Breeding for polyploidy in ornamental crops..

FLA511-breeding of ornamentals

Course instructors:DR. K.V. PRASAD DR.DVS.RAJU DR.KANWAR PAL

What is polyploidyThe presence of more than two paired sets

of chromosomes.

Numerical change in a whole set of

chromosomes.

Triploid (3N), tetraploid (4N), pentaploid

(5N), hexaploid (6N)

The polyploidy is of

two types Autopolyploidy

more than two copies of a

single genome.

Allopolyploidy

two or more genomes and

each genome ordinarily

present in 2 copies

Autopolyploidy•within a species

•multiplication of the

same set of

chromosomes

• Induced artificially by

colchicine Ex-

Antirrhinum, Cosmos,

Dimorphotheca

Traits in species , suited for

induction of polypoidy- 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.

Effect of polyploidy:1.. Increased fruit weight, fruit size, seed size, crop

load, flower size etc.

2.. Reduction in fertility (in odd ploidy level

individuals).

3.. Change in growth pattern.

4.. Can be used to create higher diversity.

5.. Greater ability to colonize new habitats than

diploid ancestors.

6.. increase blooming period (marigold, Begonia,

ageratum)

Alloployploidy-

•Chromosome doubling after hybridization of 2

sps

• Interspecific polyploidy

•Caused by hybridization followed by

chromosome doubling e.g., AABB, AABBCC

•To restore fertility in inter-specific crosses by

spontaneous doubling of chromosome

(Begonia, Impatians, Kalanchoe)

Haploidy:

•Bears only one set of chromosomes

•Haploids of higher plants are sterile

•Producing pure homozygous lines for

breeding programs.

•Such plants are developed through a

culture technique developed by Guha and

Maheshwari

• Gynogenic haploids

Application in crop

improvement:

-Tracing the origin of crop

sps.

-Speciation & evolution

-Interspecific gene transfer.

-As a bridging cross

Polyploidy in ornamental crops:

ROSECN from 2n=14 to 56

Early miniatures diploid,

later ones, tetraploid.

Hybrid teas and

flouribundas 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

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

Gladiolus (x=15)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

Dianthus species-

• 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

Chrysanthemum-(x=9)•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

•Anthurium

(2n=20 to 124)•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

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. variabilis) with �2n=64, a hybrid that combined

the genomes of two species

•It is an autoallopolyploid, rather

than an allooctoploid

 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

•Jasmine(x=13)

• 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.

Important polyploid

varieties in flower

crops:Rose –pusa mohini,

aneuploid(3n+1)

Eva and J.G. Thornton-

tetraploid

Marigold –nugget, triploid

Zenith Mixed, triploid

Bougainvillea –Begum sikandar,

aneuploid(3n-2)

Mary palmer,

Tetraploid

Amaryllis -Samrat, tetraploid

Thank you…