Agriculture Reference
In-Depth Information
many selected varieties are intercrossed and all the hybrids are bulked together for propaga-
tion. Those selected crossing parents can consist of not only modern high-yielding varieties,
but also varieties bred before 1960 (before the period of high inputs) that are capable of more
efficient nutrient uptake under low-input conditions, and from old landraces as a source for
adaptability. This approach can form the base for further selection of individual, superior gen-
otypes and lines as potentially new and better adapted varieties. We can also expect to select
individual lines with a good combining ability for variety mixtures.
Variety mixtures formed by three or four existing varieties or extracted from composite
cross populations are a simple and effective way of increasing the genetic diversity within a
crop and improving yield stability (Finckh
et al
. 2000; Welsh and Wolfe 2003; Wolfe 2003).
Mixtures can overcome several agronomic problems, through combining, for instance, high
yielding types and types with a good baking quality and weed suppression in wheat. Research
by conventional scientists indicates that there are areas of common interest to both organic
and conventional plant breeders, for example, crop traits related to competitiveness against
weeds (Lemerle
et al
. 1996) and soil-borne disease prevention (Smith
et al
. 2004).
However, any breeding strategy of restoring and enlarging functional genetic diversity
requires reconsideration and adaptation of the legal and administrative frameworks. The reg-
ulations for registration are still based on the pure line practice. However, the market must be
prepared to accept heterogeneous crops and products.
In situ
and on-farm conseration of genetic resources
In order to maintain greater genetic diversity
in situ
and a wide gene pool to improve genetic
resources for the organic sector, seeds from the formal (institutionalised or commercial) and
informal (farmer-based) seed systems should be accessible to local and national breeding
programs. There is a pronounced need to identify appropriate genetic resources either for
direct use or as potential parental lines in breeding programs (Lammerts van Bueren
et al
.
2004a). There are well-organised initiatives dealing with
in situ
conservation of genetic
resources in connection with organic agriculture, for instance ProSpecieRara in Switzerland
(www.psrara.org), Arche Noah in Austria (www.arche-noah.at), the Seed Savers Exchange in
the USA (www.seedsavers.org) or the Seed Savers' Network in Australia (www.seedsavers.net).
The advantage of
in situ
conservation of genetic resources is that the accessions can coevolve
and adapt to organic farm conditions.
Evaluating and exploiting gene bank material can be of use because required characteris-
tics might have disappeared by selection under modern, high input conditions, such as low-
input tolerance and deep or intensive root architecture (Foulkes
et al
. 1998; De Melo 2003).
This is a relatively low cost method to develop valuable accessions.
Participatory selection
As the formal seed sector cannot start breeding programs for limited acreage of organic agri-
culture easily, alternative options should be developed to enhance varietal diversity. Decen-
tralised and farmers' participatory approaches are known in developing countries and can
offer an opportunity to combine knowledge and expertise of the organic farmers and that of
formal breeders. Farmers can select in existing open-pollinating varieties or take part in the
selection process of new crossings or developing base populations (see
Genetic diversity
).
There are different approaches to involving farmers in the breeding process (Ceccarelli
2000; Morris and Bellon 2004). In the traditional farmers' breeding model, farmers conduct
the whole process of:
1 selection of source germplasm;
2 trait identification (prebreeding);
