STRATEGIES FOR ENHANCEMENT IN FOOD PRODUCTION

173

Wheat and Rice: During the period 1960 to 2000, wheat production

increased from 11 million tonnes to 75 million tonnes while rice production

went up from 35 million tonnes to 89.5 million tonnes. This was due to the

development of semi-dwarf varieties of wheat and rice. Nobel laureate

Norman E. Borlaug, at International Centre for Wheat and Maize

Improvement in Mexico, developed semi-dwarf wheat. In 1963, several

varieties such as Sonalika and Kalyan Sona, which were high yielding and

disease resistant, were introduced all over the wheat-growing belt of India.

Semi-dwarf rice varieties were derived from IR-8, (developed at International

Rice Research Institute (IRRI), Philippines) and Taichung Native-1 (from

Taiwan). The derivatives were introduced in 1966. Later better-yielding semi-

dwarf varieties Jaya and Ratna were developed in India.

Sugar cane: Saccharum barberi was originally grown in north India, but

had poor sugar content and yield. Tropical canes grown in south India

Saccharum officinarum

had thicker stems and higher sugar content but

did not grow well in north India. These two species were successfully

crossed to get sugar cane varieties combining the desirable qualities of

high yield, thick stems, high sugar and ability to grow in the sugar cane

areas of north India.

Millets: Hybrid maize, jowar and bajra have been successfully developed

in India. Hybrid breeding have led to the development of several high

yielding varieties resistant to water stress.

9.2.2 Plant Breeding for Disease Resistance

A wide range of fungal, bacterial and viral pathogens, affect the yield of

cultivated crop species, especially in tropical climates. Crop losses can

often be significant, up to 20-30 per cent, or sometimes even total. In this

situation, breeding and development of cultivars resistant to disease

enhances food production. This also helps reduce the dependence on

use of fungicides and bacteriocides. Resistance of the host plant is the

ability to prevent the pathogen from causing disease and is determined

by the genetic constitution of the host plant. Before breeding is

undertaken, it is important to know about the causative organism and

the mode of transmission. Some of the diseases caused by fungi are rusts,

e.g., brown rust of wheat, red rot of sugarcane and late blight of potato;

by bacteria – black rot of crucifers; and by viruses – tobacco mosaic,

turnip mosaic, etc.

Methods of breeding for disease resistance: Breeding is carried

out by the conventional breeding techniques (described earlier) or by

mutation breeding. The conventional method of breeding for disease

resistance is that of hybridisation and selection. It’s steps are essentially

identical to those for breeding for any other agronomic characters such

as high yield. The various sequential steps are : screening germplasm

2015-16

STRATEGIES FOR ENHANCEMENT IN FOOD PRODUCTION

During the peri

od 1960 to 2000, wheat production

d fr

es to 75 million tonnes while rice production

went up from 35 million tonnes to 89.5 million tonnes. This was due to the

development of semi-dwarf varieties of wheat and rice. Nobel laureate

Norman E. Borlaug, at International Centre for Wheat and Maize

Improvement in Mexico, developed semi-dwarf wheat. In 1963, several

varieties such a

Sonalika

and

Kalyan Sona

, which were high yielding and

disease resistant, were introduced all over the wheat-growing belt of India.

Semi

Rice

aiwa

dwar

Suga

had

Sacc

did

cros

area

Mill

in Ind

yieldi

9.2.

A wi

cult

ofte

situ

enha

use

abil

unde

the

e.g.

turn

Meth

out by the conventional breeding techniques (described earlier) or by

mutation breedin

The conventional method of breedi

for disease

resistance is that of hybridi

ation and selection. It

’

s st

s are essentiall

identical to those for breeding for any other agronomic characters such

as high yield. The various sequential steps

are : screening germplasm

2015-1

mi-dwarf rice varieties were derived from IR-8, (devel

ed at International

ce Research Institute (IRRI), Phil

nes) and Taichun

Native

1 (from

wan). The derivatives we

trtr

yielding sem

arf varieties

Jaya

Ratna

were developed in India.

gar cane

Saccharum barberi

was originally grown in north India, but

d poor sugar content and yield. T

opical canes gr

ccharum officinarum

had thicker stems and higher sugar content but

not grow well in north India. These two species were successfully

ossed to get sugar cane varieties combining the desirable qualities of

yield, thick stems, high sugar and ability to grow in the sugar cane

eas of north India

llets

: Hybrid maize, jowar and bajra have been successfully developed

India. Hybrid breeding have led to the development of several high

elding varieties resistant to water stress.

2.2 Plant Breeding for Dis

sese

ista

wide range of fungal, bacterial and viral pathogens, affect the yield of

ltivated crop species, especially in tropical climates. Crop losses can

ten be significant, up to 20-30 per cent, or sometimes even total. In this

tuation, breeding and development of cultivars resistant to disease

hances food production. This also helps reduce the dependence on

e of fu

icides and bacteriocides. Resistance of the host

lant is the

ility to prevent the pathogen from causing disease and is determined

the genetic constitution of the host plant. Before breeding is

dertaken, it is important to know about the causative organism and

mode of transmission. Some of the diseases caused by fungi are rusts,

g., brown rust of wheat, red rot of sugarcane and late blight of potato;

bacteri

–

black rot of crucifers; and by viruse

s –

tobacco mosaic,

mosaic, etc.

thods of breeding for disease resistance:

Breeding is carried

t by the ntio l br di t hniq (d ibed li ) b

174

BIOLOGY

for resistance sources, hybridisation of selected parents, selection and

evaluation of the hybrids and testing and release of new varieties.

Some crop varieties bred by hybridisation and selection, for

disease resistance to fungi, bacteria and viral diseases are released

(Table 9.1).

Table 9.1

Crop Variety Resistance to diseases

Wheat Himgiri Leaf and stripe rust, hill bunt

Brassica Pusa swarnim White rust

(Karan rai)

Cauliflower Pusa Shubhra, Black rot and Curl

Pusa Snowball K-1 blight black rot

Cowpea Pusa Komal Bacterial blight

Chilli Pusa Sadabahar Chilly mosaic virus,

Tobacco mosaic virus

and Leaf curl

Conventional breeding is often constrained by the availability of limited

number of disease resistance genes that are present and identified in various

crop varieties or wild relatives. Inducing mutations in plants through diverse

means and then screening the plant materials for resistance sometimes

leads to desirable genes being identified. Plants having these desirable

characters can then be either multiplied directly or can be used in breeding.

Other breeding methods that are used are selection amongst somaclonal

variants and genetic engineering.

Mutation is the process by which genetic variations are created

through changes in the base sequence within genes (see Chapter 5)

resulting in the creation of a new character or trait not found in the parental

type. It is possible to induce mutations artificially through use of chemicals

or radiations (like gamma radiations), and selecting and using the plants

that have the desirable character as a source in breeding – this process is

called mutation breeding. In mung bean, resistance to yellow mosaic

virus and powdery mildew were induced by mutations.

Several wild relatives of different cultivated species of plants have been

shown to have certain resistant characters but have very low yield. Hence,

there is a need to introduce the resistant genes into the high-yielding

cultivated varieties. Resistance to yellow mosaic virus in bhindi

(Abelmoschus esculentus) was transferred from a wild species and

resulted in a new variety of A. esculentus called Parbhani kranti.

2015-16

BIOLOGY

for resistance sources, hybridisation of selected parents, selection a

evaluation of the hybrids and testing and release of new varieties

Some crop varieties bred by hybridisation and selection, for

disease resistance to fu

i, bacteria and viral diseases are release

(Table 9.1).

Table 9.1

arie

Resistance to diseases

bunt

limite

variou

divers

metime

sirabl

eeding.

aclona

create

er 5)

arenta

hemica

plant

cess i

mosai

ave be

shown to have certain resistant characters but have very low yield. Hence,

there is a need to introduce the resistant genes into the high-yieldin

cultivated varieties. Resistance to

llow mosaic virus

(

Abelmoschus

esculentus

) was transferred from a wild species an

resulted in a new variety of

A. esc

entus

ranti

2015-1

117744

arie

Resistance to diseases

Wheat

Himgiri

Leaf and stripe rust, hill

Brassica

Pusa swar

nim

White rust

(Karan rai)

Cauliflower

Pusa Shubhra,

Black r

ot a

C C

Pusa Snowball K-

blight

otot

Cowpea

Chilli

mosaic virus,

co mosaic viru

d Leaf curl

Conventional breeding is often constrained by the availability of

number of disease resistance genes that are present and identified in

crop varieties or wild relatives. Inducing mutations in plants through

means and then screening the plant materials for resistance so

leads to desirable genes being identified. Plants having these de

characters can then be either multiplied directly or can be used in br

Other breeding methods that are used are selection amongst som

variants and genetic engineering.

Mutati

is the process by which genetic variations are

thro

h chan

s in the base se

ence within

nes (see Cha

resulting in the creation of a new character or trait not found in the p

type. It is possible to induce mutations artificially through use of c

or radiations (like gamma radiations), and selecting and using the

that have the desirable character as a source in breeding – this pro

called

mutation breedin

. In mun

bean, resistance to

llow

virus and powdery mildew were induced by mutations.

Several wild relatives of different cultivated species of plants h

STRATEGIES FOR ENHANCEMENT IN FOOD PRODUCTION

175

All the above examples involve sources of resistance genes that are in

the same crop species, which has to be bred for disease resistance, or in a

related wild species. Transfer of resistance genes is achieved by sexual

hybridisation between the target and the source plant followed by

selection.

9.2.3 Plant Breeding for Developing Resistance

to Insect Pests

Another major cause for large scale destruction of crop plant and crop

produce is insect and pest infestation. Insect resistance in host crop plants

may be due to morphological, biochemical or physiological characteristics.

Hairy leaves in several plants are associated with resistance to insect pests,

e.g, resistance to jassids in cotton and cereal leaf beetle in wheat. In wheat,

solid stems lead to non-preference by the stem sawfly and smooth leaved

and nectar-less cotton varieties do not attract bollworms. High aspartic

acid, low nitrogen and sugar content in maize leads to resistance to maize

stem borers.

Breeding methods for insect pest resistance involve the same steps as

those for any other agronomic trait such as yield or quality and are as

discussed earlier. Sources of resistance genes may be cultivated varieties,

germplasm collections of the crop or wild relatives.

Some released crop varieties bred by hybridisation and selection, for

insect pest resistance are given in Table 9.2.

Table 9.2

Crop Variety Insect Pests

Brassica Pusa Gaurav Aphids

(rapeseed mustard)

Flat bean Pusa Sem 2, Jassids, aphids and

Pusa Sem 3 fruit borer

Okra (Bhindi) Pusa Sawani Shoot and Fruit borer

Pusa A-4

9.2.4 Plant Breeding for Improved Food Quality

More than 840 million people in the world do not have adequate food to

meet their daily food and nutritional requirements. A far greater number–

three billion people – suffer from micronutrient, protein and vitamin

deficiencies or ‘hidden hunger’ because they cannot afford to buy enough

fruits, vegetables, legumes, fish and meat. Diets lacking essential

micronutrients – particularly iron, vitamin A, iodine and zinc – increase

the risk for disease, reduce lifespan and reduce mental abilities.

2015-16

STRATEGIES FOR ENHANCEMENT IN FOOD PRODUCTION

7755

All the above examples involve sources of resistance genes that are in

the same crop species, which has to be bred for disease resistance, or in a

elated wild species.

ransfer of r

esistance genes is achieved by sexual

hybridisation between the target and the source plant followed by

selection.

9.2.3

Plant Breedi

for Developin

Resistance

to Insect Pests

Anot

prod

may

Hair

e.g,

solid

and

acid

stem

thos

disc

germ

inse

9.2.

meet

three billion people – suffer from micronutrient, protein and vitamin

deficiencies or ‘hidden hunger’ because they cannot afford to buy enough

fruits, vegetables, legumes, fish and meat. Diets lacking essential

micronutrients – particularly iron, vitamin A, iodine and zinc – increase

the risk for disease, reduce lifespan and reduce mental abilities.

2015-1

other major cause for large scale destruction of crop plant and crop

oduce is insect and pest infestation. Insect resistance in host crop plants

y be due to morphological, biochemical or physiological characteristics.

iry leaves in several plants are associated with resistance to insect pests,

g, resistance to jassids in cotton and cereal leaf beetle in wheat. In wheat,

lid stems lead to non-preference by the stem sawfly and smooth leaved

d nect

-less cotton varieties do not attract bollwor

ms. High aspartic

id, low nitrogen and sugar content in maize leads to resistance to maize

em borers.

Breeding methods for insect pest resistance involve the same steps as

ose for any other agronomic trait such as yield or quality and are as

scussed earlier

. Sour

ces of r

esistance genes may be cultivated varieties,

rmplasm collections of the crop or wild relatives.

Some released crop varieties bred by hybr

idisation and selection, for

sect pest resistance are given in Table 9.

Table 9.

Pests

Brassica

G G

auau

(rapeseed mustard)

Pusa Sem 2,

Jassids, aphids and

Pusa S

fruit bo

Okra (Bhindi)

Pusa

awaw

Shoot and Fruit bor

sa A-4

2.4 Plant Br

didi

or Improved Food Quali

re than 840 million people in the world do not have adequate food to

et their daily food and nutritional requirements. A far greater numbe

–

ree billion people – suffer from micronutrient, protein and vitamin

176

BIOLOGY

Biofortification – breeding crops with higher levels of vitamins and

minerals, or higher protein and healthier

fats – is the most practical

means to improve public health.

Breeding for improved nutritional quality is undertaken with the

objectives of improving –

(i) Protein content and quality;

(ii) Oil content and quality;

(iii) Vitamin content; and

(iv) Micronutrient and mineral content.

In 2000, maize hybrids that had twice the amount of the amino acids,

lysine and tryptophan, compared to existing maize hybrids were

developed. Wheat variety, Atlas 66, having a high protein content, has

been used as a donor for improving cultivated wheat. It has been possible

to develop an iron-fortified rice variety containing over five times as much

iron as in commonly consumed varieties.

The Indian Agricultural Research Institute, New Delhi has also released

several vegetable crops that are rich in vitamins and minerals, e.g., vitamin

A enriched carrots, spinach, pumpkin; vitamin C enriched bitter gourd,

bathua, mustard, tomato; iron and calcium enriched spinach and bathua;

and protein enriched beans – broad, lablab, French and garden peas.

9.3 SINGLE CELL PROTEIN (SCP)

Conventional agricultural production of cereals, pulses, vegetables, fruits,

etc., may not be able to meet the demand of food at the rate at which

human and animal population is increasing. The shift from grain to meat

diets also creates more demand for cereals as it takes 3-10 Kg of grain to

produce 1 Kg of meat by animal farming. Can you explain this statement

in the light of your knowledge of food chains? More than 25 per cent of

human population is suffering from hunger and malnutrition. One of the

alternate sources of proteins for animal and human nutrition is Single

Cell Protein (SCP).

Microbes are being grown on an industrial scale as source of good

protein. Microbes like Spirulina can be grown easily on materials like

waste water from potato processing plants (containing starch), straw,

molasses, animal manure and even sewage, to produce large quantities

and can serve as food rich in protein, minerals, fats, carbohydrate and

vitamins. Incidentally such utilisation also reduces environmental

pollution.

It has been calculated that a 250 Kg cow produces 200 g of protein

per day. In the same period, 250g of a micro-organism like Methylophilus

methylotrophus, because of its high rate of biomass production and

growth, can be expected to produce 25 tonnes of protein. The fact that

2015-16

BIOLOGY

Biofortification

– breeding crops with higher levels of vitamins a

minerals, or higher protein and healthie

fats – is the most practica

means to improve public health.

ding for improved nutritional quality is undertaken with t

objectives of improving –

)

Protein content and quality;

Oil content and quality;

(iii)

Vitamin content; and

o acids,

s we

ent, h

possib

s mu

elease

itam

gourd,

bath

;

fruits,

whic

to meat

grain

tement

cent of

e of t

Sing

of goo

als li

straw,

antiti

ate an

ment

pollution.

It has been calculated that a 250 Kg cow produces 200 g of prote

per day. In the same period, 250g of a micro-organism like

Methylophilus

methylotrophus

, because of its high rate of biomass production a

growth, can be expected to produce 25 tonnes of protein. The fact that

2015-1

117766

(i )

(iv)

Micronutrient and mineral content.

In 2000, maize h

rids that had twice the amount of the amin

lysine and tryptophan, compared to existing maize hybrid

developed. Wheat variety, Atlas 66, having a high protein cont

been used as a donor for improving cultivated wheat. It has been

to develop an iron-fortified rice variety containing over five times a

iron as in commonly consumed varieties.

The Indian Agricultural Research Institute, New Delhi has also r

several vegetable crops that are rich in vitamins and minerals, e.

A enriched carrots, spinach, pumpkin; vitamin C enriched bitter

bathua

, mustard, tomato; iron and calcium enriched spinach and

and protein enriched beans – broad, lablab, French and garden pe

9.3 S

(

)

Conventional agricultural production of cereals, pulses, vegetables,

etc., may not be able to meet the demand of food at the rate at

human and animal population is increasing. The shift from grain

diets also creates more demand for cereals as it takes 3-10 Kg of

produce 1 Kg of meat by animal farming.

Can you explain this sta

in the light of your knowledge of food chain

More than 25 per

human population is suffering from hunger and malnutrition. On

alternate sources of proteins for animal and human nutrition is

Cell Protein (SCP).

Microbes are being grown on an industrial scale as source

protein. Microbes like

Spirulina

can be grown easily on materi

waste water from potato processing plants (containing starch),

molasses, animal manure and even sewage, to produce large qu

and can serve as food rich in protein, minerals, fats, carbohydr

vitamins.

Incidentally such utilisation also reduces environ

pollution.

STRATEGIES FOR ENHANCEMENT IN FOOD PRODUCTION

177

mushrooms are eaten by many people and large scale mushroom culture

is a growing industry makes it believable that microbes too would

become acceptable as food.

9.4 TISSUE CULTURE

As traditional breeding techniques failed to keep pace with demand and

to provide sufficiently fast and efficient systems for crop improvement,

another technology called tissue culture got developed. What does

tissue culture mean? It was learnt by scientists, during 1950s, that

whole plants could be regenerated from explants, i.e., any part of a

plant taken out and grown in a test tube, under sterile conditions in

special nutrient media. This capacity to generate a whole plant from

any cell/explant is called totipotency. You will learn how to accomplish

this in higher classes. It is important to stress here that the nutrient

medium must provide a carbon source such as sucrose and also

inorganic salts, vitamins, amino acids and growth regulators like auxins,

cytokinins etc. By application of these methods it is possible to achieve

propagation of a large number of plants in very short durations. This

method of producing thousands of plants through tissue culture is

called micro-propagation. Each of these plants will be genetically

identical to the original plant from which they were grown, i.e., they are

somaclones. Many important food plants like tomato, banana, apple,

etc., have been produced on commercial scale using this method. Try

to visit a tissue culture laboratory with your teacher to better understand

and appreciate the process.

Another important application of the method is the recovery of healthy

plants from diseased plants. Although the plant is infected with a virus,

the meristem (apical and axillary) is free of virus. Hence, one can remove

the meristem and grow it in vitro to obtain virus-free plants. Scientists

have succeeded in culturing meristems of banana, sugarcane, potato, etc.

Scientists have even isolated single cells from plants and after

digesting their cell walls have been able to isolate naked protoplasts

(surrounded by plasma membranes). Isolated protoplasts from two

different varieties of plants – each having a desirable character – can be

fused to get hybrid protoplasts, which can be further grown to form a

new plant. These hybrids are called somatic hybrids while the process

is called somatic hybridisation. Imagine a situation when a protoplast

of tomato is fused with that of potato, and then they are grown – to form

new hybrid plants combining tomato and potato characteristics. Well,

this has been achieved – resulting in formation of pomato; unfortunately

this plant did not have all the desired combination of characteristics

for its commercial utilisation.

2015-16

STRATEGIES FOR ENHANCEMENT IN FOOD PRODUCTION

mushrooms are eaten by many people and large scale mushroom culture

is a

growing industry makes it believable that microbes too would

become acceptable as food.

9.4 T

ISSUE

ULTURE

As traditional breeding techniques failed to keep pace with demand and

to provide sufficiently fast and efficient systems for crop improvement,

another technology called

tissue culture

got developed. What does

tiss

whol

spec

any

this

medi

inor

cyto

prop

meth

call

iden

soma

etc.

to vis

and

plan

the

have

dige

(sur

differ

fuse

new

is cal

of tom

new hybrid plants combining tomato and potato characteristics. W

ell,

this has been achieved – resulting in formation

; unfortunatel

this

lant did not have all the desired

2015-1

other technolo

called

t developed. What does

ssue culture mean? It was learnt by scientists, during 1950s, that

ole plants could be regenerated from

explants,

i.e., any part of a

ant taken out and grown in a test tube, under sterile conditions in

ecial nutrient media. This capacity to generate a whole plant from

y cell/explant is called

totipotency

ou will lear

n how to accomplish

is in higher classes. It is important to stress here that the nutrient

dium must provide a carbon source such as sucrose and also

organic salts, vitamins, amino acids and growth regulators like auxins,

tokinins etc. By application of these methods it is possible to achieve

opagation of a large number of plants in very short durations. This

thod of producing thousands of plants through tissue culture is

lled

micro-prop

ation

. Each of these plants will be

enetical

entical to the original plant from which they were grown, i.e., they are

maclones

. Man

important food plants like tomato, banana, apple

c., have been

oduced on commer

cial scale using this method. T

visit a tissue culture laboratory with your teacher to better understand

d appreciate the process.

Another important application of the method is the recovery of healthy

ants from diseased plants. Although the plant is infected with a virus,

meristem

(apical and axillary) is free of virus. Hence, one can remove

meristem and grow it

to obtain virus-free plants. Scientists

ve succeeded in culturing meristems of banana, sugarcane, potato, etc.

Scientists have even isolated single cells from plants and after

gesting their cell walls have been able to isolate naked protoplasts

urrounded by plasma membranes). Isolated protoplasts from two

fferent varieties of plants – each having a desirable character – can be

sed to get hybrid protoplasts, which can be further grown to form a

w plant. These hybrids are called

somatic hybrids

while the process

called

somatic hybridisation

. Im

ine a situation when a

rotoplast

omato is fused with that of

tato, and then the

are

own – to form