Germplasm Supply, Propagation and Nursery Management of Miombo Fruit Trees - Indigenous Fruit Trees in the Tropics: Domestication, Utilization and Commercialization - page 344

Protocols that complied with the FAO code of conduct for germplasm were
developed following the germplasm collection of some of the major species,
including U. kirkiana , Sclerocarya birrea , Strychnos cocculoides , Parinari
curatellifolia and Vitex mombassae (Akinnifesi et al. , 2004; Mkonda et al. , 2004;
Swai et al. , 2004). Germplasm collection may be either for tree improvement or
for conservation (Ndugu et al. , 1995). The object of the collection mentioned at
the beginning of this paragraph was improvement and domestication, but
conservation was an implicit responsibility. For conservational collection, the
strategy is to ensure sampling of the major variation patterns in the wild in the
most economical way. The goal is to ensure that diverse genotypes are conserved
for future availability and use. Ndugu et al. (1995) suggested the need to conserve
at least 200 superior clones in field gene banks in the region, considering that most
miombo fruits are recalcitrant and that long-term seed storage in seed banks
would be impossible. On-farm conservation by farmers is another way of
maintaining live genes at low cost.
Normally, the aim of collection is to sample germplasm that is genetically
as representative as possible of a population (or provenance). This is called
'systematic sampling', and it means collecting seed from many trees in an
individual population (Dawson and Were, 1997). In addition to systematic
sampling within populations, several populations have been sampled for each
species, the idea being to get germplasm that represented the geographical
ranges of the tree species. Sometimes in the course of the collection, if
researchers decide that important characteristics have high heritability and can
therefore be selected for at the time of sampling, they can do phenotypic
selection of trees within populations. This method, called 'targeted collection',
increases the chances of capturing superior material for improvement
programmes. This has been the approach used for collecting germplasm of
Sclerocarya birrea and Uapaca kirkiana in southern Africa (Dawson and Were,
1997). For both species, seed from trees that villagers identified as producing
fruit with superior characteristics were collected. Occasionally, collectors may
also do vegetative sampling to collect scions or cuttings from superior
phenotypes, or because trees do not bear seed at the time of sampling. This
approach may be useful for the targeted collection of fruit trees such as S.
birrea and U. kirkiana , for which mature, seed-bearing trees can be difficult to
find in some locations (Dawson and Were, 1997). Details of the management
and performance of these provenances are covered by Akinnifesi et al. in
Chapter 8 of this volume and have been reported by Akinnifesi et al. (2004).
Since most of the miombo fruits have a wide natural range involving
several countries, regional issues may arise in germplasm collection. Securing
approval from the respective national genetic centres to collect germplasm may
be time-consuming and may take as long as 6 months (Ndungu et al. , 1995).
The exchange of valuable indigenous fruit germplasm across nations with
potential economic gain may face resistance. It may be easier to collect
germplasm across long distances in seed form rather than by vegetative means,
which may require special transport and storage requirements.