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Studies on Micropropagation and Plant regeneration of
Sweet Potato
(Ipomoea batatas)
Mamatha M Pillai
M Unnikrishnan ( Principal scientist )
CTCRI Trivandrum
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ACKNOWLEDGEMENT
I express my deep sense of gratitude and personal indebtedness to my guide M. Unnikrishnan, Principal
Scientist, Division of Crop Improvement, Central Tuber Crops Research Institute, Trivandrum for his valuable
guidance, constructive criticism and sincere help in the conduct of project and preparation of thesis.
I express my heartful thanks toDr. Winny Varghese, Principal, Mar Athanasius College, Kothamangalam
for his sincere encouragement in conducting the study.
I record my heartful gratitude toDr. Yamuna Anu Joseph, Head of the Department of Biotechnology, MarAthanasius College, Kothamangalam for her whole hearted support and timely help to carry out the study.
I am most grateful to Mr. Paul George, Lecturer, Department of Biotechnology, Mar Athanasius College,
Kothamangalam for his sincere guidance and help in completing this project successfully.
.I express my thanks to all the Staff members of the Department of Biotechnology, Mar Athanasius
College, Kothamangalam.
I am extremely indebted to my Parents andFriends for their consistent encouragement and unfailing help
rendered to me without whose help this work would not have been possible.
I am thankful toEach andEveryone who helped me to complete this work successfully.
I thank God Almighty who has given me strength, courage, and blessings to carry out the study
successfully.
Mamatha M Pillai
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PREFACE
Vegeculture, tropical food production based on vegetatively propagated energy crops, probably emerged
before agriculture based on cereals and grains. The tropical root and tuber crops (cassava, sweet potato, yams and
aroids) are among the oldest on earth. In many areas, especially in the wet tropics, they were the only staples and
fed extensive populations before the introduction of cereals. Today, they represent the second most important set of
food crops in developing countries, closely following the cereals. They are produced with low inputs but are an
important source of income and employment in marginal areas, especially for women. Consumed mostly by the
poorest, they contribute greatly to food security and are held in high esteem culturally. They are also cash crops and
are used for animal feed or as raw material for industrial processing.
Sometimes considered as plants of the past, they are, on the contrary, crops of the future since they allow
local production of carbohydrates, which can substitute expensively imported cereals. With world population
projected to increase from the present 6.6 bn to 8 bn by 2025, it may be argued that the demand for carbohydrates
will soon exceed the production potential of areas devoted to the cultivation of cereals. This is especially critical in
the wet tropics, where the majority of the world population lives. In circumstances of global climatic change, such a
scenario may render increased production of tropical root and tuber crops imperative. This may come about all the
sooner if some countries decide to retain their harvests of cereals, to divert it into the production of biofuels, or if
the ever-increasing cost of energy causes imported foodstuffs to become too expensive.
As a group, the tropical root and tuber crops are efficient plants and if marginal land is to be exploited to
support burgeoning populations, their potential, clearly untapped, will need to be developed. Although these species
belong to different botanical families, they are grouped together because they are vegetatively propagated, bulky
and perishable. Despite these constraints, they have proven surprisingly transferable and are now cultivated
throughout the world. In many places, they are grown together within the same plots, in home gardens or in mixed
cropping systems, complementing each other throughout the year to produce a steady supply of energy.
Vegeculture is very much alive and adapting to changing environments. However, compared to other crops
of equivalent economic importance, the tropical root and tuber crops are seriously under-researched. Considered in
most developing countries as of lesser priority, well below traditional exportcommodities inherited from the colonial era, these food crops do not receive from governments the attention they
deserve. More widely, western ethnocentric prejudices have induced an even more striking neglect of their essential
food security role.
Food scarcity and high level of malnutrition remains continued to be a developmental puzzle for the
Republic of the Marshall Islands because of a major problem of limited land resources accompanied with poor
quality, nutrient deficient soil. Vitamin A deficiency in Marshallese children is highest in the world according to
World Health Organization (WHO). The main theme of the proposed research program is to introduce sweetpotato
using emerging innovative plant tissue culture to ensure food and nutritional security. The technology generated
would also lead to in vitro germplasm conservation of sweetpotato.
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CONTENTS
1. INTRODUCTION .. 42. OBJECTIVES 83. REVIEW OF LITERATURE 94. MATERIALS AND METHODS 115. RESULTS .196. DISCUSSION .. 387. SUMMARY .. 98. BIBLIOGRAPHY 40
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1. INTRODUCTION
1.1 ROOT CROPS
The major tropical root crops of the world are Cassava (Manihot esculenta), Sweet Potato (Ipomoea
batatas), Yams (Dioscorea spp) and Taro (Colocasia esculenta). In terms of world production, these tropical root
crops are fifth behind Wheat (510 million t), Maize (490million t) Rice (466 million t) and White potatoes (299
million t) (FAO Production year book 1998.)
Tuber crops are the most important food crop of mankind after cereals and legumes. The importance of
tuber crops is mainly because of the high starch content, which make them high caloric value food and also a rich
source of starch. Starch characters make them valuable in food and industry.
1.2 IMPORTANCE OF CROP PRODUCTION AND CROP IMPROVEMENT
With the growing population, pressure on agricultural land and available food costs of rice directly affect
the low income populations which are already deficient in calories besides escalating costs of rice. In this context,
root crops are the only potential supplementary food crops as they can provide more energy per unit area than any
other field crop and are cheap source of energy.
In order to fill the anticipated energy gap, production has to be increased. Thus, expansion of area of
cultivation and crop improvement are two important and concurrent prerequisites to increase crop production.
1.3. IMPORTANCE OF SWEET POTATO
Sweet potato (Ipomoea batatas L.) ranks seventh among all food crops worldwide, with an annual income
of 115 million metric tons. Of the root and tuber crops the Sweet potato ranks third in acreage (7.9 million ha)
behind the potato and cassava. Sweet potato is grown in more than 100 countries and among the worlds root and
tuber crops, it ranks second in importance. It is consumed as a fresh vegetable (roots, petioles, leaves and stems),
staple food, snack food and it is also used for industrial starch extraction and fermentation. Sweet potato is
industrially dehydrated and used as an important component of bread flour. Sweet potato is consumed as a substitute
to rice and wheat flour, especially by the low income classes of the population in Africa and many Asian countries.
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1.3.1. MORPHOLOGY OF SWEETPOTATO
Sweet potato (Ipomoea batatas) is a dicotyledonous plant that belongs to the family Convolvulaceae. Its
large, starchy, sweet tasting tuberous roots are an important root vegetable (Woolfe, 1992).
Root System: The sweet potato root system consists of adventitious roots that absorb nutrients and water, and
anchor the plant, and storage roots that are lateral roots which store photosynthetic products
Tuber in sweet potato it is specialized root tubers which can be used as propagating material as its sprouts and
produces plants.
Stem: A sweet potato stem is cylindrical and its length, like that of the internodes, depends on the growth habit of
the cultivar and of the availability of water in the soil.
Leaves: The leaves are simple and spirally arranged alternately on the stem in a pattern. Depending on the cultivar,
the edge of the leaf lamina can be entire, toothed or lobed.
Flowers: The inflorescence is generally a cyme. The gynoecium consists ofa pistil with a superior ovary, two
carpels, and two locules that contain one or two ovules.
Fruit and Seeds: The fruit is a capsule, more or less spherical with a terminal tip, and can be pubescent or glabrous.
Sweet potato shows self incompatibility. Seed is having hard testa which requires scarification for germination.
1.4. RELEVANCE OF TISSUE CULTURE
Sweet potato and many other vegetatively propagated plants are frequently characterized by their inability
to produce seed due to the presence of one more factors, such as incompatibility, dichogamy, abnormal seed and
seeding development, seed dormancy and environmental condition which affect flowering and seed settings.
Presence of these factors poses some limitations on the use of environmental techniques for improvement
of these crops. Therefore as it has been exploited for many other crops, tissue culture technology could offer a very
valuable tool for improvement of these crops.
Tissue culture system is capable of creating genetic variability and producing plants with novel characters,
which could be more favourable than the existing crop varieties. Apart from that, culture techniques which were
http://en.wikipedia.org/wiki/Dicotyledonoushttp://en.wikipedia.org/wiki/Convolvulaceaehttp://en.wikipedia.org/wiki/Starchhttp://en.wikipedia.org/wiki/Tuberous_roothttp://en.wikipedia.org/wiki/Root_vegetablehttp://en.wikipedia.org/wiki/Root_vegetablehttp://en.wikipedia.org/wiki/Tuberous_roothttp://en.wikipedia.org/wiki/Starchhttp://en.wikipedia.org/wiki/Convolvulaceaehttp://en.wikipedia.org/wiki/Dicotyledonous7/31/2019 Mamatha Thes
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first developed by Robbins in 1972 accomplished several important applications such as germplasm conservation,
exchange of germplasm and virus elimination.
At present, germplasm of root crops is conserved by maintaining them in the field through annual
propagation. In the case of sweetpotato propagation is required every three months. Thus, the crop is mostly
exposed to the hazards of environmental stresses, pests and diseases. Conservation of germplasm through seed is
impossible due to highly heterozygosity nature of the seedling progeny. On the other hand, conservation of plantlets
regenerated through meristem culture has several advantages. The germplasm is traditionally exchanged through
tubers and cuttings which are susceptible for external as well as internal infestations. Exchange through meristem
culture holds great promise for national and international dissemination of germplasm as it assures freedom from
infestations. Adoption of this technique poses less quarantine problem too.
1.5 ADVANTAGES OFIN VITRO GENE BANK:
Low labour costs. Absence of field infection Protection against unfavorable climatic conditions. Timely access to material under maintenance. Timely access to material for pathogen cleanup. Permanent availability of (when pathogen tested) material for exchange and multiplication of disease free
planting material.
omoea batatas)
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2. OBJECTIVES OF THIS WORK
This work entitled Studies on Micropropagation, Plant regeneration, Development of Media for in vitro
flowering and Molecular characterization of Sweet potato (Ipomoea batatas) has the following objectives,
In vitro culturing of plants. Plant regeneration through somatic embryogenesis Germplasm conservation through slow growth cultures. Production of virus free plants through meristem culture.
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3. REVIEW OF LITERATURE
3.1. TISSUE CULTURE
Development of science of tissue culture is historically linked to the discovery of the cell and subsequent
propounding of cell theory. Plant tissue culture is the science of growing plant cells, tissues or organs isolated from
the mother plant, on the artificial media. It includes techniques and methods used to research into many botanical
disciplines and has several practical objectives.
The in vitro techniques were developed initially to demonstrate the totipotency of plant cells predicted by
Haberlandt in 1902. Totipotency is the ability of a plant cell to perform all the functions of development, which are
characteristic of zygote, i.e., ability to develop into a complete plant. In 1902, Haberlandt reported culture of isolated
single palisade cells from leaves in Knop's salt solution enriched with sucrose. The cells remained alive for up to 1
month, increased in size, accumulated starch but failed to divide. Efforts to demonstrate totipotency led to the
development of techniques for cultivation of plant cells under defined conditions.
The brilliant contributions from RJ. Gautheret in France and P.R. White in U.S.A. during the third and the
fourth decades of 20th century may be considered a foreword for the discovery of plant tissue culture. An
important breakthrough for continuously growing tip cultures came from White (1934, 1937), who initially used
yeast extract in a medium containing inorganic salts and sucrose. Most of the modern tissue culture media derive
from the work of Skoog and co-workers during 1950s and 1960s. Since the 1960s, research on the propagation of
plants by tissue culture at an ever increasing pace.
3.2. SWEET POTATO MICROPROPAGATION
3.12.1. Meristem culture
The meristem tip is meristem together with 1-2 primordial leaves and measuring between 0.1 -0.5 cm in
height (Biggs et al. 1985). In vitro cultures could be established in sweet potato from meristem tips 0.1 mm excised
from shoots derived from tuber sprouts (IBPGR 1987; Alconero et al. 1975).Meristem tip culture is used
successfully to remove viruses, bacteria, and fungi from plants.
3.12.2. Nodal culture
Sweet potato cultures could be initiated from nodal explants as well as internode derived callus. Nodal
culture could grow and further multiplied on Murashige Skoog medium without growth regulators where they
developed roots and could hardened and transplanted (Unnikrishnan et al. 1990).
Growth ofin vitro cultures of sweet potato improved under optimal photoautotrophic condition (without
sugar in the medium and under 100 M m-2 s-1 PPFD and enriched CO2 concentration) (Kozai et al. 1996). A two
stage protocol is reported to be more effective for micropropagation of 27 sweet potato genotypes. Initially, leaf
explants are grown on MS medium with 2, 4-D (0.1 mg/l) and zeatin (0.2 mg/l) until the base of the petiole begins
to swell (2-4 days). Then, they are transferred to a medium with zeatin (0.8 mg/l) wherein high-frequency shoot
regeneration occurs (Raja Sree et al.2001).
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Shoot tip meristem along with a leaf primordium cultured on Murashige Skoog medium with GA and
kinetin produced plantlets, which, on testing were found to be virus-free. GA and Kinetin in combination, or GA
alone, was found to be more effective for the fast development of meristem cultures (Unnikrishnan et al. 1990).The
meristem derived plants were subjected to virus indexing through serodiagnostic methods as well as by grafting
onto indicator hosts (Alconero et al. 1975). Pathogen free germplasm accessions have been used for safe exchange
of germplasm ( IBPGR 1987).
3.12.3.In vitro conservation under Slow- Growth
There are several methods by which slow growth can maintained. It is possible to limit growth by
modifying the culture medium, mainly by reducing the sugar or mineral elements concentration and reducing of
oxygen level available to culture by covering explants with a layer of liquid medium or mineral oil ( Nyman et.al,
1987). Sweet potato cultures could be kept under slow growth at 3% concentration of mannitol. Slow growth could
be also be induced by limiting incubation temperature at 16-18C. (IBPGR 1987). The cultures could be isolated in
Murashige Skoog media having 3% sucrose and mannitol each supplemented with NAA, BA (0.1 M) and GA
(0.3M), for upto 12 months at 25-28C (Unnikrishnan et al.1990). Use of osmotic retardants and low temperature
was found to induce slow-growth in sweet potato cultures. Use of low sugar medium (2%) alone, as well as
mannitol (2% and 3%), in Murashige Skoog medium was found to be effective in stretching subculture intervals
upto 14 months (Chandel et. al 1997).
3.12.4. Anther Culture
Response to anther culture was found to depend on genotype as well as on media as observed in Cassava.
Callus induction was obtained on Murashige Skoog medium supplemented with NAA and cytokinins (BA/
Kin/2ip). Regeneration was obtained on subsequent cultures on anthers on Murashige Skoog medium with 2, 4 Dand Murashige Skoog basal medium without growth regulators. The plants were transferred and established
successfully. They showed hetroploidy (chromosome number 70-80) with anomalies like lagging chromosome
and disturbed polarity of metaphase plates. Lower ploidy (2n=51) was also noticed (Mukherjee et al. 1991).
Embryoid formation and plant development from sweet potato anther-derived callus has been reported by other
workers too (Kobayashi 1991).
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4. MATERIALS AND METHODS
4.1. MATERIALS
4.2. EXPERIMENTAL PLANT MATERIAL:
Indigenous and exotic collection of sweet potato maintained in the Central Tuber Crop Research Institute
(CTCRI) of Indian Council of Agricultural Research (ICAR), Trivandrum, Kerala, India were used as the source of
experimental plant material.
4.3. MEDIA:
The successful plant tissue culture depends upon the choice of effective nutrient medium. Virtually all
tissue culture media were synthetic or chemically defined. The cells of the most plant species can be grown on
completely defined media.
The nutrient medium for most tissue culture was comprised of five groups of ingredients, inorganic
nutrients, carbon source, vitamins, growth regulators and organic supplements.
Inorganic Nutrients:Inorganic nutrients consist of macro and micro elements and their salts. Usually nutrient media contain
25mM each of nitrate and potassium.
a. Macro Nutrients
They include nitrogen, phosphorous, calcium, potassium, magnesium and sulphur.
b. Micronutrients:
Mineral elements were very important for the growth the plant. They include iron, manganese, zinc, boron,
copper, molybdenum, cobalt, and iodine. These elements are needed only in small quantities, so they are called
micro elements or miner elements.
VitaminsTo achieve the best growth of the tissue it was after essential to supplement the medium with one or more
vitamins. These include nicotinic acid (Vitamin B1), pyridoxine (vitamin B6) and myoinositol.
Carbon Source:Carbohydrates were used as the carbon source. Sucrose and glucose were commonly used one. The source
in the medium was rapidly converted into glucose and fructose. The glucose was absorbed first followed by
fructose.
Plant Growth Regulators:A balanced combination of plant growth regulators was required for substantial growth. Auxins (IAA,
NAA, 2, 4-D) were commonly used to support cell division and callus growth. Cytokinins like (TDZ, BAP) were
employed to promote cell division, regeneration of shoots, often somatic embryoids induction and to enhance
proliferation and growth of axillary buds. Gibberellins (GA3) promote shoot elongation and somatic embryoids
germination. Plant growth regulators used were made in to stocks and stored at refrigerated conditions (4+1C).
Concentration of plant growth regulators used in various modification of Murashige and Skoogs
medium (1962) was shown in the following table;
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SI.
No.
Medium (MS) NAA BA GA3 IBA 2,4-D TDZ
1. Propagation
Medium
HM1
HM3
-
-
-
-
-
-
-
0.5M
-
-
-
-
2. Meristem
culture medium 0.1M 0.1 M 0.1 M - - -
3. Callusing
Medium - - - - 0.2M 0.2M
Agar:
Solidifying agent or gelling agent used were commonly of two types; agar and phytagel in which any one
of them was used. Agar was mainly used to prepare solid and semisolid plant tissue culture media.
Activated charcoalActivated charcoal was carbonized wood which has been heated for several hours in steam. It poses strong
adsorption properties. It absorbs phenolic compounds secreted by the explants in to the tissue culture media.
pH:The pH of the medium was usually adjusted between 5.6 and 5.8 before sterilization and pH of 5.7 was
most preferable.
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4.4. PREPARATION AND STERILIZATION OF MEDIUM.
4.4.1. Preparation of Stock Solutions:
To prepare Roca et.al. CIAT 1984 medium for micro propagation. (Based on Murashige and Skoog, 1962).
Stock solution
code No.
Constituent chemicals Quantity Volume of stock to be used
for preparing 1 litre
medium.
(1)
A
Macronutrients
NH4.NO3
KNO3
MgSO4.7H2O
KH2PO4
(Dissolve in 1000ml distilled water)
82.5g
95.0g
18.5g
8.5g
20.0 ml
(2)
B
To be
Freeze
Stored.
Micro nutrients
H3BO3
MnSO4.H2O
ZnSO4. 7H2O
Na2. MoO4.242O
CuSO4. 5H2O
CoCl2. 6H2O
(dissolve in 1000ml distilled water)
0.62 g
2.176g
0.86g
0.025g
0.0025g
0.0025g
1.0 ml
(3)
C
KI
(Dissolve in 1000ml distilled water)
0.075g 1.0 ml
(4)
D
CaCl2.2H2O
(Dissolve in 100ml Distilled water)
15.0g 2.9ml
(5)
E
a) Na2 EDTA( Chelating agent)
b) Fe SO4. 7 H2O
(Dissolve in 1000ml distilled water)
1.492g
1.114g
5.0ml
(6)
F
Vitamins
Thiamine. HCl
10mg 5.0 ml
(7)
G
myo-inositol
(Dissolve in 200ml of distilled water)
0.8g 6.25 ml
Stocks (2) and (6) should be kept frozen; all others stored at 8-10oc, kept stock (5) protected from light.
Separately dissolve a) and b) in 50ml water each; heat up b) in a water bath; mix both solutions well; let cool and
then add water to complete to 200ml.
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Auxins and Gibberellic acid were dissolved initially in minimum volume of absolute alcohol and
cytokinines in KOH/NaOH (1N). Then they were made up to required volume by adding double distilled water.
pH of the medium was adjusted to 5.7 by IN NaOH or IN HCl prior to autoclaving. Then l g/l of activated
charcoal was added. Agar was added and agar in the medium was dissolved by boiling. Then the medium was
dispensed into the autoclaved/sterilized tubes and sealed with aluminum foil.
The tubes containing medium was finally sterilized by autoclaving at 15 lbs pressure at 121oC for 15
minutes. The sterilized media were kept at 25oC prior to use. (In order to check if there was any visible microbial
infection).
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METHODS
4.5. PROCEDURE FOR SWEET POTATO MERISTEM CULTURE:
Meristem culture is the in vitro culture of a generally shiny special dome-like culture measuring less than
0.1mm in length and only in one or two pairs of the youngest leaf primordia, most often excised from shoot apex.
4.5.1 Surface Sterilization and Dissection of Explants.
The apical meristem is usually a dome of tissue located at the tip of shoot and measures approximately 0.1
mm in diameter and 0.2-0.3 mm in length. The explants were quickly rinsed in 70% alcohol for 1-3 minutes in a
sterilized Erlenmeyer flask. They were then sterilized with Mercuric chloride (0.1%) for five minutes. Then it was
washed 2-3 times using sterilized distilled water.
After rinsing in distilled water, placed the material under the dissection microscope. Using the forceps,
hold the stem steady to remove the largest of the young leaves. Removed the underlying leaf primordia by inserting
the tip of the scalpel into the base of each primordium and flicking the tip of the scalpel away from the stem axis.
At this point, the apical dome should be visible, flanked by two or three of the youngest leaf primordia.
Removal of these primordia can be accomplished by scraping them off with the cutting edge or back edge of the
scalpel blade. It was important that all leaf primordia should be removed and only the apical dome (0.1mm in depth)
excised in order to increase the probability of obtaining plants, free of viruses.
4.5.2. Media Used and Its Composition:
Meristem culture was tried in Murashige and Skoogs media supplemented with NAA, BA and GA 3
denoted as HM2.
The composition of HM2 used here was.
4.5.3 Inoculation and Incubation:
The excised dome was then quickly transferred to the tube containing medium. The dome will just be
visible to the naked eye, and care must be taken to ensure that it was placed on the surface of the medium rather
than adhering to the tip of the scalpel.
Concentration in g/l M /l
MS Sucrose Agar NAA BA GA3
I bottle 30 8 0.1M 0.1M 0.1M
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The culture tubes containing explants were maintained in the culture room at 252 C. They were exposed
to artificial illumination of 2000-3000 Lux by placing them at 20-30 cm below fluorescent light for 16 hours every
day 50-90% humidity was also maintained.
4.6. METHODS FOR SWEET POTATO NODAL CULTURE
Nodal culture is an in vitro culture of node which is a part of stem where leaf arises.
4.6.1. Explant Collection and Surface Sterilization:
Explants were taken from sweet potato of different accessions and were collected in different test
tubes. The leaves, internodes etc were removed and the remaining nodes were washed in running tap water for
removing any adherent particle.
Thoroughly washed nodes were then immersed in 5% (v/v) Teepol for 20 minutes and after this, the nodes
were again washed well in tap water several times for the complete removal of detergent solution. Then it was
dipped in Bavistin (fungicide) for 10 minutes. After 10 minutes the nodes were washed thoroughly with tap water
and then it was rinsed three times with sterile distilled water.
The explants were then brought inside the laminar airflow cabinet and surface sterilization was done with
surface sterilant Mercuric chloride [0.1% (w/v)] for 5 minutes and rinsed 3 times with sterile distilled water to
remove all traces of sterilant.
4.6.2. Media Used and Its Composition:
Nodal culture was tried in two Murashige and Skoogs (MS) basal media, denoted as HM1.
The composition of MS basal media used here was;
4.6.3. Inoculation and Incubation.
Immediately after surface sterilization the plant material was aseptically transferred to solidified MS
medium. The explant was inoculated in horizontal position. The inoculation was done with care that the base of the
node was touched at the surface of the medium.
Then the cultures were incubated at 22C to 27C in light for 16 hours at the intensity of light (1800 lux)
and 8 hours dark for 15-20 days. 50-90% relative humidity was also given.
4.7. METHODS FOR PLANT REGENERATION
4.7.1. Explant Source:
Young leaves, mature leaves, nodes, internodes, anther, ovary, ovule, stigma, pith of stem, root and shoot
tip of sweet potato were used as explants which was grown at Central Tuber Crops Research Institute for callus
induction. Callus initiation occurred within two weeks of culture.
Concentration in g/l
MS Sucrose Agar Charcoal CaCl2
I bottle 30 8 1 2.9ml
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4.7.2. Media Used and Its Composition:
Two combinations of media were used for callus culture in sweet potato. These include Murashige and
Skoogs medium supplemented with 2, 4D denoted as S1i.e. callus induction medium and Murashige and Skoogs
medium supplemented with TDZ denoted as (S2) i.e. regeneration medium.
The composition of S1 used here was;
Concentration in g/l
MS Sucrose Agar 2,4-D CaCl2
I bottle 30 8 0.2mg/l 2.9ml
The composition of S2 used here was;
Concentration in g/l
MS Sucrose Agar TDZ CaCl2
I bottle 30 8 2ml 2.9ml
4.7.3. Inoculation and Incubation:
Small pieces of explants were inoculated on to freshly prepared sterile medium1 (S1) and. After 4 days, the
swollen enlarged explants were then transferred to MS medium containing TDZ (Thidiazuron, 0.2mg/l). Hence the
procedure involved placing of explants on two step media. The cultures were incubated at 25oC and 12 hours light.
4.8. PROTOCOL FOR IN VITRO CONSERVATION (SLOW GROWTH CULTURE)
4.8.1. Explant Collection and Surface Sterilization:
Explants were taken from sweet potato of different accessions and were collected in different test
tubes. The leaves, internodes etc were removed and the remaining nodes were washed in running tap water for
removing any adherent particle.
Thoroughly washed nodes were then immersed in 5% (v/v) Teepol for 20 minutes and after this the nodes
were again washed well in tap water several times for the complete removal of detergent solution. Then it was
dipped in Bavistin (fungicide) for 10 minutes. After 10 minutes, the nodes were washed thoroughly with tap water
and then it was rinsed three times with sterile distilled water.
The explants were then brought inside the laminar airflow cabinet and surface sterilization was done with
surface sterilant Mercuric Chloride [0.1 %( w/v)] for 5 minutes and rinsed 3 times with sterile distilled water to
remove all traces of sterilant.
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4.8.2. Media Used and Its Composition:
Nodal culture was tried in Murashige and Skoogs (MS) basal media, denoted as SG3. The composition of
MS basal media used here was;
4.5.3. Inoculation and Incubation.
Immediately after surface sterilization, the plant material was aseptically transferred to solidified MS
medium. The explant was inoculated in horizontal position. The inoculation was done with care that the base of the
node was touched at the surface of the medium.
Then the cultures were incubated at 22C to 27C in light for 16 hours at the intensity of light (1800 lux)
and 8 hours dark for 15-20 days. 50-90% relative humidity was also given.
4.9. METHODS FOR SUB CULTURING:
After a period of time, it becomes necessary to transfer the cultures to fresh media. A portion of tissue was
used to inoculate new culture tubes or flasks; this is known as sub culturing. For the initiation of subculture, it was
necessary to raise a population of healthy plants. In many experiments, the culture was started from a stock plant
raised by micro propagation. The established propagated plants were selected as the source of explant for sub
culturing.
For the preparation of explant in subculture, the plants were taken from the medium carefully with sterile
forceps and the basal regions were cut off with sterile scissors. Then the leaves and other unnecessary regions were
removed leaving the explants with a single internode. From the explant, each node was separated and inoculated to
fresh medium and incubated under 25C and 1000 lux illumination.
4.9.1 PROCEDURE FOR HARDENING AND FIELD ESTABLISHMENT OF PLANTS.
Sweet potato plants with well developed root and 5-6 nodes were selected. This was transferred to the
laminar air flow work station where the plantlet was carefully removed from the medium. It was washed with
running tap water in order to remove the agar residues so that we can check up the chance of contaminants on the
soil. Then it was transferred into plastic cups containing sterilized vermiculate and then covered with polythene
bags in order to maintain humidity and water. After one week, the polythene bags are removed and it was taken to
field trials (Fig. 39).
Concentration in g/l Concentration in M/l
MS Sucrose Agar Mannitol NAA BAP GA3
I bottle 20 8 20 0.5 0.1 0.3
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5. RESULTS
5.1. MERISTEM CULTURE
Sweet potato Meristem cultures were done in HM2 medium.
5.1.1. Studies on HM2 medium
Isolated meristems of five sweet potato varieties were cultured in HM2 medium for 8-12 hours per day at
3000 lux illumination and 25C temperature. The observations were taken once in every two weeks and repeated
upto 30 days. During the first week of incubation, morphological changes were observed, slight increase in tissue
volume and they differentiated in the following weeks. After one month plantlets were observed.
5.1.2. Varietal response in Sweet potato
Out of five of varieties of sweet potato, sweet potato 23 showed fast response of growth and S.823, Sree
Arun, S.665, S.685 showed medium response of growth after two months of incubation 23 variety of sweet potato
were grown upto 2cm with 4 leaves while in Sree Arun and S.685 showed shoot emergence of 1.5 cm with 2 leaves
and nodes and S.823, S.685 showed lowest growth comparing to other varieties (table 1, graph 1, figure 1).
TABLE 1: OBSERVATION OF MERISTEM CULTURE IN DIFFERENT VARIETIES OF SWEET POTATO.
Sweet potato varieties showed a delayed response of growth in S 2 medium. Out of the five varieties S.23
showed a fast response within 15 days morphological changes were observed compared to other varieties which
gave response within 30 days.
Name
of
variety
Sl no: No: of
cultures
inoculated
No: of
cultures
obtained
Observation
after 15 days
Observation
after 30 days
Remarks
S.823 1 6 4 No response Enlargment,
green
coloration
Medium
response
S.23 2 8 6 Green
coloration
Development
of buds
Fast
response
Sree
arun
3 6 5 No response Green
coloration
Medium
response
S.665 4 7 4 No response Green
coloration
Medium
response
S.685 5 6 4 No response Green
coloration
Medium
response
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GRAPH 1: MERISTEM CULTURE IN DIFFERENT VARIETIES OF SWEET POTATO
FIGURE 1: MERISTEM CULTURE
0 10 20 30 40 50 60
SreeArun
S.665
S.23
S. 685
% of Growth
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5.2. NODAL CULTURE.
Sweet potato nodal culture was tried in Murashige and Skoogs basal media (HM1).
5.2.1.. Studies on HM1 medium
In HMI, the separated nodes of five different accessions were inoculated in such a way that each accession
had five replications.
Studies involving in vitro culture of nodes of five different accessions of sweet potato genotypes revealed
different growth responses which were interpreted in the table 2, graph 2 and figure 2.
5.2.1.1. Varietal response to nodal culture
In all the accessions, the initial response was observed after one week of inoculation. The best response
was observed in genotype Gautham (graph2), which attained maximum shoot length of 5.8cm and also had well
developed root system; while response of others was recorded such as in accession S16(graph 2). i.e., 3cm , Kishan
3.2cm(graph2), Sree Retna 2.6cm(graph 2) and Sree Bhadra 3.1cm (graph 2) length of shoot after one month of
inoculation ( table2, figure 2).
In HM1, Gautham showed the best response. The average length of shoot while considering the entire
genotype cultured was found as 1.78cm after 15 days while the average length recorded after 30 days is 3.54cm
.The mean number of leaves recorded was 1.44 and 3.65 after 15 days and 30 days respectively while mean numberof root was 2.82 cm and 4.44 cm. The overall rate of development in sweet potato was found good. The positive
growth response can possibly be due to the presence of charcoal. It also promotes root formation due to its ability to
exclude light from the medium. The various physical factors and Murashige and Skoog basal medium provided
were found to be effective in the multiplication of sweet potato.
Various parameters studied for nodal culture were no. of leaves, no. of nodes and root and shoot length.
The three species responded very well after 2 months.
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Table2: OBSERVATION OF NODAL CULTURE IN DIFFERENT VARIETIES OF SWEET POTATO
Variety No: of
replica
Observation After 15 Days Observation After 30 Days
No: of
Leaves
No:
of
Nodes
Mean
shoot
length(cm)
Mean
root
length
(cm)
No: of
Leaves
No:
of
Nodes
Mean
shoot
length(cm)
Mean
root
length
(cm)
S.16
1 1 1 0.8 2.5 5 5 1.6 4
2 2 2 1.7 2 7 7 2.8 5
3 1 1 1.8 2.7 4 4 3 4.2
4 1 1 0.6 1.2 3 3 1.8 4.4
5 1 1 0.9 2 2 2 1.9 3.4
Gautham
1 1 1 1.2 1.8 6 6 2.6 5.2
2 3 3 1.9 2.5 4 4 2.3 4.8
3 2 2 1.2 2 4 4 1.6 3.2
4 3 3 2.1 3.2 6 6 5.8 5.5
5 3 3 1.8 4 5 5 2.8 4.2
Kishan
1 1 1 1.6 3 4 4 3.2 4.8
2 1 1 0.7 2.1 2 2 1.9 3.2
3 2 2 1.2 2 3 3 1.6 4.3
4 2 2 0.9 1.4 4 4 1.8 2.8
5 - - 0.4 2 2 2 2.8 3.8
Sree
Rethna
1 1 1 1.2 2.6 2 2 2.4 3.5
2 2 2 2.2 2.5 3 3 1.3 3.6
3 - - 0.7 1.3 1 1 2.4 4
4 1 1 0.6 1 3 3 2.6 3.2
5 - - 0.4 1.8 2 2 0.9 3
Sree
Bhadra
1 1 1 1.5 2.3 4 4 1.6 2.8
2 1 1 0.7 1.6 6 6 2.8 4
3 2 2 1.6 2.8 3 3 2.2 3.5
4 1 1 0.8 1.9 2 2 1.2 2.5
5 3 3 1.6 2.5 4 4 3.1 3.5
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GRAPH 2: NODAL CULTURE IN DIFFERENT VARIETIES OF SWEET POTATO
FIGURE 2: DIFFERENT STAGES OF NODAL CULTURE
0
1
2
3
4
5
No of leaves
No of nodes
Shoot length
Root length
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5.4. PLANT REGENERATION
Sweet potato plant regeneration was studied in S1 and S2 media.
5.4.1.. Studies on S1 medium
The callus response of each variety was observed and studied.
Varietal difference in callusing in S1 media
In Sweet potato callus culture, different varieties showed differential response .Retna showed very good
response as callus induction happened within 4 days. It was observed that Vardhini and Gautham exhibited callus
induction in 6 days which was a moderate response. Nandini took 8 days to respond which was comparatively low
response(Table 3. Graph 3).
Induction of callusing on explants may be due to the influence of 2, 4 D hormone present in the medium. In
this medium, no embryoid development occurred. So it was inoculated into another medium i.e. callus regeneration
medium (S2 medium). Response is shown in Table 3, graph 3 and figure 3.
5.4.1. Studies on S2 medium.
5.4.1.2. Varietal difference in callusing in S2 media
Variation in response in callus development was observed among the varieties as well as different explants.
Only the variety Retna responded with the formation of embryoids and plant regeneration using the
explants - young leaf, internode and petiole. Root formation was observed in the variety Nandini from the explant
shoot tip fig. 18.
TABLE 3: RESPONSE OF DIFFERENT VARIETIES IN CALLUSING OF SWEET POTATO IN S1 MEDIA
Variety Response
Vardhini
Good response within 6 days and
inoculated into S2 medium
Nandini
Good response within 8 days and
inoculated into S2 medium
Rethna
Very Good response within 4 days and
inoculated into S2 medium
Gautham
Good response within 6 days and
inoculated into S2 medium
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5.4.1.2. Response of different explants for callus development
Different explants of different varieties showed different responses.
Young leaf explant of Vardhini and Nandini initiated callusing within 13 days. Gautham responded within
16 days and Retna within 14 days (Table 4, fig4).
Mature leaf explants Vardhini and Gautham initiated callusing within 15 days. Nandini and Retna
responded within 13 days (Table 4, fig5).
Young petiole of Vardhini initiated callusing within 12 days and Gautham initiated callusing within 15
days. Nandini and Retna responded within 13 days (Table 4, fig 6).
Internode of Vardhini initiated callusing within 16 days. Gautham and Nandini responded within 14 days
and Retna within 17 days (Table 4, fig 7).
Root tip of Vardhini initiated callusing within 15 days. Gautham in 16 days, Nandini in 13 days and Retna
in 14 days (Table 4, fig 8).
Ovary of all varieties responded within 18-19 days. Anther explant of all varieties responded within 13
days. Ovule from immature seed as explant responded within 22 days of all varieties (Table 5, fig 9).
Stigmata of variety Vardhini responded within 24 days and Gautham responded in 23-24 days of
incubation. Nandini and Retna responded within 22 and 23 days respectively (Table 4, fig 12).
Pithexplant in Vardhini, Retna, and Nandini showed response within 14 days and Gautham responded in
17 days. Shoot tip as explant in all varieties responded within 13 days of incubation (Table 6, fig 14).
5.4.1.3. Relation between Callus colour and Plant Regeneration
Cream colored calli was observed in explants such as young leaf, shoot tip, petiole, ovary, anther, ovule and
stigma of the sweet potato varieties : Sree Vardhini, Gautham, Sree Nandini and Sree Retna (Table 4, 5, 6, fig 8-14).
Pale yellow colored calli was observed in explants : mature leaf, internode, and pith of stem of the sweet
potato varieties Sree Vardhini, Gautham, Sree Nandini and Sree Retna.
Younger parts of plant showed cream colored callus and continued dividing throughout the experiment. But
mature part of plant in callus showed pale yellow color and they became older cells and appeared brown in color. So
it may be inferred that a young part of the plant that has rapidly dividing cells responds faster in plant regeneration
than mature parts.
5.4.1.4. Plant regeneration from callus
Plant regeneration was observed in the callus developed from Sree Retna only. It was observed that within
20 days, plantlets regenerated from young leaf, petiole and mature internode. Plants regenerated from internode
developed into mature plants within 30 days (Fig 15, 16).
Organ regeneration was observed in Sree Nandini. In Sree Nandini only root development was observed
from shoot tip (Fig 18).
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TDZ (N phenyl 1, 2, 3 thidiazol 5yl) urea has been used extensively in tissue culture studies. It exhibits
strong cytokinin like activity and promotes the proliferation of axillary shoots as well as stimulated adventitious
organ regeneration and induces somatic embryo genesis.
Achievement of crop improvement through plant cell and tissue culture techniques depends upon success
in plant regeneration.
GRAPH 3:
FIGURE 3 : EXPLANTS IN S1 (INDUCTION) MEDIUM
25%
17%
33%
20%
Response of Different Varieties in S1
medium
Vardhini Nandini Retna Gautham
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Table 4: RESPONSE OF DIFFERENT EXPLANTS) IN CALLUSING IN S2 MEDIA
A. Vegetative parts
Variety Response of Explants
Young Leaf Mature leaf Young Petiole Mature Internode Root tip
Vardhini
Callus
colour
Callus
initiatio
n
Callus
colour
Callus
initiatio
n
Callus
colour
Callus
initiation
Callus
colour
Callus
initiatio
n
Callus
colour
Callus
initiatio
n
Cream
After 13
days
Pale
Yellow
colour
After 15
days
Cream After 12
days
Pale
Yellow
colour
After 16
days Cream
After 15
days
Cream
After 13
days
Pale
Yellow
colour
After 14
days
Cream After 13
days
Pale
Yellow
colour
After 16
days Cream
After 15
days
Gautham
Cream
After 16
days
Pale
Yellow
colour
After 15
days Cream
After 15
days
Pale
Yellow
colour
After 14
days Cream
After 16
days
Cream
After 16
days
Pale
Yellow
colour
After 15
days Cream
After 13
days
Pale
Yellow
colour
After 14
days Cream
After 16
days
Nandini
Cream
After 13
days
Pale
Yellow
colour
After 13
days Cream
After 13
days
Pale
Yellow
colour
After 14
days Cream
After 13
days
Cream
After 13
days
Pale
Yellow
colour
After 13
days Cream
After 13
days
Pale
Yellow
colour
After 14
days Cream
After 13
days
Rethna
Cream
After 14
days
Pale
Yellow
colour
After 13
days Cream
After 13
days
Pale
Yellow
colour
After 17
days Cream
After 14
days
Cream
After
14
days
Pale
Yellow
colour
After
13
days
Crea
m
After 13
days
Pale
Yellow
colour
After 17
days Crea
m
After
14
days
Regener
ation
of plant
in S2
medium(Retna
only
respond
ed)
No response
Responded
Shoot length
4.2cm after 20days
of inoculation
Responded
Shoot length 3.9
cm after 20days of
inoculation
Responded
Shoot length
3.2cm after 30days
of inoculation
No response
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Response of Various explants in S2 Medium
Graph 4:
A. Vegetative organs
Figure 4: Young Leaf Figure 5: Mature Leaf
0
5
10
15
20
Response of Vegetative Parts in Callusing In
S2 Medium
VARDHINI
Gautham
Nandini
Retna
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Figure 6 : Young Petiole Figure 7: Mature Internode
Figure 8: Root Tip
TABLE 5: RESPONSE OF DIFFERENT EXPLANTS IN CALLUSING IN S2 MEDIA
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A. Floral organs
Variety
Response of different explants
Ovary Anther Ovule Stigma
Vardhini
Callus
colour
Callus
initiation
Callus
colour
Callus
initiation
Callus
color
Initiatio
n
Callus
colour
Callus
initiatio
n
Cream
After 19
days
Cream After 13
days
Cream After 22
days
Cream After 24
days
Cream
After 19
days
Cream After 13
days
Cream After 22
days
Cream After 22
days
Gautham
Cream
After 19
days
Cream After 13
days
Cream After 22
days
Cream After 24
days
Cream
After 18
days
Cream After 13
days
Cream After 22
days
Cream After 23
days
Nandini
Cream
After 19
days
Cream After 13
days
Cream After 22
days
Cream After 22
days
Cream After 19
days
Cream After 13
days
Cream After 22
days
Cream After 22
days
Retna
Cream After 18
days
Cream After 13
days
Cream After 22
days
Cream After 23
days
Cream After 18
days
Cream After 13
days
Cream After 22
days
Cream After 23
days
Regene
ration
of plant
in
S2medi
um
No response No response No response No response
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Graph 5:
B. Floral organs
Figure 9 : Ovary Figure 10: Anther
0
5
10
15
20
25
OVARYANTHER
OVULESTIGMA
Response of floral organs in Callusing
VARDHINI
Gautham
Nandini
Retna
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Figure 11: Ovule Figure 12: Stigma
TABLE 6: RESPONSE OF DIFFERENT EXPLANTS IN CALLUSING IN S2 MEDIA
A. Pith and Shoot tip
Varieties
Response of explant
Pith Shoot tip
Callus colour Callus initiation Callus colour Callus initiation
Vardhini
Pale Yellow colour After 14 days Cream After 16 days
Pale Yellow colour After 14 days Cream After 16 days
Gautham
Pale Yellow colour After 17 days Cream After 16 days
Pale Yellow colour After 17days Cream After 16 days
Nandini
Pale Yellow colour After 14 days Cream After 16 days
Pale Yellow colour After 14 days Cream After 16 days
Retha
Pale Yellow colour After 14 days Cream After 16 days
Pale Yellow colour After 14 days Cream After 16 days
Regeneration
of plant in HM1medium
No response
Root was well developed in Nandini
after 20 days.
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Graph 6:
Figure 13: Shoot tip igure 14: Pith
0
5
10
15
20
VARDHINIGautham
Nandini Retna
Response of Pith and Shoot tip in Callusing
PITH
SHOOT TIP
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Plant regeneration from CallusVariety Retna
Figure 15 :Plant regeneration from Mature Leaf Figure 16 : Plant regenerated from
Young Petiole
Figure 17:Plant regeneration from Figure 18: Root development from Variety
Mature Internode Nandini
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5.5IN VITRO CONSERVATION (SLOW GROWTH CULTURE)
Sweet potato slow growth cultures were done in SG3 medium.
5.5.1. Studies on SG3 medium
In SG3, the separated nodes of four different accessions were inoculated in such a way that each accession
had five replications.
Studies involving slow growth culture of nodes of four different accessions of sweet potato genotypes
revealed different growth responses, which were interpreted in the table given below.
5.5.1.1. Varietal response of sweet potato
In all the accessions, the initial response was observed after one of the three inoculations. The bestresponse was observed in genotype Thripthi (graph 7), which attained maximum shoot length of 2.1cm and also
had well developed root system; while low response was recorded in accession Sourin( graph 7). i.e., 1.2 cm length
of shoot after one month of inoculation.
The best response was observed in genotype Thripthi which attained a maximum mean root length of
3.2cm after 30 days. The mean root length of genotype Sourin was 2.1cm and that of Kishan (graph 7) was 1.83cm
and genotype IC440221 (graph 7) was 1.08 cm (table 7, graph 7, Fig 19).
The culture remained dominant for up to three weeks. After 23 days, shoot development was seen.
Therefore it was further observed for one more week. Slow-growth of plantlets in vitro provides an attractive
alternative to freeze
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Table 7: Growth response of sweet potato in slow growth (SG3) medium
Variety No: of
replica
Observation After 15 Days Observation After 30 Days
No: of
Leaves
No: of
Nodes
Mean shoot
length(cm)
Mean
root
length
(cm)
No: of
Leaves
No: of
Nodes
Mean shoot
length(cm)
Mean
root
length
(cm)
Thripthi
1
No Response
1 1 1.2 1.8
2 2 2 1.9 2.5
3 2 2 1.2 2
4 3 3 2.1 3.2
5 3 3 1.8 4
Sourin
1
No Response
1 1 1.6 3
2 1 1 0.7 2.1
3 2 2 1.2 2
4 2 2 0.9 1.4
5 1 1 1 2
Kishan
1
No Response
1 1 1.2 2.6
2 2 2 2.2 2.5
3 2 2 1.2 1.3
4 1 1 0.6 1
5 2 2 1.4 1.8
IC440221
1
No Response
1 1 0.8 2.5
2 2 2 1.7 2
3 1 1 1.8 2.7
4 1 1 0.6 1.2
5 1 1 0.9 2
preservation of germplasm as it is simpler, cheaper and very effective. Slow growth may be achieved by
maintaining the plantlets either at a low temperature or on a medium having high osmotic concentration (Mannitol
20%) or both. In addition, the nutritional status of the medium may be lowered to restrict the growth of plantlets.
Under the conditions of slow-growth, cultures may be attended to only once in several months, and subculture may,
be necessary only after long periods say, once every 12-36 months.
In the present study, Thripthi gave best response. Due to high osmoticum, the explants of all the fourvarieties remained dormant for two weeks after that growth was observed
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Graph 7:
Figure 19: In Vitro Conservation (Slow Growth Medium)
0
1
2
3
ThripthiSourin
Kishan440221
Growth response of Different Varieties of Sweet
Potato in Slow Growth medium
No of leaves No of nodes Shoot length Root length
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5.DISCUSSION
The result of the present study was significant for rapid propagation of diverse sweet potato genotypes for
obtaining genetically stable propagules. Here in five different sweet potato accessions healthy clones were obtained.
Though the aseptic manipulation and procedure of sweet potato meristem culture was difficult, results of the
experiments were comparatively good rather than nodal cultures of sweet potato.
Once a pathogen free culture had been established new batch of cultures for propagation could be started
with shoot tip culture because they responded rapidly and readily.
The most important application of meristem culture was to produce pathogen free plants, which were
genetically identical. The totipotency of the apical meristem cells forms the basis of the meristem culture technique.
The major advantages of meristem culture are that it provides:
Clonal propagation in vitro with maximal genetic stability. The potential for removal of viral, bacterial, and fungal pathogens from donor plants. The meristem tip as practical propagules for cryopreservation and other techniques of culture storage. A technique for accurate micropropagation of chimeric material. Cultures those are often acceptable for international transport with respect to quarantine regulations.
The maintenance of aseptic conditions was necessary for obtaining contamination free cultures. Besides these
factors, temperature, humidity and light intensity also played an important role in micro propagation and meristem
culture. Therefore these techniques could be used as an effective Biotechnological tool for the crop improvement.
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6. SUMMARY
The results of the present study were highly significant for rapid propagation of diverse sweet potato
genotypes for obtaining genetically stable propagules. The nodal culture, meristem culture as well as plant
regeneration of sweet potato was successfully developed in Murashige and Skoog basal media and modified MS
media with Plant growth regulators such as NAA, GA 3,BAP,, 2,4 -D and TDZ. Mercuric chloride (0.1%) was used
as surface sterilant which gave a way to reduce contamination.
Inclusion of activated charcoal in the medium helped to absorb phenolic compounds and also to increase
the culture viability. The maintenance of aseptic condition was necessary for obtaining contamination free cultures.
Besides these factors, temperature, humidity and light intensity was found to be important in micro propagation and
meristem culture. Slow cultures provided an ideal method for germplasm conservation.
Plant regeneration is the process of growing an entire plant from a single cell or group of cells due to the
influence of plant growth regulators. Plant regeneration through somatic embryogenesis shows several advantages
as compared to other in vitro propagation systems, including its high multiplication rates, possibility of
cryopreservation of embryogenic callus, the potential for scale-up in liquid suspension cultures, the use of
bioreactors and somatic synthetic seed technologies and the fact that embryogenic cultures are suitable target tissues
for gene transfer.
Therefore these techniques can be used as an effective Biotechnological tool for the crop improvement for
the production of new traits and varieties having desirable characters such as high yield, resistance to diseases etc.
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7. Conclusion
Sweet potato is an edible tuber with high nutritional profile. It has high starch content and dietary fiber
content. In most parts of Africa and in some parts of Latin America, Sweet potato has assumed the importance of a
staple food. So it is important to have effective propagation and conservation tools to utilize this high profile tuber
crop to the maximum extent. Here in this study, micropropagation and plant regeneration of sweet potato have been
attempted. Meristem culture carried out here was proved effective as it produced pathogen-free plants. Nodal
culture also came up with flying colours as the inclusion of charcoal in the culture medium removed the excess
phenolic compounds liberated into the medium by the plantlets. Also it excluded the light from the medium thus
inducing rooting in plantlets. Thus nodal culture emerged as a promising vegetative propagation tool for sweet
potato. Plant regeneration through somatic embryogenesis also has given promising signs as an effective
propagation method As the dietary needs of the people around the world is soaring high, the dependence on tuber
crops like Sweet potato is expected to increase. Also serious research has been invested behind exploring the
functional values and value added products from Sweet potato. Hence the present study assumes paramount
significance and relevance as it sheds light into the conservation and propagation of a crop which can prove
beneficial to the growing dietary and health demands of the growing populations across the globe especially in India
and African countries.
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