Agriculture Reference
In-Depth Information
mycorrhiza is present. Repeated exposure of the difficult-to-root microcuttings
of
Pappea capensis
to 0.5 mg/l IBA improved rooting from 42 to 62%, and the
number of roots per plantlet averaged 3 (Mng'omba, 2007). Somatic embryos
of
P. capensis
were successfully germinated into plants (65%), and 65% of
plantlets survived after hardening off in a mist chamber.
Graft compatibility increased more with homografts than with heterografts
between
Uapaca kirkiana
clones, species and provenances.
Uapaca kirkiana
and
U. nitida
had weak compatibility and they may exhibit delayed
incompatibility. Although
Jatropha
and
Uapaca kirkiana
belong to same family,
there is outright incompatibility or early rejection. The technique seems
promising for the detection of early incompatibility between close and distant
related propagule sources. On the basis of a series of results, reproducible
micropropagation protocols have been developed for the rapid multiplication
of mature
Uapaca kirkiana
and
P. capensis
(Mng'omba
et al
., 2007a, b).
8.3.3 Tree management systems
Tree establishment and management
Grafting and air-layering of indigenous fruit trees have addressed precocity
problems, and enabled selection of superior fruit traits (Akinnifesi
et al
., 2006).
Using vegetative propagation approaches, especially air-layering and grafting,
clonal fruit orchards have been established at Makoka in Malawi for
Uapaca
kirkiana
from superior trees selected using participatory methods. Tree
establishment protocols used for the indigenous fruit trees were those employed
for mangoes. The rates of tree survival in the clonal orchards are generally high
for grafted
Adansonia digitata
(100%) in Zambia, for
Uapaca kirkiana
(80%) in
Malawi and for
Sclerocarya birrea
(90%) in Tanzania, but low (40%) for
Strychnos cocculoides
in Zambia (ICRAF, 2005). However, the survival of
established marcots was low in Malawi, and declined over a period due to poor
root development. Rejection in grafts is also attributed to stock/scion
incompatibility (Mng'omba, 2007).
Tree orchards established in Makoka from grafted trees started to fruit after 2
years, but fruit load only became stable after 4 years. However, limited research
has been conducted to date on management regimes of indigenous fruit trees in
terms of the responses of the trees to fertilizer, manure and irrigation.
In a recent tree management trial in Makoka, Malawi the effects of fertilizer,
manure and irrigation on the early growth and survival of
Uapaca kirkiana
,
Sclerocarya birrea
(subsp.
caffra
),
Vangueria infausta
and
Mangifera indica
(mango) were assessed. After 33 months, there was a striking pattern of high
mortality in
Uapaca kirkiana
in plots that received all the treatments (25%)
compared with those that did not receive any of the soil amendments (85%)
and in plots that received only irrigation (100%) but no fertilizer amendment
(Table 8.2). The trial showed that application of chemical fertilizer, compost
and irrigation did not improve the growth of
Uapaca kirkiana
in Malawi, and
that significant mortality may be observed with a combination of soil
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