strategies of enhancement in food production

8/4/2019 Strategies of Enhancement in Food Production

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W i t h e v e r - i n c r e a s i n g p o p u l a t i o n o f t h e w o r l d ,

enhancement of food production is a major necessity.

Biological principles a s ap plied to an imal hu sb an dry an d

plant breeding ha ve a m ajor role in our efforts to increas e

food production. Several new techniques l ike embryotran sfer technology an d tissu e culture techn iques are going

to play a pivotal role in fur th er enh an cing food produ ction.

9 . 1 ANIMAL HUSBANDRY

Anima l hu sba nd ry is th e agricultu ral practice of breeding

an d ra ising livest ock. As s u ch it is a vita l sk ill for far m ers

and is as mu ch sc ience as i t is ar t . Animal hu sban dry

dea ls with th e care an d br eeding of livestock like bu ffaloes,

cows, pigs, h orses , cattle, sh eep, camels, goats , etc., tha t

are useful to humans. Extended, i t inc ludes poul t ry

farm ing and fish eries. Fisher ies includ e rearing, catch ing,

sellin g, etc., of fish , mollu scs (sh ell-fish ) an d cru st acea n s

(pra wns , crabs , etc.). Sin ce tim e imm emorial, anima ls like

bees, silk-worm , pra wns, crabs , fish es, birds, p igs, cattle,

sheep and camels h ave been us ed by hum ans for products

like m ilk, eggs, m eat , wool, silk, h on ey, etc.

It is estima ted th at m ore then 7 0 per cent of th e world

livestock popu lation is in India a nd China . However, it is

CHAPTER 9

STRATEGIES FOR ENHANCEMENT

IN FOOD PRODUCTION

9 .1 An im a l Hu s ba nd ry

9 .2 Pla n t B re ed in g

9.3 Single Cell Prote ins

9 .4 T is s u e Cu ltu re


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su rprising to n ote that the contribution to the world farm p roduce is only

25 per cen t, i .e., the pr odu ctivity per u n it is very low. Hence, in a dd ition

to conventional pra ctices of an imal breeding an d care, n ewer techn ologies

also h ave to be app lied to a chieve imp rovemen t in qu ality an d p rodu ctivity.

9 .1.1 Manageme nt of Farm s and Farm Anim als

A professional ap proach to what ha ve been trad it iona l practices of farm

ma na gemen t gives th e mu ch n eeded boost to our food produ ction. Let us

discus s som e of the m an agement procedu res, employed in variou s an ima l

farm systems.

9.1.1.1 Dairy Farm Managem ent

Dairying is the management of animals for milk and i ts products for

h u m a n c on su m p t ion . Can y ou list the a nima ls that you w ould expectto f ind in a dairy? What are dif ferent kinds of products that can be

ma de w ith milk from a d airy farm? In da iry far m m an agement, we deal

with p rocesses an d system s th at increas e yield an d improve qua lity of

m ilk. Milk yield is pr imar ily depen den t on th e qua lity of breed s in th e

far m . Selection of good br eeds h avin g high yielding poten tial (u n der th e

clima tic condit ions of the area), comb ined with resistan ce to diseases is

very imp ortan t. For th e yield p otential to be realised th e cattle ha ve to be

well looked after they h ave to be h ous ed well, sh ould h ave adequ ate

water an d b e ma int ained d isease free. The feeding of catt le sh ould be

carried out in a scientific ma nn er with special emph as is on the qu ality

an d qu an tity of fodder. Besides, stringent cleanliness a n d hygiene (bothof the cattle an d th e h an dlers) are of para mou nt imp ortance while milking,

storage and tran sport of the m ilk an d i ts produ cts. Nowada ys, of course,

mu ch of these processes h ave become m echan ised, which redu ces chan ce

of direct contact of the p rodu ce with the h an dler. Ensu ring th ese stringent

meas u res would of cours e, require regu lar ins pections, with proper record

keepin g. It would also h elp to iden tify an d rectify the pr oblems a s ea rly

as poss ible. Regular visi ts by a veterinary doctor would be ma nd atory.

You wou ld prob ab ly find i t in terest in g if you were to pr epar e a

qu estionna ire on diverse a sp ects of da iry keeping an d th en follow it u p with

a visit to a dairy farm in you r locality and seek an swers to th e ques tions .

9.1.1.2 Poultry Farm Man agem ent

Poultry is the class of domesticated fowl (birds) used for food or for their

eggs. They typically inclu de chicken a nd du cks, an d som etimes tu rkey and

geese. Th e word pou ltry is often u sed to refer to the mea t of on ly th ese birds ,

bu t in a more genera l sen se it may refer to the mea t of other birds too.

As in dairy farming, selection of disease free and suitable breeds,

proper an d s afe far m cond it ions, pr oper feed an d water, and hygiene an d

hea lth care are imp ortant compon ents of poultry farm m an agement.


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167

You may have seen TV news or read newspaper

reports ab out the bird flu virus w hich create d a s care in

the country and drast ical ly af fec ted egg and chicken

cons um ption. Find out more about it and discuss w hetherthe pan ic reaction w as jus tified. How can w e prevent the

spread of the flu in case some chicken are infected?

9.1 .2 Animal Bree ding

Breeding of animals is an important aspect of animal

hu sba nd ry. Anima l breeding aims at increasing the yield

of animals and improving the desirable quali t ies of the

produce. For w hat k ind of characters w ould w e breed

an imals ? Would the s election of cha racters d iffer w ith

the choice of animals?

Wha t do we un derst an d by the term breed? A group

of an ima ls related by descent a nd similar in m ost cha racters

like genera l app earan ce, featu res, s ize, configura tion, etc.,

are s aid to belong to a breed. Find out the na mes of some

common breeds of cattle and poultry in the farms of your

area.

When breeding is between an imals of the s am e breed it

is ca lled inbreeding, while crosses bet ween differen t breed s

ar e called outbreeding.

Inbreeding : Inbreeding refers to the mating of more

closely related individuals within the same breed for 4-6 genera tions . Th e breeding str ategy is a s follows su perior ma les a nd

su perior females of th e sam e breed are identified an d m ated in p airs.

The progeny obtained from such matings are evaluated and superior

males and females among them are identified for further mating. A

superior female, in the case of cattle, is the cow or buffalo that produces

more milk per lactat ion. On th e other ha nd , a s u perior male is th e bu ll,

which gives rise to superior progeny as compared to those of other

males.

Try to recollect the homozygous purelines developed by Mendel as

discu ss ed in Cha pter 5 . A similar s tra tegy is us ed for developing pu relin es

in cattle as was u sed in ca se of peas. Inbreeding increas es homozygosi ty.Th u s inb reeding is n ecessa ry if we wan t to evolve a p u reline in a n y an im al.

In breeding exposes h arm fu l recessive genes t ha t are eliminated b y selection.

It also helps in accumulation of superior genes and elimination of less

desirable genes. Therefore, this a pproach , where th ere is selection at each

step, increas es th e pr oductivity of inb red popu lation. However, continu ed

inbr eeding, especially close inbr eeding, us u ally redu ces fertility an d even

produ ctivity. This is called inbree ding depression . When ever th is becomes

a problem, selected an ima ls of th e breeding popu lation sh ould be ma ted

Figure 9.1 I m p r o v e d b r e e d o f

c a t t l e a n d c h i c k e n s

(a) J ers ey (b) Legh orn

(a )

(b )


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with u nr elated s u perior an ima ls of the s am e breed. This u su ally helps

res tore fertility an d yield.

Out-bree ding : Out-breeding is th e breeding of the u nr ela ted a nima ls ,

which ma y be be tween ind ividu a l s o f the s am e breed bu t h av ing n o

common ances tors fo r 4 -6 genera t ions (ou t -c ross ing) o r between

different breeds (cross-breeding) or different species (inter-specific

hybridisation).

Out-crossing: This is th e pra ctice of ma ting of an imals with in th e sam e

breed, bu t ha ving no comm on an cestors on either side of th eir pedigree

up to 4-6 generations. The offspring of such a mating is known as an

out-cross. I t is the best breeding method for animals that are below

average in productivity in milk production, growth rate in beef cattle,

etc. A single outcross often helps to overcome inbreeding depression.

Cross-breeding: In th is m ethod, su perior ma les of one breed are ma ted

with super ior females of another breed. Cross-breeding a l lows the

des irable qua lities of two differen t br eeds t o be combin ed. Th e progeny

hybrid animals may themselves be used for commercial production.

Alternatively, they may be subjected to some form of inbreeding and

selection to d evelop n ew stable breeds th at ma y be su perior to th e existing

breeds. Many new an ima l breeds ha ve been developed by this ap proach.

Hisardale is a new breed of sheep developed in Punjab by crossing

Bikan eri ewes an d Marino ram s.

Interspecific hybridisation: In th is m ethod, ma le an d fema le anima ls

of two different r elated s pecies a re m ated. In s ome cas es, th e progeny

may combine desirable features of both the parents, and may be of

cons iderab le econom ic valu e, e.g., th e mu le (Figu re 9.2 ). Do you knoww hat cross lead s to the produ ction of the m ule?

Controlled breeding experiments are carr ied out u sing artificial

insemination . Th e semen is collected from th e male tha t

is ch osen as a pa rent a nd injected into the reprodu ctive

tra ct of th e selected fema le by the breeder. Th e semen

ma y be us ed imm ediately or can be frozen an d u sed at a

later da te. It can also be tran sported in a frozen form to

where th e fema le is hou sed. In this way desirable matings

are carried. Artificial insemination helps us overcome

several problems of normal matings. Can you d iscuss

and list s ome of them ?Often, the su ccess rate of crossing matu re male and

female an imal s i s f a i r ly low even though a r t i f i c i a l

insem in at ion is carr ied out . To improve cha nces of

su ccessfu l produ ction of hybrids, other mean s are also u sed. Multiple

O v u l a t i o n E m b r y o T r a n s f e r T e c h n o l o g y (MOET) i s one such

program me for herd imp rovemen t. In th is meth od, a cow is ad ministered

h ormones , with FSH-like activity, to ind u ce follicu lar m atu ration a nd su per

ovu lation ins tead of one egg, wh ich th ey norm ally yield p er cycle, th ey

Figure 9.2 Mule


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prod u ce 6-8 eggs . The a n imal i s e i the r m a t ed wi th an e lit e bu l l o r

artificially inseminated. The fertilised eggs at 832 cells stages, are

recovered n on-su rgically and tran sferred to su rrogate moth ers. The genetic

moth er is availab le for an other rou nd of su per ovulation. This techn ologyha s been demon stra ted for catt le, sheep, rab bits, buffaloes, ma res, etc.

High milk-yielding breeds of females and high quality (lean meat with

less lipid) meat-yielding bulls have been bred successfully to increase

herd size in a sh ort t ime.

9.1 .3 Bee-keeping

Bee-keeping or apiculture is the m aint ena n ce of h ives of h oneybees for

the p rodu ction of hon ey. It h as been a n a ge-old cottage ind u stry. Honey

is a food of high nutri t ive value and also finds use in the indigenous

system s of med icin e. Honeybee also produ ces beeswax, which finds m an y

u ses in ind u stry, such as in th e preparation of cosmetics an d polish es ofvarious kinds . The increas ed dem an d of hon ey ha s led to large-scale bee-

keeping pract ices; i t has become an establ ished income generat ing

ind u stry, wheth er practiced on a sm all or on a large scale.

Bee-keepin g can be pra cticed in an y area wh ere there a re su fficient

bee pastu res of some wild sh ru bs, fru it orchard s an d cult ivated crops.

There a re several species of h oneybees which can be reared . Of th ese, the

most common species is Apis indica. Beehives ca n be kep t in on es

courtyar d, on th e veran da h of th e hou se or even on t he roof. Bee-keeping

is not labou r -inten sive.

Bee-keeping though relatively easy does require some specialised

kn owledge and th ere are several organ isa tions tha t teach bee-keeping.Th e followin g poin ts a re importa n t for su ccess fu l bee-keepin g:

(i) Knowledge of th e natu re an d h abits of bees,

(ii) Selection of su itable location for keeping th e beeh ives,

(iii) Catch ing an d h iving of swa rm s (group of bees ),

(iv) Man agement of beehives du ring different s easons , an d

(v) Han dling and collection of honey an d of beeswax. Bees are th e pollinators

of ma n y of our crop sp ecies (see cha pter 2) su ch a s s u n flower,Brassica ,

ap ple an d p ear. Keeping beeh ives in cr op fields du ring flowerin g period

increa ses pollina tion efficiency an d imp roves th e yield ben eficial both

from th e point of view of crop yield a n d h on ey yield.

9.1 .4 Fisheries

Fish ery is a n indu str y devoted to th e catch in g, process ing or selling of fish,

sh ellfish or other a qu atic an ima ls. A large nu mb er of our popu lation is

dependent on fish , fish products an d other aqua tic animals such as pra wn,

crab, lobst er, edible oyster, etc., for food. Some of th e fresh water fish es wh ich

are very comm on include Catla,Rohu an d common carp . Some of the ma rine

fish es th at a re eaten includ e Hilsa, Sardines , Mackerel and Pomfrets.

Find out w hat fish es are commonly ea ten in y our area.


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Fish eries h as an importan t place in Indian econ omy. It provides income

an d emp loymen t to millions of fish ermen an d farm ers, par ticu larly in the

coasta l states . For ma n y, it is th e only sou rce of th eir livelihood. In order

to meet th e increas ing dem an ds on fish eries, different techn iques ha vebeen emp loyed to increas e production. For example, thr ough a qua cultur e

an d pisciculture we h ave been able to increas e the p rodu ction of aqu atic

plants an d an ima ls, both fresh -water and m arine. Find out the d ifference

betw een pisciculture and a quaculture. This h as led to th e developmen t

an d flour ish ing of th e fish ery ind u str y, an d it has brou ght a lot of income

to the far mers in particular an d th e cou ntr y in genera l. We now talk about

Blue Revolu tion as being implemen ted a lon g the s am e lin es a s Green

Revolu tion .

9 . 2 PLANT BREEDING

Traditiona l far min g can on ly yield a limited bioma ss , as food for h u ma ns

an d a nimals . Bet ter man agement pract ices a nd increase in acreage can

increase yield, bu t only to a limited extent. Plant breeding as a techn ology

ha s h elped increas e yields to a very large extent . Who in India h as not

heard of Green Revolution which was respon sible for our cou ntr y to

not m erely meet the na tiona l requiremen ts in food produ ction bu t also

helped u s even to export it? Green revolu tion was depend ent to a large

extent on plant breeding techn iqu es for d evelopmen t of high -yielding an d

diseas e resista n t varieties in wheat, r ice, ma ize, etc.

9 .2.1 What is Plant Bree ding?Plan t breeding is th e pu rposeful man ipulation of plan t species in ord er to

create des ired plant types th at a re better s u ited for cu ltivation, give better

yields and are disease resistant. Conventional plant breeding has been

pra cticed for thou sa nd s of years , since the b eginning of hu ma n civilisa tion ;

recorded evidence of plant b reeding dates ba ck to 9,000-11 ,000 years a go.

Man y present-day crops are th e resu lt of domestication in an cient times.

Today, all ou r m ajor food crops are derived from dom esticated varieties.

Classical plant breeding involves crossing or hybridisation of pure lines,

followed by ar tificial selection to p rodu ce plan ts with d esirable traits of higher

yield, nu trition an d resista nce to disea ses . With advan cemen ts in genetics,

molecular biology and tissue culture, plant breeding is now increasingly

being carried out by u sing m olecular genetic tools.

If we were to list t he tr aits or cha racters tha t th e breeders h ave tried to

incorporate into crop plan ts, th e first we would l ist wou ld b e increased

crop yield a nd imp roved qu ality. Increas ed toleran ce to environm enta l

str esses (salin ity, extreme tempera tu res, drou ght), resista nce to path ogens

(viru ses , fu n gi an d bacteria) an d increas ed toleran ce to in sect pests wou ld

be on our list too.


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Plant breeding programmes are carried out in a systematic way

worldwide in governm ent ins t itu t ions an d comm ercial comp an ies. The

ma in steps in breeding a n ew genetic variety of a crop a re

(i) Col l ec t i on o f var iab i l i t y : Genetic variability is the root of any

breedin g programm e. In m an y crops pre-existin g genetic var iab ility

is available from wild relatives of the cr op. Collection a n d p res ervation

of all th e differen t wild var ieties, species an d relatives of th e cu ltivated

sp ecies (followed by th eir evalu ation for th eir ch ar acter istics) is a

pre-r equ isite for effective exploitat ion of n at u ra l gen es availab le in

th e popu lations. The entire collection (of plants / seeds) ha ving a ll

th e divers e alleles for all genes in a given crop is called germplasm

col l ec t ion .

(ii) Eva lua t ion a nd se l ec t i on o f paren t s : Th e germp lasm is evalu ated

so as to iden tify plan ts with des irab le combination of cha racters .The se lec ted plants are mul t ipl ied and used in the process of

hybridisation. Pu relines are created wherever des irable an d possible.

(iii) C r o s s h yb r i d i s a t i o n a m o n g t h e s e l ec t ed p a r en t s : The desired

cha racter s h ave very often t o be combined from two different plan ts

(pa ren ts), for examp le h igh p rotein qu ality of one pa ren t ma y need

to be combined with disease resistan ce from a noth er paren t. This is

poss ible by cross h ybridising th e two par ents to produ ce hybrids

th at gen etically combine the desired cha racters in one plan t. Th is is

a very t ime-consuming and t ed ious process s ince the po l l en

grains from the desirable plant chosen as male parent have to be

collected a n d placed on th e stigma of th e flowers s elected as fema leparent (In chapter 2 details on how to make crosses have been

described). Also, it is n ot necessa ry that th e hybrids do comb ine th e

desirable characters; us u ally only one in few hu nd red to a th ousa nd

crosses s hows th e desirable comb ina tion.

(iv) S e l e c t i o n a n d t e s t i n g o f s u p e r i o r r e c o m b i n a n t s : This s tep

consists of selecting, am ong the p rogeny of th e hybrids, th ose plants

tha t h ave the desired chara cter comb ina tion. The s election p rocess is

cru cial to the s u ccess of th e breeding objective an d requ ires ca refu l

scientific evalua tion of th e progeny. This s tep yields plant s t ha t a re

superior to both of the parents (very often more than one superior

progeny plant may become available). These are self-pollinated for

severa l generat ions till th ey rea ch a s ta te of u n iform ity (h omozygosity?),

so th at th e cha racters will not segregate in th e progeny.

(v) Test ing, release and commercia l i sa t ion of new cul t ivars: The

n ewly selected lines are evalua ted for th eir yield a n d oth er agron omic

traits of quality, disease resistance, etc. This evaluation is done by

growing these in th e research fields an d recording their performa nce

u n d e r i d e a l f e r t i l i s e r a p p l i c a t i o n i r r i g a t i o n , a n d o t h e r c r o p

m an agemen t pr actices. The evalua tion in res earch fields is followed


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by test ing the m ater ials in farm ers fields , for at leas t th ree growing

seasons at several locations in the country, representing all the

agroclim atic zones where th e crop is u su ally grown. Th e ma terial is

evalu ated in comp ar ison to th e best a vailable local crop cultivar ach eck or referen ce cultivar.

Ind ia i s ma in ly an agr i cu l tu ra l count ry . Agr icu l tu re account s

for ap proxim ately 33 per cent of Ind ias GDP and emp loys n ear ly

62 per cen t of the popu lation. After Indias ind epend ence, one of the m ain

cha llenges facing the coun try was th at of producing enou gh food for the

increa sin g popu lation. As on ly lim ited lan d is fit for cu ltivation, In dia h as

to strive to increase yields per u nit ar ea from exist ing farm lan d. The

development of several high yielding varieties of wheat and rice in the

mid-196 0s , as a resu lt of various p lant breeding techn iqu es led to dra ma tic

increase in food production in ou r coun try. This ph as e is often referred

to as th e Green Revolu tion. Figu re 9.3 repres ents some Indian hybrid

crop s of h igh yeildin g var ieties .

(c)

(b)(a )

Figure 9.3 Some Indian hybrid crops: (a) Maize; (b) Wheat; (c) Garden peas


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

increas ed from 1 1 m illion ton es to 75 m illion ton n es while rice prod u ction

went u p from 35 million ton nes to 89.5 m illion tonn es. This was du e to the

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

Norman E. Borlaug, a t Internat ional Centre for Wheat and Maize

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

varieties su ch a s Sonalika an d Kalya n S ona, which were h igh yielding an d

diseas e resista n t, were int rodu ced all over th e wheat-growing belt of In dia.

Semi-dwarf rice var ieties were der ived from IR-8, (developed at In tern ationa l

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

Taiwan ). The derivatives were in trodu ced in 1 966. Later better -yielding sem i-

dwar f var ieties Jaya an d Ratna were developed in In dia.

Sugar cane : Sa ccha rum barberi was origin ally grown in n orth Ind ia, bu t

ha d poor su gar conten t an d yield. Tropical canes grown in s outh Ind iaSaccharum officinarum ha d thicker s tems and h igher su gar content bu t

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

crossed to get su gar can e variet ies comb ining th e desirable qua lit ies of

high yield, th ick stem s, h igh su gar an d ab ility to grow in the s u gar can e

areas of north Ind ia.

Millets : Hybrid maize, jowar an d bajra h ave been s u ccess fu lly developed

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

yielding varieties res istan t to water st ress .

9.2 .2 Plant Bree ding for Disease Resis tanc e

A wide ra n ge of fu n gal, bacterial an d viral path ogen s, a ffect th e yield of

cu ltivated crop s pecies, especially in t ropical climat es. Crop losses can

often b e significan t, u p to 20 -30 p er cent, or som etimes even tota l. In th is

si tuation, breeding and development of cult ivars resistant to disease

enhances food production. This also helps reduce the dependence on

u se of fu ngicides a nd b acteriocides. Resista nce of th e host plan t is th e

ability to prevent the pa th ogen from ca u sing disease an d is determined

by the gene t i c cons t i tu t ion of the hos t p l an t . Before b reed ing i s

un dertaken, it i s importan t to know about th e caus at ive organ ism an d

the m ode of tran sm iss ion. Some of the diseases cau sed by fu ngi are ru sts ,

e.g. , brown ru st of wheat, red rot of su garcan e an d late blight of potato;by bacteria black rot of cru cifers; an d by viru ses tobacco mosa ic,

tu rnip m osaic, etc.

Methods o f breeding for d i sease re s i s tance : Breeding is carr ied

out by the con ven t iona l breeding techn iqu es (descr ibed ea r l ier) or by

mu tat ion br eeding. The con ven t ion al meth od of breeding for diseas e

resista n ce is th at of h ybridisa tion a nd selection. Its s teps are ess ent ially

iden tical to those for breeding for an y oth er agronom ic cha racters su ch

as high yie ld. The var iou s s equen t ia l s teps are : screening germ plasm


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for resistan ce sou rces, hybridisa tion of selected paren ts, s election a nd

evaluat ion of the h ybrids an d t est ing an d r elease of new variet ies.

Some c rop va r i e t i e s b red by hybr id i sa t ion and se lec t ion , fo r

disease resistance to fungi, bacteria and viral diseases are released(Tab le 9.1 ).

Table 9.1

Cro p Varie t y Re s is tanc e to dis e as e s

Whea t Him giri Leaf and s tripe rus t, h ill bunt

Bras s ica Pus a s w arn im White ru s t

(Kara n rai)

Cauliflow er Pus a S hubhra , Black rot and Curl

Pu s a Sn ow b a ll K-1 b ligh t b la ck rot

Cow pea Pus a Kom al Bacteria l bligh t

Ch illi Pus a S ad abahar Chilly m os aic virus ,

Tobacco mos aic virus

and Leaf curl

Conven tiona l breed ing is often cons tra ined b y the availability of lim ited

nu mber of disease r esistan ce genes th at a re present an d identified in various

crop varieties or wild relatives. Ind u cin g mu tations in plan ts th rou gh diverse

mean s a nd then screening the plant ma terials for resistan ce sometimes

lead s to desirable genes b eing identified. Plan ts h aving th ese desirable

cha racters ca n th en be eith er mu ltiplied directly or can be u sed in breeding.

Other breeding meth ods tha t are u sed are s election am ongst somaclona l

varian ts an d genetic engineering.

Mutation is the process by which genetic variat ions are created

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

resu lting in th e creation of a n ew cha racter or trait not foun d in the pa renta l

type. It is pos sible to ind u ce mu tations artificially th rou gh u se of chem icals

or radiations (like gamm a rad iations ), and s electin g an d u sing the plant s

tha t h ave the desirable chara cter as a source in breeding this process is

called mut ation breeding . In mu n g bean, res ista nce to yellow mosaic

viru s a nd powdery mildew were ind u ced by mu tations.

Several wild relatives of differen t cu ltivated s pecies of plan ts h ave been

sh own to ha ve certain resista n t cha racters b u t ha ve very low yield. Hence,

th ere is a need to introdu ce the resistan t genes into th e high-yielding

cul t iva ted va r i e t i e s . Res i s t ance to ye l low mosa ic v i rus in b h i n d i

(Abelmoschus esculentus ) was t ransferred f rom a wi ld species and

resu lted in a n ew variety ofA. es culentus called Parbhan i kranti.


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All th e ab ove examp les involve sources of resista n ce genes th at are in

the s am e crop species, which h as to be bred for disease resistan ce, or in a

related wild species. Tra n sfer of res istan ce genes is ach ieved by sexu al

hybridisa t ion between the target and the source plant fol lowed by

selection.

9.2 .3 Plant Breeding for Developing Res i s tance

to Insec t Pes t s

Anoth er ma jor cau se for large scale destru ction of crop plant an d crop

produce is insect an d p est infestation. Insect resistance in h ost crop plants

ma y be du e to m orph ological, biochem ical or ph ysiological cha racteristics.

Hairy leaves in s everal plan ts a re as sociated with resista n ce to ins ect pests ,

e.g, resistan ce to jas sids in cotton an d cereal leaf beetle in wheat. In whea t,

solid st ems lead to n on-preference by th e stem s awfly an d sm ooth leavedan d n ectar -less cotton variet ies do n ot at tra ct bollworm s. High as par t ic

acid, low nitrogen a nd su gar content in ma ize leads to resistan ce to maize

stem borers.

Breeding m ethods for ins ect pest resistan ce involve the s am e steps a s

thos e for an y other a gronom ic trai t su ch a s yield or qua lity and are as

discus sed a bove. Sou rces of resistan ce genes m ay be cultivated varieties,

germplas m collection s of th e crop or wild relatives.

Some released cr op varieties bred b y hybridisation an d s election, for

ins ect pest resistan ce are given in Table 9.2.

Table 9.2Cro p Varie t y In s e c t Pe s t s

Bras s ica Pus a Gaurav Aph id s

(rapes eed mus tard)

Fla t bean Pus a S em 2 , Jas s id s , aph id s and

Pus a S em 3 fru it borer

Ok ra (Bhind i) Pus a Saw ani S hoot and Fru it borer

Pus a A-4

9 .2 .4 Plant Breeding for Im prove d Food Quality

More tha n 840 million p eople in the world d o not h ave adequ ate food to

meet th eir da ily food and nu tritional requirements . A far greater n u mb er

three billion people suffer from micronutrient, protein and vitamin

deficiencies or hidden hu nger becau se th ey cann ot afford to bu y enou gh

frui ts , vegetables, legumes, f i sh and meat . Die ts lacking essent ia l

micronu trients pa rticular ly iron, vitamin A, iodine an d zin c increas e

the r i sk fo r d i sease , r educe l i f e span and reduce menta l ab i l i t i e s .


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BIOLOGY

Biofortification breeding crops with higher levels of vitamins and

minerals, or higher protein and healthier fats is the most practical

mea ns to imp rove pub lic health.

Breeding for improved nutri t ional quali ty is undertaken with theobjectives of imp roving

(i) Prote in content and qual ity;

(ii) Oil content a nd qual ity;

(iii) Vitamin content ; and

(iv) Micronu tr ient an d m inera l content .

In 2000, m aize hybrids tha t ha d twice the am oun t of the am ino acids,

lys ine and t ryp tophan , compared to ex i s t ing ma ize hybr ids were

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

been u sed as a don or for imp roving cultivated wheat . It ha s been possible

to develop a n iron-fortified r ice variety con tain ing over five times as m u ch

iron a s in comm only consu med variet ies.

The Ind ian Agricultu ral Research Ins titute, New Delh i ha s also releas ed

several vegetable crops th at a re rich in vitam ins an d m inerals, e.g., vitamin

A enriched carr ots, spina ch, pu mp kin; vitamin C enriched bitter gour d,

bathua , mu stard, tomato; iron an d calcium enriched spinach and bathua ;

an d protein en riched bean s broad, lablab, French an d garden peas .

9 . 3 S INGLE CELL PROTEIN (SCP)

Conventiona l agricultu ral produ ction of cereals, pu lses, vegetables, fru its,

etc. , ma y not be able to meet the dem an d of food at th e rate at wh ichhu ma n an d an ima l popu lation is increasing. The s hift from grain to meat

diets also creates m ore deman d for cereals as it tak es 3-10 Kg of grain to

produ ce 1 Kg of mea t by a nima l farm ing. Can y ou explain this statemen t

in th e light of your k now ledge of food cha ins ? More tha n 25 per cent of

hu ma n population is su ffering from h u nger an d m alnu trit ion. One of the

al terna te sources of proteins for animal an d h u man nu tr it ion is Single

Cell Prote in (SCP).

Microbes ar e being grown on a n ind u strial scale as s ource of good

protein. Microbes like Spirulina can be grown easily on m aterials l ike

waste water from p otato processing plants (containing sta rch), stra w,

molass es, anima l ma nu re and even sewage, to produce large qu an tit ies

an d can serve as food rich in protein, m inera ls, fats , carbohydrate an d

vi tamins. Incidenta l ly such ut i l i sa t ion a lso reduces environmental

pollution.

It h as been calculated th at a 250 Kg cow produ ces 200 g of protein

per da y. In t he s am e period, 250 g of a m icro-organ ism likeMethylophilus

methylotrophus , because of i ts high rate of biomass production and

growth, can be expected to produ ce 25 tonn es of protein. The fact th at


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mu sh rooms are eaten by man y people and large scale mu sh room cu lture

is a growing industry makes i t believable that microbes too would

become acceptab le as food.

9 . 4 TISSUE CULTURE

As tradit ional breeding techniques fai led to keep pace with demand

a n d t o p r o v i d e su f f i c i e n t l y f a s t a n d e f f i c i e n t sy s t e m s f o r c r o p

im provement , an other tech n ology called t i s sue cul ture got developed .

What does t i ssue cul ture mean? I t was learnt by sc ient is ts , dur ing

1950s, tha t whole plants could be regenerated f rom explants , i.e.,

any par t of a plant taken out and grown in a test tube , under s ter i le

condit ion s in sp ecial nu trient m edia. This cap acity to genera te a whole

plant from an y cell/ explan t i s ca l led t o t i p o t e n c y .You will lear n h ow

to accomp lish this in higher c las ses. I t is importan t to s t ress here th atthe nu t r ien t mediu m m us t p rovide a ca rbon source such a s su c rose

an d a lso inorgan ic sa l t s , vitam ins , am ino a cids a nd growth regula tors

like au xin s, cytokin ins etc. By app lication of th ese m ethod s it is p oss ible

to achieve propagat ion of a large number of plants in very short

dura t ions . Thi s me thod of p roduc ing thousands of p lan t s th rough

t iss u e cu ltu re i s ca l led micro-propagation . Each of th ese plan ts will

be genetically identical to the original plant from which they were

grown, i .e . , they are s o m a c l o n e s . Many importa n t food plan ts like

tomato, ban an a, app le , etc . , ha ve been produ ced on commercia l sca le

u sing this m ethod. Try to visi t a t i ssu e cul tur e laboratory with you r

teacher to be t t er u nders t an d an d app recia t e the p rocess .

Anoth er imp ortan t ap plication of th e meth od is th e recovery of h ealthy

plants from diseas ed plants . Alth ough th e plan t is infected with a viru s,

th e meristem (ap ical an d a xillar y) is free of viru s. Hen ce, one ca n rem ove

th e meristem an d grow it in v itro to obtain viru s-free plant s. Scientists

ha ve su cceeded in cu ltu ring meristems of ban an a, su garcane, potato, etc.

Scientists have even isolated single cells from plants and after

digesting their cell walls have been able to isolate naked protoplasts

(su rroun ded by plasma m embra nes) . Isola ted protoplas ts from two

different variet ies of plan ts each ha ving a desirable cha racter can be

fu sed to get hybrid protoplas ts , which can be fu r th er grown to form anew plan t. Thes e hybrids a re called som atic hy brids while th e process

is ca lled som atic hybridisat ion . Ima gine a s itu ation when a p rotoplas t

of tomat o is fus ed with tha t of potato, an d th en t hey are grown to form

new h ybrid p lan ts combining tom ato an d p ota to cha racter is t ics . Well,

this h as been a chieved resu lt ing in forma tion of toma to; un fortun ately

this plant did not have all the desired combination of characterist ics

for its com m ercial utilisa tion.


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BIOLOGY

EXERCISES1. Expla in in br ief the ro le of an imal hus ban dry in h um an welfa re .

2 . If your fami ly owned a da i ry fa rm, what m easures would you u nder take

to improve th e qu al ity an d qua nt i ty of milk produ ct ion?

3. What is m eant by th e t e rm breed? Wha t a re th e objec tives of an imal

breeding?

4. Nam e the methods employed in an ima l breeding. According to you which

of the m ethods is b est? Why?

5. What i s ap icul ture? How is i t impor tant in our l ives?

6 . Discuss the ro le of fishery in enha ncement of food product ion .

7. Briefly descr ibe var ious s teps involved in plan t breeding.

8 . Expla in what i s meant b y b iofor tifica t ion .

9 . Which pa r t of the p lant is bes t su it ed for making virus - free p lant s an d

why?

10. Wha t is the major advantage of producing plan ts by micropropagat ion?

1 1. F in d o u t w h a t t h e va r io u s c o m p o n e n t s of t h e m e d iu m u s e d fo r

propagat ion of an explan t in vitro are?

12. Name an y five hybrid varieties of crop plan ts which h ave been d eveloped

in In dia.

SUMMARY

Animal husbandry is the practice of taking care and breeding domestic

animals by applying scientif ic principles. The ever-increasing demand

of food from animals and animal products both in terms of quali ty and

quan t i t y has been m e t by good an i m a l husbandr y p r ac t i ce s . T hese

pract ices include ( i ) management of farm and farm animals, and ( i i )

animal breeding. In view of the high nutri t ive value of honey and i ts

medicina l imp ortance, there ha s been a rema rkab le growth in the pra ctice

of bee-keeping or apicul ture. Fishery is another f lour ishing indust ry

meet ing the ever- increasing demand for f i sh, f i sh products and other

aquatic foods.

Plan t breeding may be us ed to create var iet ies, which are resistan tto pathogens and to insect pests. This increases the yield of the food.

This method has also been used to increase the protein content of the

plant foods and thereby enhance the quali ty of food. In India, several

varieties of different crop p lants ha ve been produ ced. All th ese m eas u res

enhance t he p r oduc t i on o f f ood . T echn i ques o f t i s sue cu l t u r e and

somatic hybridisation offer vast potential for manipulation of plants in

vitro to produce new varieties.

strategies of enhancement in food production

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