program is to improve the potential utility of crops. The incentives of
breeding for quality, therefore, depend on the extent to which quality
traits can be genetically altered, the associated costs and the market’s
willingness to pay for the improvement in quality. However, the base-
line of each breeding program is determined by genetic and economic
laws that cannot be bypassed but that can be intelligently dealt with.
Breeding targets are achieved by altering the genetic composition of
crop populations with the help of selecting for visible traits. The main
challenge is that the formulation of target traits as well as the process
of selection is based on visible characteristics, which are determined by
the invisible genetical pattern of a plant. Moreover, since most charac-
ters in living organisms are determined polygenic, the interactions of
several genes with environmental effects further modify the visible ex-
pression of a genotype. This implies that selection for a specific trait
cannot be done in an isolated manner but must also consider the extent
to which the trait:
- is correlated with the breeding objective
- has an impact on other traits, either by negative correlation to de-
sired traits or by positive correlation to undesired ones - is determined by genetical influences versus the impact of envi-
ronment and management
The success in breeding is determined by the returns at costs of se-
lection for traits included in the breeding program and at opportunity
costs for traits excluded. Making the right choices here is all the more
critical as with an increasing number of traits for selection, time and
plant materials required increase as well whereas the response to selec-
tion is likely to decrease (Simmonds, 1979). Plant breeders have to cope
with a great diversity of characters determining yield and quality of a
crop. The importance of each character varies in relation to the target
environment and the intended use of a crop. Whereas yield is clearly de-
fined as the crop’s ability to produce biomass and to partition efficiently
between productive plant parts and waste, the establishment of quality
depends on the requirements of the crop users.
If a crop is used in a variety of ways, such as potato, which is used
for end consumption as such, as well as for different kinds of process-
ing, multiple quality objectives must be fullfilled. In order to effectively
pursue selection for quality in a breeding program it will be necessary:
(1) to set priorities between yield and quality and (2) to differentiate dif-
ferent objectives of quality.
Breeding is a long-term process that requires at least about 10 to 20