Polyploidy breeding procedure

2.  Chromosome no.- 3 types – haploid, diploid, basic
number
 Haploid / gametic chr.no. (n) –
half of somatic chromosome no.
 Diploid /zygotic chr. no.(2n)-
Somatic chr.no.
 Basic no. (x) – gametic chr.no. of
a true diploid species/minimum
haploid chr.no of a species
 In regular diploids,
2n=2x

4. Polyploidy

6. Suitability of a crop for pp breeding depends on
following factors:
 Crops which are not seed propagated(ie, vegetatively
propagated crops where the economic part is not
seeds)
eg: forage crops, tubers, sugarcane, ornamentals
 Crops with low 2n no.
 Allogamy / cross pollination
eg: Poaceae against Leguminosae

7.  STEP 1
Artificial induction and/or collection of naturally
occuring pps and their maintanence.
 STEP 2
Detection of different kinds of pps.
 STEP 3
Isolation and handling of pps.

8. PP breeding includes:
1. Monoploid/Haploid breeding
2. Autoploid breeding
3. Allopolyploid/Amphi(di)ploid breeding
4. Aneuploid breeding

9. STEP 1 PRODUCTION OF HAPLOIDS
i. By induced parthenogenesis
◦ Using incompatible or irradiated pollen, haploids
can be obtained by parthenogenesis.
ii. Through wide crosses ( cross with distant species)
◦ eg: Hordeum vulgare х Elymus areanus
Monoploid barley

10. iii. Through chromosome elimination technique in
distant crosses
◦ eg: Bulbosum technique
H.vulgare х H.bulbosum
(2n=2x=14) (2n=2x=14)
Hybrid embryo
Haploid barley
(2n=x=7)
(H.bulbosum chr. eliminated)
eg: Solanum nigrum x S.luteum

11. iv. Cell culture/Tissue culture technique
v. Anther culture technique by Guha and Maheswari
◦ Used in Datura, Nicotiana, Brassica, rice, wheat,
triticale etc.
◦ Tanfeng is a haploidy derived rice variety
developed in China(1976)
vi. Through pollen culture
◦ Haploid pollen grains develop into haploid plants.
◦ Nicotiana – readily responding in anther & pollen
culture.
Technique to be followed varies depending on the
species.

12. STEP 2 DETECTION OF HAPLOIDS
i. Detection through genetic markers
◦ Use of recessive & dominant genetic markers
associated with seedling characters such as
hypocotyl colour is useful in early detection of
haploids.
◦ Eg : In potato, a dominant purple spot is present
on haploid embryo-helps to distinguish at seed
stage.
ii. Through plant morphology
◦ Haploid plants are inferior to diploids – shorter,
less longer leaves, reduced in breadth, stomata &
guard cells – smaller in size.

13. STEP 3 DIPLOIDISATION
 Colchicine treatment – most effective & widely used
method.
 Acts as inhibitor of spindle formation during mitosis &
causes duplication of homologus chromosomes
 Colchicine is readily soluble in cold water, alcohol and
chloroform but less soluble in hot water.
 Used as aqueous solution – relatively unstable. So the
solution prepared fresh before each application.
 Affects only dividing cells-applied to actively dividing
meristematic cells repeatedly at brief intervals.

14.  Methods of application:
◦ Seed treatment : Freshly prepared 0.2% solution
applied for 1-10 days.
◦ Seedling treatment : At very young stage, seedlings
are inverted and only the young shoots are dipped in
colchicine solution & roots are protected;3-24hrs
◦ Application to growing apices : 0.1-1% solution
applied to shoot apex using a dropper/cotton balls
dipped in colchicine solution placed on shoot apices-
repeated daily
0.5-1% colchicine +lemolin paste smeared on shoot
apex-repeated 2-3 times per week.
For woody plants, 1% colchicine with a wetting agent
applied on shoot apices.

17.  Includes triploid and tetraploid breeding
I. TRIPLOID BREEDING
• Produced by crossing tetraploid and diploid (4n x 2n)
• Tetraploid as female –
total qnty of seed low-
proportion of 3n seeds
high-produce vigorous
hybrids
• Diploid as female-total qnty
high-proportion of 3n seeds
low

18. • Triploids-pollen sterile-seedless-advantageous in
watermelon
• In common planting, diploid planted to provide
pollen for satisfactory seed set in triploid in 5:1 ratio

20.  Varieties Shonima & Swarna (2015) released from
Kerala Agricultural University

21.  Variety Ocean
2x
3x

22.  TV29
 produces larger shoots & biomass; yields more cured
leaf per unit area and tolerant to drought than
available diploid varieties

23. II. TETRAPLOID BREEDING
 Produced by chromosome doubling from diploid plants

24.  Possible in tobacco, Petunia etc.
 Autotetraploid maize has 43% more carotenoid
content & vitamin A.
 Successful in forage crops, ornamentals etc.
Pusa giant berseem -1st autotetraploid variety
(Egyptian clover) released for large scale cultivation –
higher green fodder yield
Vetiver variety – Sugandha – 11% more oil yield

25.  AMPHIDIPLOID – Allopolyploids diploid for all
genomes present.
 STEP 1 Production of F1 hybrids by interspecific
and intergeneric crosses
 STEP 2 Chromosome doubling by colchicine

26. DD)

29. 4

30.  Developed by Karpechenko
Chr.doubling

31.  Combines yield potential and grain quality of wheat &
disease and environmental tolerance (including soil
conditions) of rye

32.  World’s 1st interspecific cotton hybrid (1972)
 Developed by Dr. B. H. Katarki from Cotton Research
Station, Dharwad, UAS, Bangalore
G. hirsutum х G. barbadense
(Laxmi ) (SB 289 E)
Varalaxmi

33.  2n=38
 Hybrid between Brassica campestris(syn. B.rapa) and
Raphanus sativus (fodder raddish)

34.  Irregular variation in chromosome no.
 By meiotic irregularities such as non-disjunction or
lagging behind in metaphase plate result in n+1 & n-1
gametes. These gametes fertilized by normal gametes
produce aneuploids.
 In desynaptic and asynaptic plants-a no.of univalents
are seen in mid metaphase instead of bivalents which
produce aneuploids
 Triploid plants produce aneuploid plants
 Tetrasomic plants produce aneuploid gametes resulting
in aneuploid progeny.