Germplasm Supply, Propagation and Nursery Management of Miombo Fruit Trees - Indigenous Fruit Trees in the Tropics: Domestication, Utilization and Commercialization - page 361

preferences have been observed in some trials, mycorrhizal fungi do not need a
specific host nor do host plants require a particular mycorrhizal species (Muller-
Samann and Kotschi, 1994). The stimulating effects of different fungi can vary
considerably in the same host plant (Mwamba, 1995). In Sclerocarya birrea
subsp. caffra , early growth in height was enhanced by association with
mycorrhizal fungi of the genera Acaulospora and Glomus (Bâ et al. , 2000;
Mateke and Tshikae, 2002). Research on growth and survival of Strychnos
cocculoides has indicated difficulties in raising seedlings in the nursery (Taylor
et al. , 1996; Mkonda et al. , 2004). This species seems to be affected by
mycorrhizal factors as well as shade.
19.5.3 Seedling fertilization
There is a dearth of information on the fertilizer requirement of indigenous fruit
tree seedlings. In a study on the effect of soil-applied and foliar fertilization on
the growth of Uapaca kirkiana , we compared application of D-compound
fertilizer versus no fertilizer application, and foliar application versus no
application. Compared with the untreated seedlings, those with soil fertilization
showed significantly increased height growth, decreased growth in stem
diameter and root length and fewer primary roots, while fertilization did not
affect leaf number and root dry weight. Foliar application of fertilizer increased
height growth and shoot dry weight but did not affect leaf number, growth in
diameter, root length and root dry weight (Table 19.2).
19.5.4 Pest management
Several species of pests affect miombo fruit tree seeds and seedlings in the
nursery (Sileshi et al. , Chapter 20, this volume). Seed-borne microorganisms may
reduce seed viability, germination and seed longevity in storage of all types of
seeds. Diseases of seeds and germinants are often overlooked in the nursery as
the affected seeds are not visible and consequently the losses are often attributed
to poor seed. To ensure germination in the nursery, seeds need to be examined
and the problem characterized before management methods to reduce the
problem can be developed. Indigenous fruit tree seedlings also suffer from attack
by a wide range of fungi in the nursery. Fungi that cause foliage diseases in the
nursery usually require conditions of high moisture and free water for long
periods of time to establish infection. Such moisture occurs during extended
periods of rain or fog, or during continued use of overhead irrigation. Fungal
diseases may affect the roots, stem or foliage of seedlings, and can reduce
seedling survival and growth. For instance, survival of Uapaca kirkiana seedlings
in the nursery has been very low (<10%) at Msekera, Zambia (G. Sileshi,
unpublished results) compared with greater than 80% in Makoka, Malawi (T.
Chilanga, unpublished results). The low survival in Zambia was attributed to
various foliar diseases, nutrient deficiencies and possibly inadequate mycorrhizal
inoculants. Studies on the effects of three potting mixtures (unsterilized forest soil,