about heterosis breeding and acheivements in horti crops

2. • Heterosis refers to the superiority of F1 hybrids in
one or more characters over its parents.
• The term hybrid vigour is used as synonym for
heterosis.
• The term heterosis was first used by Shull in 1914.

3. Hybrid vigour:
According to shull, the developed superiority of the
hybrid is the ‘hybrid vigour.
Heterosis:
The mechanism by which superiority is develoed.

4. • Superiority over Parents:
Heterosis leads to superiority in adaptation, yield,
quality, disease resistance, maturity and general vigour
over its parents.
Generally, positive heterosis is considered as
desirable. But in some cases negative heterosis is also
desirable.

5.  Superiority of over parents
 Confined to F1
 Genetic control
 Reproducible
 Association with specific combining ability
 Effect of heterozygosity
 Conceals recessive genes
 Low frequency

6.  Increased yield
 Increased reproductive ability
 Increased size and general vigour
 Better quality
 Earlier flowering and maturity
 Greater resistance to diseases and pests
 Greater adaptability
 Faster growth rate

7. The genetical basis of heterosis is still following two
hypothesis:
• Dominance hypothesis of heterosis.
• Over dominance hypothesis of heterosis.

8. • Holds that increased vigour and size in a hybrid is
due to combination of favourable growth genes by
crossing two inbred races.

9. • Considered that there is a physiological stimulus to
development that increases with the diversity of the
uniting gametes.

10. On the basis of origin and nature have 2 types:
A.Euheterosis or true heterosis.
1.mutational heterosis
2.balanced heterosis
B.Pseudoheterosis:
On the basis of types of estimation:
Average heterosis
Heterobeltiosis heterosis
Useful heterosis

11. Mutational heterosis
Leathal(mostly),recessive, adaptively
unfavourable mutants are either eliminated by their non-
lethal dominant and adaptively superior alleles in cross
pollinated crops.
Balanced heterosis
well balanced gene combinations which are
more adaptive to environmental conditions and useful
from the agriculture point of view result in balanced
heterosis.

12. Pseudoheterosis
Also termed as an luxuriance. progeny posses
superiority over parents is in vegetative growth, but not
in yield and adaptation ,usually sterile or poorly fertile.
this concept cannot be utilized in hybrid varieties
production.

13. Average or relative heterosis:
When heterosis is estimated over mid parent value i.e.
average of two parents value.
Heterobeltiosis:
When heterosis is estimated over better parent it is called
heterobeltiosis.
Standard heterosis:
When heterosis is estimated over standard commercial
hybrid it is called as standard heterosis.
It has practical importance in plant breeding.
It is also referred as a useful or economic heterosis.

14. There are four genetic factors which affect magnitude of
heterosis in crop plants.
 Mode of Pollination
 Genetic Diversity of Parents
 Genetic base of Parents
 Adaptability of Parents

15. Marigold: High heterosis was observed in the crosses
Alaska x Hawaii(flower size)
Alaska x Cupid orange mum (flower weight)
Katrain local x Cupid orange mum (flower number).
Antirrhinum:
F1 dwarf hybrids -(Antirrhinum majus x Antirrhinum glutinosum).
-over dominance was observed in the inheritance of all characters.
Verbena:
Free flowering and heat resistant hybrids were developed.

16. China aster:
shell pink x Azure blue
AST 20 x Azure blue
AST 20 x AST 16.
these 3 were developed for manifestation of heterosis - Flower
size, Number of flowers per plant and stalk length.
Petunia:
In single multiflora and grandiflora types, heterosis
involving diallel crosses using 8 parental lines - all characters.

17. Hollyhock:
Five F1 hybrids were developed- Pusa pink
beauty, Pusa yellow
beauty, Pusa pastel pink, Pusa apricot supreme, Pusa
pastel pink supreme

18. Co-2: It is a F1 hybrid between A.E 180 × Pusa Sawani. The
crop duration is only 90 days and yield on an average of
16.51 t/ha, Fruits are fairly long with a mean length of
20.60cm, girth of 6.8cm and each wt. 33g.
Co-3: It is a high yielding F1 hybrid between Parbhani
Kranti × MDU.1. It exhibits moderate resistance to YVMV.
The variety has an yield potential of 16-18 t/ha which is
56% more than that of Parbhani Kranti. The fruit is dark
green, medium in size and suitable for fresh market.

19. Tomato
• Cross of EC-156 × Marglobe showed high heterosis
for number of fruits per plants that gave 83.18% more
yield then better parent.
• High degree of heterosis over better parent for
pericarp thickness has been observed in cross of S-14
× Pusa Ruby.

20. Brinjal:
• The cross of Pusa Purple Long × Pusa Purple Cluster
and Erangre × Pusa Purple.
• Cluster exhibited high degree of heterosis for yield
and other fruit characters.

21. Reference:
Plant Breeding principles and method – B.D.Singh.
Breeding of Horticultural Crops – Dr.N.Kumar.
Breeding and Protection of Vegetable – M.K.Rana.
Ornamental Crop Breeding – Dr.L.C.De &
S.K.Bhattacharjee.