This will describe the what is polyploidy, its type, how its induced and polyploidy in ornamental crops.

2. POLYPLOIDY IN ORNAMENTAL CROPS
Presented by: Jay Khaniya
Genetics and Plant Breeding M.Sc
(Agri.)
Submitted to: Dr. N. B. Patel
Department of Genetics and Plant
Breeding, JAU, Junagadh
GP 507: Principles of Cytology

3. Introduction
 An organism having more than two sets of
homologous chromosomes is known as polyploid and
this phenomenon is known as polyploidy.
 It was discovered by Lutz.
 It is rarely found in animals but is of general
occurrence in plants.
 A survey of the chromosome numbers of the species
in a family shows that these species generally fall in to
polyploid series e.g., 2n, 3n, 4n, 5n, 6n etc.

4. Types of Polyploidy
1) Autopolyploidy (Genome doubling): Multiplication
of one basic set of chromosomes.
2) Allopolyploidy: The combination of genetically
distinct, but similar chromosome sets.
 Autopolyploids are derived within a single species;
while Allopolyploids arise via hybridization between
two species.

5. Autoployploids
 Triploid (three sets; 3x), for example seedless
watermelons,
 Tetraploid (four sets; 4x) for example potato
 Pentaploid (five sets; 5x)
 Hexaploid (six sets; 6x)
 Heptaploid (seven sets; 7x)
 Octaploid (eight sets; 8x)

7. Origin of Polyploidy
1) Somatic doubling during mitosis
2) Non-reduction in meiosis leading to the
production of unreduced gametes
3) Polyspermaty (Fertilization of egg by two
nuclei)
4) Endoreplication (Replication of DNA but no
cytokinesis)

8. 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 nondisjunction.
 This doubling may occur in purely vegetative tissues (as in root
nodules of some leguminous plants) or at times in a branch
that may produce flowers or in early embryos (and may
therefore be carried further down).

9. 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 or formation of gametes by
mitosis instead of meiosis.
 Raphanobrassica, originated by a one step process of fusion
of two non- reduced gametes.

10. Polyspermaty (fertilization of the egg by two male
nuclei)
 Polyspermy is observed in many plants but it’s contribution
as a mechanism for polyploid formation is rather rare except
perhaps in some orchids .
Endoreplication (replication of the DNA but no
cytokinesis)
 Endoreduplication is a form of nuclear polyploidization
resulting in multiple uniform copies of chromosomes.
 It has been known to occur in the endosperm and the
cotyledons of developing seeds, leaves and stems of plants.

11. Traits in species , suited for
induction of polyploidy (by Dewey)
 Should have low CN
 Economic part should be vegetative.
 Should be cross- pollinated
 Should be perennial in habitat.
 Have ability to reproduce vegetatively.

12. Effect of polyploidy:
 Increased fruit weight, fruit size, seed size, crop load, flower
size etc.
 Reduction in fertility (in odd ploidy level individuals).
 Change in growth pattern.
 Can be used to create higher diversity.
 Greater ability to colonize new habitats than diploid
ancestors.
 Increase blooming period; (marigold, Begonia, ageratum)

13. Application in crop improvement:
 Tracing the origin of crop species.
 Speciation & evolution
 Interspecific gene transfer.
 As a bridging cross

14. Rose
 CN from 2n=14 to 56
 Early miniatures diploid, later ones, tetraploid.
 Hybrid teas and floribundas generally tetraploids
 Sterility of some diploid Interspecific hybrids arise
through genomic differences, chromosome no may be
expected to increase fertility.
 Thus sterile diploid R. rugosa x wichuriana ‘Max Graf’
spontaneously produced a tetraploid seedling, R.
kordessi
 Doubling of chromosome being tried

15.  For sterile hybrids & diploid species to avoid production of sterile triploids
after cross with tetraploid cultivars.
 Polyploidy induced in species & F1 interspecific hybrids by colchicine to
shoots of seedlings
 The frequency of tetraploid was low
 Chimerism complicating factor
 In-vitro, controlled application of spindle inhibitoRS

16. Gladiolus
 South african species-diploid
 Eurasian and central African species-tetraploid
 Sterile triploids and pentaploids found
 Indicates diploid-tetraploid and tetraploid-hexaploid crosses
 Highest chromosome no G.communis
 Some tripoids and pentaploids are fertile
 Ferlite aneuploids

17. Dianthus
 x = 15 (2n=30 to 180)
 D. chinensis- tetraploid; D.caryophyllus-diploid
 D. gratianopolitanus- both tetraploid and hexaploid
 Many desirable plant characteristics related to plant
ploidy levels
 Mixoploidy in several organs from D. caryophyllus
 Positive correlation between endopolyploidy, cell and
petal size

18. Chrysenthemum
 CN from 2x to 25x
 2n=36, 45, 47, 51, 75 by T.N. Khushoo
 Intraspecies and intrapopulation variations in ploidy
 C. indicum - 2x,4x & 6x
 C. zawadskii - 4x & 6x
 Polyploids widely distributed
 Evolution & regulation of flower size of large-flower
population possible.
 evidence of low ploidy in large-flower chrysanthemum

19. Anthurium
 Mostly diploid, some polyploid also present
 A.andreanum, A.magnificum & A.hookeri- diploid
 A.digitatum & A.wallism –tetraploid; A.scandens-
triploid.
 chloroplast number in the guard cell convenient &
reliable indicator of ploidy level in anthurium.
 Micropropagation of A. scherzerianum poses very
little risk in ploidy changes

20. Dahlia
 2n=32, others 2n=64
 Sorenson- 2n=32 species were diploid
and 2n=64 species tetraploid
 Lawrence (1929) suggested that the
2n=32 species were allotetraploids,
arising from hybrids between now-
extinct diploids with 2n=16.
 Garden dahlia (D. vŠ ariabilis) with
2n=64, a hybrid that combined the
genomes of two species
 It is an autoallopolyploid, rather than an
allooctoploid

21. Gerbera
 2n=50
 G jamesoni=tetraploid
 Tetraploid plantlets – slower proliferation, higher
vigour and thickened broad leaves.
 Tetraploid plants developed larger flowers, longer
stalks, and have improved vase-life
 No of chloroplast present in the stomata of guard
cell is indicator
 Haploid use for development of new varieties

22. Jasmine
 Important role in origin of new cultivars in essential oil
bearing plants.
 Spontaneous triploid in J. sambac & J. autumnale(Sharma
and Sharma), J. grandiflorum( Murthy and Khanna)
 Spontaneous tetraploidy in J.calophyllum (Dutta)
 Triploidy in J.grandiflorum increase concrete content and
thereby hold promise as useful avenue for improvement of
this crop.
 Attempt to induce tetraploidy in Jasmine.
 Induced tetraploidy in J. grandiflorum did not reveal
superiority.