The document discusses the advances in breeding vegetable crops, specifically focusing on taro (Colocasia esculenta), its origin, classification, and the research initiatives taken to improve its cultivation in India. Taro, a significant traditional crop in various regions, faces challenges in genetic improvement due to historical focus on other crops, yet research projects have made strides in germplasm evaluation and genetic enhancements. The breeding objectives include increasing genetic variability, improving cormel yield, and enhancing resistance to diseases among others.

1. Presented by:
SACHIN BHARDWAJ
H-2019-50-D
Ph.D. Ist
Year
ADVANCES IN BREEDING OF
VEGETABLE CROPS
Breeding in Taro
SUBMITTED TO :
Dr. Ramesh K Bhardwaj
(Principal Scientist)
Department Of Vegetable Science)

2. INTRODUCTION
BOTANICAL NAME Colocasia esculenta L.
FAMILY ARACEAE
ORIGIN South Central Asia,
probably in India or the
Malay Peninsula
CHROMOSOME
NUMBER
2n=2x=28,42
SYNONYMS Taro or colocasia or
cocoyams or arvi
POLLINATION ARTIFICIAL SELF
POLLINATION

3. INTRODUCTION
• Taro (Colocasia esculenta (L.) Schott) is a traditional crop with a long
history of cultivation in Asia and the Pacific. It is widely used as a tuber
vegetable in India, whereas it is the staple food and also very closely
associated with culture in many of the South Pacific islands.
• Taro is ordinarily grown in the homestead garden and its cormels,
petiole and leaves serve the important purpose as an instant vegetable.
• Eventhough there is no statistical data available on the area and
production of taro in India, it is a fact that taro commands a higher price
than cassava or sweet potato.
• Despite the importance of this crop, its cultivation anywhere in India is
generally a subsistent to semi-commercial crop. Though preference of
the different plant parts of taro as a vegetable was realized in India long
back, efforts rendered towards its genetic upgradation are still meagre.

4. • The Central Tuber Crops Research Institute (CTCRI), India under the
Indian Council of Agricultural Research (ICAR), Ministry of Agriculture,
Department of Agricultural Research Education has included taro as a
mandatory crop from its very inception in 1963. Because cassava and
sweet potato were more importantly grown for food, these were given high
priority for research at the CTCRI initially.
• Later, germplasm collections of the crop were assembled from various
parts of the country and research programmes were initiated mainly on
conservation and basic research programmes.
• From the end 80s when the germplasm bank got enriched with several
morphologically distinct types of taro, prioritized research projects were
initiated at the CTCRI for the upliftment of this crop in the Indian
agricultural scenario.
• Thus, two research projects, viz.
• (1) Collection, conservation and evaluation of the germplasm and (2)
Genetic improvement programme in edible taro are in operation and
have made substantial progress.

5. SYSTEMATICS
Domain: Eukaryota
Kingdom: Plantae
Phylum: Spermatophyta
Subphylum: Angiospermae
Class: Monocotyledonae
Order: Arales
Family: Araceae
Genus: Colocasia
Species: Colocasia esculenta

6. Origin and Domestication
• Various lines of ethno-botanical evidence suggest that
taro originated in South Central Asia, probably in
India or the Malay Peninsula.
• Wild forms occur in various parts of South Eastern
Asia (Purseglove, 1972). From its centre of origin,
taro spread eastward to the rest of South East Asia,
and to China, Japan and the Pacific Islands (some
authors have suggested that the island of New Guinea
may have been another centre of origin for taro, quite
distinct from the Asian centre).

7. • From Asia, taro spread westward to Arabia and the Mediterranean region. By
100 B.C., it was being grown in China and in Egypt. It arrived on the east
coast of Africa over 2,000 years ago; it was taken by voyagers, first across the
continent to West Africa, and later on slave ships to the Caribbean.
• Today, taro is pan-tropical in its distribution and cultivation. The greatest
intensity of its cultivation, and its highest percentage contribution to the diet,
occurs in the Pacific Islands.
• However, the largest area of cultivation is in West Africa, which therefore
accounts for the greatest quantity of production. Significant quantities of taro
are also grown in the Caribbean, and virtually all humid or sub-humid parts of
Asia.
• It has been suggested that the eddoe type of taro was developed and selected
from cultivated taro in China and Japan several centuries ago, and it was later
introduced to the West Indies and other parts of the world (Purseglove, 1972).

8. DISTRIBUTION
• The major taro producing countries are Ghana,
Zaire, Nigeria and Cameroon in Africa; China,
Japan, Philippines and Thailand in Asia and
Papua New Guinea, Samoa, Solomon Islands,
Tonga and Fiji in Oceania. Fiji, Tonga, Cook
Islands, Tuvala and Thailand are important taro
exporting countries.
• The exports are mainly destined to the ethnic
community settled in Australia and New Zealand.

9. SEVERAL KINDS OF TARO
• There are several kinds of taro:
• Swamp taro (Cyrtosperma chamissonis),
• Tannia (Xanthosoma sagittifolium),
• Giant taro (Alocasia macrorrhiza) and
• Ordinary or True taro (Colocasia esculenta)
• prevalent in India, of which tannia is the most
similar to the ordinary taro, and is characterized
by relatively large, sagittate leaves, a large main
corm and several cormels, which are used as
food. Ordinary taro is the most important
species in the group. There exists differing
opinions regarding the original home of the crop
as well as its taxonomy and common names

10. DIFFERENT TARO RELATED SPECIES
S.No. Local name Scientific name Edible/Ornamental/ Wild
1. Dudhmankochu (edible) Xanthosoma sagittifolium (L.) Schott Edible
2. Maankochu Alocasia indica(Lour.) Spach Edible
3. Cholakochu Colocasia esculenta (L.) Schott Edible
4. Gathikochu Colocasia esculenta (L.) Schott Edible
5. Oolkochu Amorphophallus paeoniifolius (Dennst.)Nicolson Edible
6.
Kharkol Typhonium trilobatum (L.) Schott Edible
7. Bunokochu (poisonous) Alocasia fornicata (Kunth) Schott Wild and edible after processed

11. Classification and Genetics
• Classification and Genetics
• Taro belongs to the genus Colocasia, within the sub-family
Colocasioideae of the monocotyledonous family Araceae.
Because of a long history of vegetative propagation, there is
considerable confusion in the taxonomy of the genus Colocasia.
• Cultivated taro is classified as Colocasia esculenta, but the
species is considered to be polymorphic. There are at least two
botanical varieties (Purseglove, 1972):
• i) Colocasia esculenta (L.) Schott var. esculenta;
• ii) Colocasia esculenta (L.) Schott var. antiquorum (Schott)
Hubbard & Rehder which is synonymous with
C. esculenta var. globulifera Engl. & Krause.

13. • C. esculenta var. esculenta is characterised by the possession of a
large cylindrical central corm, and very few cormels. It is referred at
agronomically as the dasheen type of taro.
• C. esculenta var. antiquorum, on the other hand, has a small
globular central corm, with several relatively large cormels arising
from the corm. This variety is referred to agronomically as
the eddoe type of taro.
• Most of the taro grown in the Asia/Pacific region is of the dasheen
type.Chromosome numbers reported for taro include 2n = 22, 26,
28, 38, and 42. The disparity in numbers may be due to the fact that
taro chromosomes are liable to unpredictable behaviour during cell
divisions. The most commonly reported results are 2n = 28 or 42

15. • Germplasm collections of taro exist at various scientific
institutions world-wide. These include the International
Institute of Tropical Agriculture (IITA) Ibadan, Nigeria;
the Philippine Root Crop Research and Training Center,
Beybey, Philippines; the Koronivia Research Station, Fiji;
the Bubia Agricultural Research Centre in Papua New
Guinea, and numerous other locations in Oceania.
• There are hundreds of agronomic cultivars of taro grown
throughout the world. These are distinguished on the basis
of corm, cormel, or shoot characteristics, or on the basis of
agronomic or culinary behaviour.

16. Morphology and Anatomy
• Taro is a herbaceous plant which grows to a height of 1-2m. The plant consists of
a central corm (lying just below the soil surface) from which leaves grow upwards,
roots grown downwards, while cormels, daughter corms and runners (stolons)
grow laterally.
• The root system is fibrous and lies mainly in the top one meter of soil.
• In the dasheen types of taro, the corm is cylindrical and large. It is up to 30cm
long and 15cm in diameter, and constitutes the main edible part of the plant.
• In eddoe types, the corm is small, globoid, and surrounded by several cormels
(stem tubers) and daughter corms. The cormels and the daughter corms together
constitute a significant proportion of the edible harvest in eddoe taro. Daughter
corms usually give rise to subsidiary shoots even while the main plant is still
growing, but cormels tend to remain dormant and will only give rise to new shoots
if left in the ground after the death of the main plant. Each cormel or each daughter
corm has a terminal bud at its tip, and axillary buds in the axils of the numerous
scale leaves all over its body.

17. • Corms, cormels and daughter corms are quite similar in their internal structure. The
outmost layer is a thick brownish periderm. Within this lies the starch-filled ground
parenchyma. Vascular bundles and laticifers ramify throughout the ground
parenchyma. Idioblasts (cells which contain raphides or bundles of calcium
oxalate crystals) also occur in the ground tissue, and in nearly all other parts of the
taro plant. The raphides are associated with acridity or itchiness of taro, a factor
which will be taken up in greater detail when the utilisation of taro is discussed.
The density and woodiness of the corm increase with age.
• Occasionally in the field, some taro plants are observed to produce runners. These
structures grow horizontally along the surface of the soil for some distance, rooting
down at intervals to give rise to new erect plants.
• In both eddoe and dasheen types of taro, the central corm represents the main
stem structure of the plant. The surface of each corm is marked with rings showing
the points of attachment of scale leaves or senesced leaves. Axillary buds are
present at the nodal positions on the corm. The apex of the corm represents the
plant’s growing point, and is usually located close to the ground level. The actively
growing leaves arise in a whorl from the corm apex. These leaves effectively
constitute the only part of the plant that is visible above ground. They determine
the plant’s height in the field.

19. • Each leaf is made up of an erect petiole and a large lamina. The petiole is
0.5-2m long and is flared out at its base where it attaches to the corm, so
that it effectively clasps around the apex of the corm. The petiole is
thickest at its base, and thinner towards its attachment to the lamina.
Internally, the petiole is spongy in texture, and has numerous air spaces
which presumably facilitate gaseous exchange when the plant is grown in
swampy or flooded conditions. For most taro types, the attachment of the
petiole to the lamina is peltate, meaning that the petiole is attached, not at
the edge of the lamina, but at some point in the middle. This peltate leaf
attachment generally distinguishes taro from tannia which has a hastate
leaf i.e. the petiole is attached at the edge of the lamina. An important
exception to this rule are the “piko” group of taro found in Hawaii; quite
uncharacteristically, they have hastate leaves.
• The lamina of taro is 20-50cm long, oblong-ovate, with the basal lobes
rounded. It is entire (not serrated), glabrous, and thick. Three main veins
radiate from the point of attachment of the petiole, one going to the apex,
and one to each of the two basal lamina lobes. Some prominent veins arise
from the three main veins, but the overall leaf venation is reticulate (net-
veined).

21. FLORAL BIOLOGY
• Natural flowering occurs only occasionally in taro, but flowering can be artificially
promoted by application of gibberellic acid (see later). The inflorescence arises from the leaf
axils, or from the centre of the cluster of unexpanded leaves. Each plant may bear more than
one inflorescence. The inflorescence is made up of a short peduncle, a spadix, and spathe.
The spadix is botanically a spike, with a fleshy central axis to which the small sessile
flowers are attached. The spadix is 6-14cm long, with female flowers at the base, male
flowers towards the tip, and sterile flowers in between, in the region compressed by the neck
of the spathe. The extreme tip of the spadix has no flowers at all, and is called the sterile
appendage. The sterile appendage is a distinguishing taxonomic characteristic between
dasheen and eddoe types of taro. In eddoe types, the sterile appendage is longer than the
male section of the spadix; in dasheen types, the appendage is shorter than the male section.
• The spathe is a large yellowish bract, about 20 cm long, which sheathes the spadix. The
lower part of the spathe wraps tightly around the spadix and completely occludes the female
flowers from view. The top portion of the spadix is rolled inward at the apex, but is open on
one side to reveal the male flowers on the spadix. The top and bottom portions of the spadix
are separated by a narrow neck region, corresponding to the region of the sterile flowers on
the spadix.

23. POLLINATION
• Maximum flowering takes place from June to Oct. The inflorescences of
different accessions differ in the dimensions of various parts. Pollination is
entomophilous and is carried out by fruit flies, which are attracted to the
inflorescence by the strong odour produced by the upper spathe.
Taro flowers show an insect trapping mechanism. The fruit flies are held in the
inflorescence for about 24 h. The flowers can be artificially self-pollinated, but
self-pollination in nature is prevented by the special morphology of the
inflorescence and by protogyny. Wind pollination does not seem to occur in
taro. The flowering process is controlled by the staminate portion of the
inflorescence.
• Fruit set and seed production occur only occasionally under natural conditions.
Fruits, when produced, occur at the lower part of the spadix. Each fruit is a
berry measuring 3-5mm in diameter and containing numerous seeds. Each
seed has a hard testa, and contains endosperm in addition to the embryo.

24. BREEDING OBJECTIVES : -
• Genetic variability
• Ideal plant type
• Cormel yield
• Taste quality of cormels
• Resistance/ tolerance to taro leaf blight
• Early maturity
• Longer keeping quality
• Density tolerance
• Incidence of flowering and floral productivity

25. Breeding Methods
 Conventional Breeding
• Collection
• Selection
• Hybridisation
• Chromosomal variations
• Polyploidy
Non conventional Breeding methods
Micropropogation
Protoplast culture
Organogenesis and embryogenesis
Genetic transformation

26. COLLECTION
• National Bureau of Plant Genetic Resources Institute, New
Delhi, a sister Institute under ICAR, meant for germplasm
collection, exchange, conservation and evaluation. The NBPGR
organizes field collection trips for all crops including tropical
tuber crops.
• Since CTCRI is the sole research institute in India dealing with
research and development programmes of tropical tuber crops,
the concerned researchers and technical staff of the Institute will
join in such trips arranged for tuber crops collection.
• Several collection trips have so far been undertaken resulting in
the procurement of a total of 4210 genetic stocks of various tuber
crops including taro at the CTCRI.

27. Number and source of taro germplasm
collections maintained at CTCRI
SR. NO ZONE NO. OF COLLECTIONS
1 SOUTH INDIA 148
2 CENTRAL INDIA 78
3 NORTH INDIA 84
4 NORTH-EAST INDIA 119
Altogether 424 indigenous collections were procured representing
genetic stocks from all over the Indian sub continent.

28. SELECTION
 Selection of desirable traits is based on phenotype.
 Effective method to make maximum use of germ
 Bolos-one, Kiyak and Denu are taro variety developed and registered through
selection and strong evaluation as variety for mid altitude agro-ecology.
 Somoa 3 – corm yeild 1-2 kg
 Two superior selections isolated from the germplasm were released (1987) for
general cultivation from CTCRI under the names ‘Sree Reshmi’ and ‘Sree
Pallavi’.

29. HYBRIDIZATION
• Taro is mainly vegetatively propagated but may also reproduce sexually. Due to
vegetative/clonal propagation, there is almost no genetic variation within the
cultivars although somatic mutations do occur thus increasing their vulnerability to
pest and diseases or changes in climatic conditions.
• Sexual hybridization of taro is well documented and techniques for pollinating and
growing seedlings have been established. Sexual hybridization is one way to generate
new cultivars with improved qualities (Strauss et al., 1979).
• Extensive breeding programs (sexual propagation) have been carried out in Samoa,
Papua New Guinea and Hawaii to produce cultivars with resistance to Taro Leaf
Blight (TLB) and with high yields. From this breeding program, promising taro
cultivars resistant to TLB have been produced in Hawaii.
• Even though sexual hybridization of taro is promising, it is a labor intensive and
lengthy process in terms of field preparation, planting of parents, induction of
flowering, pollination, development and maturation of fruit heads and seed
harvesting. In addition, the germination and planting of seedlings and screening
processes take several years.

30. • H 97 (CTCRI, Thiruvanathapuram)
• It is a hybrid between Manjavella and Accession No. 300. The plants are medium tall (1.5-
2.0 m) and characterized by the light sepia colour of the emerging leaf. The tubers are conical,
medium sized (25-35 cm) with light brown skin and white flesh with 27-29 percent starch
content. The yield ranges from 250-350 quintals per hectare.
• H 165 (CTCRI, Thiruvanathapuram)
• It is a hybrid between Chadayamangalam Vella and Kalikalan. The plants are medium tall
(1.5-2.5 m), generally non-branching and bear thick conical tubers. Tubers have golden brown
skin and cream flesh. Starch content of the tubers is 23-25 percent. It yields 330-380 quintals
per hectare.
• H 226 (CTCRI, Thiruvanathapuram)
• It is a hybrid between Malyan 4 and Ethakkakaruppan. The plants are tall (2.0-2.5 m)
occasionally branching and the leaves have a characteristic green colour. The tubers are
medium sized (25-35 cm) with creamy skin, light purple rind and white flesh; and 28-30
percent starch. The yield varies from 300-350 quintals per hectare.
• Sree Visakham (CTCRI, Thiruvanathapuram)
• It is a hybrid between Accession No. 1501 and S 2312. Its plants are predominantly
nonbranching and tall (2.0-2.5). Tubers are medium sized, conical with brown skin, cream rind
and light yellow flesh. Average carotene content is 466 IU and starch content 25-27 percent.
The tuber yield varies from 350-380 quintals per hectare. It is tolerant to cassava mosaic virus

31. • Sree Rekha (CTCRI, Thiruvanathapuram) It is a top cross hybrid having
long, conical tubers with light brown skin and creamy flesh. It matures in ten
months and produces average yield of 450-480 quintals per hectare.
• Sree Prabha (CTCRI, Thiruvanathapuram) It is a top cross hybrid and
produces short, conical tubers with brown skin and yellow flesh. It matures
in ten months and produces average yield of 400-450 quintals per hectare.
• Sree Sahya (CTCRI, Thiruvanathapuram) Its plants are tall (2.0-2.5 m),
predominantly non-branching with dark brown petioles and a prominent
spiny stipular marks. Tubers are medium long with light brown skin, cream
rind and white flesh. The starch content varies from 29-31 percent. Tuber
yield varies from 350400 quintals per hectare.
• Sree Prakash (CTCRI, Thiruvanathapuram) It is an early maturing
variety and takes 7-8 months to reach marketable maturity. The plants are
erect and relatively short (1.0-1.5 m), generally non-branching with highly
retentive of leaves. Tubers are medium sized with 29-31 percent starch
content. Tuber yield varies from 350-400 quintals per hectare. It is tolerant to
cassava leaf spot.
• Samoa 2 : Parental Lines : Pacific x malaysian (corm yeild 1-3 kg)

32. POLYPLOIDY
• Chromosome counts taken from well spread metaphase plates of root tip cells revealed
that diploids (2n = 28) and triploids (2n = 42) occur in Indian taros in almost equal
proportion.
• The frequency of the ploidy types showed clear difference in ploidy-wise distribution
in the different zones of the country. Although both the types occur in all the regions,
the diploids predominate in South India over the triploids while the triploids
convincingly out-numbered the diploids in the north (Sreekumari and Mathew, 1991).
• Several factors are known to influence the frequency of polyploids in different eco-
geographical regions. Zeven (1980) pointed out that polyploids in general have larger
dimensions and greater adaptability which apparently enable them to thrive better in a
wide range of higher latitudinal and altitudinal zones.
• Indian taros, triploids are endowed with better adaptability in higher altitudes and they
enjoy a wider distributional tendency than their diploid cousins.
• They are two high yielding good cooking quality triploid selections viz. Sree Reshmi
and Sree pallavi from the CTCRI, Trivandrum.

33. • Sree Pallavi is a high yielding variety of Taro
( Colocasia esculenta ) with good cooking quality. A
tall variety (1-1.5 m) with large number of small
sized tubers (20-25 per plant). Low tillering type.
Duration is 6.5 - 7 months and average yield is 15 -
18 T / Ha. Starch content is 16-17 % and protein
content is 2-3 % on fresh weight basis.
• Sree Rashmi is a high yielding variety of Taro
(Colocasia esculenta ) with good cooking quality
and taste.Plants are tall (100 - 150 cm). Duration is 7
-8 months and average yield is 15 - 20 T / Ha. Starch
conetent is 15 % and protein content is 2.5 % on
fresh weight basis. This variety is having edible
leaves, corms and cormels which are acrid free. It
can give economic yield under low inout levels also.
• Sree Kiran is the first hybrid taro variety in India.
Good cooking quality. Cormels are round to oval
shape and tubers are with long keeping quality.

34. CHROMOSOMAL VARIATIONS
• Karyomorphological analysis revealed that in
addition to numerical variation, structural differences
of chromosomes were also apparent in many
collections.
• The data of chromosome size showed that along with
autotriploid evolution, chromosome size has not
undergone noticeable degree of change. However,
considerable degree of heterogeneity exists in regard
to distribution of various chromosome types viz. m,
sm, st & t-types

35. MICROPROPAGATION
• Intensive clonal propagation of axenic and disease-free taro through tissue culture is another
option, which involves excising taro apical and axilary buds, decontaminating them and
culturing in vitro in sterile nutrient medium.
• The cultured bud can then be grown into a plantlet, and intensive sucker production induced
by the application of plant growth regulators.
• Tuia (1997) developed an efficient taro multiplication protocol using Murashige and Skoog
(1962) medium with 30 g/L sucrose, 7.75 g/L agar and the growth regulators, TDZ and BAP.
• Multiplication is done in three stages:
• (I) 0.5 mg/L TDZ for four weeks,
• (II) 0.8 mg/L BAP for three weeks and
• (III) 0.005 mg/L TDZ for three weeks.
• Following multiplication, small suckers are allowed to develop into larger plantlets by first
culturing individual suckers in hormone-free liquid MS medium for two to four weeks
followed by culturing in agar-solidified MS medium with monthly subcultures.
• If the meristem is cultured rather than the whole bud, it is possible to eliminate viruses, which
are particularly problematic in vegetatively propagated crops.

37. PROTOPLAST CULTURE
• Regeneration of taro plants from protoplasts has been
reported in C. esculenta var. antiquorum (Murakami et al.,
1995).
• The frequency of regeneration has been reported to be very
low and also a lengthy process.
• Protoplast culture has not been reported in C. esculenta
var. esculenta possibly due to the lack of an efficient and
routine callus initiation protocol. Regenerative callus is a
prime requirement for an efficient protoplast culture
(Murakami et at., 1995). There are no reports of attempts
to improve taro through protoplast fusion.

38. ORGANOGENESIS AND SOMATIC
EMBRYOGENESIS
• Initiation of highly regenerable callus is the first step towards an efficient
regeneration system. Callus initiation protocols have been well established in
Colocasia esculenta var. antiquorum (Jackson et al., 1977). However, these
protocols do not appear to be suitable for cultivars belonging to Colocasia
esculenta var. esculenta.
• In a small number of cases, induction of organogenic callus in Colocasia
esculenta var. esculenta has been reported. Yam et al (1990; 1991) reported
some success using axillary buds, half-strength MS macronutrients, one tenth-
strength MS micronutrients, full- strength MS vitamins, 25 ml/L taro corm
extract (TE) and the plant growth regulator 2,4,5-trichlorophenoxyacetic acid
(2,4,5-T).
• TE is an important requirement for callus initiation. However, TE is an
undefined component of a culture medium and so it is not possible to achieve
consistency in both the combination and concentration of components in each
“individual” taro extract.

39. • There are three reports of somatic embryogenesis in taro (Thinh, 1997; Verma et al.,
2004; Deo et al., 2009).
• Using MS medium Verma et al (2004) developed a two-step protocol (initially on
medium supplemented with 2.2 mg/L 2,4-D and 0.44 mg/L TDZ followed by a culture
phase with 1.1 mg/L TDZ) to regenerate somatic embryos from petiole explants, with a
maximum of 25-30 somatic embryos generated per explant.
• Thinh (1997) induced somatic embryos from the petiole fourth from the apical dome
using MS medium containing 1.0-2.0 mg/L TDZ. Both reports follow direct somatic
embryogenesis. Thinh (1997) stated that the somatic embryos were obtained from C.
esculenta var. antiquorum however, Verma et al (2004) did not state whether the variety
was esculenta or antiquorum. To date, there is only one report of an efficient protocol
for indirect somatic embryogenesis (that is via an intervening callus and subsequent
initiation of cell suspension culture from embryogenic callus) including an effective
regeneration protocol for somatic embryos in C. esculenta var. esculenta
• (Deo et al., 2009) with somatic embryos formation efficiency at a rate of
approximately 500-3000 per mL settled cell volume (SCV) and 80-100 per gram solid
media-derived callus with embryo conversion rate into plants of approximately 60 %.
• Corm slices derived from in vitro taro plants are cultured on half-strength MS medium
containing 2.0 mg/L 2,4-D for 20 days in darkness followed by subculture on the same
medium but containing 1.0 mg/L TDZ under the same conditions.

40. • Embryogenic callus eventuated after 75 days and continued to do so for 100 days.
Using 1.0 mg/L 2,4-D and 0.5 mg/L TDZ also produced embryogenic callus but at
a lower frequency than 2.0/1.0 combination. Due to differences in genotypes
response to plant growth regulators, these concentrations might be more effective
to other taro genotypes. Callus derived from both hormonal regimes was
proliferated on halfstrength MS containing TDZ (1.0 mg/L), 2,4-D (0.5 mg/L) and
glutamine (800mg/L) and upon transfer to half-strength MS it differentiated into
embryos which germinated on the same medium.
• Cell suspension was formed by putting callus pieces (~ 0.5 g) in liquid half-
strength MS medium containing TDZ (1.0 mg/L), 2,4-D (0.5 mg/L) and glutamine
(100 mg/L) and agitating on a rotary shaker at 90 rpm with weekly subculture (for
details see Deo, 2008)
• Embryo formation was induced when suspension cells were plated on half-
strength MS containing TDZ (0.1 mg/L), 2,4-D (0.05 mg/L), glutamine (100 mg/L)
and sucrose (50 g/L). Maturation and germination was achieved on half-strength
MS containing IAA (0.1 mg/L), BAP (0.05 mg/L).
• Even though various parameters were studied and optimized, a large number of
embryos did not develop past the globular stage indicating that production of a
large number of embryos does not always translate into a high regeneration rate.
Thus, further studies are required to refine the parameters affecting embryo
maturation and germination. Consequently, this regeneration system can be used
for mass propagation of clean planting material.

42. GENETIC TRANSFORMATION
• Production of improved plant varieties via genetic transformation
offers an attractive alternative to conventional breeding.
• Genetic transformation of Colocasia esculenta var. esculenta,
however has been largely neglected possibly due to the difficulties in
developing an efficient regeneration system or the lack of focus on a
crop of low significance to developed nations where a large portion
of funding and expertise resides.
• The development of a plant transformation system requires a method
of transferring genes into plant cells, a gene conferring the useful new
trait together with a promoter directing the appropriate level and
pattern of expression, an effective selective agent to suppress the
growth of non-transformed cells and the ability to regenerate plants
from single transformed cells (He et al., 2008).

43. • Transformation in Colocasia esculenta var. esculenta via microprojectile bombardment
(He et al., 2004) and Agrobacterium tumefaciens (He et al., 2008) has also been reported.
The efficiency of transformation via biolistics was reported to be very low with only one
stably transformed plant generated while a slightly higher frequency of transformation was
achieved via Agrobacterium where six stable transgenic plants were generated.
• Deo (2008) described the development of effective transformation system in the esculenta
variety using both Agrobacterium tumefaciens and microprojectile bombardment of
regenerable embryogenic suspension cultures. Putative stably transformed embryos
expressing the gfp reporter gene with an efficiency of ~ 200 and ~ 17 per mL SCV were
generated using microprojectile bombardment and Agrobacterium tumefaciens, respectively.
However molecular characterization of these embryos was not done.
• The previous research groups (He et al., 2004; 2008) used regenerable callus as the target
tissue for transformation which might have resulted in low frequency of transformation.
• Embryogenic suspension cultures are considered to be an excellent target tissue for genetic
transformation since they
• (i) can be easily proliferated and thus provide ample target tissue,
• (ii) consist of small cell clumps allowing maximal exposure to the transforming agent
thereby facilitating the identification of independent transformation events within the
dispersed cell clusters under selection and
• (iii) allow the recovery of non-chimeric transformants due to the unicellular origin of
embryos.

44. Development of molecular markers for blight resistance
in taro using bioinformatics tools
• The preliminary data set from the SRA section of NCBI was used for the
molecular marker development for blight disease resistance in taro. A total of
6,479,882 sequences obtained initially were reduced to 6,319,834 after pre-
processing.
• The processed sequences were reduced to 79,608 sequences after de novo
assembly and were finally assembled to 8547 contigs and 59,242 singlets.
• The contigs were then processed with various prediction pipelines to predict
SSRs and SNPs. The tools, QualitySNP and AutoSNP were employed to detect
the SNPs present within the contig sequences.
• MISA and SSRIT were used to predict the SSRs within the sequences.
• QualitySNP identified 518 synonymous and 44 non-synonymous SNPs from
the 8547 contigs. MISA identified 967 mono, 1484 di, 558 tri, 14 tetra, 2
penta, 9 hexa and 393 compound SSRs. Five hundred and sixty two SNPs and
3034 SSRs were predicted in silico for blight resistance in taro.

45. Agro-economic evaluation and variety
release
• Elite cultivars are selected from the germ
plasm by conducting field evaluation trials.
The desirable ones based on specific
characteristics (early maturity, ideal plant type,
good cormel shape, disease tolerance, good
cooking quality etc.) will be selected for
further evaluation.

46. A set procedure is followed for the release of elite varieties for
general cultivation, the sequence of which is given below: -
• Identification of desired type through germless evaluation
• Un replicated row trial (20-30 plants per row)
• Replicated row trial (20-30 plants per row per replication)
• Preliminary yield trial (RBD, 3 replications)
• Advanced yield trial (RBD, 3 replications, 2seasons)
• On farm trial within the state (10 locations, 2 seasons, local variety as check)
• Approval from Scientific Research Committee (SRC), CTCRI (appropriate
name to be given for the variety)
• Submitting the details before the State Variety release Committee for
consideration for release
• Approval of the Committee
• Multiplication for generating sufficient planting material
• Official release of the variety for general cultivation within the state

47. • For release of the variety at the national level, uniform regional trials are to be
conducted at different zones (usually undertaken by AICRP on tuber crops) and
approval to be obtained from the Central Variety Release Committee.
• It generally takes 5-6 years for an elite germplasm to reach the variety release stage.
Based on the procedure for state level release, four varieties were released in taro in the
country. They are two high yielding good cooking quality triploid selections viz. Sree
Reshmi and Sree pallavi from the CTCRI, Trivandrum, one blight tolerant variety
Muktakeshi from the Regional Centre of CTCRI at Bhuvaneswar, India and another
high yielding variety Kovur from the Andhra Pradesh Agricultural University, India.
• The released varieties are triploids indicating that although esculenta (diploids) forms
are available, these would be preferred in areas where Colocasia is a staple food as in
the South Pacific Islands and the Carribeans. Esculenta forms are not popular in areas
where cereals form the staple food probably due to their large size and low keeping
quality in contrast to smaller size and better keeping quality of var. antiquorum
(Velayudhan, et al.,1998).
• In India, selection during cultivation would have been for more and more number of
cormels as only cormels are used mostly as vegetable in this country as cereals form
the staple food. It is therefore probable that the nature of staple food of the people
determines the preponderance of one form over the other in areas of cultivation of this
crop, which is true as far as cultivation of taro in India is considered.

48. ACHIEVEMENTS
• Variety ‘Mukthakesi’ released from Regional
Centre of CTCRI is tolerant to Colocasia leaf
blight, a serious disease in certain parts of the
country.
• Muktakeshi is an erect medium tillering variety with
round corm and cylindrical cormels. They are
resistant to taro leaf blight under field conditions,
field tolerant to dasheen mosaic, aphids, cut worm
and scale insects. This variety is suitable for uplands
and lowlands during summer and rainy seasons
• They are two high yielding good cooking quality
triploid selections viz. Sree Reshmi and Sree
pallavi from the CTCRI, Trivandrum.
• High yielding variety Kovur from the Andhra
Pradesh Agricultural University, India.

49. • Pani saru - 1 is a variety of
taro with good cooking
quality. Cormels have elliptical
shape. They can be grown in
upland and low/submerged
conditions. They are field
tolerant to leaf blight.
• Pani saru - 2 is a variety of
taro with good cooking
quality. Cormels are round to
elliptical shape. They can be
grown in upland and low
land/water logged/ swampy
conditions. They are field
tolerant to leaf blight

50. • In taro, lines were identified viz., C-292, C-
465, C-621, TCR 368, TCR 947 A, TCR 961,
E-14, H-9, I-17 and HOB T2-1, having
moderate tolerance to TLB.

51. Present Constraints in Taro Production
• From the foregoing presentation, it is clear that there are several constraints
that limit the scope of present-day taro cultivation and production.
• i) The Taro Leaf Blight Disease: This disease automatically precludes the
development of a taro export trade in many countries, and in some cases
threatens the internal food supply. Research must continue in order to
develop resistant cultivars, or to identify effective control measures.
• ii) The Taro Beetle: At present, this is the most serious pest of taro in the
region. There is no effective control measure at present, and it may yet take
several years before the biological control measures being developed can be
tested and disseminated to farmers.
• iii) Laboriousness of the Production System: Taro production at present is
very labour intensive, the labour required is greater, coupled with even
lower yields.

52. • iv) Scarcity of Planting Material: Like most of the other tropical root crops, the
planting material for taro is bulky, making it expensive to transport over long
distances. It is also perishable, and cannot be stored over a long time. The net effect
of these two factors is that the availability of planting material is frequently a
limiting factor in taro production. With planting material being so scarce, it is not
surprising that some farmers use whatever planting material they can get. All the
preaching by extension agents about discriminating against disease-carrying or
low-yielding cultivars is only partially heeded.
• v) Post Harvest Handling and Marketing: At present, the bulk of taro produced is
handled and marketed as the fresh corm. The corm itself has a high water content,
and cannot be stored for more than a few days at ambient temperatures. Post
harvest losses are therefore heavy, and transportation costs are high. The
development and use of processed forms is a partial solution. Frozen taro, Poi, and
taro chips are examples. However, for a commodity that has so much cultural and
sentimental baggage attached to it, there is likely to be rejection of forms that do
not retain the traditional patterns of culinary preparation, presentation and
consumption. Marketing channels also need to be improved, as an incentive for
farmers to produce taro for cash.
• vi) Limited Taro Research and Extension: The amount of research currently being
done on taro is very little. A similar neglect of the crop is found in the extension
services, so that the technical knowledge base of the producers is very low.. They
can also take steps to strengthen the extension services.

53. Research Priorities
• Most of the above constraints in the taro production system can be effectively tackled and possibly solved
through research. The major research priorities at present are:
• i) Control of the Taro Leaf Blight
• It is amazing how very little research is being done on this problem at present. The technological
breakthrough which gives promise for this work is that taro flowering can now be induced reliably by use
of gibberellin. With this method, thousands of new genotypes have been produced, and there is hope that
through recurrent selection, good quality resistant cultivars can be identified, tested, and distributed.
• ii) Taro Beetle Control
• The search for chemical and cultural control methods having proved unsatisfactory, attention has now
turned to biological control. Taro beetle remains a very serious problem in the region and there is yet no
satisfactory control measure. Again the breeding programme is on the lookout for lines that may show
tolerance to the taro beetle, although given the versatility of the beetle in terms of host range, the prospects
might be less bright than expected.
• iii) Taro Germplasm Conservation.
• Within the region, there is a very large pool of taro germplasm (on farmers’ fields, in research stations, and
in the wild). Many of these genotypes are being lost daily for various reasons. There is a need to conserve
and characterise the taro in the region. Such a collection would not only insure against further genetic
erosion of the germplasm, but would serve as a source of desired genotypes for various countries in the
region. The foundations for such germplasm conservation have been laid at the Papua New Guinea
University of Technology and other locations where protocols for taro tissue culture have been developed.
Hopefully, this will permit in vitro maintenance of the germplasm to complement accessions that are
maintained in the field.
• .

54. • iv) Improved Production Practices
• There is still a lot of taro production that relies on age-old, traditional production
methods. Research into various agronomic practices is needed in order to improve
productivity. In particular, simple methods for rapid generation and multiplication of
planting material need to be explored. More effective low-technology methods of
multiplying planting material need to be devised. At the other end of the
technological spectrum, it may be possible, for example, for tissue culture to be
explored as a method for routine commercial production of planting materials. Also,
as new cultivars are produced and released, there is need to establish, through
research, the best agronomic practices with respect to spacing, water requirements,
weed control, fertilizer, maturity, etc.
• v) Post-harvest Handling and Utilization
• The aim here should be to find ways to minimise post-harvest losses. New culinary
forms of preparing and presenting taro should be explored, as well as development
of storable processed forms.
• All the above research priorities need to be addressed in order to sustain the taro
industry in the region. Research is expensive and money is scarce; food security and
in the cash economy. This will lead them to establish the appropriate policy
framework within which taro production and promotion can occur. Also, the more
taro can be placed on a cash crop footing, the easier it will be to acquire the
resources to support research into the crop.

55. FUTURE PERSPECTIVES
• Taro is an ecologically unique crop. It is able to grow in ecological conditions which other crops may find
difficult or adverse. There are at least three such situations:
• a) Waterlogged and hydromorphic soils.
• b) Saline Soils: Some taro cultivars can tolerate salinity, and can grow in 25-50% sea water. Such saline
conditions would prove lethal to most other crops.
• c) Shady conditions: Taro has long been known to be shade tolerant.. Shade tolerance in taro enables it to
grow well as an intercrop between tree crops (e.g. coconuts), because it can profitably exploit the diffuse
light reaching the plantation floor.
• Because the above ecological conditions are difficult for other crops, there is less likely to be competition
with taro in exploiting them. So, the place of taro in these ecological conditions is reasonably assured. This
attachment will continue to propel and fuel taro cultivation far into the future. It will also continue to
ensure a vibrant internal and external market for taro.
• Even the rice cultures of south India have well appreciated that the field production system for taro is very
similar to that of rice. Land that has been prepared for flooded rice is equally suitable for flooded taro.
Thus, taro fits well as an alternative crop in the rice-based cropping systems.
• The problems that beset taro production in the India region are numerous, and have been discussed above.
However, given adequate research effort and the appropriate policy framework, most of the problems can
be easily surmounted. Taro can then continue to perform its age-old functions of providing food security,
boosting the economy through internal and external cash earnings, and playing a critical role in the socio-
cultural life of the people.

56. • OBJECTIVE: The main objective of the taro breeding program is to
develop through sexual hybridization high-yielding, diseaseand pest-tolerant
cultivars with good corm quality characteristics acceptable to the farmers and
consumers in the South Pacific region and migrants from the Pacific living in
other countries.
• MATERIAL AND METHODS : The seedlings derived from the crosses are
evaluated in a series of trials: seedling, preliminary, intermediate, advance,
and on-farm trials in Western Samoa and in some regional countries
• Crosses were made among 40 selected clones and cultivars in December,
with emphasis on high yield, high corm quality, and dry-matter content

58. • RESULTS : In the advance trials , the clone 84045-9 gave yields
comparable to 'Alafua Sunrise' and had high dry matter, high taste
rating, and tolerance to drought. In the on-farm trials, 'Alafua
Sunrise' outyielded Talo Niue and Manua but was rated lower in
taste tests by Western Samoans.
• In the advance and on-farm trials conducted in, the clone 86038-
38 yielded slightly lower than 'Alafua Sunrise', but it was similar to
Talo Niue in quality with yields significantly better than Talo Niue.
• The clone 84014-5 also appeared to be promising as it gave high
yields, had high dry matter, and was rated above 'Alafua Sunrise' in
taste tests, but the corm shape was poor and the flesh color yellow

59. AIM :
The present work was intended to establish an efficient and reproducible direct regeneration
protocol in Colocasia esculenta and to compare the levels of total phenolics and free radical
scavenging activity in in vitro regenerated and wild type plants.

60. • Materials and Methods:
• The corms of Colocasia esculenta var. Sreekiran was collected from Central
Tuber Crop Research Institute, Thiruvanthapuram, Kerala, India.
• In vitro micropropogation protocol of the C. esculenta plant was optimized using
meristem as explant. The surface sterilized explants were inoculated on MS
supplemented with varied concentration and combination of auxin and
cytokinins. The cultures were maintained at 26ºC under a 12 hrs photoperiod.
Total phenolic content and free radical scavenging assay was carried out in wild
type plants and compared with in vitro micropropagated plants using DPPH
method. Statistical analysis of the data was carried out using STATISTICA 13
software. An efficient in vitro micropropagation protocol was established for C.
esculenta
• RESULT: The present investigation revealed that the C. esculenta is having strong
antioxidant activity. The antioxidant activity increased in micropropagaetd
plants. This may be due to stress induced in vitro conditions.

61. • Aim:
• To study somatic embryogenesis, organogenesis and plant regeneration in taro.
• Material and Methods :
• Callus was initiated in three different ‘‘esculenta’’ taro cultivars by culturing corm
slices in the dark on half-strength MS medium supplemented with 2.0 mg/l 2,4-
dichlorophenoxyacetic acid (2,4-D) for 20 days followed by subculture of all corm
slices to half-strength MS medium containing 1.0 mg/l thidiazuron (TDZ).
Depending on the cultivar, 20–30% of corm slices produced compact, yellow,
nodular callus on media containing TDZ

62. • RESULTS:
• Histological studies revealed the presence of typical embryogenic cells
which were small, isodiametric with dense cytoplasms.
• Somatic embryos formed when callus was transferred to hormone-free
medium and *72% of the embryos germinated into plantlets on this
medium.
• Simultaneous formation of roots and shoots during germination, and
the presence of shoot and root poles revealed by histology, confirmed
that these structures were true somatic embryos.
• Plants derived from somatic embryos appeared phenotypically normal
following 2 months growth in a glasshouse. This method is a
significant advance on those previously reported for the esculenta
cultivars of taro due to its efficiency and reproducibility