Germplasm Supply, Propagation and Nursery Management of Miombo Fruit Trees - Indigenous Fruit Trees in the Tropics: Domestication, Utilization and Commercialization - page 347

superior Uapaca kirkiana trees clonally propagated and raised in the nursery
and established in a clonal gene bank at Makoka (Akinnifesi et al ., Chapter 8,
this volume). The aim of participatory domestication is not only to involve
farmers in selecting the most promising cultivars and planting materials, but
also to conserve, multiply and disseminate these materials.
19.3 Propagation by Sexual Techniques
Most miombo fruit trees can be propagated by seed. Uapaca seed does not
require pretreatment but soaking in cold tap water overnight hastens
germination (Ngulube, 1996). Germination is fairly uniform, reaching 30%
after 4 weeks and 90% after 6 weeks. Up to 100% germination has been
achieved at Makoka nursery (Akinnifesi et al. , 2007).
Propagation of Strychnos cocculoides by seed has been successful, with
80% germination for seeds sown in the propagation box during summer
(Taylor et al. , 1996; Mkonda et al. , 2004). In Botswana, seeds sown in winter
took more than 9 weeks to germinate, whereas those sown in summer
germinated within 3 weeks. Germination of Vangueria infausta is reportedly
sporadic until the seeds are scarified or treated with hydrogen peroxide
(Msanga and Maghembe, 1989). At Veld Products Research in Botswana, no
difficulty in germination of Vangueria infausta has been observed with seeds
sown in the summer months. Over 70% germination has been recorded within
21 days of sowing in sandy beds (Taylor et al. , 1996). In the following sections
we provide a brief review of progress made in understanding seed viability in
storage and the seed treatments required to obtain uniform germination of
miombo fruit trees in southern Africa.
19.3.1 Viability in storage
Seed viability under storage condition and germination vary from species to
species and depend on various factors. The seeds of some miombo fruit tree
species lose viability during storage, whether at room temperature (around 20°C)
or in a cold room (7-10°C) (Hans, 1981; Ngulube and Kananjii, 1989; Prins and
Maghembe, 1994). Characteristics such as a very hard seed coat, physiological
dormancy and low viability contribute to the poor germination of many
indigenous fruit species, such that it is difficult to obtain sufficient propagules for
planting (Kwapata, 1995). Some species, such as Uapaca kirkiana , have
recalcitrant seeds, i.e. seeds that do not tolerate low temperatures and lose their
viability if stored for any length of time, even under conditions that are normally
conducive to seed longevity (Dawson and Were, 1997). In U. kirkiana seed
viability is limited to a maximum of 4 months after removal from the fruit (Hans,
1981). According to Hans (1981), the viability of seeds of U. kirkiana can drop
from 80 to 20% within 4 months. This is due to the high water content of the
seed (48% of sun-dried seeds on a fresh weight basis). The seed has an inner
membrane, an endosperm and two leafy green cotyledons. It has no dormancy