PROSPECTS OF HETEROSIS BREEDING TOWARDS FOOD SECURITY

1. PROSPECTS OF HETEROSIS
BREEDING TOWARDS FOOD
SECURITY
PRESENTED
BY:
OM PRAKASH YADAV
Regd. No.: J-17-M-507
Division of Plant Breeding and Genetics
Sher-e-Kashmir University of Agricultural
Sciences & Technology, Jammu

2. HETEROSIS
Superior performance of heterozygous F1 hybrid plants
in terms of increased biomass, size, yield, speed of development,
fertility, resistance to disease and insect pest, or to climatic
rigors of any kind compared to the average of their homozygous
parental inbred lines (Shull, 1952 & Falconer, 1996).
Other term of heterosis should be used only when the
hybrid is either superior or inferior to both the parent (Powers,
1944).

3. HISTORY
❖ Heterosis was first described by Charles Darwin (Darwin
1876) and rediscovered by Shull (1908) and East(1908).
❖ Term coined by “Shull” in (1952) as “ stimulation of
heterozygosity”.
❖ Maize hybrid was first utilized in field on a large scale in
USA in 1930s.
❖ Hayes and Jones (1916) reported hybrid vigor for cucumber
mainly contributed to notable increasing of fruit size and
number.

4. SALIENT FEATURES OF HETEROSIS
❖ Heterosis leads to superiority in adaptation, yield,
quality, disease resistance, maturity and general vigour
over its parents.
❖ It is confined only to F1 generation of a cross.
❖ The magnitude of heterosis has positive association with
heterozygosity and specific combining ability variance.
❖ The frequency of desirable heterotic combinations is
very low.
❖ In heterosis, effect of deleterious recessive genes are
inhibit by the favorable effect of dominant genes.

5. Classes of Heterosis

6. GENETIC BASIS OF HETEROSIS
Genetic basis
of Heterosis
Dominance Over-
dominance
Epistasis

7. DOMINANCE MODEL
❖Inhibit of deleterious or inferior
alleles.
❖Heterosis depend on number of
dominant genes.
❖Both parents should differ in
dominant genes.
❖Hybrid and parents are both
similar there are no heterosis.
❖Dominance is considered more
popular one.
Devenport, 1907
P1 P2
AAbbCCdd x aaBBccDD
F1 AaBbCcDd

8. OVER-DOMINNACE HYPOTHESIS
❖ Heterosis is the result of the superiority of heterozyote
over its both homozygotes.
❖ According this hypothesis heterozygotes atlest some of the
loci are superior to both the relevant homozygotes.
Ex. Aa > AA and aa
❖ East (1936) proposed that heterozygotes for more
divergent alleles would be more heterotic than those
involving less divergent ones.
A1A4 > A1A3 > A1A2------------- so on
Ex. Sickle cell anemia
❖ Objections : Lack of clear evidence showing over
dominance .
(East, 1908 and Shull, 1910)

9. EPISTATIC MODEL FOR HETEROSIS
❖ The epistasis hypothesis considers epistatic interactions
between non-allelic genes at two or more loci as the main
factor for the superior phenotypic expression of a trait in
hybrids.
(Powers,1945)

10. BIOMETRICAL BASIS OF HETEROSIS
❖MID-PARENT HETEROSIS:- It indicates that a trait displays hybrid
performance that is significantly better than the average (mid parent)
value.
Mid parent Heterosis (MH) = [ (F1-MP)/ MP ] x 100
❖BETTER-PARENT HETEROSIS:- Indicates that a hybrid trait
performs significantly better than the better of two homozygous parents.
Better parent Heterosis (BH)/Heterobeltiosis
= [ (F1- BP)/ BP ] x 100
❖USEFUL HETEROSIS/STANDARD HETEROSIS :- Indicates that a
hybrid trait performs significantly over the standard commercial check
variety.
Useful Heterosis= [ (F1- CC)/ CC ] x 100
➢Useful Heterosis is direct practical value in plant breeding.

11. CROSS POLLINATED
CROPS EXPLOITING
HETEROSIS
➢CEREALS:
MAIZE
PEARL MILLET
SORGHUM
➢VEGETABLES:
ONION
SPINACH
FABA BEAN
➢OILSEED:
SUNFLOWER
MUSTARD

12. Maize (Zea mays L.) is the third most
important crop among the cereal crops
known as Queen of cereals.
➢In Jammu and Kashmir, maize is
important crop used for human
consumption in mid and higher hills and
feed and fodder for animals.
➢The average yield is comparatively very
less than natural average productivity
which is namely due to cultivation of low
yielding cultivars .
➢Hybrid maize technology particularly
single cross hybrids has substantially
increased maize grain production and
productivity at national and international
level.
MAIZE

13. REASONS FOR EXPLOITATION OF HETEROSIS:
❖ Highly genetic diverse
❖ Highly cross pollinated crop
❖ No emasculation needed
❖ Low cost of seed production
❖ Availability of CMS lines
❖ Protandry nature.

14. HYBRID PRODUCTION
The most common types of hybrids in maize are
single-cross, three-way and double-cross hybrids:
➢ A single-cross hybrid is made by crossing two
inbred lines. single crosses give maximum degree
of heterosis and produce uniform plant.
➢A double-cross hybrid is made by crossing two
single-cross hybrids.
➢A three-way hybrid is made by crossing a
single-cross hybrid with an inbred line.
Two other types of hybrids are top-crosses
and double top crosses:
➢A top-cross hybrid is made from an open-
pollinated variety crossed with an inbred line.
➢A double top cross hybrid is a hybrid progeny
between a simple cross and an open pollinated
varieties..

15. CASE STUDIES
Heterosis are observed for important traits in maize
Traits Heterosis (%) BP/
MP/UH
Reference
Ear yield –4.3 to 17.3 MP Silva & Filho, 2003
Ear height (cm) 36.56 to 102.37 BP Kumar, et al. 2014
Grain yield per plant (g) 82.80 to 304.70
-71.02 to 29.88
10.77 to 269.58
UH
SH
MP
Kumar, et al. 2014
Patil, et al. 2017
Patil, et al. 2017
Lysine content 8.29 to 15.78 - Lal, et al. 2011
Seed weight (g/ear) 101.7 BP Auger et al. 2005
Ear length (cm) 48.3 BP Auger et al. 2005
Seed number 46.0 BP Springer and Stupar, 2007
Day to maturity - 4.46 to 4.00 SH Kumar, et al. 2014

16. Source: Directorate of Economics and Statistics, Department of Agriculture
and Cooperation (2010-11).
Production of hybrid maize in India

17. Pearl millet (Pennisetum glaucum) is the most widely grown type
of millet.
India is the largest producer of pearl millet. Rajasthan is the
highest-producing state in India.
REASONS FOR EXPLOITATION OF HETEROSIS:
❖ Highly cross pollinated crop
❖ No emasculation needed
❖ Low cost of seed production
❖ Availability of CMS lines.
❖ Protogyny
PEARL MILLET

18. HYBRID PRODUCTION USING CGMS
Pearl millet, sorghum and sunflower etc. crops use
cytoplasmic genetic male sterility system in hybrid seed production
that is caused by an interaction of sterility inducing factors in
cytoplasmic with genetic factors in nucleus.
STEPS INVOLVED:
❖ Multiplication of CMS (A) line.
❖ Multiplication of maintainer (B) and restorer lines (R).
❖ Production of hybrid seed ( A X R).

19. PARENTAL LINES
❖ A line:- it is the male sterile parent line.
❖ B-line :- The male-sterile line is maintained by
crossing with a B-line, its know as 'maintainer line'.
❖ R-line:- the male fertile line carries genes for fertility
restoration.

20. Heterosis are observed for important traits in pearl millet
Traits Heterosis (%) BP/
MP/UH
Reference
Plant height -32.38 to 76.17
-38.39 to 19.49
MP
UH
Vetriventhan et al. 2008
Grain yield per plant -42.86 to 139.39
-52.97 to 131.70
−47.71 to 143.28
MP
BP
BP
Vetriventhan et al. 2008
Patel et al. 2016
Ear head length −22.62 to 28.52
−18.65 to 25.91
BP
SH
Patel et al. 2016
Total protein content −11.11 to 11.07 BP Patel et al. 2016
Fodder yield /plant -47.74 to 115.40
-140.30 to 22.68
BP
SH
Chittora and Patel et al. 2017
Days to maturity -15.36 to -6.56 BP Krishnan et al. 2017
Test weight (g) 5.93 to 15.77 BP Krishnan et al. 2017
CASE STUDIES

21. Pearl millet productivity during 1960-85 and 1986-2010 in India
Source: DAC, Government of India as on 7 February 2012 available at
http://www.agricoop.nic.in
During first 25 years (1960-85) of hybrid development, the crop productivity
increased @ 6.3 kg/ha/year. This increase went up to over 20 kg/ha/year in next 25
years (1986- 2010).

22. SELF POLLINATED CROPS
EXPLOITING HETEROSIS
❖CEREALS:-
Rice

23. HYBRID RICE
❖The Father of Hybrid Rice - Yuan Longping
❖ Hybrid rice is the crop grown from F1 seeds of cross
between two genetically dissimilar parents.
❖Rice heterosis was first reported by Jones (1926) who
observed that some F1 hybrids had more culms and greater
yield than their parents.

24. Male sterility used in hybrid rice
❖Cytoplasmic genetic male sterility
❖Environment sensitive genetic male sterility
❖Chemically induced male sterility
❖Transgenic male sterility

25. Cytoplasmic genetic male sterility
❖It is caused by an interaction between genetic factor(s) present in
cytoplasm and the nucleus. Absence of a sterility inducing factor
either in the cytoplasm or in the nucleus makes a line male fertile.

26. Environment sensitive genetic male sterility
This is a genetic male sterility system in which sterility expression is conditioned
by environmental factors.
• Types of EGMS
There are two types of EGMS which are currently being used in rice:
PGMS - Photoperiod sensitive genetic male sterility
Genetic male sterile lines which respond to the photoperiod or duration
of day length for expression of pollen sterility and fertility behavior. Most of the
PGMS lines remain male sterile under a long-day (>14 hrs) conditions and revert
back to fertility under short-day (< 14 hrs) conditions.
Example - N9044S and N5088S
TGMS - Thermo sensitive Genetic Male Sterility
Genetic male sterile lines whose male sterility/fertility alteration is
conditioned by different temperature scheme. Most of the TGMS lines remain
male sterile at a high temperature (>23.3°C) and they revert back to fertility at a
lower temperature (<23.3°C). The critical sterility/fertility points vary from
genotype to genotype.
Example - Norin PL12, ID24, IR32364

27. Two-line system hybrid rice

28. Chemical Induced Male Sterility
This non-genetic method of inducing male sterility involves the use of chemical
called hybridizing agents (CHA) or gametocides.
❖The ideal gametocides should :
✓Selectively induce male sterility without adversely affecting the female
fertility.
✓Have systemic effects so as to sterilize both early and late panicles.
✓Have a broad range of effectivity in order to withstand adverse environmental
conditions.
✓Have minimum side effects on plant growth and panicle development.
Ex. MG1 and MG2 (Mostly used in rice)
❖For developing hybrids by using gametocides :
✓The female line should have a synchronous flowering habit
✓The line should respond to chemical treatment
✓The parents should possess good outcrossing traits

29. Importance of Hybrid Rice
❖Rice is the staple food of more than 60 % of the world
population.
❖Rice hybrids have shown 15-20 % higher yield potential
than inbred rice varieties under farmer’s field conditions.
❖Hybrids have shown their ability to perform better under
adverse condition of drought and salinity .
❖Rice hybrids increases profitability at the household level
and will help in achieving food security at the national
level.

30. ❖Grain yield in rice exhibits heterosis ranging from 2 to 369%
(Virmani et al., 1981)
❖Based on the experience that the magnitude of heterosis is found
in the order……
Indica x Japonica
Indica x Javanica
Japonica x Javanica
Indica x Indica
Japonica x Japonica

31. Traits Heterosis (%) BP/
MP/UH
Reference
Yield per plant -10.9 to 369
-54.9 to 139
SH
BH
Joshi, 2001
Panicle no. per plant -19.5 to 98.1
-10.8 to 80.5
SH
BH
Joshi, 2001
Plant height(cm) -15.65 to 10.00
-21.30 to -0.29
MP
BP
Das et al. 2017
Days to maturity -9.60 to 8.00 SH Naik et al. 2018
Test weight (g) -33.11 to 11.28 SH Naik et al. 2018
Harvest index -10.24 to 13.95 SH Kumar et al. 2016
Panicle length (cm) -22.31 to 25.87 SH Krishna et al.
2018
CASE STUDIES
Heterosis are observed for important traits in Rice

32. Area under Hybrid Rice in Asia
It is estimated that around 3+ Million Hectares is under Hybrid Rice cultivation in
India in 2016 which is around 7% of the total Rice cropped area in India.
Vadlamani 2016

33. Progressive increase in area and production of hybrid rice seed
During 15 years (1995-2010) of hybrid development area 99.02%
and production 98.67% increase.
Source : Rice Knowledge Management Portal http://www.rkmp.co.in

34. crop 1990 2017 Increase(%)
Maize Area
Production
5.90
8.96
9.22
28.72
35.86
68.80
Rice Area
Production
36.68
74.94
43.78
111.01
16.21
32.49
Wheat Area
Production
23.50
49.84
30.60
98.51
23.20
49.40
Total
cereals
Area
Production
-
162.5
128.0
277.49
-
41.44
Food Security
The World Food Summit of 1996 defined food security as existing "when all people at all
times have access to sufficient, safe, nutritious food to maintain a healthy and active life".
Food crops production increased of major crops between 1990 to
2017 in India.
Area (million hectares), Production (million tonnes).

35. Although heterosis is widely utilized in crop production, its
genetic and molecular basis is still elusive. It is arguable that
heterosis arises in crosses between genetically distinct individuals.
Various genetic models have been proposed to explain
heterosis, such as dominance and overdominance hypothesis
earlier.
With the recent advancements in functional genomics,
epigenetics, transcriptomics, proteomics, and metabolomics-related
technologies, systems-level approaches have been adopted to
understand the molecular basis of heterosis.
ADVANCES IN HETEROSIS

36. ❖Heterosis is common phenomenon in maize, sorghum and other
species.
❖It is likely that a common biological mechanism underlying
heterosis is existed in a wide variety of different species.
❖At gene expression level, both additive and non-additive mode of
differential gene actions have been shown to be involved in the
manifestation of heterosis.
❖Recently, mounting evidences of the epigenetic machinery was
provided to explain heterosis .
Summary