The Role of Indigenous Fruit Trees in Sustainable Dryland Agriculture in Eastern Africa - Indigenous Fruit Trees in the Tropics: Domestication, Utilization and Commercialization - page 217

11.4.1 Selection of superior quality varieties
The priority indigenous fruit trees identified in this chapter remain in a wild or
semi-domesticated form. One notable characteristic of wild tree species is their
enormous genetic variability (Simons, 1996; Leakey and Simons, 1998; Leakey
et al ., 2002). It is also very well known that fruits supplied from wild sources can
never be uniform and reliable because production can vary considerably from
year to year and from location to location (Teklehaimanot, 1997). Therefore,
there is a need to improve these trees through the selection and domestication
of varieties of superior quality (Simons, 1996; Leakey and Simons, 1998;
Leakey et al ., 2003; Leakey, 2005). Selection and domestication can be a
means of ensuring quality and supply of raw materials. Selection is one of the
steps of tree improvement. There is some evidence in other fruit trees that
qualitative traits, such as fruit taste, are usually much more strongly inherited
from selected individuals. The genetic gain we would expect in one cycle of
selection for a desirable qualitative trait such as fruit taste would be much higher
than that expected for a quantitative trait such as tree height, such that 60%
of the progeny might be similar to their parents (Simons, 1996). Therefore,
there is a good case for phenotypic selection of desirable fruits. Opportunities
are even greater using vegetative propagation to develop cultivars. Although
some success has been achieved in the improvement of some fruit- and nut-
producing wild trees in some villages in West and Central Africa (Tchoundjeu et
al ., 2006), scaling up these activities at country, regional and continental levels is
a challenge.
Historically, several tree domestication activities have not been successful
because they did not consider the participation of local people in the tree
selection process. Therefore, plus-tree selection criteria, which should incorporate
local people's values, knowledge and priorities, must be developed in partnership
with local communities.
11.4.2 Domestication of selected superior varieties
Domestication is a set of actions aiming at improving the quality or production
of a species (Harwood et al ., 1999). Essential paths in domestication include the
development of propagation techniques, testing the genetic material, and
utilizing the improved planting stock. There are two alternative approaches to
domestication: the horticultural and forest-tree breeding approaches. The
horticultural approach tends to emphasize the use of clonal varieties;
outstanding individuals from existing populations are identified and propagated
by grafting or other vegetative means (John and Brouard, 1995). Traditionally,
the improvement of many tropical fruit trees, such as avocado, mango and
orange, has used this approach (Harris et al ., 2002). Forest tree breeding, on the
other hand, relies largely on sexual reproduction for propagation. Procedures
are developed for crossing among selected trees to generate new populations for
domestication. Therefore, considerably larger gains can be made by combining
the traditional horticultural and forestry tree breeding approaches (John and