Detailed explanation of the hybridization prosses and it's importance in agriculture

1. Hybridization

2. • Introduction
• History
• Objectives
• Procedures in hybridization
• Consequences of hybridization
Content:

3. •Hybridization refers to the crossing of two
individuals or plants with dissimilar
genotype. It is the most important among
the methods of plant breeding.
•What is Hybrid – Definition?
The outcome of crossing of two individuals
or plants with dissimilar genotype is called
as hybrid.
Introduction

4. • 1717: Thomas Fairchild: it produced the
first artificial hybrid , the Fairchild’s mule,
by crossing sweet William (Dianthus
barbatus) with carnation (Dianthus
caryophyllus).
• 1800-1835: Knight T.A (England): First
used Artificial Hybridization in Fruit
Crops.
• 1866: Mendel G.J (Austria): published his
discoveries in “Experiments in plant
hybridization”, cumulating in the
formulation of laws of inheritance in
garden pea and discovery of unit factors
History

5. • 1890: Rimpu (Sweden): First made
inheritance cross between bread wheat
(Triticum aestivum) and rye (Secale cereale),
which later on gave birth to triticale (
Triticosecale).
• 1917: Jones: developed first commercial
hybrid maize
• 1927: Karpencheko: developed first
intergeneric hybrid between Radish and
Cabbage in Russia
Rabbage ( Brassicoraphanus )
Wheat
Rey
Triticale
×
Maize

6. • Towards the end of nineteenth century, hybridization was
widely used for crop improvement.
• With the help of genetic principles, the breeder is able to
predict the kind of progeny he is likely to obtain from a
given cross.
• Today, hybridization is the most common method of crop
improvement, and the vast majority of crop varieties have
resulted from hybridization.

7. • To create genetic variability.
• To bring together desired qualitative characters found in
different plants or plant lines into one plant or plant
line i.e. to transfer desired characters from
other varieties to the considered one.
• To make F1 useful as hybrid variety.
• Improvement of one or more quantitative characters.
Objectives

8. Procedure of hybridization
1.Selection of parents
2.Selfing of parents
3.Emasculation
4.Bagging
5.Collection and Storage of pollen
6.Cross pollination
7.Labelling
8.Collection of hybrid seeds

9. SELECTION OF PARENTS
• First step in hybridization.
• Desirable male & female plants are
selected.
• Parent plants should be healthy &
vigorous.
• Parents to be grown in isolation & self
pollinated to bring homozygosity in
desirable traits.
• All important characters to be combined
should be kept in mind.
• Both parents should mature at the same
time.

10. • Make the parents pure in its characters.
• Done by artificial self fertilization.
• Bisexual flowers - covered using paper bags before anthesis to
prevent natural cross pollination.
• Self pollination will occur inside the paper bags.
• In cross pollinated crops male & female flowers are bagged
separately before anthesis.
• When stigma becomes receptive, pollen grains are collected &
brushed on stigma – this is artificial pollination.
• Process continued till parent becomes homozygous or pure for its
particular character.
SELFING OF PARENTS

11. • Removal of stamens from female parent before they
burst & shed pollen.
• Done to prevent self pollination.
• Done in flower buds expected to open in the following
day.
• Such flower buds are recognized by their enlarged
unopened corolla.
• Emasculation can be done by any of the following
methods.
EMASCULATION

12. FORECEPS AND SCISSORS METHOD
• Done in large flowers.
• Buds are opened & anthers removed using sterile forceps & needles or
scissors.
• No injury to be caused to other floral parts – calyx, corolla & especially
pistil.
HOT OR COLD WATER OR ALCOHOL TREATMENT
• For small flowers like that of rice, sorghum, etc. that are difficult to be
emasculated by forceps, scissors, etc.
• Emasculation is done by dipping panicles in hot water for a definite
period.
• Ideal temperature is between 45° C and 50° C.
• Gynoecia can withstand a temperature at which anthers are killed.
• Also done by dipping inflorescence in cold water or alcohol for a definite
period.

13. MALE STERILITY METHOD
• In self pollinated crops, emasculation is eliminated by the use of male sterile
plants in which anthers are sterile.
• Male sterility can be induced by spraying Zinc methyl arsenate in rice, Maleic
hydrazide for cotton and wheat etc. on immature flower buds.
Male sterility
Hot water treatment
Foreceps method

14. BAGGING
• After emasculation flower buds are kept enclosed in bags of
ideal sizes, made of plastic, cellophane or Paper.
• Bags are tied by thread, wire, pins, etc.
• This process is called bagging.
• Both male & female flowers - bagged separately to prevent
contamination (foreign pollen).
• Bagging is usually done before anthesis.

15. • Pollen grains for crossing are collected from bagged male
flowers.
• Pollen/anthers collected in petri dishes or paper bags just after
dehiscence.
• Stored in vials or capsules for future use.
COLLECTION AND STORAGE OF POLLEN

16. CROSSING OR CROSS POLLINATION
• It is defined as artificial cross pollination between genetically
unlike parents.
• Viable pollen is collected from desired male plant & transferred
on to the stigma of the desired emasculated female parent.
• Pollen grains are collected in petri dishes.
• Bag is temporarily removed from the female parent & the
collected pollen are dusted on stigma.
• In crops like Bajara, Jowar, etc. hand cross pollination is
tedious, since flowers are small.
• In such crops male & female plants are grown side by side and
male & female inflorescences are enclosed in one bag.
• After crossing female flowers are again bagged.

17. LABELLING
• Emasculated & crossed flowers are properly bagged, tagged &
labeled.
• Labeling is done either on bag itself or on separate labels.
• Labels are tagged to bags using thread.
• Label should bear following details :
–Reference number
–Date of emasculation
–Date of crossing
–Details of male and female
parents

18. COLLECTION OF HYBRID SEEDS
• After maturity of seeds, crossed heads of
desirable characters are harvested &
collected along with labels in separate
envelopes.
• In the next season, seeds of each head are
sown separately to raise F1 generation.
• All plants of F1 are genetically similar &
look exactly alike.
• Plants of F1 are progenies of crossed
parents & are hybrids.
• They may exhibit hybrid vigor –
increased growth, size, yield, function,
etc. over the parents.

19. • Segregation and recombination produce a large
number of genotypes in F1 The number of different
genotypes possible in F2 increases geometrically
with an increase in the number of segregating
genes.
• Homozygosity increases rapidly with continued
selfing.
Consequences of hybridization

20. • The frequency of completely homozygous plants also
increases rapidly. By F7, about 73 percent of the plants
become completely homozygous even when 20 genes
are segregating.
• Transgiessive segregation may occur, but usually the
recovery of such recombinants will be very difficult.

21. https://www.researchgate.net/publication/344606353_Plant_Hybridizati
on_Aims_objectives_and_procedure_of_hybridization
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