Fruit breeding 656

Fruit breeding concepts

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COURSE TITLE: BREEDING OF
FRUIT CROPS
COURSE CREDIT: 2+1
COURSE NO. : FSC 506
OBJECTIVE: To impart
comprehensive knowledge about
the principles and practices of
breeding of fruit crops.

ASSIGNMENT: DEFINITION AND OBJECTIVES
OF FRUIT BREEDING

SUBMITTED BY: REETIKA SHARMA
(J-19-M-656)
SUBMITTED TO: DR. PARSHANT BAKSHI
(ASSOCIATE PROFESSOR)
DIVISION OF FRUIT SCIENCE
SKUAST JAMMU.

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Contents:
Definition of fruit breeding.
Objectives of fruit breeding.
Apomixis
Mutation Breeding
Polyembryony
Fruit breeding: Fruit breeding as an organized activity is a
19
th
century innovation. It is expounded as an art or a science
based on principles of genetics and cytogenetics of fruit crops
by which current progress was achieved through emphasis on
increased adaptability through hardiness, lowered chill
requirement, photoperiod insensitivity, resistance to biotic
stress, plant architectural modifications, and selection of
colour mutations.
Note: Thomas Andrew Knight (1759-1838) was the first to
improve fruits by selection from genetic recombination
derived from inter - pollinations of clones.
Objectives of fruit breeding: The fruit breeding must have
well defined objectives which are both economically and
biologically reasonable. It is long term process due to the long
juvenile period of most fruit trees and it requires high
investment for testing which makes fruit breeder to plan and
follow sound principles in breeding. In broader sense fruit
breeding is performed to fulfill the objectives:
A. Increasing in the production of fruits to meet out for
consumption :
 Ever increasing demand for fruits.

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 Nutrional security as fruit are rich source of
vitamins,minerals, sugars and acids.
 Protective food.
Note: ICMR recommendation – 90g/day/person.
Present availability – 45g/day/person.
 Processing industrial requirement .
 Varieties for low input requirement per unit area
production and for biotic and abiotic stress situation
B. To increasing the quality of fruits in terms of size,shape,
attractiveness,nutritional values etc.
Eg: Mango-ideal size,250-300 g ,attractive red blush on
shoulder, Pomegranate-ideal,size 250-300 g ,attractive red
skin,dark red aril etc. and Grape-bunchsize 400-500 g,berry
size 16-18 mm .
C. Broadening the genetic base :
Many minor fruit crops has narrow genetic base (Eg:
jack, jamun, sapota, pomegranate.etc) done to untopped
genetic potentialities. fruit breeding specially through
exploration, domestication , conservation will help in the
broadening the genetic base.
Eg : jack fruit , annonaceous members , jamun , mango ,
tropical fruits like bread fruit , litchi , bilimbi , avocado ,
cherries etc .

D. Development of new varieties or hybrids to suits the
requirements of processing industries :

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 Mango fruit – with high pulp recovery, less fibre
content.
 Grapes-suited for wine industry.
 Guava & papaya-jam and jelly industry.
 Banana varieties-for chips industries.
 Pineapple-for canning industries.
E. Development of varieties or hybrids resistant to various
pest and diseases , physiological disorders and abiotic
stresses .
Pests:
 Fruit borer- Pomegranate.
 Citrus- Citrus butterfly.
 Stem borer- Different fruit crops.
 Fruitfly- Different fruit crops.
 Sucking pests - Different fruit crops.
Diseases :
 Papaya – Ring spot virus
 Pomegranate – bacterial blight
 Grape – powdery & downy mildew
 Banana – viruses etc.
Physiological disorders: biennial bearing-mango,spongy
tissue, fruit cracking etc.
F. For development of varieties/ hybrids with special
characters.
Example:

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 Transgenic banana – with vaccine
 Guava variety – with high vitamin C
 Grape/strawberry – with high antioxidants etc .
 Karonda – with high iron content
Varieties/hybrids show tolerance or resistance to abiotic
stresses – rootstock breeding programme
E.g : dogridge- grape
G. Development of varieties/hybrids with longer shelf life .
Identification of varieties which can withstand cold storage
conditions in fruits during storage.
H. Developing of varieties/hybrids with seedlessness
characters – through polyploidy , parthenocarpy etc .
Example :
 Guava–triploid –seedless guava – TNAU
 Jamun–triploid–seedless jamun – TNAU
 Mango – rudimentary seed – Sindhu.
Objectives of fruit breeding with respective to need and
location:
 Maximaisation of quality production per unit area with
low cost of production(more production/unit input cost)
eg:HDP-following mechanization.
 Regular, early and prolific bearing per unit canopy area.
 Developing varieties free from biotic and abiotic stresses.

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Example: Varieties resistant to pest and diseases, Varieties
resistant to salinity, drought, waste, land etc.
 Development of varieties with good quality as desired by
the consumers/market forces.
Example: Development of seedless variety in grape, Papaya
variety taiwan-medium size fruits with more number of cuts,
Optimum fingers in banana
 Breeding of variety with ideal canopy architecture with
high photosynthetic efficiency,better aeration, suitability
for HDP, adoptability for mechanization.
 Breeding varieties with high shelf life –for fresh market
uniform quality standards-for processing industry.
Example:
 Alphanso- can be stored for 15 days(free from fibre,
good sugar acid, and excellent aroma.)
 High phenols and anthocyanin contents in grape varieties
suitable for wine industry
 Varieties with cylindrical shape in pineapple suitable for
canning industry.
 Guava variety with red/pink pulp with soft seeds
In general the breeding objective for scion cultivars are as
follow:
 Dwarf growth stature
 Regular precocious and prolific bearing per unit canopy
area
 High productivity with good quality fruits.

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 Resistance to biotic and abiotic stresses
 Attractive fruit colour with pleasant aroma
 Suitable for processing amd export
 Good keeping and transport quality
 Wide geographical adoption/adaptability. eg: dogridge
,rangpur lime
 Easily propagated, preferably through asexual means eg:
cuttings, layerings, polyembryony
 It should be compatible with most of the scion cultivers
having strong scion stock union and more longevity
 It should be resistant to biotic and abiotic stresses.
 It should impart dwarfing effect on scion without
affecting the productivity of scion cultivers.
 The rootstocks should be free from sukering habit. Eg:
guava,apple,pears,ber.

Breeding for rootstocks

 Wide geographical adoption/adaptability. eg: dogridge
,rangpurlime
 Easily propagated, preferably through asexual means eg:
cuttings, layerings, polyembryony
 It should be compatible with most of the scion cultivers
having strong scion stock union and more longevity
 It should be resistant to biotic and abiotic stresses.
 It should impart dwarfing effect on scion without
affecting the productivity of scion cultivars.
 The rootstocks should be free from sukering habit. Eg:
guava,apple,pears,ber.

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Breeding objectives of temperate fruit crops:
 Higher yield.
 Good appearance and eating quality
 Resistance to important diseases and pests
 Good storage and shelf life
 Climatic adaptation and frost resistance
 Fruit quality (fresh and drying purpose)
 Late blooming
 Increased fruit size, increased flesh-to-pit ratio
 Low chilling requirement for subtropical areas
 Control of tree size and vigor
 Extending seasonality
 Resistance to cracking
Breeding objectives of tropical fruit crops:
 Higher yield.
 Good appearance and eating quality
 Resistance to important diseases and pests.
 Good storage and shelf life.
 Climatic adaptation.
 Tolerant to low temperature (below 16°C) for the
sub tropical areas.
 Drought tolerance to reduce dependence on
irrogation.
 Increased dwarfness and stability.
 Resistance to fruit cracking.
 To reduce dependence of chemicals.

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INTRODUCTION:
Apomixis, derived from two Greek word "APO" (away from)
and "mixis" (act of mixing or mingling). It refers to the
occurrence of an sexual reproductive process in the place of
normal sexual processes involving reduction division and
fertilization. In other words apomixis is a type of reproduction
in which sexual organs of related structures take part but seeds
are formed without union of gametes. Seeds formed in this
way are vegetative in origin. When apomixis is the only
method of reproduction in a plant species, it is known as
obligate apomixis. On the other hand, if gametic and
apomictic reproduction occurs in the same plant, it is known
as facultative apomixis. The first discovery of this
phenomenon is credited to Leuwenhock as early as 1719 in
Citrus seeds.
Apomixis is widely distributed among higher plants. More
than 300 species belonging to 35 families are apomictic. It is
most common in Gramineae, Compositae, Rosaceae and
Rutaceae. Among the major cereals maize, wheat and pearl
millet have apomictic relatives.
APOMIXIS:
Apomixis Long back, Winkler (1908) defined apomixis as
"the substitution for sexual reproduction or another asexual

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reproductive process that does not involve nuclear or cellular
fusion (i.e. fertilization)". Stebbins (1914) and later Nygren
(1954) presented an excellent review on apomixis in
angiosperms, which can be referred to for greater details.
Here, a brief account of apomixis, is furnished only from the
point of view of breeding.
Types of apomixes:
Mainly four types of apomixis phenomenon are suggested by
Maheshwari (1954)
1. Recurrent Apomixis An embryo sac develops from
the MMC or megaspore mother cell (archesporial cell)
where meiosis is disturbed (sporogenesis failed) or from
some adjoining cell (in that case MMC disintegrates).
Consequently, the egg-cell is diploid. The embryo
subsequently develops directly from the diploid egg-cell
without fertilization. Somatic apospory, diploid
parthenogenesis and diploid apogamy are recurrent
apomixis. However, diploid parthenogenesis / apogamy
occur only in aposporic (somatic) embryo-sacs.
Therefore, it is the somatic or diploid aposory that
constitutes the recurrent apomixis. Such apomixis occurs
in some species of Crepis, Taraxacum, Paa (blue grass),
and Allium (onion) without the stimulus of pollination.
Malus (apple), and Rudbeckia where pollination appears
to be necessary, either to stimulate embryo development
or to produce a viable endosperm.

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2. Non -recurrent Apomixis An embryo arises directly
from normal egg-cell (n) without fertilization. Since an
eggcell is haploid, the resulting embryo will also be
haploid. Haploid parthenogenesis and haploid apogamy,
and androgamy fall in this category. Such types of
apomixis are of rare occurrence. They do not perpetuate
and are primarily of genetic interest as in com.
3. Adventive Embryony: Embryos arise from a cell or a
group of cells either in the nucellus or in the
integuments, e.g. in oranges and roses. Since it takes
place outside the embryo sac, it is not grouped with
recurrent apomixis, though this is regenerated with the
accuracy. In addition to such embryos, regular embryo
within the embryo sac may also develop simultaneously,
thus giving rise to poly-embryony condition, as in Citrus,
Opuntia.
4. Vegetative apomixes: In some cases like Poa bulbosa
and some Allium, Agave and grass species, vegetative
buds or bulbils, instead of flowers are produced in the
inflorescence. They can also be reproduced without
difficulty. However, Russian workers do not group this
type of vegetative reproduction with apomixis. Now,
different apomictic phenomena in each of the recurrent
and non-recurrent apomicts are considered in relation to
the development of the embryo sac or embryo.

Advantages of apomixis in plant breeding:

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The two sexual processes, self-and cross fertilization,
followed by segregation, tend to alter the genetic
composition of plants reproduced through amphimixis.
Inbreeding and uncontrolled out breeding also tend to
break heterozygote superiority in such plants. On the
contrary, apmicts tend to conserve the genetic structure
of their carriers. They are also capable of maintaining
heterozygote advantages generation after generation.
Therefore, such a mechanism might offer a great
advantage in plant breeding where genetic uniformity
maintained over generation for both homozygous,and
heterozygosity is the choicest goal. Additionally,
apomixis may also affect an efficient exploitation of
maternal influence, if any, reflecting in the resultant
progenies, early or delayed because it causes the
perpetuation of only maternal individuals and maternal
properties due to prohibition of fertilization. Maternal
effects are most common in horticultural crops,
particularly fruit trees and ornamental plants.
MUTATION BREEDING:
 Mutations: Sudden heritable change in the characteristic
of the plants is termed as mutations.
 It may be spontaneous (without any treatment that is
natural mutations) or induced (artificially induced by
treatment with certain physical or chemical agents ) in
plant population.
 Treating a biological material with a mutagen in order to
induce mutations is known as mutagenesis.

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 When mutations are induced for crop improvement the
entire operation of induction and isolation of mutants is
termed Mutation breeding.



CONDITIONS FOR MUTATION BREEDING:
 The objectives of breeding program should be clearly
defined.
 The variety, cultivar selected for treatment should be best
performing and requires improvement for some specific
character or traits either monogenic or polygenic.
 Plant parts used for mutagenic treatment: depends on
plant parts used for multiplication.
 If sexually propagated plants: Seeds, pollen grains are
treated.
 If asexually propagated plants: Buds, cuttings, suckers,
explants, rhizomes etc are used.
Dose of mutagen: An optimum dose of mutagen is that
which produces the maximum frequency of mutations
and causes the minimum killing.
 Dose of mutagen also depends upon intensity and time of
treatment.
 LD-50 :It is the dose of mutagen which would kill 50
percent of the treated individual.

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MUTAGENS:
 Agents used for induction of mutations are known as
mutagens.
 There are different types of mutagens are used.
A. Physical mutagens:
 Ionizing radiations:
a. Particulate radiations: α - rays, β- rays, fast neutron,
thermal neutrons.
b. Non particulate radiations: X-rays,γ-rays.
c. Non ionizing radiations: Ultraviolet radiations (Major
source of spontaneous mutation)
Chemical mutagens:
1. Alkylating agents- Sulphur, mustard, nitrogen mustards,
EMS(Ethyl methane sulphonate), MMS (Methyl methane
sulphonate), EI (Ethylene imine).
2. Acridine dyes – Acriflavin, acridine orange, acridine
yellow, Ethidium bromide.
3. Base analogues: 5-Bromo uracil, 5-Chloro uracil.
4.Others: Nitric acid, Hydroxyl amine.

DEVELOPMENT AND ACHIEVMENTS OF
MUTATION IN FRUIT CROPS:
 Mango :Rosica from Peruvian variety –Rosado-da-
lca.
 Papaya :Pusa Nanha (low bearing dwarf variety) -
from local variety (15 k rad-gamma radiation).
 Grape: Marvel seedless- from Delight.
 Banana: Highgate –from Gross Michel, Motta
Povan- Poovan.
 Orange : Washington Navel- Obtained from orange.

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 Grape fruit: Marsh and Thompson, Star ruby and
Rio red from Ruby

Polyembryony is the occurrence of more than one embryo in
a seed which consequently results in the emergence of
multiple seedlings. The additional embryos result from the
differentiation and development of various maternal and
zygotic tissues associated with the ovule of seed. Earlier,
polyembryony is said to have an abnormal feature but now it
is considered as a desirable character in citrus, mango, jamun,
rose apple, almond, etc. to obtain true to type planting
material. In the usual process of plant reproduction, egg cell
(female) of ovule fertilizes with the male gamete which in
turn culminates in embryo (zygotic). On the other hand, in
some of the crops, somatic cells of ovule (usually nucellus)
start producing embryo without fertilization results in the
occurrence of more than one embryo in the seed
(polyembryony). The formation of embryo without sexual
process is called apomixis (Apo=away from+ mixis = act of
mixing) and seed is called apomictic seed, whereas the
condition is called polyembryony. In most of the cases, sexual
embryo and nucellar embryo developes simultaneously which
is known as facultative polyembryony. Polyembryony was
first reported by Leeuwenhoek in citrus as early as 1719 and
the different cases of polyembryony in plants were studied by
Braun in 1859. In 1878 Strasburger demonstrated the
formation of plural embryos in many genera of angiosperms.
It has become apparent that polyembryony is not an abnormal
feature but rather a desirable character. About 244 species of
144 genera belonging to 59 angiosperm families are reported
to exhibit either polyembryony.
Among different ways of polyembryony, activation of some
sporophytic cells of the ovule in the formation of embryo is

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more common. The embryos arising from the maternal
sporophytic cells (outside the embryo sac) are called
adventive embryos. The maternal cells which involves in
embryo development are nucellus and integument. The
embryo develop 2 from nucellus is called nucellar embryony
which is common feature in the families of horticultural
importance. Polyembryony in horticultural crops is associated
with nuceller embryony because it frequently results in
polyembryonic seeds from which multiple seedlings
germinate.
Classification of polyembryony
Polyembryony may be classified on the basis of frequency.
i. Strictly polyembryonic Plant species in which the
frequency of multiple embryos in less than 7% is
described as strictly polyembryonic.
ii. ii. Nearly monoembryonic In case of nearly
monoembryonic plant species the frequency of
polyembryony varies between 6-10%.
iii. iii. Polyembryonic - If the per cent of multiple seed is
more than 10% this condition is called polyembryony
and plants are called polyembryonate.
Polyembryony may also be classified on the basis of genetic
composition.
i. Gametophytic Multiple embryos arises from the
gametic cells of the embryo sac (synergid, antipodal)
after or without fertilization. In this case haploid
embryos are formed.
ii. Sporophytic : When multiple embryos arise either
from zygote or from sporophytic cells of ovule
(nucellus, integument) and the resulting embryo will
be diploid. Hence citrus, mango and jamun exhibit true
and sporophytic polyembryony.
Polyembryonate crops

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Among horticultural crops, citrus, mango, jamun, rose apple,
almond, peach, onion, etc are polyembryonic in nature.
However citrus is the most important group exhibiting these
traits. Except Citrus grandis (pummelo), C. latifolia (Tahiti
lime) and Citrus medica (Citron) all other species are
polyembryonic. In case of mango (Mangifera indica),
polyembryony is variety-dependant. Bappakai, Chandrakaran,
Kensington, Kitchner, Kurukkan, Muvandan, Mylepelian,
Nekkare, Olour, Peach, Prior and Starch are polyembryonic
while mango varieties of commercial importance are
monoembryonic. Most of the polyembryonic mango varieties
are used as root stocks as they have poor fruit quality.
Polyembryony is also common in jamun (Syzygium cumini)
and rose apple (Syzygium jambos).
Degree of polyembryony Number of embryos varies with
species and varieties. Seeds of highly polyembryonic species
contain even more than 8 embryos. However the occurrence
of 2-4 embryos is common. The intensity of occurrence of
seeds containing multiple embryos may range up 3 70% in
highly polyembryonic species. The emergence of seedlings is
not directly correlated with the number of embryos. Usually
less number of seedlings is emerged with respect to the
number of embryos. The intensity of occurrence of multiple
seedlings increases with the increase in the number of
embryo. In citrus, the occurrence of one seedling/seed was
more than 50% whereas the intensity of emergence of two
seedlings/seed was 36.1%. The per cent of 3, 4, 5 and 6
seedlings/seed was 7.5, 1.8, 0.6 and 0.1% respectively.
Identification of nucellar seedlings
In case of facultative polyembryony, both sexual and nucellar
embryos are formed and they germinate in the form of
seedlings. Between them only nucellar seedling possesses the
genetic make-up of mother plant and are true to type but its

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morphological identification is difficult. However nuceller
embryos can be distinguished from the zygotic embryo by
their lateral position in the embryo sac, irregular shape, and
lack of suspensor. The zygotic seedlings are frequently
smaller than nucellar seedlings but variation enough in height
or size alone could not be used as a criterion for selection. In
mango zygotic seedlings are vigorous and possessed big
cotyledons. Visual identification of nucellar seedlings is not
an effective method, thus it becomes often necessary to grow
seedlings for 4-5 years to fruiting before nucellar seedlings
can be distinguished from zygotic ones. In citrus, zygotic
seedling can also be identified if one variety is crossed with
trifoliate orange as the zygotic seedlings will have trifoliate
leaves. For a more rapid advance in the propagation program,
it is necessary to identify zygotic seedlings at an early stage
(as a seedling) and for this purpose biochemical and
molecular methods are used. Since the identification of
embryos with isozyme markers is influenced by the
environment, as well as by the stage of development of the
plant and its organs, making this method unreliable for
identification. Recently, molecular techniques such as RAPD,
RFLP, and SSR are available which give reliable results. Two
seedlings/seed in rose apple Three seedlings/seed in rose
apple
Significance of polyembryony
 The adventives embryos develop from nucellar embryo
provide uniform seedlings for root stocks which yield
consistent results in fruit production.
 The nucellar seedling as a root stock has a tap root and,
therefore develops a better root system.
 The nucellar seedlings show a restoration of the vigour
lost after repeat vegetative propagation.

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 Polyembryony has ecological significance as it increases
the probability of survival under varied conditions.
 Nucellar polyembryony is the only practical approach to
raise virus-free clones of polyembryonatic citrus species
in nature.
 Disease-free plants can also be obtained through nucellar
embryo culture.
In spite of significance in plant propagation,
polyembryony has a drawback as it interferes with the
hybridization programme. In hybridization, zygotic
embryo is the outcome, but polyembryony hampers the
growth of zygotic embryo and thus affects the
hybridization in plants.