Plant hybridization aims, objectives and types of hybridization

1. Hybridization: Aims, objectives and types of
hybridization
Madankar KS
Ph.D. Research scholar
Institute of Agricultural Science
Banaras Hindu University,
Varanasi

2. Plant hybridization
• The mating or crossing of two plants
or lines of dissimilar genotype is
called hybridization.
• In plant hybridization, one of the
plants is taken as the female plant
and the other as the male plant.
• Pollen grains from the male parent
are made to pollinate the stigma of
the flowers of the female parent.
• The seeds obtained from such a cross
are called F1 hybrid seeds and the
progeny raised from it is called F1
(First Filial) generation.

3. Conti….
• The chief objective of hybridization is to
create variation.
• When two genotypically different plant
are crossed, the genes from both the
parents are brought together in F1.
• Segregation and recombination produce
many new genes combination in F2 and
subsequent generations.
• The degree of variation produced in F2
depends on the number of heterozygous
genes in F1.

4. Objectives of hybridization
A. Combination Breeding: Combination breeding is the transfer of one or
more characters from other varieties to a particular variety. These
characters may be oligogenic or polygenic. In this way, genes for
disease resistance, quality traits etc can be transferred.
B. Transgressive Breeding: Transgressive breeding is based on
transgressive variation of characters in segregating generations like F2.
A cross is made between two strains of plants and the F2 is screened for
transgressive variations. Transgressive segregation is the segregation of
characters beyond the parental limits, in the segregating generations
like F2.
C. Production of Hybrids: Hybrid (F1) plants show higher vigor and
yield when compared to parents, in some cases. This phenomenon is
called hybrid vigor. F1 seeds can be raised in bulk through hybridization
and distributed directly for cultivation, especially in cross-pollinating
crops.

5. Types of hybridization
Based on the genetic difference between parents, hybridization can be
classified into:
1. Inter-varietal Hybridization
2. Distant Hybridization
Inter-varietal hybridization
The cross between the members of the same species (intra-specific) is
called inter-varietal hybridization. In this type of hybridization, different
cross patterns can be used.
• Simple Cross: In this case, two parents are used to produce an F1
hybrid.it is also called single cross.
Parent A × Parent B F1 hybrid
• Complex Crosses: In complex crosses, more than two parents are
involved. Such crosses can be called convergent crosses since they bring
genes from different sources together.eg,
Three way cross F1 (A × B) × C
Double cross F1 (A × B) × F1(C × D)

6. • Hybridization between the
members of different species or
hybridization beyond species
level is called distant
hybridization. Thus, it may be
interspecific (intra-generic) or
inter-generic. When conventional
methods of hybridization fails,
para-sexual methods are used in
such cases.
Distant hybridization
Conti….
• Para-sexual hybridization is the technique of fusing somatic
protoplasts when reproductive cells fail to fuse or fertilize.

7. History of plant hybridization
 1717: Thomas Fairchild: Developed first Inter specific hybrid between
sweet William and Carnation Species of Dianthus popularly known as Fair
Child’s mule.
 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 (genes).
 1890: Rimpu (Sweden): First made inheritance cross between bread wheat
(Triticum aestivum) and rye (Secale cereale), which later on gave birth to
triticale.
 1917: Jones: developed first commercial hybrid maize
 1927: Karpencheko: developed first intergeneric hybrid between Radish
and Cabbage in Russia.

8. Procedure of hybridization
1.Set up your
objective
2. Selection of
Parents
3. Evaluation
of parents
4. Evaluation
of parents
5.Emasculation
6. Bagging 7. Tagging
8. Pollination
9. Harvesting
F1 Seeds

9. Set up your objective
• Objective of hybridization should be set before the
hybridization programme.
• It will help in selection of parents.
• If our goal is development of high yielding resistant
variety, then we need to select one of the parent that
is high yielding and another one is resistance to
particular disease.

10. Selection of parents
• The choice of the parents depends on
the objective of the crosses.
• In combination breeding, the genetic
diversity of the parents is not
important. In the case of transgressive
breeding, genetically diverse plants
are selected as parents.
• If the characteristics of the parents are
not completely known, they are
evaluated for the agronomic features.

11. Evaluation of parents
• In case of parents which are
new to the region they must
be evaluated foe there
adaptability.
• Further to ensure
homozygosity, they must be
evaluated.

12. Emasculation
• Emasculation is the removal of
immature anthers from a bisexual
flower.
• Depending upon the crop species,
the method of emasculation differ.
• Normal practice is hand
emasculation.

13. Bagging
• The emasculated inflorescences of
female plants are covered using
butter paper bags or cloth bags.
• However, in the case of cross-
pollinated crops, male plants may
also be bagged if desired, so as to
avoid pollen mixture.
• The bags are removed 2-3 days after
pollination.

14. Tagging
• Emasculated flowers are tagged
properly after bagging.
• Circular or rectangular tags may be
used.
• Details of the cross, date of
emasculation, date of pollination
and the number of flowers
emasculated must be noted on the
tag.
• Carbon pencil or permanent ink may
be used for tagging.

15. Pollination
• Mature, fertile and viable pollen
grains are collected from the male
parent and dusted on the stigma of
the female parent.
• Care should be taken to see that
the pollen grains are dusted at the
optimum stage of viability.

16. Harvesting F1 seeds
• Crossed seeds are harvested carefully and
stored to raise the F1 generation.
• Further handling of the hybrids depends on
the objective of the cross.
• In the case of hybrid seed production, the F1
seeds are directly released to farmers.
• In the case of combination breeding and
transgressive breeding, F2 is raised and the
most appropriate solution program is used.
• Harvest of crossed seeds must be done on
individual plant basis
• Seeds collected from individual plants are to
be stored in appropriate containers with
proper label and stored.

17. THE END