Germplasm Supply, Propagation and Nursery Management of Miombo Fruit Trees - Indigenous Fruit Trees in the Tropics: Domestication, Utilization and Commercialization - page 363

It is well known that long-term storage of the seeds of tree species currently
plays a very minor role in the conservation of indigenous fruit trees. Ex situ
conservation of germplasm in gene banks with duplicate collections in various
centres is essential. Centres of diversity should also be identified and in situ
conservation activities should be concentrated in these areas. The conservation
of indigenous fruits could be achieved in a manner similar to that of forest genetic
resources, through a diversity of approaches combining strictly forest protected
areas with multiple-use areas managed by local people, with natural forest
extensively managed primarily for the production of fruits and planted orchards
under intensive management (Kemp, 1992; Palmberg-Lerche, 1997). Range-
wide collection and orchard establishment of superior phenotypes of the various
species from the SADC could achieve some of these conservation objectives.
Encouragement of the use of community-owned orchards of selected superior
phenotypes is an indirect way of conserving genetic resources on the farm.
Seedlings of some miombo fruit trees, such as Uapaca kirkiana , show high
mortality in the nursery. Mortality could result from various stress factors, including
diseases, inappropriate growing media and nutritional deficiencies (Mhango,
2000; Swai, 2002), that directly or indirectly affect plant growth and biomass
allocation, commonly expressed as the root-to-shoot ratio. Therefore, factors
leading to the mortality of seedlings should be worked out in detail and methods
to reduce mortality need to be devised. Pests are responsible for perhaps the most
noticeable damage to seeds and seedlings. Therefore, integrated nursery pest
management needs to be developed (Sileshi et al. , Chapter 20, this volume).
Vegetative propagation techniques, especially grafting and to lesser extent
air-layering, need to be given greater attention for priority species, especially
Vangueria infausta , Adansonia digitata , Uapaca kirkiana , Ziziphus mauritiana ,
Strychnos cocculoides , Sclerocarya birrea and Parinari curatellifolia , which
appear to be amenable to grafting (Akinnifesi et al. , 2004). Grafting and
rooting of cuttings should be tried on a large scale for species such as Uapaca
kirkiana , in which seed viability and seedling survival are poor, and for
Flacourtia indica and Parinari curatellifolia , in which germination is more erratic
and slow.
As farmer nurseries evolve and move from the production of low-cost tree
seedlings for basic food security and ecosystem system services to higher-value
ones for income generation and market, it can be expected that the quality
of individual tree seedlings produced will gain much higher importance.
Decentralized tree germplasm systems may perform well in terms of providing
the quantities required but could fall short on the quality and diversity goals of
society (Place and Dewees, 1999). Tree seedling quality needs to be given
more attention in future assessments in order to keep pace with the anticipated
evolution of farmer nurseries, where diversity in production is expected to
become more important.
Large-scale domestication of high-value indigenous fruit trees has not yet
been promoted by governments in southern Africa (Akinnifesi et al ., Chapter 8,
this volume), unlike in Latin America, where there are many initiatives (C.
Clement, personal communication; Clement et al. , Chapter 6, this volume). As
in the cases of South-east Asia (Carandang et al. , 2007) and West Africa