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International Journal of Horticulture 2014, Vol.4, No.15, 1
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http://ijh.biopublisher.ca
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multiplication of pathogen-free potato cultivars. At an
interval of 21 days, at least 3 single node cuttings can
be obtained from a single microplant. Therefore,
theoretically 3
15
(14 million) micro plants can be
obtained from a single virus free mericlone in a year.
Single node culture is important in potato production
because rapid multiplication of disease-free seed
potatoes is the main bottleneck in production of
certified seeds in Kenya. Although single node culture
is the main approach employed in micropropagation
of potatoes in Kenya, little is known about the
multiplication rate of different potato genotypes when
they are multiplied through single-node culture. This
study was therefore undertaken to determine the
multiplication rate of selected potato genotypes when
they are micropropagated through single node culture.
Materials and methods
Seven potato cultivars (Table 1) commonly grown by
farmers in Kenya and currently conserved in
in vitro
form at the National Potato Research Centre, Tigoni
were involved in the trial.
Table 1 Potato cultivars used in the trial
Potato cultivar
Source of original germplasm
Year of release in Kenya
Kenya Mpya
CIP
2010
Sherekea
CIP
2010
Purple Gold
CIP
2010
Dutch Robyjn
The Netherlands
1945
Tigoni
CIP
1998
Kenya Karibu
CIP
2006
Desiree
The Netherlands
1972
The study was carried out in the plant tissue culture
laboratory at the National Potato Research Centre,
Tigoni between July and December 2013 (season 1)
and between January and May 2014 (season 2).
Preparation of growth media
The solid media consisted of the Murashige and
Skoog (1962) basal salts supplemented with glycine
(0.2 g/l), nicotinic acid (0.05 g/l), pyridoxine (0.05 g/l),
inositol (10 g/l), thiamine (0.01 g/l), giberellic acid
(0.001 g/l), and sucrose (30 g/l). The pH of the media
was adjusted to 5.8 using 1N NaOH or 0.1 m HCl.
Two and a half grams of phytagel was added to one
litre of the media as a solidifying agent. The culture
media was dispensed into 1 litre pyrex jars, the jars
were covered using aluminium foil and the
auctoclaved at 121
℃
for 15 minutes. Thereafter, 20
ml of the media was poured into each 500 ml plastic jars.
Preparation of the experimental materials
Seven tubers of each of the seven popular Kenyan
potato cultivars (Table 1) were potted. Four weeks
after potting, the plants were transferred to
thermotherapy chamber for heat treatment for one
month for virus elimination. The thermotherapy room
was maintained at a constant temperature of 38
℃
±2
and photoperiod of 16\8 during the entire period; the
high temperature increased the rate of production of
virus-free materials. Thereafter, 4-5 nodes from the
apical end of the sprouted plants were excised and
placed in 5% hypochlorite solution for 10 minutes and
then rinsed 3-4 times with distilled water. The
meristems were then dissected from each node under a
microscope and the meristem tips were carefully
transferred into plastic jars containing standard culture
media (Murashige and F. Skoog, 1962). Thirty
meristem tips of each variety were cultured (each jar
had 10 meristem tips), they were then incubated in a
growth chamber under 16 hrs of light and 8 hrs of
darkness at 22 ±2
℃
. After 10 weeks the meristems
developed into plantlets; these formed the experimental
materials.
Culturing of the single node cuttings
For each of the seven potato cultivars, the three plastic
jars containing the ten-week old
in vitro
plantlets were
used. Each jar, containing 10 plantlets was treated as a
replicate. From each jar, the 10 plantlets were cut into
single node cuttings and from each plantlet; one single
node cutting was selected and cultured for three weeks
in another jar containing solid media. There were 10
such single node cuttings in each jar. This was also
done for the two remaining jars to make three
replicates per potato cultivar. Each single node cutting
measured 5 mm and had one axial bud and the
subtending leaf.
The single node cuttings were