Principles of Plant Genetics and Breeding

Cicarelli contest that most farmers are interested in
avoiding or reducing temporal variability, while most
breeders focus on avoiding geographic variability. To
achieve temporal variability, breeders should develop
heterogeneous cultivars rather than uniform ones. This
will give yield stability over time.
Concept of decentralized participatory
plant breeding
Decentralized participatory plant breeding is the
concept of actively involving farmers in the plant breeding
process, rather than simply delivering a prepackaged
seed product to farmers. Farmers are involved in the
selection process of the early segregating populations so
that the final products are adapted to the target environments
in which they will be used for production. This
approach to breeding should be distinguished from a
multilocation performance evaluation of breeding lines
that is part of most conventional cultivar development
programs. Also, participation of the farmer should be
emphasized in order to make decentralized breeding
accomplish its objective of taking advantage of the
farmers’ knowledge of the crop and the production
environment.
The concept of participatory plant breeding is not
novel, since farmers, from the time of the invention of
agriculture, have selected among existing variability to
advance genotypes with useful characteristics. In fact,
farmers in developing countries continue this practice
by selecting and saving seed from the most appealing
plants in the current season’s crop for planting the next
season’s crop. However, the modern application of
decentralized participatory plant breeding is attributed
to N. W. Simmonds who in 1984 used the term “decentralized
selection” to refer to the selection process with
emphasis on selecting for specific adaptation to specific
environments, rather than evaluating the mean performance
of genotypes across different environments.
The scientific basis of this approach to breeding rests
on G × E and its interpretation. In Chapter 23, the
concept of G × E and its importance in plant breeding
was discussed in detail. It was indicated that the type
of G × E interaction determines the type of cultivar a
plant breeder releases for use by farmers. Where evaluations
reveal a crossover G × E interaction (i.e., the rank
in genotypes changes in different environments), the
breeder is confronted with a more complex decision
regarding the kind of cultivar to release. Some argue
that the traditional action by most plant breeders is to
EMERGING CONCEPTS IN PLANT BREEDING 463
release genotypes with the highest average performance
(yield), discarding the best or worst performers at the
extremes of the scale. This habit has been described as
“negative interpretation of G × E interactions”, and is
motivated by a desire to release a cultivar with wide
adaptation for seed production. This approach to
plant breeding suits the crop production practices of
developed countries where production conditions can
be readily manipulated or supplemented to become
conducive to optimal plant performance. However, in
developing economies, most farmers produce crops
under marginal conditions. Consequently, it is important
to consider genotypes that perform best under
favorable conditions as well as those that perform
well under less favorable conditions. In other words,
selection should be for specific adaptation, both favorable
and less favorable. Such a selection approach is
described by some as “positive interpretation of G × E
interactions”.
Conventional plant breeding versus
decentralized participatory plant breeding
There are certain key features, with advantages and disadvantages,
of conventional and decentralized participatory
plant breeding approaches.
Key features of conventional breeding
The key features of conventional plant breeding may be
summarized as follows:
1 Breeders formulate breeding objectives and initiate
cultivar development at their research facility.
2 Promising genotypes in advanced stages of cultivar
development are evaluated at selected sites by
breeders.
3 Superior genotypes that are uniform and have wide
adaptation are released through formal channels.
4 Farmers may visit on-farm trials on field days at
research stations, but are not actively involved in the
breeding process.
5 Breeders continue to develop superior cultivars to
replace older cultivars.
Advantages
1 The process is generally simplified, not having the
added management challenges of supervising farmers.
2 Usually, only one genotype is released as a cultivar.