Germplasm Supply, Propagation and Nursery Management of Miombo Fruit Trees - Indigenous Fruit Trees in the Tropics: Domestication, Utilization and Commercialization - page 357

The potential of meeting the great demand for germplasm for scaling up in
the short run is low for most macrovegetative propagation approaches. All
known approaches to vegetative propagation are inherently slow and are
feasible for only a few hundreds or thousands of farmers. For instance,
rootstocks of Uapaca kirkiana need to attain pencil thickness before grafting is
possible, and this requires about 1 year of growth. In order to be able to deliver
high-quality propagules of superior indigenous fruit trees in sufficient quantities
it is important to exploit the potential of tissue culture.
Recently, in vitro culture of Uapaca kirkiana and Pappea capensis (plum)
was undertaken, with the objective of developing a reproducible clonal
protocol for rapid regeneration and multiplication, and to determine early graft
compatibility using in vitro techniques (Mng'omba, 2007; Mng'omba et al .,
2007a, b). Based on a series of results, reproducible micropropagation
protocols have been developed for the rapid multiplication of mature U.
kirkiana and P. capensis (Mng'omba, 2007; Mng'omba et al. , 2007a, b). The
technique is promising for the detection of early incompatibility between close
and distantly related propagule sources. Graft compatibility was greater for
homografts than for heterografts among and between U. kirkiana clones,
species and provenances (Mng'omba, 2007).
Results also showed that in vitro propagation of U. kirkiana is feasible with
sprouts excised from preconditioned trees (Mng'omba, 2007). Better results were
obtained when micropropagation of U. kirkiana was undertaken in such a way
that stock plants were not stressed. Repeated exposure of the difficult-to-root
microcuttings of P. capensis increased the success of in vitro culture (Mng'omba,
2007). Somatic embryos of P. capensis were successfully germinated into plants
(65%), and there was 65% plantlet survival after hardening off in a mist chamber.
Nkanaunea et al. (2004) investigated the effects of age and type of rootstock
and light intensity on the success of micrografting U. kirkiana in Malawi.
Comparison of a factorial combination of three rootstock ages (2, 3 and 4
months), two types of rootstock (rooted and unrooted) and four light intensities
(photosynthetic photon flux density 0, 45, 135 and 225 mol/m 2 /s) indicated a

significant effect of those factors on the success of micrografts. The best
micrograft success was achieved when 2-month-old rooted rootstocks were used
and the cultures were incubated under illumination at 45

mol/m 2 /s (Nkanaunea

et al. , 2004).

19.5 Nursery Management

Until recently, techniques for seed treatment and enhancing growth in the
nursery using ideal propagation media and optimum fertilizer regimes have not
been available to farmers. There has also been a lack of information on the
ecological requirements of many miombo fruit tree species. For example, the
requirement for inoculation with rhizobia and mycorrhizal symbionts has not
been studied.
Nursery management is a crucial aspect of providing good-quality planting
materials in adequate quantities (Wightman, 1999). Tree seedling quality has