Response of Two Sweet Potato (Ipomoea batatas L. Lam) Varieties
Regenerated on Low Cost Tissue Culture Medium
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alternative source of sucrose. The low cost medium
consisted of 100 mL/L of macronutrients’ stock
solution, 10 mL/L of magnesium sulphate stock
solution, 0.2 g/L of Stanes Iodized Microfood®, 30 g/L
of table sugar and 3 g/L of gelrite. The MS salts
supplemented with 30 g/L of table sugar and 3 g/L of
gelrite were used as the control. Both media were
sterilized by autoclaving at a temperature of 121 °C and
15 pounds of pressure per square inch for 15 minutes.
2.3 Preparation of Explants
Nodal explants were obtained from healthy
mother stock plants and washed with running tap
water. They were then disinfected with 70% v/v
ethanol for six minutes and 1.5% sodium
hypochlorite containing a drop of Tween 20®
for 20
minutes. The explants were then rinsed four times
using sterile distilled water and kept in the laminar
hood flow under sterile conditions.
2.4 Culture Initiation
The damaged ends of the sterile explants were
spliced off with a sterile scalpel into 2 cm long pieces.
They were then inoculated on the culture media and
the culture bottles labeled with the variety type and
date of culture. The cultures were then transferred into
the growth room where they were arranged in a
completely randomized design with nine replications
per variety and incubated at a temperature of 28 °C
with a photoperiod of 16 hours light and eight hours
darkness. The cultures were regularly checked and the
progress in leaf formation, node development, root
production and plant height recorded at intervals of 14
days for six weeks.
2.5 Data Analysis
Analysis of variance was done using STATA®
statistical program to ascertain the differences
between the two sweet potato varieties for the
parameters measured. Separation of means was done
using Tukey’s test at 5% significance level.
3. Results and Discussion
With the increasing human population, there is an
urgent need to increase food productivity to meet the
expected rise in demand. Attention has shifted to
biotechnological techniques to increase food
production. Tissue culture is one of these techniques
and has really boosted propagation of vegetative crops
and aided crop transformation through genetic
engineering. Tissue culture involves asexual
propagation to generate whole plants from small plant
parts or cells [7]. The technique allows thousands of
genetically identical plants to be derived from a single
cell or tissue within a short time. Successful in vitro
plant regeneration protocols are also paramount in
successful genetic modification. Tissue culture has
been applied for many years now in production of
seedlings for many vegetatively propagated crops
including sweet potato. However, farmers from many
developing countries have not benefited fully from
this technology, a factor attributed to the high cost of
production. Efforts have been made to lower
production costs but this has mainly concentrated on
crops such as banana and cassava with little done on
sweet potato. Sugarcane juice has been reported as an
alternative source of carbon for banana and plantain
tissue culture [8]. A lot of work has also been done in
reducing the cost of tissue culture for cassava [5, 9].
However, the differential response of various crop
varieties to tissue culture makes the work of designing
cost efficient media even more difficult.
The results of this study indicate that genetic
make-up of a crop affects its response to tissue culture.
The two sweet potato varieties exhibited significant (P
< 0.05) differences in node development from the first
week of culture with KEMB 36 producing more nodes
compared to Tainurey (Fig. 1). The variety KEMB 36,
therefore, had a higher regeneration index compared
to Tainurey hence best suited for this medium because
a high number of planting materials can be obtained.
However, the variety had small inter-nodal space making