This document discusses polyploidy breeding. It defines polyploidy as having three or more sets of chromosomes, which can occur naturally or through induction. There are various ways polyploids can originate, such as somatic doubling during mitosis, non-reduction during meiosis producing unreduced gametes, or polyspermaty fertilization. Polyploidy has been used in crop improvement by creating autopolyploids through doubling chromosome sets within a species, or allopolyploids by hybridizing between species. Examples of naturally occurring polyploids include wheat and strawberry. Both natural and artificial polyploids can provide benefits like overcoming hybridization barriers and increasing stress tolerance.

1. Polyploidy breeding
PRESENTED BY:
K NIKILESH
Reg. no.: 11408963
ROLL.NO:B41
SECTION:H1435

2. Introduction
 Polyploidy:-
 Which involves three or more sets of chromosomes , and
may occur naturally or by induction.
 Nearly all plants probably have some polyploid tissues.
Examples:
i. Plant endosperm is triploid.
ii. Wheat is hexaploid (6N) and the strawberry is
octaploid (8N).

3. Origin of polyploids
There are various modes for the origin of polyploids.
1. Somatic doubling during mitosis,
2. Non-reduction in meiosis leading to the production of
unreduced gametes,
3. Polyspermaty:-fertilization of the egg by two male nuclei
4. Endoreplication:-replication of the DNA but no
cytokinesis.

4. somatic doubling during mitosis,
 Chromosome doubling can occur either in the zygote to
produce a completely polyploid individual or locally in
some apical meristem to give polyploid chimeras.
 In somatic doubling the main cause is mitotic non-
disjunction. This doubling may occur in purely vegetative
tissues like in root nodules of some leguminous plants or
at times in a branch that may produce flowers or in early
embryos.

5. Non-reduction in meiosis leading
to the production of unreduced
gametes
 Non reduction could be due to meiotic non-
disjunction (failure of the chromosome to separate
and subsequent reduction in chromosome
number), failure of cell wall formation.
 Example:- Raphanobrassica, originated by a one
step process of fusion of two non- reduced
gametes.

7. Radish
(Raphanus
sativus, n = 9)
cabbage
(Brassica
oleracea, n = 9)
Raphanobrassica
Amphidiploid
(4n = 36)
Raphanobrassica

8. factors promoting polyploidy
 The mode of reproduction
 The mode of fertilization
 The breeding system
 The growth habit of the plant
 Size of chromosomes etc.
an interspecific hybrid having a complete diploid chromosome set from
each parent form is known as “ amphidiploid”. If the parental
species are polyploids, the derivative will be called as “
amphipolyploid”.

9. Types of polyploids
Autopolyploidy
 (genome doubling)
doubling of the same
chromosome set .
 Autopolyploids are
derived from within a
single species
Allopolyploidy
 is the product of inter-
specific hybridization
 allopolyploids arise via
hybridization between
two species

10. Bread
Wheat
Evolutionof naturalpolyploids

11. Artificial Allopolyploid
 Artificial or synthetic allopolyploids have been
synthesized in some crops with two main objectives,
viz.
1)Either to study the origin of naturally available
alloploids or
2) To explore the possibilities of creating new species.

12. Breeding of Autopolyploids
Cells/individuals having autopolyploid (doubled)
chromosome numbers may originate in one of the
following several ways:
(1) Spontaneous
(2) Due to treatment with physical agents
(3) Regeneration in vitro
(4) Colchicine treatment

13. Application of Allopolyploidy in Crop
Improvement

14. Conclusion
 With knowledge of the origins, variations and
characteristics of different types of polyploids,
there are many opportunities for developing and
utilizing polyploids in plant improvement
programmes.
 Significant opportunities include developing sterile
cultivars, overcoming barriers to hybridization,
restoring fertility in wide hybrids, enhancing flower
size, increasing heterosis and vigor, and improving
pest resistance and tolerance to environmental
stresses.

15. Thank you….