CHAPTER I INTRODUCTION

1.1 ORIGIN AND HISTORY OF SILK Silk – the queen of textile specially appreciated for its luster

and elegance. The silk garments are worldwide used particularly for

festivals and other auspicious occasions. Silk cools and warms

simultaneously. Silk garments are perfect for summer and winter. It

can absorb up to 30% of its weight in moisture without feeling damp.

In spite of its delicate appearance, silk is relatively robust. Because of

its protein structure, silk is the most hypoallergenic of all fabrics. Silk

is also fire retardant. Silk has an age old history; the exact history of

silk is somewhat of a mystery. Historians said that silk production,

called Sericulture, originated in China 10,000 years ago. However

ancient Chinese legends contribute the origination of Sericulture to

the Chinese empress Si Ling Chi who ruled in 2,600 BC. It is also

believed that it is originated in the foot hills of Himalayas.

With the improvement of civilizations, the early man needed

materials made from fibers not only for clothing but also for

household textiles. Animal and vegetable sources of fibers discovered

in prehistoric times, bred and cultivated to increase sophisticated

processing.

The earliest mythical work “Samhita of Rigveda” is at least 6000

years old. It is perhaps believed that the oldest of the Vedas i.e. the

Rigveda don’t give direct information regarding silk, but the synonym

“urna” [generally translated silk] occurs in Rigveda.

The Epic era is another important period in the Indian history.

The great epics namely Ramayana, Mahabharata and Bhagavata are

the three gems that came out as extraordinary contributions from the

great sages.

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The first in the order was Ramayana. The great sage “Valmiki”

mentioned about silk garments in Ramayana. Similar references are

plenty in the other two epics also. Lord Krishna was often described as

dressed with Kashi pitambara [Banaras silk]. References of Kashmiri

silk are also found in Mahabharata. The widely used Indian Sanskrit

word Kausheya or Kshauma signifying silk or cocoon has been

frequently used in the ancient Sanskrit literature which does not

resemble to have any other origin. And thus, it is concluded that silk

existed in India at least 6000 years ago [Ananthraman and Dandin

1992].

1.2 STATUS OF SERICULTURE

1.2.1 Present status of Sericulture in World

More than 25 countries in Asia, Africa and South Africa are

presently engaged in silk production. Some European countries like

France, Italy and Spain which had a long standing in the production

of silk are no more engaged in it, while the industry declined fastly in

other major traditional silk producing countries like Japan, South

Korea. As a result, Sericulture is fast growing in a number of

developing countries like China and India. India with its monopoly in

the production of muga silk has the characteristic of being the only

country producing all the four types of commercially exploited silks

viz., Mulberry, Tasar, Eri and Muga [Balsubramanian 2000]. Major

emphasis in the country’s production has been on mulberry silk. India

is the major silk producing country accounting for 15,000 MT of raw

silk.

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1.2.2 Present status of Sericulture in India

Mulberry raw silk production is mainly distributed in

Karnataka, Andhra Pradesh and Tamilnadu in the tropical belt, and

West Bengal and Jammu and Kashmir in the sub-tropical and

temperate zones respectively. These five traditional states together

contribute for about 99% of the country’s total mulberry raw silk

production. Remaining small quantity comes from the states of

Assam, Bihar, Maharashtra, Kerala, Madhya Pradesh, Orissa, Punjab,

Rajasthan and Uttar Pradesh, which are called non traditional states.

Among these non traditional states Maharashtra stands first in silk

production.

1.2.3 Present status of sericulture in Maharashtra

In Maharashtra, 22 major districts are producing mulberry silk.

Initially Khadi Village Industry Board, Vidarbha Vikas Mahamandal,

Udyog Sanchanalaya were giving support to silk industry separately.

Presently silk industry is spreading widely. Dept. of Handloom and

Power loom is promoting the industry by merging these three

departments and creating the new department called Director of

Sericulture which is at Nagpur since from 1997. During 2007-08 the

area under mulberry plantation was 4112 ha while silk production

was 129 MT which is quite less than the actual demand of silk in

Maharashtra. Paithan dist. Aurangabad, Yeola dist. Nasik, Solapur

and Andhalgaon dist. Bhandara are the main places in Maharashtra

where silk weaving is done by traditional weavers [Kalantri et al.2009].

In recent years, sericulture has come to be recognized as one of the

most important, rural agro-based, providing occupation. To grow the

industry, Central Silk Board is giving assistance in training, research

and various schemes of funds to boost the Sericulture in

Maharashtra.

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1.3 TYPES OF SILK IN INDIA

The mulberry silk is produced by the silkworm Bombyx mori L. -

a monophagous insect [Ito 1960] feeding on the leaves of mulberry

Morus sp. It is the most superior and excels all other natural silks in

quantity, quality and popularity. The tasar silk is produced by the

silkworm Antheraea mylitta which feed mainly on the leaves of

Terminalia tomentosa [Asan], T. arjuna [Arjun], Shorea robusta [Sal],

Quercus incana. China and India are the leading producers of Tasar

silk. The Eri silkworm is Philosamia ricini which feed mainly on the

leaves of Recinus communis [castor] while the leaves of Heteropanax

fragrans [Kesseru], Tapioca and Papaya etc are also fed. The muga silk

is produced by Antheraea assama which feed mainly on the leaves of

Machilus bombycina [Som] and Litsea polyantha [Solu].

Sericulture being an agro-based, labor intensive cottage

industry is known for low investment and quick and high returns and

hence, fits well in the socio-economic structure of India.

Sericulture is the art and science of rearing silkworm to produce

silk. Mulberry and silkworm are the two important components of

mulberry sericulture involving mulberry cultivation and silkworm

rearing. It is the only one cash crop in agriculture sector that gives

returns within 30 days. In addition, various activities like silk reeling,

twisting, throwing, dyeing, weaving, printing, designing, marketing

etc. create enormous opportunities for employment in Sericulture.

Sericulture is a popular agro based labor intensive cottage industry in

rural India; it plays a vital role in enriching rural economy and

provides employment to rural folk. The prefix ‘SERI’ is popularly

known as ‘Self Employment Remunerative Industry’. It has become an

unconstrained mine in rural economy. Sericulture in India has turned

out to be a highly remunerative occupation providing attractive

returns throughout the year.

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In Sericulture, the most important factor is the cultivation of

selected mulberry varieties, showing desirable agronomical and

commercial traits. Therefore, it is very important to select high

yielding varieties with better quality leaves and with low inputs. In

addition, they should exhibit wide adaptability and tolerance to varied

climatic factors and resistance to pests and diseases. Among the

important factors contributing for the successful harvest of cocoon

crops, mulberry leaf stands first & it has importance of about 38.2 %,

climate37 %, rearing 9.3 %, silkworm race 4.2 %, silkworm egg 3.1

%, others 6.6 %. Hence, the profitability depends on the quantity &

quality of leaves produced in a unit area over a unit time [Bose, 1989].

1.4 GENUS MORUS SP. L. Mulberry belongs to the genus Morus sp.L. of the family

Moraceae. Regarding the origin of Morus sp., Parkar [1818] opinioned

that the genus was probably indigenous to China and was later

naturalized in West Asia, Southern Europe and America. Vavilov

[1926] and Janaki [1948] considered China as the centre of its origin.

However, others [Dhar and Ahsan, 1989; Bano and Kachroo, [1975];

Malik and Farooq, [1988] suggest that the sub-Himalayan region of

India may be the probable place of origin of the genus.

Mulberry is an outstanding bio-energy plant. In addition to

being fed to silkworms, mulberry is used in medicine, aqua-culture,

agro-forestry, social forestry, water-shed management and drought

prone area development program. [Philip, 1989; Tiku and Bindroo,

1989; Bari, 1990; Munirajappa et al. 1995]. It is a fast growing

deciduous woody perennial plant. It can be grown in places with

rainfall ranging from 600mm to 2500mm.When the rainfall is low the

growth is limited due to moisture shortage and result in low leaf yield.

It is found that mulberry requires temperature ranging from 24oC to

28oC for better growth and leaf yield.

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Mulberry plants do not grow well if the temperature is below 13oC and

above 38oC. Mulberry can be grown in all types of soil and climatic

conditions and pH ranging from 6.5 to 7.0. But it flourishes well in

soils that are flat, deep, fertile, well drained, loamy to clayey, and

porous with good moisture holding capacity. It has a deep root

system. The leaves are simple, alternate, stipulate, petiolate, entire or

lobed. Mulberry basically a tree, in Sericulture it is being maintained

as small bushes through repeated pruning and training. The chief

mode of propagation of this highly heterozygous crop in tropical

countries like India, Pakistan, Bangladesh is chiefly through stem

cuttings while in temperate countries the seed is the major source of

propagation.

Most of the species of the genus Morus and cultivated varieties

are diploid, with 28 chromosomes. However, triploids (2n= (3x) =42)

are also extensively cultivated for their adaptability, vigorous growth

and quality of leaves.

Among the food plants, mulberry alone contributes about 90 % of

raw silk production of the world; the other 10 % is from non-mulberry

(Tasar, Eri, and Muga) food plants. It has been well-known that nearly

75% of the protein is directly derived from the mulberry leaf, which is

the primary source of the silkworm for biosynthesis of its silk. Silk

protein is composed of sericin and fibroin, are totally derived from the

mulberry leaves. It is calculated that about 60 % cost of production of

silk is from mulberry alone. This shows the importance of food plant

in the economics of Sericulture [G.Boraiah 1994]. Hence, it is required

to develop varieties with wider adaptability and higher yield potential

to maintain the profitability in Sericulture industry.

India being a vast country with complex agro-climatic zones, there

is wide scope for having a number of elite mulberry varieties for

cultivation in different areas. Providing the best variety over the

existing ones is the aim of any crop improvement program.

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Thus, there is a need for improvement of mulberry varieties in terms

of nutritive value and quantity, to ensure profitable production of

cocoon per unit area. High leaf productivity brings in the reduction of

cocoon production cost.

In summary, mulberry breeding aims at evolving new varieties,

showing increased yield, improved quality, palatability and wide range

of adaptability, good response to agronomic inputs and resistance or

tolerance to harmful biotic and abiotic factors. Since mulberry is a

highly heterozygous plant, these goals can be achieved either by

employing conventional methods like introduction, selection and

hybridization or by non-conventional breeding methods like mutation

breeding, polyploidy breeding, tissue culture, protoplast fusion,

biotechnology and genetic engineering.

1.5 PREVIOUS WORK ON MUTATION STUDIES

MORUS SP. L. The use of induced mutations in plant breeding is known as

mutation breeding. The vegetative propagated crops like mulberry are

very suitable plant for application of mutation breeding methods.

Since large variations can often be observed in the irradiated plants.

Mutations in mulberry are spontaneous or induced. Since the

frequency of spontaneous mutation is low, artificial induction of

mutations is necessary through irradiation or by treating with

chemicals. Mutations can be induced by physical mutagen i.e.

through irradiations, both ionizing [X-rays, β-rays, gamma rays and

fast neutrons] and non-ionizing [ultra violet rays] radiations and

mutations also can be induced by certain chemicals, such as Ethyl

methane sulphonate [EMS], Methyl methane sulphonate [MMS],

Diethyl sulphate [DES], which are quite often used. Mutagenesis has

been proved to be extremely useful in creating a new variability in the

existing gene pool.

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Of late, genetically effective radiations have been widely used for

induction of mutation in mulberry [Hazama, 1967, 1968a, 1968b;

Nakajima, 1973; Fujita, 1974; Kukimura, et al. 1976; Aliev, 1977;

Fujita, et. al. 1980].

Mutation breeding make use of the possibility of altering genes by

exposing seeds or other parts of the plant to chemical or physical

mutagen [ Dwivedi et al. 1986,1987; Jayaramaiah and Munirajappa

1987; Ramesh, 1997; Mitra and Bhowmik, 1999].

Radiation as a tool for inducing variability in crop plants was

reported by Stadler [1928]. The investigation relating to the effect of

radiation has been extensively reviewed by Sparrow and Konzak

[1958]. Radiations [X-rays and Gamma rays] are shown to affect

biological events such as germination, survival per cent, growth and

vigor of the plant [Iqbal et al., 1974; Raghuvanshi and Singh 1974;

Mishra and Raghuvanshi, 1988; Kumar and Prasad, 1990; Acharya

and Tiwari, 1995].

EMS is a prevailing mutagen that has been extensively used in

genetic research. Of all the mutagens available today, gamma rays

and EMS have been found more potent for mulberry [Sastry et al.,

1983; Yang and Yang 1991]. EMS is a monofunctional –ethylating

agent that has been found to be mutagenic in wide variety of genetic

test systems from viruses to mammals. In higher organisms, there is

clear-cut evidence that, EMS is able to break chromosomes, although

the mechanism involved is not well understood, but there is some

evidence that EMS can cause base-pair insertion or deletions as well

as more extensive intragenic deletions [Gary and Sega, 1984]. Among

chemicals mutagens, EMS [Ethyl methane sulphonate] is particularly

effective in giving a wider spectrum of mutated morphological

characters. S30, S36, S41 and S54 are some of the beneficial mutants

produced through chemical mutagenesis [Sastry et al. 1974].

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Further artificial induction of mutation is necessary and helpful in

order to rectify one or two undesirable traits or other wise in improved

morpho-economical traits using gamma irradiation and chemical

mutagens like EMS.

In spite of number of reports concerning promising mutants

obtained in countries like Japan, China and Russia, very few attempts

have been made to evolve commercial mulberry mutants in India

[Sastry, et al., 1974; Jayaramaiah and Munirajappa, 1987;

Ramesh,1997]

During 1950s, induced mutagenesis was widely practiced in the

US, Europe, Japan and China. Tojyo, [1966], Hazama, [1967]. Katagiri

[1970] has done extensive work on irradiation of mulberry by using

gamma rays and obtained variations in leaf color, shape, size and

internodal distance. Irradiation has become one of the plant breeder’s

most valuable tools.

In India, Swaminathan [1964] at the Indian Agricultural

Research Institute, New Delhi initiated a major program on

mutagenesis in different crops including mulberry plant. These

studies were broadly aimed at understanding the process of mutation,

testing the effectiveness of various mutagens, identifying optimum

dose and the best method of treatment for different crop species;

isolation of mutants of basic and applied value; clarify the biological

effects of radiation-treated media. Initial studies on induced mutations

were mainly directed to find optimum combination of mutagen and

dose to obtain the best response. The frequency of induced mutations

almost doubles those naturally occurring and they have been looked

as a powerful tool for the development of new cultivars.

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1.6 RESEARCH CONSIDERATION Mutations are the only source of variations in sterile plants. It

offers the breeder a rapid method to increase genetic variation which

otherwise, would require many years to achieve through conventional

breeding. Successful exploitation of various mutagenic agents for

inducing aberrations has become one of the most important lines of

modern research. Since mulberry is a highly heterozygous plant,

inducing mutation artificially might also be beneficial either to create

variability or rectify the defects if any in the well adopted genotype

cultivars. Hence, present research project was to study the effect of

EMS solution and gamma irradiation and rectify the defects by

induced mutagenesis. In nutshell keeping the above aspects in view,

the present investigation aimed at improving the already existing

cultivars viz.V1, S36 and S1635 by inducing gamma irradiation and EMS

to improve morpho-economical traits. The present work represents

the following objectives.

1.7 AIMS AND OBJECTIVES 1] To study the mutagenesis in mulberry plant by physical mutagen

like gamma radiation and chemical mutagen like EMS solution of

various concentrations with respect to changes in phenotypic and

physico-chemical characteristics.

2] To induce early vigor of plant

3] To induce higher biomass production ability

4] To improves the nutritional composition of the leaves

5] To delay the early maturing of leaves

6] To introduce a new variety of the plant by rectifying the defects.

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