important in wheat breeding. Fundamentally,
fi ve types of genetic resources are available to breeders for the development of new
germplasm:
- Adapted cultivars and lines
- Exotic germplasm
- Old landraces and cultivar populations
- Wild and cultivated relatives
- Mutant genotypes
Each type of parent material appears to be used more in the pursuit of certain goals
than others. However, the chance of broadening genetic variation is lowest when
utilising adapted cultivars and lines. The strategy to “cross the best with the best”
resulted in a narrowing genetic variation of new cultivars and a stagnation in the yield
improvement during the last 10–20 years in most European wheat-growing regions.
Compared to adapted parents, the use of wild and cultivated relatives as parents in
traditional breeding is time-consuming in many cases. A good example of this is
wheat varieties carrying the 1RS.1BL rye translocation , which required 33 years from
the original cross to the registration of the fi rst cultivar (Rabinovich 1998 ).
The increasing need for new genetic variation via alien gene introgression has
enhanced the importance of pre-breeding activities. Separate pre-breeding projects
parallel to the cultivar development were established in many large breeding pro-
grams recently to exploit the genetic variation of wild and cultivated relatives as
well as old landraces and cultivar populations. The main goal is to improve the
effi ciency of the introduction from alien genetic resources into adapted germplasm
with new breeding tools. Pre-breeding offers a background of germplasm research
for commercial plant cultivar breeding and also represents an excellent opportunity
for cooperation between the public and private sectors.
3.4.3 New Breeding Methods
Several new methods have been elaborated over the last 30 years to improve the
effi ciency of wheat breeding, to widen the genetic variation and to shorten the selec-
tion time. One method which has been routinely introduced in wheat programmes
3 Wheat Breeding: Current Status and Bottlenecks