Agriculture Reference
In-Depth Information
and low-input methods are unable to find a variety in the catalogue that is
adapted to their agricultural environment. The vast majority (over 95%) of
varieties used in organic agriculture were initially bred for conventional
systems [1].
Due to the expense of registering a variety and the limited markets for
organic seed, private-sector breeders must add organic breeding activi-
ties to existing conventional activities, and in general cannot spend more
than 10% of their breeding investment on organic systems [2]. Because
conventional systems can be buffered by inputs, the natural environmental
variability encountered by modern varieties is generally limited, which
makes it possible to breed varieties with apparent broad adaptation. This
reduces the need for genetic diversity in commercial varieties [3] but these
varieties are only superior in a narrow range of production environments
where growing conditions are standardized and stress is minimized [4].
Many authors have pointed to a need for greater diversity in agriculture
[1,3,5-12]. Due to greater heterogeneity of environmental conditions
(both spatial and temporal) in organic systems, there is a particular need to
increase genetic diversity on organic farms [13-18].
If the target environments are too different to select a single variety
or population that has acceptable performance everywhere, breeders may
target very focused regions for different varieties or heterogeneous popu-
lations that may then evolve specifi c adaptation. When varieties have dif-
ferent performance relative to each other when changing environments,
variety-by-environment interactions, or more commonly, genotype by
environment (G E) are present. In this case, an analysis of G E is a
method of choosing the best variety or population for each target environ-
ment [4]. Usually, signifi cant G E interactions imply that selection needs
to be conducted in the target environment. Where this direct selection in
the target environment is important, decentralization of the selection pro-
cess is necessary and this often leads to participatory selection [19,20]
because of the need to reduce differences between selection sites and the
target environments. Decentralized selection on regional research stations
may still not be representative of on-farm environments and management.
Farmer participation brings more than just more representative testing lo-
cations, as farmers have in-depth knowledge of environmental conditions
and plant traits that are adaptive under their conditions. The positive use
 
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