Ecology and Biology of Uapaca kirkiana, Strychnos cocculoides and Sclerocarya birrea in Southern Africa - Indigenous Fruit Trees in the Tropics: Domestication, Utilization and Commercialization - page 333

rooted propagules in the nursery and ramet survival in the field may decline
with time because of the difficulty of tap root development, fertilizer and
mycorrhiza requirements (Akinnifesi et al ., 2004). Top-grafting has also been
successful in the field (Mkonda et al ., 2001; J. Mhango, unpublished results).
Tissue culture research has also proved to be promising for detecting early
stock/scion compatibility in U. kirkiana (Mng'omba et al ., 2007; Chapter 19,
this volume. Current effort involves the use of tissue culture to determine
scion-rootstock compatibility. Compatibility differs between heterografts and
homografts, and also between species, provenance and clones (Mng'omba et
al ., 2007). However, excessive accumulation of phenolic compounds remains a
challenge when using tissue culture to multiply Uapaca .
18.2.3 Strychnos cocculoides (Baker)
Strychnos cocculoides belongs to the family Loganiaceae. This is a
semideciduous small tree, 2-9 m high, with spreading branches and a compact,
rounded crown, which grows on both deep and loamy sands (Storrs, 1995).
The bark is thick, creamy-brown, deeply corky and ridged longitudinally. The
branchlets are hairy, purple or blackish-purple with strong paired spines curved
downwards (Ruffo et al ., 2002). The leaves are opposite, oval to circular in
shape and up to 5 cm long, green to yellowish green in colour, and
conspicuously five-veined from the base.
Ecology
The genus Strychnos is widespread in the tropical parts of Africa, South
America and India but the species S. cocculoides is restricted to central and
southern Africa (AFT Database; Ruffo et al ., 2002; ICUC, 2004). In southern
Africa, S. cocculoides grows naturally in Brachystegia woodlands, mixed
forests, deciduous woodlands and lowlands. The biophysical limits are an
altitude of 0-2000 m, mean annual temperature of 14-25°C and mean annual
rainfall of 600-1200 mm. The species grows in a range of soil types from less
fertile, deep sandy soil on rocky slopes, acidic clays to red or yellow-red loams.
Strychnos cocculoides is usually associated with other species in the
miombo woodlands. It has been reported as one of the dominant or
codominant species together with species such as Acacia spp., Combretum
spp., Terminalia spp., Adansonia digitata , Millettia stuhlmannii , Uapaca spp.,
Trichilia emetica , Sclerocarya birrea , Guibourtia conjugata , Hymenocardia
ulmoides , Pteleopsis myrtifolia , Xeroderris stuhlmannii , Albizia versicolor ,
Albizia adianthifolia , Afzelia quanzensis , Burkea africana , Pterocarpus spp.,
Pseudolachnostylis maprouneifolia , Dialium schlechteri , Lonchocarpus capassa ,
Syzygium cordatum and Garcinia livingstonei in Mozambique and Zimbabwe
(Duarte-Mangue and Oreste, 1999; Nyoka and Muskoyonyi, 2002). It is also
an associated species in the Terminalia-Combretum woodlands together
with Sclerocarya birrea , Saccharopolyspora spinosa , Piliostigma thonningii ,
Terminalia sericea and Combretum spp. (Nyoka and Muskoyonyi, 2002).