| dc.description.abstract | A study on propagation of Uapaca kirkiana using tissue culture-techniques was done
G '
at Bunda College of Agriculture. Experiments were conducted on In Vitro and In Vivo
seed germination; axillary shoot proliferation using seedling stem nodal sections;
direct organogenesis and callus development from stem shoot sections, adult tree leaf
and cotyledonous explants; and root development. Explants were fruits obtained from
a local market, some fruits direct from trees and adult tree explants were obtained
from Uapaca kirkiana provenance near the College.
Treatments in the seed germination experiments included surface sterilization of seeds
with four different concentrations of sodium hypochlorite (NaOel) and four exposure
times; primary and secondary seed-coat removal; split-plot treatments of two fruit
sources (market and direct from trees) as main factors, and two seed germination
media - Murashige & Skoog (MS) and Woody Plant Medium (\VPIYf) as subplot
factors. Another seed germination experiment was set up in a green house with the
two fruit sources as main factors and primary seed-coat removal and non-removal as
sub- factors.
The axillary shoot proliferation experiment used seedling stem nodal sections as
explants. Treatments included 0, 5, 10, 20, 40, 80, and 160 mg/l of kinetin growth
regulator supplement on WPM media in a preliminary test. A detailed experiment
followed with a split-plot design which included five indole butyric acid (IBA) levels
(0.0,0.25,0.50, 1.00,2.00 mgll) as main factors and the same five levels of kinetin
as sub-factors. The direct organogenesis and callus experiments tested three types of
tree organs which included adult stem shoot sections, leaf sections and cotyledonous
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leaf sections. MS basal salts media were supplemented with 2mgll lAA +2mgll
kinetin+ 1Omgll inositol and White vitamins and glycine + 80mg(l adenine sulphate +
IOmg/1tyrosine for direct organogenesis; and 2mglllAA + O.5mgJIkinetin for callus
development.
Explants for rooting experiment were obtained from axillary shoot proliferation
plantIets and tested on rooting media in a split-plot design. The main factors were two
basal salts (MS and \VPM) and subfactors were five IBA growth regulator levels (0.0
IBA, 0.5 IBA, 0.5 IBA + 0.5 NAA + 0.5 BAP, 1.0 IBA and 2.0 IBA in mgll. The
containers used for media were 25mm x 150mm belli co tubes with 20 ml quantities.
Each treatment had N=20 cultures.
Incubation of cultures was done under 16 hours light illumination at 4511EM~-1 except
for callus cultures which were incubated under 24 hour darkness. Temperatures were
maintained within the range of 25 to 28°C. The data collected was subjected to
Analysis of Variance and regression analysis where necessary.
"... ,.
Optimum concentration of NaOCl "for surface sterilization for the U kirkiana seeds
was 2% for 20 minutes. Removal of both primary and secondary seed-coats promoted
the number of aseptic seedlings. The !viS medium gave significantly higher frequency
of normal seedlings (90%) and multiple seedlings/seed (90%) than \VPM medium in
the first experiment. When the experiment was repeated the effect of the two media
did not significantly differ. Primary seed-coat removal improved in vivo germination
from 55% to 780/0and from 35% to 95% for market fruits and fruits direct from trees
respectively. The seeds exhibited apomixis with a maximum of 9 seedlings/seed for
VIl
in vitro, and 2 seedlings/seed for in vivo germination.
The high number of shoots that developed per axillary nodal bud section was achieved
with supplementation of 0.50 mg/l kinetin alone (1.3 shoots) or combined with 0.25
mg/l IBA (I.Ishoots), 2.0 mgll kinetin alone (1.1shoOLS)or combined with 0.5 mgll
IBA (1.3 shoots).
The direct organogenesis and callus cultures did not regenerate into adventitious
plantlets but just developed callus and embryoids. The stem sections had a high callus
development frequency (67.5% partial and 15% full) followed by cotyledonous
sections (27.5% partial and 200/0 full). Adult tree leaf explant callus development
failed because all cultures had fungal contamination. The subcultured calli
proliferated fastest on \VPM supplemented with 3.0 mg/l IAA. Higher ratios of kinetin
to auxin (IAA) slowed calli proliferation. In the rooting experiments, MS media
containing 1.0 and 2.0 mg/l IBA promoted rooting at 65% (1.7 roots/plantlet) and
60% (1.3 roots/plantlet) respectively, than lower levels of IBA. The MS media
promoted better rooting (0.7roots/plantlet) than the WPM media (0.4 roots/plantlet).
Further investigation on media protocols to improve adventitious axillary shoot
proliferation and rooting performance to ensure high field survival of the U. kirkiana
plantlets is suggested. Chemical names used: 6-furfurylaminopurine (kinetin);
benzyladenine (BA); N6-benzylaminopurine (BAP); 1 H-indole-3-butyric acid (IBA);
2-naphthaleneacetic acid (NAA); indole-3-acetic acid (IAA); and gibberellic acid
(GA3)· | en_US |
