International Journal of Horticulture, 2017, Vol.7, No.17, 138-145
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process but
in vitro
system provides the detailed description of the whole phenomenon. Thus microtuber
production is one of the strategies under this perspective.
In Potato,
in vitro
tuberization is a highly complex phenomenon that can be induced under
in vitro
conditions.
Because of their small size and weight, microtubers have remarkable benefits for getting disease free plant
material, easy storage and transportation (Kefi et al., 2000; Kanwal et al., 2006) over conventionally grown seed
potatoes. The other benefits are the less chance of drying out while storage, short dormancy time and high rate of
survival in direct transfer to soil (Kefi et al., 2000). Therefore different research groups around the globe are trying
to bring about this revolution (Gopal et al., 2004; Zhijun et al., 2005; Zhang, 2006). Various evidences for
resilient and consistent analogies between
in vitro
and field grown tubers for their induction, growth and
development have been documented in literature.
There are several components such as the rapid and near synchronous induction and growth that can be modified
by using a range of exogenous compounds and even altering growth conditions, make the microtuber a valuable
model system (Coleman et al., 2001). This technique reduces the time taken to yield seed tubers, lessen the
number of field generations needed and ultimately in higher class seed tubers (Jones, 1994). Keeping in view the
above mentioned benefits of
in vitro
tuberization approach, this study was designed. In this research study,
photomixotrophic conditions for a proficient and expedite
in vitro
tuberization system in selected local genotype
of potato (cv. PRI-Red) was optimized. In addition to this, photomixotrophic conditions in terms of their effect on
morphological, anatomical, physiological and biochemical characteristics of microtubers were evaluated.
2 Material and Methods
Potato genotype to be used
: Local Pakistani Potato cultivar, PRI-Red was collected from Potato Research
Institute, Sahiwal, Pakistan.
Explant to be used
:
In vitro
micropropagated shoot was used as explant.
Culture media for in vitro tuberization
: Nine different media were formulated for
in vitro
tuberization of cv.
PRI-Red. Each medium contains basal MS salt and vitamins, supplemented with 60 g/L, 80 g/L and 100 g/L
sucrose; 0, 3.75, 4.75, 4.5 mg/l, 5 mg/l Kinetin and 0, 3.75, 4.75, 5.5 mg/l, 6 mg/l BAP, alone or in combination.
These media formulations were referred as; TM1, TM2, TM3, TM4, MPm5, MPm6, TM7 and TM8 and TM9
(details of these media is given in Table 1). All media components were mixed together, adjusted to pH 5.7-5.8
and solidified with 2.66 g/l Gellan gum powder. Thereafter, these media were autoclaved at 121˚C and 15 psi for
20 minutes.
Table 1 Tuberizationmedia (TM): MSN* (MS salt = 4.33 g/l, Myoinositol = 0.1 g/l, Nicotinic acid = 1 g/l, Pyridoxine HCl = 1 g/l,
Thymine HCl = 2 g/l, Glycine = 4 g/l, Gellan gum powder = 2.66 g/l)
TM1
TM2
TM3
TM 4
TM 5
TM 6
TM 7
TM 8
TM 9
Sucrose
60 g/L 100 g/L 80 g/L 80 g/L 100 g/L 80 g/L
80 g/L 80 g/L 80 g/L
Kinetin
0 mg/l
0 mg/l
3.75 mg/L 4.75 mg/L 4.75 mg/L 0 mg/l
0 mg/l
4.5 mg/L 5 mg/L
BAP
0 mg/l
0 mg/l
0 mg/l
0 mg/l
0 mg/l
3.75 mg/L 4.75 mg/L 5.5 mg/L 6 mg/L
Nutrient spp.
MSN* MSN* MSN*
MSN*
MSN*
MSN*
MSN* MSN* MSN*
In vitro
tuberization:
In vitro
micropropagated shoots of selected genotypes (cv. PRI-Red) were cultured on all
nine
in vitro
tuberization media describe. For culturing, the micropropagated shoots were excised in such a
manner that each cutting contained 1-2 buds. All operations were accomplished in sterile conditions, under
laminar air flow hood. Cultures were maintained in dark conditions at 21
0
C as well as some cultures were kept at
26±1˚C for 16/8 hrs light/dark regimes. Subsequent maintenance of these cultures was achieved by biweekly
subcultures.
